WEBVTT - Why Does the Year Have 365 Days in It? 0:00:00.200 --> 0:00:02.400 Hey, please take a second and leave us a review 0:00:02.480 --> 0:00:06.279 on Apple Podcasts, Spotify, or wherever you listen to the podcast. 0:00:06.960 --> 0:00:07.480 Thanks a lot. 0:00:09.520 --> 0:00:13.319 Hey, welcome to Sign Stuff reproduction of iHeartRadio. I'm Horrid 0:00:13.520 --> 0:00:16.200 cham And in this year end episode, we are answering 0:00:16.239 --> 0:00:20.079 the question why is a year a year? Why do 0:00:20.079 --> 0:00:22.480 we have three hundred and sixty five days in the year? 0:00:23.280 --> 0:00:26.319 Is it changing? And will the new year always be 0:00:26.440 --> 0:00:29.000 the same? This is the second in our two part 0:00:29.000 --> 0:00:31.800 holiday special, so be sure to check out last week's 0:00:31.840 --> 0:00:35.879 episode about whether the North Pole is moving. Today, we're 0:00:35.880 --> 0:00:38.960 going to continue our conversation with my friend and planetary 0:00:39.000 --> 0:00:41.720 scientist Matt Siegler, and he's going to fill us in 0:00:41.800 --> 0:00:45.320 on the physics of our annual spin around the Sun. 0:00:45.800 --> 0:00:47.960 So get ready to count down the new year with 0:00:48.159 --> 0:00:51.400 Science as we answer the question why is a year 0:00:51.880 --> 0:01:02.240 a year? Hey? Everyone, Happy new Today we're celebrating another 0:01:02.400 --> 0:01:05.440 orbit around our lovely Sun and the end of our 0:01:05.480 --> 0:01:09.160 first year on Science Stuff. On behalf of everyone involved 0:01:09.160 --> 0:01:14.000 in the show. Thanks for tuning in to get you 0:01:14.040 --> 0:01:16.679 into party mode. We're going to continue my conversation with 0:01:16.800 --> 0:01:21.039 planetary scientists doctor Matt Siegler. Doctor Siegler is a professor 0:01:21.080 --> 0:01:25.360 at the University of Hawaii's Institute for Geophysics and Planetology, 0:01:25.720 --> 0:01:28.560 and he works with NASA and the European Space Agency 0:01:28.760 --> 0:01:31.679 on several missions. On our last episode, we talked about 0:01:31.680 --> 0:01:35.360 how you can't really trust the North Pole no matter 0:01:35.440 --> 0:01:38.240 if you're talking about the magnetic North Pole, the spin 0:01:38.319 --> 0:01:40.959 axis of the Earth, or even the GPS top of 0:01:40.959 --> 0:01:44.320 the world. It's all changing. So I wanted to ask 0:01:44.360 --> 0:01:48.040 doctor Siegler if the same applies to the year, as 0:01:48.040 --> 0:01:51.120 our orbit around the Sun changed since the Earth was formed, 0:01:51.480 --> 0:01:54.400 or will it change in the future. Here's my chat 0:01:54.440 --> 0:01:59.360 with doctor Siegler. Okay, let's stitch over to the new year. Matt, 0:01:59.400 --> 0:02:00.720 are you looking for to the new year? 0:02:01.080 --> 0:02:03.360 Oh? Yeah, it's a very exciting new year. 0:02:05.680 --> 0:02:08.280 You sound excited. Did you do anything specially in Hawaii 0:02:08.360 --> 0:02:09.280 for New Years? 0:02:09.440 --> 0:02:14.680 Apparently there is a massive, massive home fireworks display world 0:02:14.720 --> 0:02:17.160 that goes on here such that it becomes kind of 0:02:17.240 --> 0:02:19.720 out of control and chaotic where the skies are just 0:02:20.160 --> 0:02:20.639 lit up. 0:02:20.960 --> 0:02:22.519 Well, good luck with that. So I thought it'd be 0:02:22.560 --> 0:02:26.360 fun to talk about in the Solar System whether the 0:02:26.520 --> 0:02:29.040 year has changed for Earth and also where are the 0:02:29.120 --> 0:02:31.360 years like in other planets. So let's start with the 0:02:31.360 --> 0:02:35.200 planet Earth. We talk about how the north pole is 0:02:35.280 --> 0:02:39.160 changing on Earth. Is the year changing for planet Earth also? 0:02:39.320 --> 0:02:40.280 Or is it pretty constant? 0:02:40.639 --> 0:02:45.600 Yeah, the year is not really as malleable as the 0:02:45.639 --> 0:02:48.679 spin axis. In a way, the year is how long 0:02:48.800 --> 0:02:52.040 we go to take one revolution around the Sun, Okay, 0:02:52.280 --> 0:02:56.560 and so that period ends up being pretty constant. You know, 0:02:56.639 --> 0:02:59.040 we talked about how oval the Earth's orbit is, but 0:02:59.120 --> 0:03:02.200 it's still take the same period to go around. It 0:03:02.200 --> 0:03:04.480 will just go faster at some parts of it and 0:03:04.560 --> 0:03:05.680 slower at other parts. 0:03:06.480 --> 0:03:09.600 Okay, here's what's going on. The Earth's orbit around the 0:03:09.639 --> 0:03:13.080 Sun is pretty much a circle. If someone showed you 0:03:13.080 --> 0:03:16.680 a picture of that orbit, you'd probably say, yep, that's 0:03:16.680 --> 0:03:20.520 a circle. But actually it's not quite a perfect circle. 0:03:20.800 --> 0:03:24.600 It's a little bit about one point six percent ovalish 0:03:24.840 --> 0:03:28.920 or elliptical. And this has a few interesting consequences. First 0:03:28.960 --> 0:03:30.960 of all, it means we're not always at the same 0:03:31.040 --> 0:03:35.200 distance from the Sun. In January, we're about three million 0:03:35.240 --> 0:03:38.800 miles closer to the Sun than in June. Now, that 0:03:38.840 --> 0:03:41.080 doesn't affect too much how hot it feels on Earth. 0:03:41.360 --> 0:03:43.800 As we'll talk about later, the tilt of the Earth 0:03:44.040 --> 0:03:46.720 has a bigger effect on the seasons. But it does 0:03:46.840 --> 0:03:49.800 mean that the Sun looks a little bit smaller in 0:03:49.920 --> 0:03:54.200 June than in January, about three point three percent smaller. 0:03:54.760 --> 0:03:57.000 And it also means that our speed around the Sun 0:03:57.320 --> 0:04:01.520 changes throughout the year. In January, the Earth is swinging 0:04:01.560 --> 0:04:05.320 around the Sun a little faster than in June, about 0:04:05.360 --> 0:04:08.600 two thirds of a mile per second faster. So if 0:04:08.680 --> 0:04:11.520 it feels like the holidays in New Year go by fast, 0:04:11.800 --> 0:04:15.640 you can blame it on the earth slightly elliptical orbit. Okay, 0:04:15.680 --> 0:04:18.599 now the question is how did we get that orbit? 0:04:20.040 --> 0:04:22.719 I have two questions. The first question is what determined 0:04:22.800 --> 0:04:24.800 how long our year was going to be? Is it 0:04:24.839 --> 0:04:27.320 tied to the formation of the Solar system. 0:04:27.760 --> 0:04:31.000 Yeah, so, as the planets formed, they had a certain 0:04:31.200 --> 0:04:34.640 time period over their orbit. And there is actually a 0:04:34.640 --> 0:04:38.000 really interesting story about that that we think the way 0:04:38.040 --> 0:04:41.840 the planets formed, Jupiter and Saturn were at slightly different 0:04:41.960 --> 0:04:45.560 distances to the Sun than they are today, and that 0:04:45.800 --> 0:04:49.479 actually ended up with them going into a resonance, which 0:04:49.520 --> 0:04:53.160 is every one time Juwber goes around, Saturn goes around 0:04:53.200 --> 0:04:56.520 twice or something like that. Right, And so what happened 0:04:56.560 --> 0:04:59.320 then was that the gravity of the two giant planets 0:04:59.320 --> 0:05:02.640 would yank on you each other, and that eventually caused 0:05:02.680 --> 0:05:06.120 Saturn to move around and then slingshot out into the 0:05:06.120 --> 0:05:10.360 outer Solar System, and that messed up Neptune's orbit and 0:05:10.400 --> 0:05:13.919 fired it kind of out into the Coiper Belt and 0:05:14.240 --> 0:05:17.320 may have knocked around all these icy objects out there 0:05:17.360 --> 0:05:20.359 and caused them to go haywire and fall into the 0:05:20.360 --> 0:05:22.919 inner Solar System, and some of them hit the Earth 0:05:23.000 --> 0:05:25.919 and Moon and Mars. And that might be one of 0:05:25.920 --> 0:05:28.880 the main reasons we have water here on Earth is 0:05:29.560 --> 0:05:32.719 because of this chaotic change of years. 0:05:34.000 --> 0:05:36.680 Yes, scientists don't really know why we have so much 0:05:36.760 --> 0:05:39.520 water here on Earth. Some of the water in our 0:05:39.560 --> 0:05:42.839 oceans and lakes probably came from water that was trapped 0:05:42.920 --> 0:05:46.120 inside the Earth when the Earth formed that was then 0:05:46.320 --> 0:05:50.320 burped out into our atmosphere by volcanoes. But that's not 0:05:50.480 --> 0:05:53.599 enough water to fill up the oceans. So scientists have 0:05:53.600 --> 0:05:56.040 a theory that the rest of the water on Earth 0:05:56.360 --> 0:06:00.480 came from space, from icy comets or astero It's from 0:06:00.520 --> 0:06:03.800 the far out Kuiper Belt in our Solar system. And 0:06:03.880 --> 0:06:06.560 what doctor Siegler is saying is that the reason that 0:06:06.680 --> 0:06:10.360 water ended up here to create deep oceans and maybe 0:06:10.440 --> 0:06:14.880 life and us was the orbital Shenanigans of the planets 0:06:14.960 --> 0:06:18.279 Jupiter and Saturn. So as you look back and give 0:06:18.360 --> 0:06:21.400 thanks this holiday season and New Year, be sure to 0:06:21.400 --> 0:06:23.799 give a shout out to the planets Jupiter and Saturn 0:06:24.040 --> 0:06:27.279 for putting us here. Now, could that have happened to 0:06:27.520 --> 0:06:30.760 us here on Earth? Were we thrown into this orbit 0:06:30.880 --> 0:06:35.360 in that crazy chaotic young Solar system? Sort of? Actually 0:06:35.400 --> 0:06:39.640 our planet came about from two smaller planets crashing into 0:06:39.680 --> 0:06:43.719 each other. Could that have happened to Earth? Could something 0:06:43.720 --> 0:06:46.360 have happened to make us have a different year in 0:06:46.400 --> 0:06:48.640 our past? Or can it happen in the future. 0:06:48.880 --> 0:06:51.680 Yeah, And so this is something we're learning from studying 0:06:51.720 --> 0:06:55.320 other Solar systems or exoplanets, right, is that a lot 0:06:55.360 --> 0:06:58.760 of the planets seem to migrate around closer or farther 0:06:58.839 --> 0:07:02.400 away from their star over time. And so I think 0:07:02.440 --> 0:07:05.400 the ideas that the Earth has not migrated a ton 0:07:05.560 --> 0:07:08.760 over its time. But the Earth we think formed kind 0:07:08.760 --> 0:07:10.560 of like a pre Earth that was a little bit 0:07:10.600 --> 0:07:14.000 smaller than Earth. And then there was another planet about 0:07:14.040 --> 0:07:18.440 the size of Mars that crashed into us, and most 0:07:18.440 --> 0:07:21.280 of that material became the Earth, but some of it 0:07:21.400 --> 0:07:24.360 got thrown into a disc kind of like Saturn, and 0:07:24.480 --> 0:07:25.400 that formed the Moon. 0:07:25.760 --> 0:07:28.680 Oh so the pre Earth could have had a different orbit, 0:07:28.760 --> 0:07:29.720 could have had a different year. 0:07:29.840 --> 0:07:32.800 Yeah. Yeah, So you had these two planets that one 0:07:32.880 --> 0:07:34.720 was a little closer to the Sun than the Earth 0:07:35.080 --> 0:07:37.480 and so it had a shorter year, right, and then 0:07:37.520 --> 0:07:39.400 one was a little farther from the Earth and had 0:07:39.440 --> 0:07:40.200 a longer year. 0:07:40.320 --> 0:07:40.680 Uh huh. 0:07:41.000 --> 0:07:43.720 And they got into some kind of gravity tug of 0:07:43.760 --> 0:07:45.600 war and crashed into each. 0:07:45.360 --> 0:07:49.920 Other, and that's when the year was born. Yes, that's 0:07:49.960 --> 0:07:54.120 when the Earth year was born. Oh before that, there 0:07:54.160 --> 0:07:56.760 was no Earth year after that impact. Now the year 0:07:56.840 --> 0:08:00.880 was born, yes, when it just happened forzero point five 0:08:01.120 --> 0:08:06.480 six billion years ago, not yesterday. No, And we can 0:08:06.520 --> 0:08:09.640 tell when that started because the rocks on the Moon 0:08:09.760 --> 0:08:12.800 that formed at the same time haven't been all messed 0:08:12.880 --> 0:08:15.200 up by weather, and so we can date a rock 0:08:15.280 --> 0:08:19.679 from the Moon and figure out how old the Earth is. Whah. 0:08:20.480 --> 0:08:23.480 That's fascinating. And we don't think it's changed since then, 0:08:23.800 --> 0:08:25.560 Like the Earth year hasn't changed much. 0:08:25.840 --> 0:08:28.960 No, I mean there's some perturbations to the year from 0:08:29.160 --> 0:08:32.160 how much Jupiter might yank on us and alter our 0:08:32.280 --> 0:08:34.559 orbit a little bit, right, pull us out a little 0:08:34.559 --> 0:08:37.600 towards Jupiter. Venus might pull us in a little bit. 0:08:37.679 --> 0:08:41.040 But on average, the year has not changed substantially. 0:08:41.080 --> 0:08:43.559 I see it has changed, but just a little bit. Yeah, 0:08:43.600 --> 0:08:44.800 and what do you think is going to happen in 0:08:44.840 --> 0:08:46.880 the future. I think we're going to be stuck with 0:08:46.960 --> 0:08:51.040 our year for quite a while. Actually this is not 0:08:51.400 --> 0:08:55.360 quite true, Doctor Sieger says. There is something that is 0:08:55.400 --> 0:08:58.080 going to affect how long our gear is going to 0:08:58.120 --> 0:09:01.400 be in the future. So when we come back, we'll 0:09:01.400 --> 0:09:04.480 talk about what that effect is and how other orbital 0:09:04.520 --> 0:09:08.280 effects are going to fundamentally change how we celebrate the 0:09:08.360 --> 0:09:11.040 new year. So don't say goodbye to the old year 0:09:11.320 --> 0:09:11.760 just yet. 0:09:12.160 --> 0:09:12.840 Stay with us. 0:09:13.160 --> 0:09:27.480 We'll be right back. Hey, welcome back. We're talking about 0:09:27.480 --> 0:09:31.240 the physics of the new year, and so far we've 0:09:31.360 --> 0:09:34.480 learned the Earth's orbit around the Sun is not a 0:09:34.480 --> 0:09:38.440 perfect circle, and it's the result scientists theorize of two 0:09:38.480 --> 0:09:43.080 planets crashing into each other. But once the crash settled 0:09:43.240 --> 0:09:46.040 and the debris became the Earth and the Moon, our 0:09:46.200 --> 0:09:49.920 orbit around the Sun has been pretty stable. But that's 0:09:49.960 --> 0:09:52.160 not always going to be true. 0:09:53.280 --> 0:09:56.360 I guess in the long long future, roughly three or 0:09:56.360 --> 0:10:01.320 four billion years from now, the Sun have expanded enough 0:10:01.480 --> 0:10:04.520 that the outer atmosphere of the Sun will cause some 0:10:04.640 --> 0:10:07.880 drag on the Earth and that might cause it to 0:10:08.040 --> 0:10:11.160 lose a little bit of its momentum. Huh, and then 0:10:11.200 --> 0:10:13.240 it would slowly spiral down. 0:10:13.080 --> 0:10:15.679 In into the Sun. Yeah, so the year will get 0:10:15.720 --> 0:10:18.040 shorter and short. Well, first of all, like, if we're 0:10:18.120 --> 0:10:20.640 being dragged by the atmosphere of the Sun, we're probably 0:10:20.640 --> 0:10:21.920 not here, like we're cooked. 0:10:22.080 --> 0:10:25.320 Yeah. Yeah, so hopefully we're all living somewhere else. 0:10:26.679 --> 0:10:29.960 We might see the Earth's year get shorter and shorter 0:10:30.040 --> 0:10:31.720 as it drags into the Sun. 0:10:31.960 --> 0:10:35.760 Yeah. And it's kind of questionable or depending on what 0:10:35.920 --> 0:10:39.560 model you might assume of how a star expands, whether 0:10:39.640 --> 0:10:42.920 it's enough drag to cause the Earth to spiral in 0:10:42.960 --> 0:10:45.679 all the way, or if it just slows us down 0:10:45.720 --> 0:10:47.520 a little bit and we end up a little closer 0:10:47.600 --> 0:10:51.000 to the venus or crash in the venis sudden. I 0:10:51.040 --> 0:10:54.400 guess we won't see, but we can imagine that there 0:10:54.440 --> 0:10:56.319 are some interesting ways. 0:10:56.360 --> 0:10:57.800 Hopefully we'll see from a distance. 0:10:58.040 --> 0:10:58.360 Yeah. 0:10:58.480 --> 0:11:01.360 So the idea is that the long term of our 0:11:01.400 --> 0:11:05.320 solar system is that the outer atmosphere of the Sun 0:11:05.360 --> 0:11:08.920 will expand away. There'll be a white dwarf star, you know, 0:11:09.000 --> 0:11:12.800 where the core of the Sun that remains is. And 0:11:13.000 --> 0:11:16.280 I suppose the Earth will be a little closer, probably 0:11:16.320 --> 0:11:19.240 because of this drag, and have a shorter year, but 0:11:19.559 --> 0:11:22.480 hopefully there will still be some hulk of what used 0:11:22.480 --> 0:11:26.440 to be the Earth going around there. And whether after 0:11:26.520 --> 0:11:28.640 that it can never be a place where life could 0:11:28.720 --> 0:11:31.480 re emerge, that's going to be an interesting, big question, 0:11:31.679 --> 0:11:33.880 I see. But going through the outer atmosphere of the 0:11:33.880 --> 0:11:35.719 Sun will be a traumatic period for. 0:11:35.640 --> 0:11:38.280 The Earth, meaning there might not be anything alive to 0:11:38.360 --> 0:11:40.319 celebrate New Years. 0:11:45.000 --> 0:11:46.400 It's hard to do a sad one. 0:11:48.760 --> 0:11:52.520 That's pretty good. So the year will get shorter, according 0:11:52.520 --> 0:11:55.559 to scientists, maybe a few billion years in the future 0:11:55.840 --> 0:11:59.760 when the Sun expands and engulfs the Earth, making it 0:12:00.240 --> 0:12:03.760 into a smaller orbit. Now, in general, the orbit of 0:12:03.800 --> 0:12:07.160 a planet depends on how close it is to the Sun. 0:12:07.559 --> 0:12:10.240 Planets close to the Sun move really fast and their 0:12:10.360 --> 0:12:13.120 orbits are short, and planets that are far from the 0:12:13.160 --> 0:12:17.880 Sun move slowly and their orbits take longer. For example, 0:12:18.200 --> 0:12:21.080 mercury is the closest planet to the Sun, and its 0:12:21.200 --> 0:12:24.720 orbit takes eighty eight Earth days. In other words, a 0:12:24.840 --> 0:12:29.280 year on Mercury is only eighty eight days long. But Neptune, 0:12:29.520 --> 0:12:32.440 the farthest planet from the Sun, has an orbit that 0:12:32.480 --> 0:12:36.920 takes around sixty thousand Earth days or about one hundred 0:12:36.960 --> 0:12:40.080 and sixty three Earth years. So if you want it 0:12:40.080 --> 0:12:43.120 to feel younger or older, you could just move to 0:12:43.160 --> 0:12:45.800 another planet. I'm just trying to find a way to 0:12:45.800 --> 0:12:46.680 make myself younger. 0:12:46.880 --> 0:12:49.679 Yeah. Well, if you measure it by years, then you 0:12:49.720 --> 0:12:52.160 want to go further out in the source. Right, So 0:12:52.200 --> 0:12:55.000 we have Mercury is close to the Sun and so 0:12:55.080 --> 0:12:59.280 it's year is only eighty eight days long. Uh huh. Yeah, 0:12:59.320 --> 0:13:02.160 so you might feel pretty old pretty quickly if your 0:13:02.200 --> 0:13:03.360 birthday is every three. 0:13:03.240 --> 0:13:07.000 Months, as opposed to if you move to like Saturn. 0:13:07.280 --> 0:13:10.040 Yeah, you go out to Saturn and your year is 0:13:10.080 --> 0:13:13.560 about thirty Earth years, right, so you're barely a year 0:13:13.600 --> 0:13:14.840 old and Saturn, yeah. 0:13:14.679 --> 0:13:16.320 It'd be like one and a half basically. 0:13:16.679 --> 0:13:20.480 Yeah, so there you're a Saturnian infant. 0:13:20.679 --> 0:13:24.160 Oh my goodness. Okay. There are two interesting things about 0:13:24.160 --> 0:13:27.480 the physics of the New Year. The first is one 0:13:27.480 --> 0:13:30.560 that most people know, and that is that the orbit 0:13:30.640 --> 0:13:33.720 of the Earth is not quite three hundred and sixty 0:13:33.760 --> 0:13:37.840 five days long. It's actually three hundred and sixty five days, 0:13:38.120 --> 0:13:42.200 five hours, and forty eight minutes, Meaning the Earth doesn't 0:13:42.200 --> 0:13:45.200 spin in place a full three hundred and sixty five 0:13:45.280 --> 0:13:47.920 times in the time it takes to go around the 0:13:48.000 --> 0:13:51.960 Sun and back to the same spot. It spins a 0:13:52.120 --> 0:13:55.240 little bit more. But we celebrate the new year when 0:13:55.240 --> 0:13:58.000 we fad three hundred and sixty five days, which means 0:13:58.080 --> 0:14:01.000 the new year we celebrate is not actually how long 0:14:01.040 --> 0:14:04.240 it takes to go overround the Sun, and we build 0:14:04.280 --> 0:14:07.720 up this difference for three years until every fourth year 0:14:08.120 --> 0:14:10.600 we add a whole new day to the year on 0:14:11.120 --> 0:14:14.439 leap years, So if you really wanted to celebrate going 0:14:14.480 --> 0:14:17.360 around the Sun a full orbit, you should wait until 0:14:17.400 --> 0:14:20.480 about six am on New Year's Day to set off 0:14:20.520 --> 0:14:24.600 those fireworks. The other interesting thing about the physics of 0:14:24.640 --> 0:14:27.760 the new year is that the new year also doesn't 0:14:27.840 --> 0:14:31.360 celebrate the passing of the seasons. We're used to thinking 0:14:31.360 --> 0:14:33.520 that a year is when we've had a full cycle 0:14:33.600 --> 0:14:37.640 of winter, spring, summer, and fall, but actually our orbit 0:14:37.720 --> 0:14:41.240 and the seasons are slowly going out of sink. 0:14:42.560 --> 0:14:46.960 We celebrate New Year's conspicuously around the winter solstice, right, 0:14:47.240 --> 0:14:51.320 but those events have changed where they would fall in 0:14:51.360 --> 0:14:52.800 the year over time. 0:14:52.720 --> 0:14:56.080 Because of the wobble of the spinactive of the Earth. Yeah, 0:14:56.120 --> 0:14:59.040 all right, this one's a little hard to explain. Right now. 0:14:59.160 --> 0:15:02.800 We celebrate the New ye near the winter solstice, which 0:15:02.840 --> 0:15:05.600 is the longest night of the year for people in 0:15:05.640 --> 0:15:08.600 the Northern hemisphere, and it's the longest night of the 0:15:08.680 --> 0:15:12.480 year because that's when the northern hemisphere is tilted the 0:15:12.520 --> 0:15:18.240 most away from the Sun. Then six months later, when 0:15:18.280 --> 0:15:20.760 the Earth has gone through half of its orbit, the 0:15:20.800 --> 0:15:25.000 northern hemisphere is tilted the most towards the Sun, making 0:15:25.040 --> 0:15:28.240 it the longest day of the year for people above 0:15:28.360 --> 0:15:32.880 the equator. This is called the summer solstice, and right now, 0:15:33.080 --> 0:15:37.160 those two solstices fall on December twenty first and June 0:15:37.320 --> 0:15:40.320 twenty first. But as we talked about in the previous 0:15:40.360 --> 0:15:44.920 episode about the North Coal, the Earth is wobbling, which 0:15:44.920 --> 0:15:49.480 means its spin axis is rotating and changing direction, sort 0:15:49.480 --> 0:15:51.800 of like a top that wobbles as it spins on 0:15:51.840 --> 0:15:55.840 a table. Scientists think that in thirteen thousand years, that 0:15:55.960 --> 0:15:58.760 wobbling is going to make the Earth tilt in the 0:15:58.800 --> 0:16:02.880 opposite direction, which means the winter and summer solstices are 0:16:02.920 --> 0:16:07.360 going to switch. In thirteen thousand years, the summer solstice 0:16:07.480 --> 0:16:10.520 is actually going to be on December twenty first, and 0:16:10.560 --> 0:16:15.240 the winter solstice will be June twenty first. In other words, 0:16:15.360 --> 0:16:18.080 in thirteen thousand years, those of us in the Northern 0:16:18.080 --> 0:16:21.360 Hemisphere are going to be celebrating New Year's Day in 0:16:21.400 --> 0:16:25.000 the middle of summer. It's going to be hot, and 0:16:25.200 --> 0:16:28.080 at least in the United States, if the United States 0:16:28.120 --> 0:16:30.960 still exists in thirteen thousand years, we're going to be 0:16:30.960 --> 0:16:34.280 celebrating the fourth of July in the dead of winter. 0:16:34.960 --> 0:16:38.080 And that's because the seasons follow the tilt of the Earth, 0:16:38.480 --> 0:16:41.520 and the tilt of the Earth is changing regardless of 0:16:41.560 --> 0:16:43.360 our orbit around the Sun. 0:16:46.120 --> 0:16:49.600 Earth has a round enough orbit that the electricity of 0:16:49.640 --> 0:16:52.680 the Earth's orbit is not a predominant cause of season. 0:16:54.000 --> 0:16:56.840 I see, yeah, so it's mostly just this tilt. 0:16:56.920 --> 0:16:59.520 But that's wobbling. So that means that in like ten 0:16:59.560 --> 0:17:03.360 thousand years, it's going to be summer in New Year's Yes. 0:17:03.720 --> 0:17:06.920 If you're in the northern hemisphere, what so everyone will 0:17:06.960 --> 0:17:07.680 be like Hawaii. 0:17:09.440 --> 0:17:12.720 So our year is not really defined by the seasons. 0:17:12.840 --> 0:17:17.920 Yeah, seasons will slowly drift over thousands of years time scales, 0:17:18.040 --> 0:17:20.840 thirteen thousand year time scales, right, it will change. Oh 0:17:21.840 --> 0:17:24.159 so yeah, So that's why I don't know when we 0:17:24.200 --> 0:17:27.919 talk about stoneheads being aligned for the summer solstice, I 0:17:27.920 --> 0:17:30.440 think maybe it's not aligned in the same way as 0:17:30.440 --> 0:17:32.720 it was when they built it. 0:17:34.359 --> 0:17:37.359 What does that mean? It means New Year's Day is 0:17:37.440 --> 0:17:39.040 totally unrelated to the seasons. 0:17:39.280 --> 0:17:42.480 Yes, in the long game, New Year's Day is totally 0:17:42.560 --> 0:17:43.639 unrelated to the season. 0:17:43.720 --> 0:17:47.400 It's also arbitrary and changing at the same time. Yes, 0:17:48.760 --> 0:17:51.680 these things we think are like, you know, set points 0:17:51.680 --> 0:17:55.439 in our lives, in our cycle of society are really 0:17:55.640 --> 0:17:58.640 in the long run due to physics changing. 0:17:58.520 --> 0:17:59.680 Yeah, or due to culture. 0:18:00.400 --> 0:18:02.160 You know, that's wild. 0:18:02.640 --> 0:18:04.120 Yeah, nothing is fixed. 0:18:04.359 --> 0:18:07.800 You can't trust anything. Man, Just live with the impermanence. 0:18:08.200 --> 0:18:11.760 He live in the moment. Just enjoy the holidays. 0:18:11.960 --> 0:18:13.439 Yes, okay. 0:18:13.520 --> 0:18:15.840 So to recap, the length of the year that we 0:18:15.920 --> 0:18:18.480 have right now on Earth is the result of a 0:18:18.560 --> 0:18:23.080 gigantic crash that happened billions of years ago that merge 0:18:23.200 --> 0:18:26.199 two small planets together and put them in a single 0:18:26.400 --> 0:18:30.280 orbit around the Sun. That orbit is pretty constant. The 0:18:30.400 --> 0:18:33.280 length of the year is not changing, even though the 0:18:33.480 --> 0:18:36.320 orbit is not a perfect circle, and we move around 0:18:36.320 --> 0:18:39.520 the Sun at different speeds at different times of the year. 0:18:40.000 --> 0:18:42.359 But what is changing is the tilt of the Earth, 0:18:42.640 --> 0:18:45.959 which is what determines the seasons. So in the future, 0:18:46.160 --> 0:18:49.320 we're going to be celebrating new Years in opposite seasons 0:18:49.400 --> 0:18:52.840 from how we celebrated today. People in the northern hemisphere 0:18:52.880 --> 0:18:55.600 will celebrate it in the middle of summer, and people 0:18:55.640 --> 0:18:58.480 in the southern hemisphere will celebrate it in the middle 0:18:58.600 --> 0:19:03.320 of winter. Case it's still a celebration of surviving another 0:19:03.400 --> 0:19:07.879 spin around the Sun plus or minus five hours and 0:19:08.200 --> 0:19:11.320 forty eight minutes. All right, When we come back, we're 0:19:11.359 --> 0:19:14.680 going to recap our favorite episodes of the year, including 0:19:14.800 --> 0:19:17.800 which one surprised me the most and which one was 0:19:17.840 --> 0:19:21.240 the most fun to make. So stay with us, we'll 0:19:21.280 --> 0:19:38.480 be right back. Hey, welcome back, Okay. In this third segment, 0:19:38.760 --> 0:19:40.719 I thought it'd be fun to recap some of our 0:19:40.760 --> 0:19:44.040 favorite episodes of the year. In twenty twenty five, we 0:19:44.160 --> 0:19:47.760 made forty three episodes on a wide range of topics. 0:19:47.960 --> 0:19:51.360 We asked questions about animals, like do our pets lie 0:19:51.400 --> 0:19:59.040 to us, can animals appreciate music? And do animals have consciousness? 0:20:00.840 --> 0:20:04.800 We wondered about space topics like what's inside a black hole? 0:20:06.720 --> 0:20:12.320 Or where are all the aliens? And can we terraform mars? 0:20:13.040 --> 0:20:16.600 We also explored questions about technology like what is a 0:20:16.680 --> 0:20:20.600 quantum computer? Can we upload our brains to the cloud? 0:20:21.600 --> 0:20:26.720 And can you survive being cryogenically frozen? And we answered 0:20:26.840 --> 0:20:30.320 questions about evolution and the human body and brain like 0:20:30.680 --> 0:20:32.960 why do we have five fingers? Do we have to 0:20:33.000 --> 0:20:35.760 wait thirty minutes after eating before you can go swimming? 0:20:37.040 --> 0:20:40.160 And it is food coloring that for you? I could 0:20:40.200 --> 0:20:42.600 go on and on. So if you haven't gone through 0:20:42.640 --> 0:20:45.200 our archive in a while, I encourage you to go 0:20:45.280 --> 0:20:48.480 check it out. I guarantee all the episodes are fascinating. 0:20:49.240 --> 0:20:51.400 To pick which ones to recap, I ask the people 0:20:51.400 --> 0:20:54.119 who work on the show to pick their favorite episodes. 0:20:54.640 --> 0:20:58.520 So first up is our sound mixer, engineer and general 0:20:58.680 --> 0:21:02.879 manager of the show, Casey pegram. Casey is the reason 0:21:03.000 --> 0:21:05.840 I and every guest on the show sound great. And 0:21:05.920 --> 0:21:10.000 believe me, we're recording pretty suboptimal conditions most of the time. 0:21:10.480 --> 0:21:12.359 So the fact that the show stays on track and 0:21:12.520 --> 0:21:15.080 sounds like it was all recorded in the studio. Is 0:21:15.119 --> 0:21:18.879 all thanks to his magic. Back in October, Casey picked 0:21:18.880 --> 0:21:23.520 this episode as his favorite Don't pull the plug and 0:21:23.520 --> 0:21:27.119 get ready to live inside our electronic mind as we 0:21:27.280 --> 0:21:31.160 answer the question can you upload your brain to a computer. 0:21:32.280 --> 0:21:35.359 So, the idea of mind uploading, which is like a 0:21:35.440 --> 0:21:40.280 hypothetical future technology, is that if you make a simulation 0:21:40.560 --> 0:21:44.840 of the human brain, and you make it refined enough, 0:21:45.160 --> 0:21:47.879 it will be as good as the real thing. And 0:21:48.080 --> 0:21:50.880 the hope is that if it's good enough, we can 0:21:51.119 --> 0:21:55.280 use this technology to migrate over to machines. 0:21:55.760 --> 0:21:59.800 Yeah, it's in principle possible for you to capture that 0:22:00.080 --> 0:22:02.760 level of detail from a human brain. We do it 0:22:02.800 --> 0:22:07.720 from animal brains all the time. Unfortunately, those methods. 0:22:07.359 --> 0:22:08.800 Require that you die. 0:22:10.280 --> 0:22:13.120 We don't yet have wadys of looking at it without 0:22:13.320 --> 0:22:17.199 taking chunks of your brain out, essentially pickling them and 0:22:17.240 --> 0:22:18.760 then slicing them into. 0:22:18.760 --> 0:22:22.560 Very very thin sections of brain. But what you're getting 0:22:22.840 --> 0:22:26.600 is the instant after you had actually died. So I 0:22:26.640 --> 0:22:29.960 don't think you would want to be necessarily preserved in 0:22:30.040 --> 0:22:31.080 that state, right. 0:22:32.160 --> 0:22:34.960 Casey said he found this episode interesting because of the 0:22:35.040 --> 0:22:39.320