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Speaker 1: Yeah, or hey, do you find yourself speeding up or

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Speaker 1: slowing down as we get older? Kind of both both?

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Speaker 1: How's that possible? Well, I'm faster at falling asleep on

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Speaker 1: the couch, that's true. I'm faster at finding a place

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Speaker 1: to sit down as soon as I get somewhere, But

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Speaker 1: I'm getting slower at the same time that time seems

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Speaker 1: to go faster. Do you think there's like a maximum

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Speaker 1: speed to that if we live to be like nine

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Speaker 1: years old, like Yoda with the years just passed by

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Speaker 1: in a blink. Well, first of all, I definitely want

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Speaker 1: to be Yoda. I don't want to look like Yoda

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Speaker 1: when I'm Somebody needs to tell Yoda about sunscreen. Although

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Speaker 1: my ears are getting bigger, but my light serious skills

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Speaker 1: are getting worse. As long as you can still do

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Speaker 1: those flips, well you know what he said. He said,

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Speaker 1: do or do not? There is no try. Hi am

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Speaker 1: or Handma cartoonists and the creator of PhD comics. Hi,

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Speaker 1: I'm Daniel. I'm a particle physicist and a professor at

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Speaker 1: U C Irvine, and I don't think I will ever

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Speaker 1: do a backflip in my whole life. Oh, I feel

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Speaker 1: bad for you. You've never done a backflip or a

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Speaker 1: front flip except underwater. I've done one underwater, but you know,

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Speaker 1: not like standing on the ground. And I feel like

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Speaker 1: I've sort of passed the age where you could like

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Speaker 1: learn to do that in the future. I still do backflips.

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Speaker 1: You can do a standing backflip. Yeah, that's amazing. I

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Speaker 1: think we have to see a video of that. Yeah. Well,

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Speaker 1: usually do it at those trampoline places. Yeah. I can

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Speaker 1: do backflips while skydiving. Yeah. Have you skydive? Actually have

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Speaker 1: jumped out of an airplane once? Did you do a backflip?

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Speaker 1: We did all sorts of crazy maneuvers, but I had

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Speaker 1: somebody strapped to my back, so it's sort of like

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Speaker 1: a double backflip. You had someone strapped to your back,

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Speaker 1: or someone had you strapped through their front. It was

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Speaker 1: basically like Baby Buern skydiving. Welcome to our podcast Daniel

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Speaker 1: and Jorge Explain the Universe, a production of My Heart

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Speaker 1: Radio in which our goal is to make your brain

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Speaker 1: and do backflips as you understand the incredible beauty and

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Speaker 1: mystery of our universe. We seek to dive into all

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Speaker 1: of the crazy mysteries about how things work unraveled the

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Speaker 1: explanations that humanity has discovered for what's actually out there

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Speaker 1: in the universe and what rules it is following. We

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Speaker 1: talk about all of that on the podcast and make

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Speaker 1: sure we can explain all of it to you. That's right.

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Speaker 1: It is a vast universe moving slowly and fast at

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Speaker 1: the same time, and we are here to help you

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Speaker 1: do those mental gymnastics to put it all inside of

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Speaker 1: your brain. We hope that you get that feeling of

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Speaker 1: satisfaction when you land that triple backflip of understanding quantum

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Speaker 1: mechanics and general relativity in squeezing all that into your brain.

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Speaker 1: Do you think we usually stick de landing on the podcast.

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Speaker 1: I think we usually stick something somewhere at the wall.

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Speaker 1: Usually we just throw back points at the wall and

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Speaker 1: and I hope something sticks. Thank God for good editors.

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Speaker 1: But it is a wonderful and interesting universe with all

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Speaker 1: kinds of rules in it. It seems that kind of

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Speaker 1: govern how things can happen, what things can do, what

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Speaker 1: particles and energy and forces and waves can do out there.

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Speaker 1: That gives us this interesting and very complex universe that

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Speaker 1: we live in, and a very human thing to do

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Speaker 1: when understanding the universe is to try to figure out

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Speaker 1: what are the rules, What are the laws, what are

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Speaker 1: the limits, what are the things that we are not

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Speaker 1: allowed to do. It's like we're still children pushing up

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Speaker 1: against the boundaries, trying to understand what's allowed and what's not.

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Speaker 1: And now we're translating that to understanding what things in

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Speaker 1: the universe can do. What is a particle allowed to

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Speaker 1: do when it whizzes around a black hole? How fast

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Speaker 1: can it go when it rides the shock wave from

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Speaker 1: a supernova? Wait? Are we trying to figure out the

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Speaker 1: rules so we can break them or so we can

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Speaker 1: avoid getting into trouble? What does that mean? To get

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Speaker 1: into trouble? As the universe gonna punish us if we

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Speaker 1: go faster than the speed of light. No dessert for

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Speaker 1: a week, we might get a time out from the universe.

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Speaker 1: No screen time for a few millennium go over the

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Speaker 1: black hole and have your time dilated. No. I think

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Speaker 1: we are trying to break the rules because that helps

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Speaker 1: us understand what the rules are. I mean, if you

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Speaker 1: think that there's a hard and past rule in physics

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Speaker 1: and then you break it, then you discover the universe

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Speaker 1: is different from the way you thought it was. And

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Speaker 1: that's exactly the process of science. That's what we are

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Speaker 1: hoping to do, right, to pull back the veil of

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Speaker 1: our ignorance and understand how the universe actually is. But wait,

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Speaker 1: if you break a rule, then it wasn't really a rule,

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Speaker 1: was it. No, it wasn't a rule. But then you

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Speaker 1: try to figure out what the new rule is, what

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Speaker 1: the real rule is. We hope we think that the

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Speaker 1: universe does follow some set of rules, and that we

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Speaker 1: can approximate or learn those rules over time. Well, the

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Speaker 1: universe definitely rules, and there are lots of amazing things

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Speaker 1: to consider and discover, including those rules themselves. It seems

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Speaker 1: like the universe does kind of have limits about what

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Speaker 1: you can and can't do in it. It certainly does.

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Speaker 1: There are things that happen in the universe and things

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Speaker 1: that just don't ever happen, And something we do a

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Speaker 1: lot in science is take to that and wonder like,

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Speaker 1: why is it a muon doesn't ever decay directly to

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Speaker 1: an electron? Why is it that the universe is made

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Speaker 1: of these particles and never those kinds of particles? And

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Speaker 1: we think that all of these things are clues that

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Speaker 1: there are reasons for the universe to do one thing

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Speaker 1: and never some other thing, And we're trying to uncover

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Speaker 1: those rules and deduce from them what the underlying mechanics

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Speaker 1: are of the workings of the universe. Daniel wonder if

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Speaker 1: that's a philosophically impossible task. I mean, isn't it impossible

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Speaker 1: to prove a negative which means you can never prove

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Speaker 1: that a rule can't be broken, which means you can

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Speaker 1: never prove that something is a rule that's certainly true.

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Speaker 1: And a great example of that is a deep question

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Speaker 1: about the nature of matter, like is matter itself stable?

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Speaker 1: We are made of protons. We think that protons might

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Speaker 1: live forever, but we don't know because we've never seen

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Speaker 1: a proton fall apart. Like you put a proton out

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Speaker 1: into empty space, we don't know how long they last.

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Speaker 1: We've watched a bunch of protons for a bunch of

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Speaker 1: years and none of them fell apart. That doesn't mean

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Speaker 1: that eventually one day they might all fall apart. We

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Speaker 1: can't prove that they won't, so we should just give up. Man,

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Speaker 1: you can never prove anything, you know. What we can

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Speaker 1: do is make statistical limits. We can say we're very

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Speaker 1: confident that the lifetime of a proton is longer than

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Speaker 1: the current age of the universe. We don't know if

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Speaker 1: it's infinity or if it's just very, very long, but

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Speaker 1: that doesn't mean we don't know anything. We certainly know

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Speaker 1: that the lifetime of our proton is not ten minutes

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Speaker 1: or one minute, right, or we wouldn't even be here.

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Speaker 1: So we can certainly learn things about the universe, even

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Speaker 1: if we can never know for sure what those rules are.

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Speaker 1: I am nine certain that is unsatisfactory and welcome to philosophy.

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Speaker 1: But the universe does seem to have sort of rules

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Speaker 1: that things seem to fall on. One of them. Maybe

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Speaker 1: the biggest one that affects our everyday live is the

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Speaker 1: speed of light that let me you all the time,

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Speaker 1: Like when you're going to the post office and stuff,

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Speaker 1: you're like, oh, I wish I could drive there faster.

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Speaker 1: But this dang speed of light. Yeah, I mean it

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Speaker 1: affects everything, right, It means there's a speed limit to

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Speaker 1: how fast things can happen. Because it doesn't just apply

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Speaker 1: to the life, It applies to everything in the universe. Right, Yeah,

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Speaker 1: that's true. It probably applies to the people listen to

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Speaker 1: this podcast because it limits how fast that download can happen.

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Speaker 1: You write, everything in the universe, all information, and all matter,

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Speaker 1: is limited to the speed of light. That means if

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Speaker 1: you want to download all of the Explain the Universe

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Speaker 1: back catalog and it's seven point twenty one gigabytes or whatever,

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Speaker 1: it's gonna take a while because information takes time to transit.

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Speaker 1: I wonder how many people out there cursing the speed

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Speaker 1: of light because they can't hear our voices fast enough.

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Speaker 1: One maybe or zero. I think that our voices arrive

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Speaker 1: at just the right speed. We're like wizards in the

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Speaker 1: Lord of the Rings. We arrived precisely when we intended

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Speaker 1: to arrive. Yeah, that's true. Although maybe people are out

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Speaker 1: there listening to us at like two x speed, and

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Speaker 1: so we already are breaking the rules. I wonder if

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Speaker 1: anyone puts this at speed of light, plate this podcast

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Speaker 1: is finished as soon as you started it. Yeah, maybe

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Speaker 1: before it started. Maybe people are out there listening to

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Speaker 1: us at half speed because we're going too quickly, or

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Speaker 1: maybe somebody's playing us at negative speed, which would reveal

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Speaker 1: some interesting and deep secrets about the universe. If you

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Speaker 1: play the podcast backwards, you actually hear the rules of

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Speaker 1: the antimatter universe, the anti rules of the antimatter universe,

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Speaker 1: which means what you should do, which maybe should be

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Speaker 1: any religion. I forgot what this podcast is supposed to

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Speaker 1: be about. Now it's about anti religion. I think we

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Speaker 1: kind of went a little off key there. It's about

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Speaker 1: the speed of light and the speed of things in

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Speaker 1: the universe. Because it's easy to be a very basic

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Speaker 1: principle in the universe, right the information, light particles, they

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Speaker 1: don't seem to be able to go faster than a

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Speaker 1: very specific number out there in the universe. Yeah, this

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Speaker 1: is a discovery made just about a hundred and twenty

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Speaker 1: years ago that the universe does seem to have a

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Speaker 1: speed limit. No matter how fast you're going, you throw

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Speaker 1: that baseball out of your spaceship, it will never go

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Speaker 1: faster than a certain speed. No light, no photon, no particle,

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Speaker 1: nothing in the universe, no information even seems can transfer

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Speaker 1: from one place in the universe to another faster than

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Speaker 1: this stubborn speed limit. It's fascinating, and it's forced us

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Speaker 1: to rethink the nature of space and time and simultaneity

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Speaker 1: and all sorts of crazy stuff. Or at least, that's

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Speaker 1: what it seems like. We haven't seen anything move faster

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Speaker 1: than the speed of light. But you gotta wonder if

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Speaker 1: maybe there are exceptions to that rule I made. There

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Speaker 1: are special situations or circumstances in which that could happen,

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Speaker 1: and so do they. On the podcast, we'll be asking

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Speaker 1: the question, what's the fastest that a charged particle can go? Now?

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Speaker 1: Charges is like a particle that's had a lot of coffee,

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Speaker 1: or it's just pumped up with excitement, or just the

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Speaker 1: plane of electromagnetic charge. I can't speak to the emotions

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Speaker 1: of these particles or their caffeine intake, certainly not. And

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Speaker 1: I think, like a molecule, caffeine is probably much much

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Speaker 1: bigger than an electron. So I don't even know how

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Speaker 1: that would work. How do electrons zip coffee? Right, there's

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Speaker 1: a philosophy question for you without an answer. Maybe if

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Speaker 1: the electron is part of the caffeine molecule technically, then

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Speaker 1: it would be supercharged. Yeah, that's right. Our electrons that

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Speaker 1: are part of caffeine, do they have a different experience

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Speaker 1: than electrons that are part of something heavy and slow? Yeah?

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Speaker 1: I guess it depends on whether they like coffee or not.

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Speaker 1: Are they part of a latte molecule or expressing molecule.

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Speaker 1: I think they probably have a lot of fun. But

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Speaker 1: back to the question at hand. It's interesting that there

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Speaker 1: is an overall speed limit to the universe, something that

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Speaker 1: nothing can ever exceed. But practically speaking, there are also

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Speaker 1: other limits to how fast particles can go, especially if

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Speaker 1: they have other attributes to them, mass or charge, and

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Speaker 1: in this case we're thinking about the old fashioned electromagnetic charge,

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Speaker 1: and so this is an interesting question, and as usually,

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Speaker 1: we were wondering how many people out there had thought

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Speaker 1: about this, whether charge particles have a different speed limit

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Speaker 1: than non charged particles. So thank you very much to

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Speaker 1: everybody out there who answers these questions on the podcast.

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Speaker 1: It's a lot of fun for us to hear what

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Speaker 1: you are thinking. And if you would like to share

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Speaker 1: your thoughts on the podcast, please don't be shy right

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Speaker 1: to us. Two questions at Daniel and Jorge dot com.

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Speaker 1: Just think about it for a second. How fast do

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Speaker 1: you think charge particles can go? Here's what people had

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Speaker 1: to say. My quick answer it will be like ninety

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Speaker 1: nine point nine of speed of light. But does just

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Speaker 1: a guess with speed of light minus plunks, constant multiply

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Speaker 1: something that makes units consistent. As far as I know,

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Speaker 1: the maximum speed would be the speed of light. And

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Speaker 1: it's only particles that have mass that cannot achieve speed

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Speaker 1: of light, so I think that would be the speed

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Speaker 1: of light. I suppose my answer depends on whether or

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Speaker 1: not charge particles have mass, and I'm honestly not sure

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Speaker 1: if they do or not. If they are masthless, my

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Speaker 1: I would guess that they travel at the speed of light.

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Speaker 1: But if they do have mass and their mass is

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Speaker 1: non zero, I would say they travel at a significant

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Speaker 1: fraction of the speed of light, maybe upwards of speed

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Speaker 1: of light. Uh. The fastest charge particle could move in space,

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Speaker 1: I would think would be the speed of light, if

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Speaker 1: not the speed of light. All right, everyone seemed to

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Speaker 1: have the speed of light as the limit, or at

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Speaker 1: least ninety nine a lot of nine in these answers.

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Speaker 1: I give it a nine out of ten for that

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Speaker 1: vault attempt. Yeah, most people seem on board the idea

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Speaker 1: that the speed of light is the speed limit, but

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Speaker 1: that massive particles can't reach the speed of light. So

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Speaker 1: people definitely know there's a limit to things, and that

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Speaker 1: limit is less for things that have mass, and so

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Speaker 1: the question is discharge also give them a different speed limit. Well,

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Speaker 1: let's dig into this topic generally speaking, Daniel, what is

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Speaker 1: the speed limit that the universe seems to have so

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Speaker 1: special relativity? Einstein's description of space and time and motion

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Speaker 1: and how all those things interact tells us that the

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Speaker 1: speed limit is the speed of light in a vacuum,

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Speaker 1: which is about three hundred million meters per second, which

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Speaker 1: is first of all, a very very fast number. It's huge, right,

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Speaker 1: three hundred million meters in a second is an extraordinary

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Speaker 1: distance to traverse in just one second. And on the

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Speaker 1: other hand, it's very very slow because things in the

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Speaker 1: universe are far apart. So even if you can fly

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Speaker 1: three millions in a second, it can still take you

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Speaker 1: years to get to the next star, thousands of years

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Speaker 1: to get across the galaxy, and millions of years to

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Speaker 1: get to other galaxies. Yeah, although I wassuming you don't

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Speaker 1: want to go that far, it is pretty much instantaneous, right,

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Speaker 1: if you're not the traveling type or want to go

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Speaker 1: to another galaxy or planet, it's pretty much instantaneous, right,

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Speaker 1: at least to our brains. Yeah, it's pretty much instantaneous.

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Speaker 1: You know, light takes about a nanosecond to go afoot,

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Speaker 1: So if you're looking at something like your computer screen,

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Speaker 1: it's about a foot away, you're seeing the computer screen

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Speaker 1: as it looked a nanosecond ago. But you know, the

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Speaker 1: human eye also can't really distinguish things that happen faster

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Speaker 1: than like a thirty milliseconds. So for all extents and

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Speaker 1: purpose is it's instantaneous on the sort of scale of

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Speaker 1: things that we live in, right, But I guess it

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Speaker 1: is interesting this idea that there's nothing instantaneous kind of

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Speaker 1: in the universe, right that the even light or pretty

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Speaker 1: much anything just information in general, things, events, the actual

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Speaker 1: existence of things can't sort of move faster in this

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Speaker 1: universe than the speed of light. Yeah, it makes our

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Speaker 1: universe local. It means that you can only be influenced

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Speaker 1: by things around you. And what we mean by around

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Speaker 1: you depends on that speed of light. If the speed

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Speaker 1: of light was much much faster than things that could

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Speaker 1: influence you, things that we would say are local would

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Speaker 1: be things that are also further away. If the speed

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Speaker 1: of light was much much slower than the universe would

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Speaker 1: be sort of more local. You could only be influenced

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Speaker 1: by things that were closer to you. We talked in

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Speaker 1: the podcast several times about this concept of a light cone,

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Speaker 1: the sort of cone of things in your past that

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Speaker 1: can influence you. Things that are nearby can influence you

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Speaker 1: fairly recently. Things that are really really far away can

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Speaker 1: only influence you from the past. Things that happen in

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Speaker 1: like Andromeda right now can't affect us, and that can

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Speaker 1: be good news. Right If aliens are building a death

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Speaker 1: ray and shooting get at us, then it won't arrive

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Speaker 1: here for quite a little while. Yeah, I feel like

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Speaker 1: it's a very philosophical question too, and an impact just

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Speaker 1: on the very nature of existence. Like a giant pink

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Speaker 1: unicorn suddenly appeared on top of Jupiter. To us, that

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Speaker 1: wouldn't really exist until several minutes later, right, because that

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Speaker 1: information would take some time to get to us. As opposed,

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Speaker 1: it depends on what you mean by exists. We wouldn't

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Speaker 1: know it existed, We couldn't prove that it existed, So

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Speaker 1: in that sense, it wouldn't be real in the way

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Speaker 1: that it wouldn't appear in our experiments, right, But to

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Speaker 1: somebody else on Jupiter, they would be able to see it, right, Yeah,

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Speaker 1: that's what I mean that for us, it wouldn't exist,

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Speaker 1: right Yeah, in the same way that if the Sun disappeared,

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Speaker 1: we wouldn't notice for eight minutes because it takes that

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Speaker 1: long for light from the Sun to reach here. So

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Speaker 1: the universe as we see it is not the universe

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Speaker 1: as it is right now. And more deeply, relativity says

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Speaker 1: that there is no sort of universal definition of right now,

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Speaker 1: that time and the universe depends on where you are

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Speaker 1: and how fast you are going. This sort of requires

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Speaker 1: us to give up this concept that there is a

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Speaker 1: universe that's marching forward in time uniformly, sort of an

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Speaker 1: ancient Newtonian view, right. And so it's called the speed

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Speaker 1: of light, but it should actually be called the speed

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Speaker 1: of anything in the universe. We just call it the

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Speaker 1: speed of light because basically light is the only thing

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Speaker 1: we know that can go at that speed, or the

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Speaker 1: first thing we knew that could go at that speed. Yeah,

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Speaker 1: it really should be called the speed of everything, or

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Speaker 1: maybe the speed of anything. But it's the sort of

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Speaker 1: maximum speed limit of any kind of information, any field.

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Speaker 1: For example, in the universe, when it wiggles, information can't

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Speaker 1: move through that field faster than the speed of light,

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Speaker 1: and so that limit applies to every field, including the

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Speaker 1: electromagnetic field, for which photons are a ripple in that field,

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Speaker 1: and because they have no mass, they can move at

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Speaker 1: that maximum speed. It's true for any massless ripple in

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Speaker 1: a field. So, for example, we think that gravitational waves

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Speaker 1: travel at the feed of light as well, because those

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Speaker 1: ripples in the gravitational field, or equivalently, ripples in the

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Speaker 1: curvature of space, so we think those also move at

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Speaker 1: the speed of light. And if there are other particles

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Speaker 1: out there we haven't discovered that are massless, they would

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Speaker 1: also move at the speed of light. Are there other

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Speaker 1: particles we've discovered that are massless gluons, which are the

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Speaker 1: particles that helped transmit the strong force. They are also massless,

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Speaker 1: so they move at the speed of light. But gluons

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Speaker 1: are weird because they interact very strongly with themselves, and

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Speaker 1: so you never sort of see a gluon by itself.

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Speaker 1: They conform weird states like glue balls, but those have

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Speaker 1: energy inside of them, so they have mass, So the

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Speaker 1: glue balls don't move at the speed of light, even

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Speaker 1: if individual gluons do. Interesting, so photons are the only

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Speaker 1: particles that we know of that can move at the

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Speaker 1: speed of light. Well, I think gluons count is moving

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Speaker 1: at the speed of light, even though they don't go

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Speaker 1: very far. Gravitational waves aren't a particle. If gravity is

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Speaker 1: quantized and made of gravitons, then those are probably massless

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Speaker 1: and would move at the speed of light. But we

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Speaker 1: don't know if gravitons exist. Yeah, so, so technically photons

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Speaker 1: are the only particle we know of. What do you

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Speaker 1: have against gluhons? You know, then you say a little

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Speaker 1: while ago that they don't quite you don't never see

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Speaker 1: them move with the speed of light. Yeah, you can't

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Speaker 1: like shoot a gluon across the universe and have a

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Speaker 1: travel like a photon. But you know a gluon which

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Speaker 1: is exchanged between two quarks, that does happen at the

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Speaker 1: speed of light. The speed of information of the strong

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Speaker 1: force is the speed of light. All right, Well, photons

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Speaker 1: and gluons, I guess they they're stuck together in that category.

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Speaker 1: But again, maybe give us an into the sense. What

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Speaker 1: does it mean to move at the speed of light?

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Speaker 1: What is it like? It's a fun question. What is

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Speaker 1: it like to move at the speed of light. You

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Speaker 1: would like to be able to put yourself in that

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Speaker 1: frame and say, I'm moving along with a photon. What

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Speaker 1: is the photon? See? It's not something you can really

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Speaker 1: do because photons don't have a frame. Like if a

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Speaker 1: spaceship is flying by the Earth, you can put yourself

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Speaker 1: in this frame where the spaceship is at rest and say, okay,

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Speaker 1: I'm moving with the spaceship. What do I see? I

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Speaker 1: see the same thing as the spaceship. You can't do

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Speaker 1: that with a photon because the photon is never at rest.

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Speaker 1: There's no like frame you can put yourself in to

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Speaker 1: say I'm moving with the photon. Photons always move at

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Speaker 1: the speed of light relative to anybody, So no matter

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Speaker 1: where you are in the universe and how fast you're going,

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Speaker 1: that photon is zipping away from you at the speed

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Speaker 1: of light, and so you can't sort of like put

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Speaker 1: yourself in the point of view of a photon. M mmm.

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Speaker 1: So there's sort of like pure motion, right, because they

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Speaker 1: don't have mass, so they don't have a substance to them,

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Speaker 1: so all of their energy is in their speed. Yeah,

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Speaker 1: all of their energy is in their speed exactly. They

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Speaker 1: are just motioned. There's nothing to them, Like if you

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Speaker 1: could catch up with a photon, it was sort of

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Speaker 1: disappear in a puff of motionlessness. You know, they are

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Speaker 1: only motion, but it's it's like a wiggle in the

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Speaker 1: like a kinetic field. Right, Yeah, it's the motion of

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Speaker 1: that field. But isn't it a wiggle like a little perturbation. Yeah,

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Speaker 1: pure kinetic energy. Right, And people right in they're confused

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Speaker 1: about that because they say, well, it's energy, and energy

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Speaker 1: is mc squared, So doesn't that mean the photon has mass? Right?

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Speaker 1: And the wrinkle there is that equals mc squared only

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Speaker 1: applies to particles at rest, because the m there applies

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Speaker 1: to its rest mass. There's another term there which we

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Speaker 1: don't often talk about. The full equation is like E

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Speaker 1: squared equals M squared c to the fourth plus p

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Speaker 1: squared c square. There's a term there for momentum, and

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Speaker 1: so for a particle that has mass and momentum, there

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Speaker 1: are two terms there. There's the mass term and the

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Speaker 1: momentum term. Photons don't have any mass, so they just

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Speaker 1: have the momentum term. The equation for photon is E

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Speaker 1: equals pc momentum times the speed of light. So photons

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Speaker 1: are really weird because they don't have mass, but they

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Speaker 1: do have momentum, so they can like push things. Right,

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Speaker 1: that's how solar sales work. Right. They catch sunlight and

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Speaker 1: they transfer that momentum to motion, and that's how you

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Speaker 1: can sail out of the solar system. So photons do

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Speaker 1: have momentum and they go at the speed of light,

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Speaker 1: but there are a couple of caveats to that, maybe

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Speaker 1: not just for photons, but for everything else. Let's dig

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Speaker 1: into the ways that the rules that don't apply. But first,

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Speaker 1: let's take a quick break. All right, we're talking about

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Speaker 1: the speed limit of the universe and how it applies

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Speaker 1: to a charged particle, because I guess the charged particle

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Speaker 1: is a little bit different. Yeah, particles that have charge

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Speaker 1: also have mass, and the rules for massive particles and

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Speaker 1: for charge particles are a little bit different than the

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Speaker 1: rules for massless chargeless photons. Yeah, we've been talking about

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Speaker 1: how the speed limit applies to photons, which I guess

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Speaker 1: it does, but it almost only applies to photons and

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Speaker 1: I guess gluons. But it limits how fast photons can go.

430
00:21:48,400 --> 00:21:50,920
Speaker 1: But there are caveats to that rule. Right, it's not

431
00:21:50,960 --> 00:21:54,520
Speaker 1: necessarily the case that photons go at the speed of light. Yeah,

432
00:21:54,560 --> 00:21:57,080
Speaker 1: there are caveats to that rule. When we say that

433
00:21:57,119 --> 00:22:00,119
Speaker 1: photons always travel at the speed of light, when we mean,

434
00:22:00,160 --> 00:22:02,919
Speaker 1: but we don't often say, is that that's true in

435
00:22:03,040 --> 00:22:07,760
Speaker 1: your local inertial frame. If space is not curved, basically

436
00:22:07,840 --> 00:22:11,959
Speaker 1: the playground of special relativity, operate in flat space and

437
00:22:12,000 --> 00:22:14,959
Speaker 1: have things whizzing around near each other, that's what you're

438
00:22:15,000 --> 00:22:18,240
Speaker 1: going to observe. But if space is curved or expanding,

439
00:22:18,600 --> 00:22:21,880
Speaker 1: or things are really really far away from you, then

440
00:22:21,920 --> 00:22:25,000
Speaker 1: you can no longer apply those rules, and things start

441
00:22:25,040 --> 00:22:27,920
Speaker 1: to get really weird. It seems like a very limiting

442
00:22:28,440 --> 00:22:32,720
Speaker 1: caveat I mean local flat space. That's almost never true.

443
00:22:32,720 --> 00:22:35,760
Speaker 1: And if you're there, then you're bending space, which means

444
00:22:35,760 --> 00:22:39,640
Speaker 1: it doesn't apply to that's true, although you're not that massive,

445
00:22:39,960 --> 00:22:42,560
Speaker 1: and so you don't really bend space. Oh thanks, I've

446
00:22:42,560 --> 00:22:47,720
Speaker 1: been working out, and no matter how curved the universe is,

447
00:22:47,760 --> 00:22:51,880
Speaker 1: you can always find a locally flat approximation to it. Right,

448
00:22:51,920 --> 00:22:54,879
Speaker 1: space is always flat. In a local approximation, you can

449
00:22:54,880 --> 00:22:57,480
Speaker 1: always put a tangent on some surface and say, oh,

450
00:22:57,560 --> 00:23:00,320
Speaker 1: in this vicinity, I can assume I'm in flats space,

451
00:23:00,480 --> 00:23:02,760
Speaker 1: and that's sort of the issue is that special relativity

452
00:23:02,800 --> 00:23:05,480
Speaker 1: applies in our local vicinity where we can assume things

453
00:23:05,480 --> 00:23:09,160
Speaker 1: are flat, but then over larger distances we can't really

454
00:23:09,200 --> 00:23:12,320
Speaker 1: make that assumption, and that's why things break down. Well,

455
00:23:12,359 --> 00:23:14,200
Speaker 1: I guess the question is how do they break down

456
00:23:14,240 --> 00:23:17,200
Speaker 1: when when space is not flat, when it's a little

457
00:23:17,200 --> 00:23:20,280
Speaker 1: curved or a lot curve, does like go faster than

458
00:23:20,280 --> 00:23:21,959
Speaker 1: the speed of light or slower than the speed of light.

459
00:23:22,080 --> 00:23:24,879
Speaker 1: The space is curved between you and another galaxy, then

460
00:23:24,920 --> 00:23:27,280
Speaker 1: you have two different frames. You have your frame, you

461
00:23:27,280 --> 00:23:30,080
Speaker 1: have the frame in that galaxy, and how you translate

462
00:23:30,200 --> 00:23:34,200
Speaker 1: velocity from one frame to another is a little bit arbitrary.

463
00:23:34,240 --> 00:23:36,720
Speaker 1: You can do it in lots of different ways because

464
00:23:36,760 --> 00:23:39,520
Speaker 1: space is curved between you. We talked about this once

465
00:23:39,560 --> 00:23:41,919
Speaker 1: in the podcast. That has to do with like comparing

466
00:23:42,119 --> 00:23:46,040
Speaker 1: whether two vectors are parallel and comparing their length, and

467
00:23:46,080 --> 00:23:49,120
Speaker 1: if space is curved between two points, then how you

468
00:23:49,400 --> 00:23:52,720
Speaker 1: move that vector over that space depends on the path

469
00:23:52,840 --> 00:23:55,440
Speaker 1: that you've taken. So it's sort of not well defined

470
00:23:55,560 --> 00:23:58,119
Speaker 1: in the sense that there's like many ways that you

471
00:23:58,119 --> 00:24:01,320
Speaker 1: could do it and get different and service so you

472
00:24:01,400 --> 00:24:05,320
Speaker 1: can't really compare velocities in two different frames, if this

473
00:24:05,480 --> 00:24:09,240
Speaker 1: curvature or expansion between them. Yeah, it gets really tricky

474
00:24:09,240 --> 00:24:12,040
Speaker 1: and complicated, and we spend a whole hour talking about this.

475
00:24:12,119 --> 00:24:14,879
Speaker 1: I remember, but I guess what's the takeaway? There are

476
00:24:14,880 --> 00:24:17,440
Speaker 1: many ways to compute the velocity of a photo going

477
00:24:17,440 --> 00:24:19,879
Speaker 1: from between here and another galaxy. But do some of

478
00:24:19,880 --> 00:24:22,560
Speaker 1: these solutions tell you that this light is moving faster

479
00:24:22,720 --> 00:24:24,840
Speaker 1: or slower than the speed of light? Or do they

480
00:24:24,840 --> 00:24:26,760
Speaker 1: all tell you it's moving slower than the speed of light?

481
00:24:26,960 --> 00:24:28,720
Speaker 1: Some of them tell you that those photons are moving

482
00:24:28,760 --> 00:24:30,440
Speaker 1: faster than the speed of light, and some of them

483
00:24:30,440 --> 00:24:32,440
Speaker 1: tell you that the photons are moving slower than the

484
00:24:32,480 --> 00:24:34,640
Speaker 1: speed of light. So there's an infinite number of ways

485
00:24:34,640 --> 00:24:38,000
Speaker 1: that you could do this, compare velocities in one galaxy

486
00:24:38,080 --> 00:24:40,680
Speaker 1: to another because there are different reference frames. There's also

487
00:24:40,680 --> 00:24:42,320
Speaker 1: sort of a standard way that we do it, which

488
00:24:42,359 --> 00:24:44,960
Speaker 1: is that we just try to like extrapolate our frame

489
00:24:45,040 --> 00:24:46,879
Speaker 1: out to the end of the universe, even though we

490
00:24:46,880 --> 00:24:49,200
Speaker 1: know that doesn't really work. And those galaxies are moving

491
00:24:49,200 --> 00:24:51,000
Speaker 1: away from us faster than the speed of light, so

492
00:24:51,080 --> 00:24:53,240
Speaker 1: things seem to be breaking that speed of light limit.

493
00:24:53,280 --> 00:24:55,800
Speaker 1: Because you've done this thing of extending your inertial frame

494
00:24:56,000 --> 00:24:57,840
Speaker 1: out to the end of the universe, which you're not

495
00:24:58,000 --> 00:25:00,360
Speaker 1: technically allowed to do. The other way you can look

496
00:25:00,359 --> 00:25:02,159
Speaker 1: at it is to say they have their frame, we

497
00:25:02,200 --> 00:25:05,440
Speaker 1: have our frame, and space is expanding between those frames.

498
00:25:05,840 --> 00:25:07,800
Speaker 1: So nothing's breaking the speed of light limit. It's just

499
00:25:07,840 --> 00:25:11,200
Speaker 1: that space itself is growing and in its own frame,

500
00:25:11,240 --> 00:25:13,640
Speaker 1: everything is moving less than the speed of light. That's

501
00:25:13,640 --> 00:25:15,639
Speaker 1: what I mean when I say there's like different ways

502
00:25:15,680 --> 00:25:18,600
Speaker 1: you could assign that velocity. They're all sort of reasonable

503
00:25:18,680 --> 00:25:21,760
Speaker 1: and give you different answers. So there are those important capiats,

504
00:25:21,800 --> 00:25:25,000
Speaker 1: But in your local inertial frame, like your the laboratory,

505
00:25:25,000 --> 00:25:27,399
Speaker 1: the measurements you're going to actually make, you're never going

506
00:25:27,440 --> 00:25:29,880
Speaker 1: to observe anything going faster than the speed of light.

507
00:25:30,160 --> 00:25:32,760
Speaker 1: M M, I see. So even the local bending of

508
00:25:32,800 --> 00:25:34,879
Speaker 1: space can only slow down the speed of light. Is

509
00:25:34,920 --> 00:25:37,800
Speaker 1: that what you're saying? Like, if I'm orbiting a black hole,

510
00:25:37,840 --> 00:25:40,399
Speaker 1: for example, and space has really warped around me and

511
00:25:40,400 --> 00:25:42,760
Speaker 1: I run those experiments, what what would I see there?

512
00:25:42,760 --> 00:25:45,160
Speaker 1: I think you're breaking the assumption because we're talking about

513
00:25:45,160 --> 00:25:47,480
Speaker 1: a local flat frame, and if you're near a black hole,

514
00:25:47,680 --> 00:25:50,359
Speaker 1: then you're definitely not in a local, flat frame. So

515
00:25:50,359 --> 00:25:52,240
Speaker 1: I would say that if your space is pretty local

516
00:25:52,320 --> 00:25:55,000
Speaker 1: and pretty flat, you're always going to see photons moving

517
00:25:55,080 --> 00:25:57,399
Speaker 1: at the speed of light. So there's one caveat we

518
00:25:57,400 --> 00:26:00,040
Speaker 1: haven't talked about yet. But if you are near a

519
00:26:00,040 --> 00:26:03,840
Speaker 1: black hole or something else than spaces bendy and crazy

520
00:26:03,920 --> 00:26:06,359
Speaker 1: and the velocities get insane, and you could see photons

521
00:26:06,400 --> 00:26:09,960
Speaker 1: moving at zero velocity. For example, as a photon climbs

522
00:26:09,960 --> 00:26:13,080
Speaker 1: out of the gravity well or tries to climb out

523
00:26:13,080 --> 00:26:14,919
Speaker 1: of the gravity well of a black hole, to you,

524
00:26:15,000 --> 00:26:17,719
Speaker 1: it appears to go at zero velocity. Right, photons are

525
00:26:17,760 --> 00:26:20,399
Speaker 1: contained within a black hole. How could they do that

526
00:26:20,440 --> 00:26:22,720
Speaker 1: if they were moving at the speed of light Because

527
00:26:22,760 --> 00:26:25,680
Speaker 1: the bending nous of space there makes all these velocities

528
00:26:25,720 --> 00:26:28,720
Speaker 1: a little wonky to calculate. But would you ever see

529
00:26:28,760 --> 00:26:32,560
Speaker 1: it go faster? Probably not right. That only happens when

530
00:26:32,600 --> 00:26:35,639
Speaker 1: you have space expanding. Yeah, I believe that's true. The

531
00:26:35,760 --> 00:26:39,080
Speaker 1: bending of space can only effectively slow down the speed

532
00:26:39,080 --> 00:26:41,320
Speaker 1: of light that you observe. In order things to appear

533
00:26:41,359 --> 00:26:43,000
Speaker 1: to go fasten the speed of light, you need space

534
00:26:43,040 --> 00:26:46,720
Speaker 1: to expand rather than to curve. Well, there's another caveat

535
00:26:46,760 --> 00:26:49,520
Speaker 1: to this also is that the space has to be empty. Yes,

536
00:26:49,600 --> 00:26:51,359
Speaker 1: that's right. The limit that we talk about is the

537
00:26:51,359 --> 00:26:53,840
Speaker 1: speed of light in a vacuum, as if there's nothing

538
00:26:53,880 --> 00:26:56,359
Speaker 1: out there in space for these photons to interact with.

539
00:26:56,440 --> 00:26:59,200
Speaker 1: But we know that light slows down as it passes

540
00:26:59,280 --> 00:27:02,800
Speaker 1: through material hills or at the index of refraction tells

541
00:27:02,840 --> 00:27:06,040
Speaker 1: you the speed of light through that material. So light

542
00:27:06,119 --> 00:27:09,840
Speaker 1: traveling through glass goes slower than light traveling through a vacuum,

543
00:27:10,040 --> 00:27:12,520
Speaker 1: Like traveling through air goes a little bit slower than

544
00:27:12,600 --> 00:27:15,840
Speaker 1: light traveling through a vacuum. And that's not because somehow

545
00:27:15,880 --> 00:27:19,000
Speaker 1: the air molecules or the glass molecules like effect the

546
00:27:19,080 --> 00:27:21,600
Speaker 1: space that the light travels in. It's because light keeps

547
00:27:21,720 --> 00:27:24,240
Speaker 1: running into things, right, like trying to move through a

548
00:27:24,240 --> 00:27:26,800
Speaker 1: crowded room. The float that keeps bumping into the air

549
00:27:26,840 --> 00:27:29,680
Speaker 1: and glass molecules and then getting re emitted on the

550
00:27:29,760 --> 00:27:31,920
Speaker 1: other side. But it still has to sort of something

551
00:27:31,960 --> 00:27:34,440
Speaker 1: has to happen when they bump. The speed that we're

552
00:27:34,440 --> 00:27:37,240
Speaker 1: talking about here is basically the average speed from one

553
00:27:37,280 --> 00:27:39,400
Speaker 1: side of the material to the other side of the material.

554
00:27:39,560 --> 00:27:40,840
Speaker 1: You can think about it as the light sort of

555
00:27:40,960 --> 00:27:44,600
Speaker 1: zig zagging between molecules or atoms that it's interacting with

556
00:27:44,680 --> 00:27:46,880
Speaker 1: each of those zigs or each of those zags, it's

557
00:27:46,920 --> 00:27:49,480
Speaker 1: still moving at the speed of light. Of photon is

558
00:27:49,520 --> 00:27:51,840
Speaker 1: always moving at the speed of light, but it sort

559
00:27:51,840 --> 00:27:54,480
Speaker 1: of gets absorbed. It takes time to get re emitted,

560
00:27:54,560 --> 00:27:56,199
Speaker 1: and so that sort of slows it down. It's like

561
00:27:56,240 --> 00:27:58,000
Speaker 1: if you send your teenager on an errand to the

562
00:27:58,040 --> 00:28:00,359
Speaker 1: store and they stop and chat at their friends house

563
00:28:00,560 --> 00:28:02,600
Speaker 1: every block, it's can take them a lot longer to

564
00:28:02,640 --> 00:28:05,719
Speaker 1: get there, even if they're driving at top speed between

565
00:28:05,720 --> 00:28:08,520
Speaker 1: all of their friends houses. That's an interesting neighborhood you

566
00:28:08,520 --> 00:28:12,439
Speaker 1: live in where your teenagers is driving and stopping to

567
00:28:12,480 --> 00:28:15,320
Speaker 1: talk to their friends at the same time. Hopefully they

568
00:28:15,320 --> 00:28:17,600
Speaker 1: are being the speed limit there. Fortunately, I don't have

569
00:28:17,640 --> 00:28:20,560
Speaker 1: teenagers who can drive yet, so maybe my analogies will

570
00:28:20,560 --> 00:28:24,359
Speaker 1: improve when I have some data. So it's if space

571
00:28:24,480 --> 00:28:28,840
Speaker 1: is empty and it's not bend deep or distorted or expanding,

572
00:28:29,040 --> 00:28:31,320
Speaker 1: then light goes at the speed of light. But now

573
00:28:31,359 --> 00:28:34,840
Speaker 1: what about particles that are not light? Pretty much everything

574
00:28:34,840 --> 00:28:39,240
Speaker 1: else besides gluons. What if a particle, for example, has mass. Yes,

575
00:28:39,400 --> 00:28:41,920
Speaker 1: so photons can go with the speed of light if

576
00:28:41,920 --> 00:28:43,800
Speaker 1: they're in a vacuum and not near a black hole,

577
00:28:43,840 --> 00:28:48,440
Speaker 1: for example. But electrons, particles with mass, they can never

578
00:28:48,520 --> 00:28:50,840
Speaker 1: actually reach the speed of light. Oh yeah, is there

579
00:28:50,880 --> 00:28:53,800
Speaker 1: a particular reason for that. It's sort of interesting and philosophical.

580
00:28:53,880 --> 00:28:56,840
Speaker 1: It's not like there's a lower speed limit for electrons.

581
00:28:56,840 --> 00:29:00,479
Speaker 1: It's not like electrons can only go speed of light

582
00:29:00,520 --> 00:29:02,760
Speaker 1: and they're always pegg there. It's just that they ask

583
00:29:02,800 --> 00:29:05,840
Speaker 1: emp tonically can approach the speed of light, So there's

584
00:29:05,840 --> 00:29:08,520
Speaker 1: no actual limit there. They just get closer and closer

585
00:29:08,520 --> 00:29:10,800
Speaker 1: and closer to the speed of light as you add

586
00:29:10,840 --> 00:29:14,400
Speaker 1: more energy, but they never actually get to the speed

587
00:29:14,400 --> 00:29:16,920
Speaker 1: of light. Yeah, that's weird. So you're saying that it's

588
00:29:16,920 --> 00:29:20,120
Speaker 1: a speed limit, not because like if I just create

589
00:29:20,320 --> 00:29:23,360
Speaker 1: an electron or a proton or a cord going at

590
00:29:23,360 --> 00:29:26,160
Speaker 1: the speed of light, maybe can that can happen. It's

591
00:29:26,200 --> 00:29:29,760
Speaker 1: just that for any electron or a particle with mass

592
00:29:29,800 --> 00:29:32,320
Speaker 1: that starts address I can, I can never get it

593
00:29:32,360 --> 00:29:34,880
Speaker 1: to the speed of light. A particle with mass moving

594
00:29:34,880 --> 00:29:37,640
Speaker 1: at the speed of light would have infinite kinetic energy.

595
00:29:37,760 --> 00:29:40,880
Speaker 1: So if you could create a particle with infinite kinetic energy,

596
00:29:40,920 --> 00:29:43,240
Speaker 1: then yes, it would be moving at the speed of light. Otherwise,

597
00:29:43,320 --> 00:29:45,280
Speaker 1: taking a particle and getting it to the speed of

598
00:29:45,360 --> 00:29:48,680
Speaker 1: light would require giving it infinite kinetic energy. And the

599
00:29:48,720 --> 00:29:50,960
Speaker 1: key concept, of course is that these particles have mass.

600
00:29:50,960 --> 00:29:53,080
Speaker 1: So why is it that having master means that you

601
00:29:53,200 --> 00:29:55,440
Speaker 1: require infinite energy to get to the speed of light,

602
00:29:55,480 --> 00:29:58,520
Speaker 1: whereas a photon with a non infinite energy can move

603
00:29:58,600 --> 00:30:01,240
Speaker 1: at the speed of light it and the key concept there,

604
00:30:01,240 --> 00:30:03,960
Speaker 1: of course, is the mass of the particle. Mass is

605
00:30:04,040 --> 00:30:07,600
Speaker 1: this property of particles like resist changes to their motion.

606
00:30:08,280 --> 00:30:10,480
Speaker 1: So you have an electron, it's gonna stay at rest

607
00:30:10,560 --> 00:30:12,480
Speaker 1: unless you give it a push, and it's going to

608
00:30:12,520 --> 00:30:15,120
Speaker 1: stay at certain velocity unless you give it a push.

609
00:30:15,320 --> 00:30:18,240
Speaker 1: And mass is that ability to resist changes in motion.

610
00:30:18,280 --> 00:30:20,400
Speaker 1: So it takes energy to speed it up. So you

611
00:30:20,440 --> 00:30:22,760
Speaker 1: give the electron to push, it speeds up as it

612
00:30:22,760 --> 00:30:26,200
Speaker 1: gets faster and faster, though it takes bigger pushes more

613
00:30:26,360 --> 00:30:28,920
Speaker 1: energy to take it up the next level and speed.

614
00:30:29,160 --> 00:30:31,960
Speaker 1: It's not a linear relationship, right, And that's just kind

615
00:30:31,960 --> 00:30:35,440
Speaker 1: of how the universe is, right, Like, that's just what

616
00:30:35,840 --> 00:30:38,320
Speaker 1: mass is. It's not like they have mass and therefore

617
00:30:38,440 --> 00:30:41,400
Speaker 1: they're hard to push the more you go. It's like

618
00:30:41,440 --> 00:30:44,440
Speaker 1: the definition of mass is the fact that some particles

619
00:30:44,640 --> 00:30:46,800
Speaker 1: gets harder and harder to push. Yeah, I think it's

620
00:30:46,840 --> 00:30:49,560
Speaker 1: important to understand what things we understand and what things

621
00:30:49,560 --> 00:30:52,960
Speaker 1: we just like observe and define. Right. We have observed

622
00:30:53,240 --> 00:30:55,880
Speaker 1: that things that have internal energy in them have this

623
00:30:56,040 --> 00:30:59,880
Speaker 1: property of inertia. An electron has some internal energy to it,

624
00:31:00,160 --> 00:31:03,160
Speaker 1: protons have some internal energy to it, the mass of

625
00:31:03,160 --> 00:31:05,320
Speaker 1: the corks and then also the mass of the binding

626
00:31:05,400 --> 00:31:08,200
Speaker 1: energy between the corks. Anything with internal energy seems to

627
00:31:08,240 --> 00:31:12,120
Speaker 1: have this property of inertia, of resisting changes to its motions.

628
00:31:12,120 --> 00:31:14,880
Speaker 1: So yeah, sort of a deep philosophical mystery why that is,

629
00:31:14,880 --> 00:31:16,440
Speaker 1: Why do we live in the universe that way and

630
00:31:16,480 --> 00:31:19,200
Speaker 1: not some other way? But it's something that we've observed

631
00:31:19,200 --> 00:31:21,800
Speaker 1: in the universe and try to describe in our theories,

632
00:31:21,840 --> 00:31:24,560
Speaker 1: and those theories are very effective when we test them

633
00:31:24,560 --> 00:31:27,160
Speaker 1: out in nature, So that's why we believe they are true,

634
00:31:27,240 --> 00:31:29,720
Speaker 1: even if we don't know why the universe is this

635
00:31:29,760 --> 00:31:32,760
Speaker 1: way and not some other way. Yeah, it's a massive issue.

636
00:31:32,920 --> 00:31:34,800
Speaker 1: And how is this related to the Higgs boson and

637
00:31:34,840 --> 00:31:37,479
Speaker 1: the Higgs field, because I know everyone talks about how

638
00:31:37,520 --> 00:31:40,320
Speaker 1: the Higgs field is what gives particles mass. Is this

639
00:31:40,400 --> 00:31:43,320
Speaker 1: inertial mass that's related to the speed of light, related

640
00:31:43,360 --> 00:31:46,000
Speaker 1: to the Higgs field and Higgs boson. So most generally

641
00:31:46,400 --> 00:31:50,400
Speaker 1: mass is just internal stored energy of some kind, and

642
00:31:50,520 --> 00:31:52,880
Speaker 1: most of the mass in your body doesn't come from

643
00:31:52,920 --> 00:31:56,040
Speaker 1: the mass of the particles of your body. So for example,

644
00:31:56,120 --> 00:31:59,920
Speaker 1: you're mostly protons and neutrons, and those protons have massive

645
00:32:00,080 --> 00:32:02,840
Speaker 1: from their corks, but they also have mass from how

646
00:32:02,880 --> 00:32:06,360
Speaker 1: those corks are bound together. So the internal stored energy

647
00:32:06,360 --> 00:32:10,200
Speaker 1: the proton is mostly the energy of those particles bound together.

648
00:32:10,320 --> 00:32:11,920
Speaker 1: A little bit of the mass of the proton does

649
00:32:12,000 --> 00:32:14,400
Speaker 1: come from the mass of those particles, like the corks

650
00:32:14,400 --> 00:32:17,400
Speaker 1: that are inside the proton, and those corks they get

651
00:32:17,440 --> 00:32:20,760
Speaker 1: their inertial mass from the Higgs boson, but again it's

652
00:32:20,800 --> 00:32:25,480
Speaker 1: internal stored energy. The corks themselves, like the true theoretical object,

653
00:32:25,640 --> 00:32:28,280
Speaker 1: is massless, but as the cork moves through the universe,

654
00:32:28,280 --> 00:32:31,080
Speaker 1: it interacts with this Higgs field and it creates this

655
00:32:31,200 --> 00:32:34,760
Speaker 1: like effective cork, this object which is moving differently because

656
00:32:34,760 --> 00:32:37,400
Speaker 1: of its interactions with the Higgs field in such a

657
00:32:37,400 --> 00:32:39,880
Speaker 1: way that it moves as if it had mass. So

658
00:32:39,960 --> 00:32:42,080
Speaker 1: it is inertial mass that we're talking about, and some

659
00:32:42,200 --> 00:32:44,160
Speaker 1: of the inertial mass in the universe comes from the

660
00:32:44,200 --> 00:32:46,640
Speaker 1: Higgs boson, but not all of it, right, In fact,

661
00:32:46,680 --> 00:32:48,640
Speaker 1: most of it doesn't come from the Higgs field and

662
00:32:48,720 --> 00:32:51,560
Speaker 1: Higgs boson. Most of it just comes from this fact

663
00:32:51,720 --> 00:32:55,640
Speaker 1: of the universe that things with energy are are hard

664
00:32:55,680 --> 00:32:58,600
Speaker 1: to move in the universe and impossible to get moving

665
00:32:58,640 --> 00:33:00,760
Speaker 1: at the speed of light. Yeah, exact, you often hear

666
00:33:00,800 --> 00:33:03,200
Speaker 1: their frame that as things approach the speed of light,

667
00:33:03,240 --> 00:33:06,400
Speaker 1: they get more massive, as if like an electron is

668
00:33:06,440 --> 00:33:09,120
Speaker 1: getting as heavy as a car for example, if it

669
00:33:09,160 --> 00:33:11,800
Speaker 1: goes near the speed of light. And as some sort

670
00:33:11,800 --> 00:33:13,920
Speaker 1: of an old fashioned idea that is trying to convey

671
00:33:14,000 --> 00:33:16,960
Speaker 1: to you this concept that as something approaches the speed

672
00:33:16,960 --> 00:33:19,320
Speaker 1: of light, it takes more energy to move it up

673
00:33:19,360 --> 00:33:22,400
Speaker 1: in velocity than it did when it was moving slower.

674
00:33:22,440 --> 00:33:25,480
Speaker 1: We don't really think about things literally gaining mass. It's

675
00:33:25,520 --> 00:33:27,800
Speaker 1: just that it takes a bigger push to notch them

676
00:33:27,840 --> 00:33:30,600
Speaker 1: up to the next level of velocity. Right, Although it's

677
00:33:30,640 --> 00:33:32,880
Speaker 1: kind of true, right, I mean, the idea is that

678
00:33:33,040 --> 00:33:36,760
Speaker 1: mass is the resistance to movement or to increasing your movement.

679
00:33:36,920 --> 00:33:39,520
Speaker 1: Then yeah, as it gets harder, because the universe, as

680
00:33:39,560 --> 00:33:43,840
Speaker 1: it gets harder, technically it is sort of gaining mass, right,

681
00:33:43,880 --> 00:33:46,080
Speaker 1: It doesn't really hang together though, Like if you want

682
00:33:46,120 --> 00:33:48,280
Speaker 1: to use that mass and F equals m A, it

683
00:33:48,320 --> 00:33:51,320
Speaker 1: doesn't really work because then that mass is like weirdly

684
00:33:51,440 --> 00:33:55,320
Speaker 1: directionally dependent, because if you're moving along the x axis

685
00:33:55,320 --> 00:33:57,440
Speaker 1: for example, now you have like a lot of mass

686
00:33:57,480 --> 00:33:59,840
Speaker 1: along the x axis, but you don't have that mass

687
00:34:00,000 --> 00:34:02,760
Speaker 1: along the y axis, right, Like turnting can give you

688
00:34:02,760 --> 00:34:04,920
Speaker 1: a push along the y axis with a certain force

689
00:34:04,960 --> 00:34:06,640
Speaker 1: and you get one acceleration, but if they give you

690
00:34:06,640 --> 00:34:09,759
Speaker 1: a push along the x axis with that same force,

691
00:34:09,760 --> 00:34:12,200
Speaker 1: they get a different acceleration. The more general way to

692
00:34:12,200 --> 00:34:14,160
Speaker 1: think about it is just in terms of momentum. This

693
00:34:14,320 --> 00:34:18,719
Speaker 1: this equation for relativistic momentum which includes this factor. So

694
00:34:18,760 --> 00:34:21,240
Speaker 1: we just leave mass as the rest mass of an object,

695
00:34:21,320 --> 00:34:23,319
Speaker 1: like how massive would it be if it was at rest,

696
00:34:23,400 --> 00:34:28,080
Speaker 1: and this extra resistance to accelerating at high speeds. We

697
00:34:28,320 --> 00:34:31,120
Speaker 1: fold that into the definition of momentum, which then helps

698
00:34:31,160 --> 00:34:33,000
Speaker 1: fix up F equals I may, which in the end

699
00:34:33,080 --> 00:34:36,160
Speaker 1: is just F equals the derivative of momentum with respect

700
00:34:36,200 --> 00:34:39,920
Speaker 1: to time. So this is whole topic of relativistic kinematics,

701
00:34:39,920 --> 00:34:42,640
Speaker 1: which I think we dug into in another episode. Yeah,

702
00:34:42,840 --> 00:34:44,080
Speaker 1: I think what you're trying to say is that an

703
00:34:44,080 --> 00:34:47,520
Speaker 1: electron looks less massive depending on which angle you're looking

704
00:34:47,520 --> 00:34:50,360
Speaker 1: at it, Like the electron has a good angle and

705
00:34:50,400 --> 00:34:53,400
Speaker 1: a bad angle. I think the concept of relativistic mass

706
00:34:53,440 --> 00:34:56,480
Speaker 1: things actually getting heavier as you get to higher mass,

707
00:34:56,680 --> 00:34:58,920
Speaker 1: doesn't really hang together if you try to propagate it

708
00:34:58,960 --> 00:35:00,640
Speaker 1: through all the equations. But it's sort of an old

709
00:35:00,680 --> 00:35:03,000
Speaker 1: fashioned way of thinking about things. All right, that's how

710
00:35:03,080 --> 00:35:05,800
Speaker 1: mass effects how fast you can go in the universe.

711
00:35:05,920 --> 00:35:08,879
Speaker 1: Now let's talk about how other things might affect how

712
00:35:08,920 --> 00:35:12,040
Speaker 1: fast you can move through the universe, including whether space

713
00:35:12,160 --> 00:35:14,880
Speaker 1: is empty or not. So let's get into that. But

714
00:35:14,960 --> 00:35:30,000
Speaker 1: first let's take another quick break. All Right, we're asking

715
00:35:30,000 --> 00:35:32,680
Speaker 1: the question what is the fastest that a charge particle

716
00:35:32,800 --> 00:35:35,520
Speaker 1: or pretty much any particle can go, right, because there

717
00:35:35,560 --> 00:35:37,839
Speaker 1: are a lot of caveats to this idea that nothing

718
00:35:37,840 --> 00:35:39,640
Speaker 1: can move faster than the speed of light. One of

719
00:35:39,640 --> 00:35:42,680
Speaker 1: those caveats was that space had to be empty. But

720
00:35:42,800 --> 00:35:45,120
Speaker 1: what happens if space is not empty? Yeah, we talked

721
00:35:45,120 --> 00:35:48,320
Speaker 1: about photons moving through glass, photons moving through water, but

722
00:35:48,480 --> 00:35:51,520
Speaker 1: you might imagine, well, what about space between here and Andromeda?

723
00:35:51,560 --> 00:35:54,319
Speaker 1: For example? That's mostly empty, right, Or what about the

724
00:35:54,360 --> 00:35:57,919
Speaker 1: space outside of Earth in our solar system that's mostly empty? Right?

725
00:35:58,120 --> 00:36:01,560
Speaker 1: Photons surely spend most of their time whizzing around basically

726
00:36:01,560 --> 00:36:03,600
Speaker 1: at the speed of light. What turns out, space is

727
00:36:03,640 --> 00:36:07,000
Speaker 1: almost never empty. The space in our solar system is

728
00:36:07,040 --> 00:36:10,160
Speaker 1: filled with particles from the Sun. The Sun pumps out

729
00:36:10,160 --> 00:36:13,440
Speaker 1: a solar wind of protons and electrons and other stuff

730
00:36:13,440 --> 00:36:16,560
Speaker 1: that's always blowing through the Solar system. So photons traveling

731
00:36:16,600 --> 00:36:19,719
Speaker 1: through our solar system are constantly running into these protons

732
00:36:19,719 --> 00:36:23,200
Speaker 1: and these electrons and interacting with them. Really interesting. So

733
00:36:23,440 --> 00:36:25,879
Speaker 1: you're saying, like the space between us and the Sun

734
00:36:26,200 --> 00:36:28,759
Speaker 1: is not perfectly clear. There's all kinds of stuff in it,

735
00:36:28,920 --> 00:36:30,880
Speaker 1: which means that the speed of light in our solar

736
00:36:30,920 --> 00:36:34,000
Speaker 1: system is slower than the speed of light, a tiny, tiny,

737
00:36:34,080 --> 00:36:36,880
Speaker 1: tiny little bit slower. This is very dilute. Is like

738
00:36:36,920 --> 00:36:39,840
Speaker 1: not very many protons per cubic meter, you know, between

739
00:36:39,920 --> 00:36:42,680
Speaker 1: us and Jupiter, for example, but there are some. And

740
00:36:42,719 --> 00:36:45,560
Speaker 1: so if you're talking technically, like our photons that bounce

741
00:36:45,560 --> 00:36:47,879
Speaker 1: off Jupiter and then come back to Earth, are those

742
00:36:47,920 --> 00:36:50,080
Speaker 1: moving at the speed of light? Technically they're moving at

743
00:36:50,120 --> 00:36:52,600
Speaker 1: a little bit less than the speed of light. And

744
00:36:52,640 --> 00:36:56,080
Speaker 1: that's also true for photons from Andromeda, for example, because

745
00:36:56,120 --> 00:37:00,959
Speaker 1: the space between us and other galaxies is also not empty, right, yeah,

746
00:37:01,000 --> 00:37:03,200
Speaker 1: because there's a lot of stuff in between us and

747
00:37:03,200 --> 00:37:05,080
Speaker 1: and Drama. Not. Even though it's hard to see what

748
00:37:05,120 --> 00:37:07,880
Speaker 1: the naked eye, you probably imagine the university these clusters

749
00:37:07,920 --> 00:37:11,719
Speaker 1: of stars grouped into galaxies, and that's basically where everything is.

750
00:37:12,280 --> 00:37:15,160
Speaker 1: But don't forget that the universe is mostly gas, right.

751
00:37:15,239 --> 00:37:17,959
Speaker 1: Stars are a tiny fraction in the universe, So really

752
00:37:17,960 --> 00:37:20,359
Speaker 1: you should be thinking about the gas in those galaxies,

753
00:37:20,600 --> 00:37:24,320
Speaker 1: and it's also gas between the galaxies. Think of the

754
00:37:24,400 --> 00:37:27,160
Speaker 1: universe not as a bunch of dots of stars clustered

755
00:37:27,200 --> 00:37:30,280
Speaker 1: into galaxies, but like a cosmic web of gas filaments,

756
00:37:30,320 --> 00:37:32,880
Speaker 1: and where those filaments overlap and intersect, then you have

757
00:37:32,920 --> 00:37:35,680
Speaker 1: these deep pools that form stars and visible light and

758
00:37:35,719 --> 00:37:38,680
Speaker 1: all that cool stuff. But between the galaxies there are

759
00:37:38,719 --> 00:37:42,759
Speaker 1: these very long tendrils of gas between Us and Andromeda,

760
00:37:42,800 --> 00:37:45,960
Speaker 1: for example, a huge amount of gas. They estimate like

761
00:37:45,960 --> 00:37:49,160
Speaker 1: a significant fraction of all the matter in the universe

762
00:37:49,200 --> 00:37:54,160
Speaker 1: are kind of matter is actually between galaxies, not in galaxies. Yeah,

763
00:37:54,239 --> 00:38:00,479
Speaker 1: like of the matter in the universe is basically small, right, Yeah,

764
00:38:00,480 --> 00:38:04,520
Speaker 1: they call this the warm hot intergalactic medium. I'm not

765
00:38:04,560 --> 00:38:06,760
Speaker 1: even gonna talk about why they call it warm hot.

766
00:38:08,000 --> 00:38:10,440
Speaker 1: But the acronym for it is w H I M,

767
00:38:10,640 --> 00:38:12,480
Speaker 1: which you know, they didn't choose on a whim, but

768
00:38:12,560 --> 00:38:15,279
Speaker 1: they did because it spells out whim. It's just a

769
00:38:15,280 --> 00:38:17,960
Speaker 1: whimsical name, you know, for something that's warm hot. Now,

770
00:38:17,960 --> 00:38:20,000
Speaker 1: why do they call it warm hot because it's not

771
00:38:20,520 --> 00:38:23,120
Speaker 1: cool warm. They call it warm hot because it's sort

772
00:38:23,120 --> 00:38:26,920
Speaker 1: of between warm and hot. And remember, if you were

773
00:38:26,960 --> 00:38:29,560
Speaker 1: out there in space, you would freeze your tissue off.

774
00:38:29,680 --> 00:38:32,640
Speaker 1: But these particles are fairly high speed, and so we

775
00:38:32,760 --> 00:38:36,080
Speaker 1: say that they have a fairly high temperature. This intergalactic

776
00:38:36,120 --> 00:38:39,200
Speaker 1: plasma can actually be fairly hot on a temperature scale,

777
00:38:39,200 --> 00:38:41,640
Speaker 1: even though it's very very dilute, so it doesn't contain

778
00:38:41,680 --> 00:38:43,880
Speaker 1: a lot of heat. But because of the speed of

779
00:38:43,920 --> 00:38:47,080
Speaker 1: the particles, they say it's fairly hot, not fast enough

780
00:38:47,120 --> 00:38:49,719
Speaker 1: to call it actually hot, not slow enough to call

781
00:38:49,760 --> 00:38:52,520
Speaker 1: it is warm. So it's sort of like warm too hot,

782
00:38:52,719 --> 00:38:55,600
Speaker 1: So they call it warm hot. It's not a whim

783
00:38:55,680 --> 00:38:59,040
Speaker 1: or a hymn, it's a whim. It should be W

784
00:38:59,320 --> 00:39:01,640
Speaker 1: T H I M, but then it'll be like with them,

785
00:39:02,000 --> 00:39:06,000
Speaker 1: I get the lukewarm intergalactic medium, wouldn't really fly there, No,

786
00:39:06,160 --> 00:39:09,160
Speaker 1: I suppose not, And so that slows down photons that

787
00:39:09,160 --> 00:39:12,799
Speaker 1: are moving through the universe between galaxies. So when you're

788
00:39:12,800 --> 00:39:14,279
Speaker 1: looking up at the night sky and know that all

789
00:39:14,280 --> 00:39:16,360
Speaker 1: the photons that are traveling towards you were traveling a

790
00:39:16,760 --> 00:39:19,279
Speaker 1: little bit less than the speed of light, even the

791
00:39:19,320 --> 00:39:22,719
Speaker 1: ones coming from other galaxies. But wait, wait, wait, isn't

792
00:39:22,719 --> 00:39:26,520
Speaker 1: the space between our galaxies also expanding? So space everywhere

793
00:39:26,719 --> 00:39:30,240
Speaker 1: is expanding, right, and the expansion happens simultaneously at every

794
00:39:30,239 --> 00:39:32,799
Speaker 1: point in space at the same rate for things are

795
00:39:32,840 --> 00:39:34,880
Speaker 1: near each other. However, that's a pretty small effect. And

796
00:39:34,880 --> 00:39:37,360
Speaker 1: also things that near each other have gravity, so the

797
00:39:37,400 --> 00:39:40,480
Speaker 1: gravity and Dromeda is actually pulling it towards us faster

798
00:39:40,560 --> 00:39:43,960
Speaker 1: than space is expanding between us. So you can basically

799
00:39:44,000 --> 00:39:47,040
Speaker 1: ignore the expansion of space when you're thinking about photons

800
00:39:47,040 --> 00:39:50,879
Speaker 1: from Andromeda, because they're like in our local gravitational bubble, right,

801
00:39:50,920 --> 00:39:53,400
Speaker 1: But it's it's still expanding, which is speeding up the

802
00:39:53,480 --> 00:39:55,360
Speaker 1: speed of light a little bit. But you're saying that

803
00:39:55,400 --> 00:39:58,600
Speaker 1: the effect of the whimsical gas in between is slowing

804
00:39:58,600 --> 00:40:01,279
Speaker 1: it down more than the expand sin is speeding it up. Yes,

805
00:40:01,320 --> 00:40:03,279
Speaker 1: so the expansion would be moving and Dromeda away from us,

806
00:40:03,280 --> 00:40:05,880
Speaker 1: but gravity is holding Andromeda in place, sort of the

807
00:40:05,880 --> 00:40:08,200
Speaker 1: same way that gravity holds the Earth around the Sun.

808
00:40:08,360 --> 00:40:10,400
Speaker 1: You're right there, the photons from Andromeda are moving through

809
00:40:10,480 --> 00:40:13,640
Speaker 1: expanding space. Because they're moving towards us, that would actually

810
00:40:13,680 --> 00:40:16,759
Speaker 1: be slowing down their effective speed. Okay, now let's talk

811
00:40:16,760 --> 00:40:20,239
Speaker 1: about charge particles. We know that particles with mass have

812
00:40:20,719 --> 00:40:24,120
Speaker 1: extra limitation with respect to the speed of light, and

813
00:40:24,120 --> 00:40:26,040
Speaker 1: we know that space is not empty. Does having a

814
00:40:26,160 --> 00:40:30,719
Speaker 1: charge affect you more than having mass? Like, does it

815
00:40:30,760 --> 00:40:33,520
Speaker 1: somehow give you a boost through this plasma or does

816
00:40:33,520 --> 00:40:36,959
Speaker 1: it slowly down more? Well, interestingly, there are no particles

817
00:40:37,000 --> 00:40:40,239
Speaker 1: that have charge and don't have mass. Right so the

818
00:40:40,239 --> 00:40:42,960
Speaker 1: photon has no charge and no mass. But if you're

819
00:40:42,960 --> 00:40:44,880
Speaker 1: a charge particle number one, that means that you have

820
00:40:44,960 --> 00:40:48,040
Speaker 1: mass like the electron and the corks. All the particles

821
00:40:48,040 --> 00:40:50,240
Speaker 1: that have charged also have mass, So that right away

822
00:40:50,280 --> 00:40:52,440
Speaker 1: means if you have charge, you can't go at the

823
00:40:52,440 --> 00:40:54,799
Speaker 1: speed of light. Really wouldn't that make you think they're

824
00:40:54,800 --> 00:40:57,480
Speaker 1: somehow related? Yeah, it's a really fascinating clue and one

825
00:40:57,520 --> 00:41:00,759
Speaker 1: that we just don't understand at all. Possible that one

826
00:41:00,800 --> 00:41:04,480
Speaker 1: day in the future we will discover a massless charged particle,

827
00:41:04,960 --> 00:41:08,439
Speaker 1: but none exists currently in our universe that we know about. Well,

828
00:41:08,440 --> 00:41:12,680
Speaker 1: gluons have charged, they just don't have electromagnetic charge, right,

829
00:41:12,800 --> 00:41:15,719
Speaker 1: that's right. They have color charge charged for the strong force. Yeah,

830
00:41:15,760 --> 00:41:17,960
Speaker 1: that's a really good point. And we do sometimes discover

831
00:41:18,080 --> 00:41:21,400
Speaker 1: new categories of particles, like the Higgs boson was a

832
00:41:21,440 --> 00:41:24,360
Speaker 1: particle like no particle we had seen before. It's the

833
00:41:24,400 --> 00:41:27,040
Speaker 1: first scale or particle that we've ever found before, a

834
00:41:27,080 --> 00:41:30,920
Speaker 1: particle without any spin. And so it's possible to discover

835
00:41:31,040 --> 00:41:33,440
Speaker 1: new categories of particles that we haven't seen before in

836
00:41:33,440 --> 00:41:36,719
Speaker 1: the universe, or we might discover that that's impossible for

837
00:41:36,760 --> 00:41:39,200
Speaker 1: some reason we haven't learned yet. But the higgs boson

838
00:41:39,600 --> 00:41:42,640
Speaker 1: has massed to it, right, it interacts with itself, but

839
00:41:42,680 --> 00:41:45,080
Speaker 1: it does the higgs boson have charge. The higgs boson

840
00:41:45,120 --> 00:41:48,000
Speaker 1: doesn't have electric charge. No, But it was interesting because

841
00:41:48,000 --> 00:41:50,640
Speaker 1: it also doesn't have quantum spin like all the other

842
00:41:50,680 --> 00:41:53,440
Speaker 1: particles do. So the higgs boson does have mass but

843
00:41:53,520 --> 00:41:55,960
Speaker 1: no charge. The higgs boson has mass but no charge.

844
00:41:56,000 --> 00:41:57,920
Speaker 1: But we don't have any particles that have charge but

845
00:41:58,000 --> 00:42:00,920
Speaker 1: no mass. Oh, it seems so if you have charge,

846
00:42:01,000 --> 00:42:04,200
Speaker 1: then you usually have mass. That's the pattern so far.

847
00:42:04,440 --> 00:42:06,239
Speaker 1: We don't know if that's a hard and fast rule

848
00:42:06,360 --> 00:42:09,520
Speaker 1: or just sort of like a coincidence or electromagnetic charge.

849
00:42:09,560 --> 00:42:13,040
Speaker 1: I should say, right, yes, exactly, electromagnetic charge. So now,

850
00:42:13,040 --> 00:42:15,240
Speaker 1: if you're a proton flying through space on an electron

851
00:42:15,280 --> 00:42:18,360
Speaker 1: flying through space, you obviously can't move at the speed

852
00:42:18,400 --> 00:42:21,080
Speaker 1: of light just because you have mass. So if you're

853
00:42:21,160 --> 00:42:23,719
Speaker 1: charged particle, that also means you have mass, which means

854
00:42:23,719 --> 00:42:25,719
Speaker 1: you can't travel at the speed of light. How does

855
00:42:25,760 --> 00:42:27,799
Speaker 1: the charge affect your motion? Does it make you go

856
00:42:27,920 --> 00:42:31,520
Speaker 1: faster or slower through this plasma in the universe? Well? Both.

857
00:42:31,600 --> 00:42:33,760
Speaker 1: First of all, it allows you to go really fast

858
00:42:34,000 --> 00:42:36,560
Speaker 1: because having a charge means that you can get accelerated

859
00:42:36,600 --> 00:42:40,000
Speaker 1: by cosmic electric fields or magnetic fields. For example, you

860
00:42:40,040 --> 00:42:42,560
Speaker 1: can be near a black hole or a pulsar, which

861
00:42:42,560 --> 00:42:45,279
Speaker 1: have very very strong magnetic fields and you can gain

862
00:42:45,440 --> 00:42:48,040
Speaker 1: huge acceleration. And so it allows you to sort of

863
00:42:48,080 --> 00:42:51,600
Speaker 1: like tap into cosmic accelerators to get to really really

864
00:42:51,680 --> 00:42:55,040
Speaker 1: high energies. But then on the flip side, it also

865
00:42:55,160 --> 00:42:58,960
Speaker 1: slows you down because particles that have charge interact with photons,

866
00:42:59,440 --> 00:43:02,640
Speaker 1: and the unit verse is filled with photons, if photons

867
00:43:02,760 --> 00:43:05,880
Speaker 1: left over from the Big Bang, from the cosmic microwave

868
00:43:05,920 --> 00:43:09,920
Speaker 1: background radiation that's everywhere in the universe, and so charge

869
00:43:09,960 --> 00:43:13,359
Speaker 1: particles flying through the universe interact with those photons, which

870
00:43:13,440 --> 00:43:16,799
Speaker 1: constantly sap their energy. Mm I think you're saying that.

871
00:43:16,840 --> 00:43:18,960
Speaker 1: You know, if you have charge, that means that you

872
00:43:19,040 --> 00:43:22,280
Speaker 1: can be pulled by something that has the opposite charge

873
00:43:23,080 --> 00:43:24,919
Speaker 1: ahead of you, right, But it could also maybe slow

874
00:43:24,920 --> 00:43:26,919
Speaker 1: you down if the thing is behind you. Absolutely could.

875
00:43:26,960 --> 00:43:30,040
Speaker 1: You have magnetic fields and electric fields from cosmic objects

876
00:43:30,040 --> 00:43:33,400
Speaker 1: can accelerate or decelerate these particles. But also just the

877
00:43:33,440 --> 00:43:35,520
Speaker 1: whole universe is filled with a fog. If you're an

878
00:43:35,560 --> 00:43:38,239
Speaker 1: electron and you're flying through the universe, there really is

879
00:43:38,360 --> 00:43:42,160
Speaker 1: no empty space. You see photons everywhere and they're all

880
00:43:42,239 --> 00:43:44,719
Speaker 1: interacting with you. And there's this effect that if a

881
00:43:44,840 --> 00:43:48,640
Speaker 1: particle is moving really really really really really fast, then

882
00:43:48,640 --> 00:43:52,080
Speaker 1: it tends to interact with this cosmic microwave background photons

883
00:43:52,120 --> 00:43:54,120
Speaker 1: in a way that SAPs its energy and turns it

884
00:43:54,120 --> 00:43:57,200
Speaker 1: into other particles. And so there's basically like an effective

885
00:43:57,239 --> 00:44:00,200
Speaker 1: limit to how fast a charge particle can move through

886
00:44:00,200 --> 00:44:03,960
Speaker 1: the universe because of its interaction with the cosmic microwave

887
00:44:04,000 --> 00:44:07,080
Speaker 1: background radiation. Meaning like, if I'm a proton flying through

888
00:44:07,120 --> 00:44:10,480
Speaker 1: space and uh I hit a photon head on, it's

889
00:44:10,480 --> 00:44:14,439
Speaker 1: going to slow me down, right, because the photon has momentum. Right,

890
00:44:14,520 --> 00:44:16,560
Speaker 1: You're gonna interact with that photon, and some of your

891
00:44:16,680 --> 00:44:18,560
Speaker 1: energy is going to get used up to create a

892
00:44:18,560 --> 00:44:21,080
Speaker 1: new particle, like a delta particle or some other low

893
00:44:21,120 --> 00:44:23,000
Speaker 1: mass particle, and then you can go fly off in

894
00:44:23,000 --> 00:44:25,480
Speaker 1: another direction, but you've lost some of that energy. What

895
00:44:25,560 --> 00:44:27,480
Speaker 1: if the photon hits you from behind, when did it

896
00:44:27,560 --> 00:44:31,480
Speaker 1: push you? Yeah, that's possible, and photons move faster than protons,

897
00:44:31,520 --> 00:44:33,879
Speaker 1: so they can catch up to a proton and give

898
00:44:33,920 --> 00:44:36,759
Speaker 1: it a little push. But the overall effect from a

899
00:44:36,760 --> 00:44:40,200
Speaker 1: proton like flying through this fob of photons, is that

900
00:44:40,280 --> 00:44:43,279
Speaker 1: it gets slowed down. It's like compressing the space in

901
00:44:43,320 --> 00:44:45,680
Speaker 1: front of it. You mean, like, there's an average speed

902
00:44:45,760 --> 00:44:47,799
Speaker 1: of all the photons in the universe, and if you're

903
00:44:47,800 --> 00:44:51,080
Speaker 1: going faster than that average speed, then you'll hit the

904
00:44:51,080 --> 00:44:53,160
Speaker 1: photons kind of like bugs in your windshield. I'm not

905
00:44:53,200 --> 00:44:55,360
Speaker 1: sure how to calculate the average speed of a photon.

906
00:44:55,760 --> 00:44:58,239
Speaker 1: But think about like the number of directions that a

907
00:44:58,280 --> 00:45:00,440
Speaker 1: photon could hit you. In. Most of the those ways

908
00:45:00,440 --> 00:45:02,840
Speaker 1: it would slow you down. In only a few ways

909
00:45:02,840 --> 00:45:05,600
Speaker 1: they would speed you up because you're you're moving in

910
00:45:05,640 --> 00:45:08,920
Speaker 1: a certain direction relative to the maybe the average direction

911
00:45:08,960 --> 00:45:11,040
Speaker 1: of all the photons. Yeah, that's right. And also, as

912
00:45:11,040 --> 00:45:13,800
Speaker 1: you move really fast through space, you tend to contract

913
00:45:13,840 --> 00:45:16,120
Speaker 1: the space in front of you, which increases the density

914
00:45:16,120 --> 00:45:18,520
Speaker 1: of the photons in front of you that you're hitting.

915
00:45:18,600 --> 00:45:21,200
Speaker 1: So there's a special relativistic effect there also, And what

916
00:45:21,280 --> 00:45:24,160
Speaker 1: this means is that really really high energy particles gets

917
00:45:24,200 --> 00:45:27,160
Speaker 1: slowed down. So we have cosmic accelerators out there, the

918
00:45:27,160 --> 00:45:30,799
Speaker 1: centers of galaxies and pulsars whatever, spewing out super high

919
00:45:31,000 --> 00:45:34,319
Speaker 1: energy charged particles, but then they basically screeched to a halt.

920
00:45:34,440 --> 00:45:36,960
Speaker 1: It's really really hard to have charged particles a crazy

921
00:45:37,040 --> 00:45:39,400
Speaker 1: high energy in the universe because the universe is kind

922
00:45:39,400 --> 00:45:42,279
Speaker 1: of like sticky for those charged particles. And that means

923
00:45:42,280 --> 00:45:44,439
Speaker 1: something really cool. It means that if you see one

924
00:45:44,440 --> 00:45:47,359
Speaker 1: of these particles, it can't have come from very far

925
00:45:47,440 --> 00:45:51,200
Speaker 1: away because very very high energy particles can't go very

926
00:45:51,200 --> 00:45:53,799
Speaker 1: far at our universe, they're sort of local, or they

927
00:45:53,800 --> 00:45:56,719
Speaker 1: started off with a super duper duper crazy amount of

928
00:45:56,760 --> 00:45:59,759
Speaker 1: energy to start with. Yeah, exactly, they would have to

929
00:45:59,760 --> 00:46:02,840
Speaker 1: have double bonkers energy if they come from really far away.

930
00:46:02,960 --> 00:46:05,120
Speaker 1: So you're saying that the whole universe is filled with

931
00:46:05,160 --> 00:46:07,920
Speaker 1: a little bit of light pollution, which kind of slows

932
00:46:07,960 --> 00:46:10,200
Speaker 1: everything down, makes it even harder to go at the

933
00:46:10,239 --> 00:46:14,400
Speaker 1: speed of light. And as time goes on, that light pollution,

934
00:46:14,440 --> 00:46:18,000
Speaker 1: the cosmic microwave background radiation is cooling, and so this

935
00:46:18,040 --> 00:46:21,080
Speaker 1: effect is fading because the universe is expanding, that light

936
00:46:21,160 --> 00:46:23,719
Speaker 1: is cooling, it's getting more and more dilute. So as

937
00:46:23,760 --> 00:46:26,520
Speaker 1: time goes on, the universe gets like less sticky for

938
00:46:26,640 --> 00:46:29,920
Speaker 1: charge particles, which means that these charged particles, these protons

939
00:46:29,960 --> 00:46:33,120
Speaker 1: coming out of cosmic accelerators can go faster and faster

940
00:46:33,280 --> 00:46:36,040
Speaker 1: as time goes on, or further and further at their

941
00:46:36,040 --> 00:46:38,719
Speaker 1: top speed. You mean like this light pollution of the

942
00:46:38,760 --> 00:46:41,840
Speaker 1: universe is kind of dissipating in a way. Yeah, precisely.

943
00:46:41,960 --> 00:46:45,120
Speaker 1: The fog is clearing very very slowly, Isn't the universe

944
00:46:45,160 --> 00:46:50,080
Speaker 1: also filled with like quantum vacuum energy, like particles popping

945
00:46:50,080 --> 00:46:52,560
Speaker 1: in and out. All space has quantum fields in it,

946
00:46:52,600 --> 00:46:55,480
Speaker 1: and those quantum fields can never relax down to zero,

947
00:46:55,600 --> 00:46:58,640
Speaker 1: so there's always some energy and space. We think that's

948
00:46:59,000 --> 00:47:01,840
Speaker 1: very very small. We also think that might be what's

949
00:47:01,880 --> 00:47:05,200
Speaker 1: causing the expansion of the universe. It's not something that

950
00:47:05,239 --> 00:47:08,280
Speaker 1: we understand very well. So then, if something is flying

951
00:47:08,320 --> 00:47:12,120
Speaker 1: through space, does it interact with those that vacuum quantum

952
00:47:12,360 --> 00:47:15,520
Speaker 1: fields particles popping up? It doesn't necessarily slow it down,

953
00:47:15,560 --> 00:47:17,840
Speaker 1: It just gives it inertia. So interacting with the Higgs

954
00:47:17,840 --> 00:47:20,160
Speaker 1: field is how the particle gets mass. It doesn't have

955
00:47:20,239 --> 00:47:22,440
Speaker 1: to slow it down. So it's possible to interact with

956
00:47:22,440 --> 00:47:25,319
Speaker 1: these quantum fields without slowing down. All right. Well, then

957
00:47:25,360 --> 00:47:27,280
Speaker 1: now to wrap it up and to answer the question

958
00:47:27,320 --> 00:47:29,759
Speaker 1: we set out to answer at the beginning, Daniel, what's

959
00:47:29,800 --> 00:47:32,680
Speaker 1: the fastest that a charge particle can go? Super duper

960
00:47:32,760 --> 00:47:36,279
Speaker 1: duper duper duper fast, but not actually the speed of

961
00:47:36,360 --> 00:47:39,960
Speaker 1: light and not for very far in the universe? You mean,

962
00:47:40,000 --> 00:47:45,680
Speaker 1: po Yeah, there's no actual limit, right, These particles can

963
00:47:45,760 --> 00:47:48,399
Speaker 1: keep approaching the speed of light but never actually get there.

964
00:47:48,760 --> 00:47:50,960
Speaker 1: And for charge particles, they just can't do it for

965
00:47:51,120 --> 00:47:53,920
Speaker 1: very far. So even if I did a perfect backflip

966
00:47:54,000 --> 00:47:55,960
Speaker 1: at the Olympics. You would only give me a nine.

967
00:47:57,440 --> 00:48:00,440
Speaker 1: I would give you a warm hot score. Yes, our right. Well,

968
00:48:00,480 --> 00:48:04,520
Speaker 1: another reminder that the universe has these strange rules. If

969
00:48:04,560 --> 00:48:06,960
Speaker 1: you think about them, they're kind of strange. But that's

970
00:48:07,040 --> 00:48:09,160
Speaker 1: kind of the job that we as humans have is

971
00:48:09,200 --> 00:48:13,160
Speaker 1: to figure out what are the rules and when can

972
00:48:13,200 --> 00:48:15,480
Speaker 1: you break them? And that's the job of us experimentalists

973
00:48:15,480 --> 00:48:17,320
Speaker 1: to go out there and actually try to break the

974
00:48:17,400 --> 00:48:19,480
Speaker 1: rules of the universe. All right, Well, we hope you

975
00:48:19,560 --> 00:48:22,200
Speaker 1: enjoyed that. Thanks for joining us, See you next time.

976
00:48:30,080 --> 00:48:32,880
Speaker 1: Thanks for listening, and remember that Daniel and Jorge explain

977
00:48:32,960 --> 00:48:35,800
Speaker 1: the Universe is a production of I Heart Radio. For

978
00:48:35,960 --> 00:48:38,920
Speaker 1: more podcast from my heart Radio, visit the i heart

979
00:48:39,000 --> 00:48:42,600
Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your

980
00:48:42,640 --> 00:48:49,120
Speaker 1: favorite shows. Yeah,