Speaker 1: Welcome to Tech Stuff, a production from iHeartRadio. Hey there,
Speaker 1: and welcome to tech Stuff. I'm your host Jonathan Strickland.
Speaker 1: I'm an executive producer with iHeartRadio and how the tech
Speaker 1: are here. It is time for a classic episode. This
Speaker 1: one is called How Lego Works. Originally published on February
Speaker 1: twenty fourth, twenty sixteen. This was really cool because this
Speaker 1: came out shortly after we were learning about how Lego
Speaker 1: had detected gravitational waves, which up to that point had
Speaker 1: largely been a hypothetical concept. So this was one of
Speaker 1: those things where we finally figured out a way to
Speaker 1: detect something that had been hypothesized about but previously undetected,
Speaker 1: So really cool use of technology. Then the Ligo Observatory
Speaker 1: had picked up a gravitational wave, and this was huge
Speaker 1: news around the world. And in case you were wondering,
Speaker 1: what the heck is this news all about? How did
Speaker 1: they pick up that gravitational wave? What exactly is the
Speaker 1: technology powering our sensors to detect this stuff? How does
Speaker 1: it all work? That's what this episode's all about. So
Speaker 1: this was the very first time anyone had been able
Speaker 1: to measure a gravitational wave directly So today we're going
Speaker 1: to talk all about what that means and how it happened. Now,
Speaker 1: to begin with, we need to lay some groundwork and
Speaker 1: to really get an understanding of what gravitational waves are.
Speaker 1: So gravitational waves ultimately were one of the predictions made
Speaker 1: by a certain Albert Einstein with this theory of general relativity.
Speaker 1: So in that theory, Einstein presented this idea that our
Speaker 1: universe is filled with spacetime. If you're a fan of
Speaker 1: science fiction, you have undoubtedly come across that term star
Speaker 1: trek is all about the spacetime continuum, and that you've
Speaker 1: got to be careful. You could rip a hole in
Speaker 1: the fabric of spacetime. As far as we know, that's
Speaker 1: not really that possible. I mean, black holes could sort
Speaker 1: of be that maybe, But at any rate, spacetime itself
Speaker 1: is this calling it stuff is probably the wrong way
Speaker 1: of putting it, but it is like a fabric and
Speaker 1: mass hangs inside this fabric, And by mass, i'm talking
Speaker 1: about stuff like stars or even an entire solar systems
Speaker 1: or galaxies that hang in this fabric, and just like
Speaker 1: you would see in a two dimensional display, it ends
Speaker 1: up curving the fabric around the mass. We often talk
Speaker 1: about this in terms of a very simple example that's
Speaker 1: easy to imagine. You get some sort of stretching material.
Speaker 1: Often you'll just hear someone say, okay, get a trampoline.
Speaker 1: You've got a trampoline, and you put a big, heavy
Speaker 1: bowling ball on the trampoline. So that bowling ball is
Speaker 1: going to deform the trampoline surface. It's no longer going
Speaker 1: to be straight. It's going to end up curving around
Speaker 1: the bowling ball to some extent, creating kind of a
Speaker 1: dmple where the bowling ball has has created this impression
Speaker 1: inside the trampoline, and as long as the bowling ball
Speaker 1: is there, that impression is going to stay. This is
Speaker 1: sort of the like the way spacetime curves around giant
Speaker 1: masses like stars and black holes things like that. Of course,
Speaker 1: we have to remember that spacetime is actually four dimensional,
Speaker 1: not a two dimensional thing like a trampoline. I mean,
Speaker 1: I know that trampolines technically have three dimensions, but we're
Speaker 1: really looking at a surface, so it's more like a
Speaker 1: two dimensional plane. In reality. In spacetime it's four dimensional
Speaker 1: because you've got the three spatial dimensions plus time, and
Speaker 1: that is a little difficult to get your head around.
Speaker 1: But that's why we tend to look at this two
Speaker 1: dimensional example. It's a lot easier for us to imagine.
Speaker 1: So let's go a little further with that analogy to
Speaker 1: kind of talk about gravity. See Einstein proposed that gravity
Speaker 1: was a manifestation of this curved space time. And if
Speaker 1: we take that trampoline example, Let's say that you have
Speaker 1: a regular trampoline. You haven't put the bowling ball on
Speaker 1: there yet, so it's a nice flat surface, and you
Speaker 1: have a marble, and you roll the marble across the
Speaker 1: surface of the trampoline. So if there's nothing else there,
Speaker 1: and if the trampoline is level, if the surface is level,
Speaker 1: the marble should just roll in the straight line from
Speaker 1: one side of the trampoline to the other, no problem.
Speaker 1: Now let's say you put that big, heavy bowling ball
Speaker 1: on the trampoline. It creates that dimple, and then you
Speaker 1: try and roll the marble across the trampoline surface. Well,
Speaker 1: now that dimple is going to end up affecting the
Speaker 1: pathway of the marble. It's going to start to spiral
Speaker 1: inward toward the bowling ball. Ultimately it'll end up making
Speaker 1: contact with the bowling ball, and Einstein said, that's essentially
Speaker 1: what gravity is. It's that you've got these large masses
Speaker 1: that curves spacetime to the extent that smaller masses are
Speaker 1: spiraling inward toward the large mass. It's just happening on
Speaker 1: a scale that's much much, much larger than any bowling ball,
Speaker 1: marble example. But that this isn't essentially what we see
Speaker 1: when we see planets orbiting a sun, or we see
Speaker 1: a moon orbiting a planet, or we see star systems
Speaker 1: orbiting a galaxy, you know, the center of a galaxy,
Speaker 1: and it's all because of this curve spacetime. Now, all
Speaker 1: of that already is pretty heavy stuff. And keep in mind,
Speaker 1: there was not really any way to directly observe this.
Speaker 1: It was mostly the the just Einstein using logic to
Speaker 1: work all this out and math, logic and math, and
Speaker 1: ultimately it fit with what we saw of the universe.
Speaker 1: But we weren't able to test a lot of this.
Speaker 1: But then it gets even more mind blowing because now
Speaker 1: we have to get to gravitational waves. So Einstein said
Speaker 1: that if a mass were large enough and either changed
Speaker 1: shape rapidly enough or it changed its movement in some way,
Speaker 1: really really quickly. It would cause ripples of space time
Speaker 1: to move outward from that event at the speed of light.
Speaker 1: And those ripples are what we call gravitational waves, which
Speaker 1: are different from gravity waves. By the way, I have
Speaker 1: been known to accidentally say gravity waves instead of gravitational waves,
Speaker 1: but the two are different things. A gravity wave is
Speaker 1: a wave that exists because of gravity. In other words,
Speaker 1: it's a physical wave of some sort of fluid system,
Speaker 1: whether it's atmosphere or water or some other liquid. That's
Speaker 1: a gravity wave on a planet's surface. It's not the
Speaker 1: same thing as a gravitational wave, which is really a
Speaker 1: ripple of space time, and like I said, it moves
Speaker 1: outward from that event at the speed of light. And
Speaker 1: stuff that could cause significant gravitational waves, things that would
Speaker 1: be big enough for us to potentially pick up here
Speaker 1: on Earth if we had the right equipment, would include
Speaker 1: things like two black holes orbiting or colliding with one another,
Speaker 1: which in fact, that was the event that we were
Speaker 1: able to pick up with the Ligo facilities. And I'll
Speaker 1: talk about those in just a bit. But there could
Speaker 1: be other stuff too, like neutron stars orbiting one another
Speaker 1: fast enough would generate gravitational waves, or a supernova explosion
Speaker 1: would create one as well. And each of these events
Speaker 1: give off a huge amount of energy, and some of
Speaker 1: that energy gets converted into making these gravitational waves. So
Speaker 1: one takeaway from this prediction something that Einstein said would happen,
Speaker 1: is that any event that produces gravitational waves is an
Speaker 1: event in which energy is being lost, So you would
Speaker 1: expect to see less energy within that system afterward than before.
Speaker 1: And it would be a hundred years from the time
Speaker 1: of publication of the theory of general relativity to the
Speaker 1: time when scientists announced that they had detected a gravitational
Speaker 1: wave directly. And that's because gravitational waves are devilishly difficult
Speaker 1: to detect. And that's some alliteration for you right there.
Speaker 1: So gravitational waves are invisible. They don't emit any sort
Speaker 1: of electromagnetic radiation, so we can't see them. We can't
Speaker 1: detect them with radio detectors, nothing like that, and that
Speaker 1: makes it pretty tricky to figure out where they are.
Speaker 1: But they do just pass through the universe. They don't
Speaker 1: get absorbed or scattered the way electromagnetic radiation does. If
Speaker 1: you hold up a mirror and light hits the mirror,
Speaker 1: light will bounce off the mirror. That's not the case
Speaker 1: with gravitational waves. They pass right through, so it's a
Speaker 1: very different thing than electromagnetic radiation. And while they're generated
Speaker 1: from enormous events, the gravitational waves aren't very strong. By
Speaker 1: the time they get to Earth. They are pretty weak,
Speaker 1: so weak that you would need an incredibly sensitive tool
Speaker 1: in order to pick them up. And also you have
Speaker 1: to be searching at the right time, because if the
Speaker 1: event that generated the gravitational waves happened a billion years ago,
Speaker 1: but the location is four billion light years from Earth,
Speaker 1: then we would have to wait another three billion years
Speaker 1: for those gravitational waves to get to us, because again,
Speaker 1: they travel at the speed of light. That's their limit.
Speaker 1: So you have to be at the right place at
Speaker 1: the right time to pick these things up, and in
Speaker 1: some cases you might argue that that's incredibly fortuitous. Although
Speaker 1: to be fair, it looks like the events that could
Speaker 1: generate gravitational waves happen pretty frequently throughout the universe. But
Speaker 1: the universe is huge, so if they're happening far away,
Speaker 1: far enough away, will take a very long time for
Speaker 1: that information to get to us. So before the announcement
Speaker 1: on February eleventh, twenty sixteen, scientists had observed phenomena that
Speaker 1: supported the existence of gravitational waves, but were not direct
Speaker 1: observations of a gravitational wave. Here's an example. A pair
Speaker 1: of astronomers in Puerto Rico in the nineteen seventies noticed
Speaker 1: that there was a binary pulsar system and they went
Speaker 1: back to the theory of general relativity because this was
Speaker 1: a sort of system that would be exactly the type
Speaker 1: to generate gravitational waves according to the predictions from general relativity,
Speaker 1: and because general relativity predicted, hey, if it can create
Speaker 1: gravitational waves, it's going to lose energy over time, they
Speaker 1: ended up coming up with the hypothesis that, well, over time,
Speaker 1: this binary pulsar system should start to slow down because
Speaker 1: it's losing energy. It can't keep up at the speed
Speaker 1: it's going. So they decided to keep an eye on it.
Speaker 1: And by keeping an eye on it, I mean they
Speaker 1: continue to observe this pulsar system over the course of
Speaker 1: eight years, and by the end of the eight year period,
Speaker 1: they were comparing the findings they were observing to the
Speaker 1: predictions made by general relativity, and they were matching up.
Speaker 1: It was unfolding exactly the way Einstein predicted it should
Speaker 1: unfold based upon his theory of general relativity, which is
Speaker 1: incredible when you think about it, that the observations are
Speaker 1: matching up so neatly against the predictions. You know, it
Speaker 1: just shows how how keenly aware Einstein was of how
Speaker 1: our universe appears to work. Keeping in mind that general relativity,
Speaker 1: while an amazing idea collection of ideas, really it doesn't
Speaker 1: encompass everything that we know, right. It doesn't really address
Speaker 1: quantum mechanics, for example, at least not in a way
Speaker 1: that incorporates it with classical physics. But based upon what
Speaker 1: it did cover, it seems like it was an incredibly
Speaker 1: accurate theory, all right. So this was really considered strong
Speaker 1: but indirect support of gravitational waves, because again the astronomers
Speaker 1: didn't observe gravitational waves directly. They couldn't see them or
Speaker 1: detect them, but they could see the effects, and again
Speaker 1: it was matching up with the predictions made from general relativity.
Speaker 1: So it was good indirect evidence that gravitational waves existed.
Speaker 1: Then there was an event a couple of years ago
Speaker 1: that you might have heard about when a team of
Speaker 1: researchers working on the BICEP two telescope, which is an
Speaker 1: Antarctica had announced that they thought they might have discovered
Speaker 1: evidence of gravitational waves that supported a hypothesis called cosmic inflation.
Speaker 1: That's a lot of information right there, So let me
Speaker 1: explain what all that means. Cosmic inflation is a hypothesis
Speaker 1: that relates to the Big Bang theory. So, with the
Speaker 1: Big Bang theory, you've got this event in which the
Speaker 1: universe undergoes a period of rapid expansion. Cosmic inflation is
Speaker 1: kind of that rapid expansion on steroids. The idea being that, well,
Speaker 1: when we look at our universe and we look at
Speaker 1: what we can observe, it appears that our observations don't
Speaker 1: quite match up with what we would expect if we
Speaker 1: had just steady expansion since the Big Bang. In other words,
Speaker 1: we look at all the information we have available to us,
Speaker 1: and it looks to us that it doesn't quite match up.
Speaker 1: Something's got to be wrong. Well, one possible explanation is
Speaker 1: that shortly after the Big Bang, and by shortly, I
Speaker 1: mean tend to the negative thirty sixth power seconds after
Speaker 1: the Big Bang, So you take a ten, you put
Speaker 1: a decimal point behind the ten, then you move the
Speaker 1: decimal point to the left thirty six times that you
Speaker 1: put seconds behind that. We're talking a fraction of a
Speaker 1: fraction of a fraction of a second. The universe underwent
Speaker 1: massive expansion, and it only lasted from that point to
Speaker 1: about ten to the negative thirty third power or thirty
Speaker 1: second power seconds. So again an instant. It's completely unimaginable,
Speaker 1: at least for myself, how short an amount of time
Speaker 1: this was. But that's how quickly the universe expanded significantly,
Speaker 1: and then it slowed, but it continued to expand. Now,
Speaker 1: if in fact, cosmic inflation is correct, it solves a
Speaker 1: lot of the problems we have between the what we
Speaker 1: observe today and what we believe happened with the Big Bang,
Speaker 1: and reconciles those differences. If cosmic inflation is wrong, then
Speaker 1: something else that we believe is wrong. Right. It means
Speaker 1: that what we observe either isn't representative of reality somehow
Speaker 1: we're not getting a big enough picture to understand it,
Speaker 1: or that the Big Bang theory itself is flawed in
Speaker 1: some fundamental way. Hey, we'll be back with this heavy
Speaker 1: subject of detecting gravitational waves with LEGO after this short break,
Speaker 1: so the BIS of two team what they were looking
Speaker 1: for was some evidence of gravitational waves that would have
Speaker 1: been generated during the Big Bang. This would end up
Speaker 1: supporting the cosmic inflation hypothesis. And the way they did
Speaker 1: this was they were looking at the cosmic microwave background
Speaker 1: or CMBAM. Now, the cosmic microwave background emerged about three
Speaker 1: hundred eighty thousand years after the Big Bang. This was
Speaker 1: still a period where the universe was so dense that
Speaker 1: I could not pass through it. It was dark and dense,
Speaker 1: but the cosmic microwave background formed around that time, and
Speaker 1: the hypothesis stated, well, gravitational waves would have affected the
Speaker 1: cosmic microwave background, polarizing some of those some of those
Speaker 1: particles really not particles, but some of that energy polarizing
Speaker 1: some of the cosmic microwave background in such a way
Speaker 1: that if you were to observe it, you could see
Speaker 1: the effect of a gravitational wave passing through the cmb
Speaker 1: And then as the universe expand expanded, rather that mark
Speaker 1: would also expand. It's kind of like imagine leaving a
Speaker 1: fingerprint on some sort of stretchy material and then stretching
Speaker 1: that material out, the fingerprint is still there. It's deformed,
Speaker 1: but still there. That's what the BICEP two team was
Speaker 1: looking for, was this pattern in the CMB that would
Speaker 1: indicate that gravitational waves from the Big Bang had passed through,
Speaker 1: and if they found that, that would be a huge
Speaker 1: support for cosmic inflation. And in the spring of twenty fourteen,
Speaker 1: they announced that they believed they had found such evidence,
Speaker 1: and they also invited other researchers to take a look
Speaker 1: at their data and see if it was verifiable or
Speaker 1: maybe they overlooked something. And in the fall of twenty fourteen,
Speaker 1: another team said, we're sorry, but it looks to us
Speaker 1: like space dust might have created a false positive that
Speaker 1: what you thought it was the polarized CMB that you
Speaker 1: had been looking for was actually just space dust that's
Speaker 1: not actually part of the CMB. And so that ended
Speaker 1: up kind of putting a dampener on the whole celebration
Speaker 1: of finding gravitational waves to support cosmic inflation. But even
Speaker 1: if it was completely verified, even if BICEP two had
Speaker 1: irrefutable evidence that they had found the presence of gravitational
Speaker 1: waves through a you know, the way it affected the CMB.
Speaker 1: Even then that's not direct detection. It's still indirect. You're
Speaker 1: looking at the way it's affected something else. So you know,
Speaker 1: again we're still not discovering one. And part of that
Speaker 1: is that BICEP two is a telescope. It's looking at
Speaker 1: through the electromagnetic spectrum, and again, gravitational waves don't show
Speaker 1: up that way. So no telescope would help you find
Speaker 1: a gravitational wave directly. You might be able to find
Speaker 1: how it affected something else, but not the wave itself.
Speaker 1: Now that's not the case with the LIGO observatories. Actually
Speaker 1: it's technically one observatory, but it has four different facilities,
Speaker 1: two detectors and two research facilities that are all part
Speaker 1: of the LIGO observatory. LIGO itself is an acronym and
Speaker 1: it stands for Laser Interferometer Gravitational Wave Observatory. So it's
Speaker 1: a pair of giant detectors built on the surface of
Speaker 1: the Earth. One is located in Hanford, Washington, the other
Speaker 1: is in Livingstone, Louisiana. Now they're about just a little
Speaker 1: under two thousand miles apart, or just over three thousand
Speaker 1: kilometers apart from each other, and that's really important. I'll
Speaker 1: explain why in a little bit. So to understand how
Speaker 1: they work, we also have to talk about something else
Speaker 1: that gravitational waves do as they pass through space. They
Speaker 1: stretch and compress space itself. So again, if you were
Speaker 1: if you were to take a piece of elastic, I'd say,
Speaker 1: you've got a rubber band, a nice thick rubber band,
Speaker 1: and you cut it so that it's just one strip.
Speaker 1: When you pull on that rubber band, it stretches along
Speaker 1: the line where you're applying force, So it stretches in
Speaker 1: that direction, in the perpendicular direction ninety degrees from where
Speaker 1: you're pulling. It compresses, it gets more narrow, and then
Speaker 1: when you let it return to its normal shape, it
Speaker 1: gets you know, the long part ends up getting shorter
Speaker 1: and the narrow part ends up getting wider as a result,
Speaker 1: gravitational waves do this to reality. They do this to
Speaker 1: actual space. They stretch and compress, and it happens several
Speaker 1: times as the wave oscillates through. Really I should just
Speaker 1: say as the wave passes through, rather than oscillates. The
Speaker 1: distortion oscillates, but the wave passes through, so That means
Speaker 1: the actual distance changes between two points as that gravitational
Speaker 1: wave passes through that area. So if we were to
Speaker 1: magnify this effect, and I mean magnify it to a
Speaker 1: ludicrous degree, you would be able to see it. You
Speaker 1: would actually be able to witness this. You could stand
Speaker 1: ten feet away from someone else and when the gravitational
Speaker 1: wave passes through, it would make it look like the
Speaker 1: two of you suddenly got further away and then closer
Speaker 1: to each other, and then further away and closer to
Speaker 1: each other, even though you haven't moved anywhere, because the
Speaker 1: distance itself is stretching and compressing. So why don't we
Speaker 1: see that? I mean, if these celestial events that produce
Speaker 1: gravitational waves happen on the order of something like every
Speaker 1: fifteen minutes, why are we all noticing this whibbly wobbly effect. Well,
Speaker 1: it's because the actual distortion that happens here on Earth
Speaker 1: is much much much smaller in magnitude, so much more
Speaker 1: so much smaller that it's difficult to even explain. But
Speaker 1: if you were to have a supernova explode in the
Speaker 1: Milky Way galaxy, in our galaxy, the gravitational waves generated
Speaker 1: by that explosion would maybe be powerful enough to distort
Speaker 1: the distance between the Earth and the Sun by about
Speaker 1: the diameter of a hydrogen atom, so not noticeable to
Speaker 1: any degree, and not at least to human senses. So
Speaker 1: if you were to even go on a smaller scale,
Speaker 1: let's say that you pick two points that are a
Speaker 1: kilometer apart here on the surface of the Earth, the
Speaker 1: amount of distortion would be equivalent to a few thousandth
Speaker 1: of the diameter of a proton, So you're talking about
Speaker 1: a subatomic particle, and just a tiny, tiny, tiny fraction
Speaker 1: of that subatomic particles diameter would be the amount of
Speaker 1: distortion that would happen across a kilometer worth of distance
Speaker 1: here on Earth. Again, that means it's so small that
Speaker 1: it's incredibly difficult to detect, so much so that Einstein
Speaker 1: himself was pretty sure we would never be able to
Speaker 1: directly detect gravitational waves because he could not imagine a
Speaker 1: system that would be sensitive enough to pick up such
Speaker 1: a minute change, a distortion that's happening so quickly because
Speaker 1: it's a fraction of a second, and it's so small
Speaker 1: as to be unnoticeable. So the other problem here is
Speaker 1: not just that it's such a very tiny effect that
Speaker 1: lasts a short amount of time. It's also that a
Speaker 1: lot of other stuff could create false positives. You can
Speaker 1: have incredibly instrumentation, but if that instrument is really really sensitive,
Speaker 1: any sort of interference could set off and you could
Speaker 1: end up getting false readings. So a change in air
Speaker 1: pressure or temperature, or seismic activity, even a heavy truck
Speaker 1: driving nearby could set off false results. So you'd have
Speaker 1: to come up with a really clever way to measure distortion,
Speaker 1: to limit vibration, and to eliminate the chance that it
Speaker 1: was a false positive. And Lego is the answer to
Speaker 1: all of that. So the Lego Observatory is actually the
Speaker 1: result of decades of collaborative work among different scientific research
Speaker 1: centers and internet national bodies and universities, and all started
Speaker 1: back in nineteen seventy nine. That's when the National Science
Speaker 1: Foundation approved funds for Caltech and MIT to develop laser
Speaker 1: interferometer research and development. And a few years later, in
Speaker 1: nineteen eighty three, Caltech and MIT submitted a proposal for
Speaker 1: a kilometer scale detector. But keep in mind, all right,
Speaker 1: so in nineteen seventy nine you get the funding for
Speaker 1: R and d nineteen eighty three, there's the submission of
Speaker 1: a proposal for a kilometer scale detector. There wouldn't be
Speaker 1: approval for a detector until nineteen ninety, so almost a
Speaker 1: decade later, and which turns out was probably okay, because
Speaker 1: we really didn't have the technological ability to detect things
Speaker 1: on a scale small enough to register a gravitational wave
Speaker 1: in the first place. But still, you know, a decade's
Speaker 1: delay before you even get approval is still pretty rough.
Speaker 1: Construction didn't begin until nineteen ninety four. The inauguration of
Speaker 1: the Ligo Observatory took place in nineteen ninety nine, but
Speaker 1: even then that didn't mean that the observatory was online
Speaker 1: collecting data. It didn't do that until two thousand and two.
Speaker 1: And here's the kicker. Eventually scientists came to the conclusion
Speaker 1: that this Ligo observatory was not sensitive enough to detect
Speaker 1: gravitational waves. That despite the fact that it was this
Speaker 1: large detector or pair of large detectors, actually because again
Speaker 1: one in Louisiana one in Washington, it wasn't sensitive enough
Speaker 1: to be effective. So it was not quite back to
Speaker 1: the drawing board, but it did mean that they had
Speaker 1: to think about how they would upgrade these facilities so
Speaker 1: that they could be sensitive enough to pick up a
Speaker 1: gravitational wave. So in twenty ten, Ligo went offline to
Speaker 1: undergo a big overhaul, and it took four years of
Speaker 1: construction and testing to get it into shape and another
Speaker 1: year to set it up for new observations, which means
Speaker 1: that it wasn't until twenty fifteen that it was ready
Speaker 1: to come back online. By now it was called the
Speaker 1: Advanced Ligo Observatory and it began collecting data in September
Speaker 1: twenty fifteen. Literally days after it had come online, it
Speaker 1: picked up a gravitational wave. So that's pretty phenomenal that
Speaker 1: just a couple of days, just a few days really
Speaker 1: after it had been turned on again in twenty fifteen,
Speaker 1: we got a hit. So that was incredibly exciting. So
Speaker 1: how did this happen? How does it actually work? Well,
Speaker 1: we have to take a look at what interferometers are
Speaker 1: all about. An interferometer uses a technique in which electromagnetic
Speaker 1: waves are superimposed on one another in order to get information. Now,
Speaker 1: Ligo does this with a laser beam because it's a
Speaker 1: laser interferometer, and the laser beam gets shot through a
Speaker 1: beam splitter, and the beams, the two beams that result
Speaker 1: go down two long vacuum tubes. So both of the
Speaker 1: Lego detectors are in an L shape. So you've got
Speaker 1: these long, long vacuum tubes that extend two and a
Speaker 1: half miles or about four kilometers out from the crux
Speaker 1: from the angle where they meet up, and each one
Speaker 1: is you know, they're both the same length. They have
Speaker 1: to be exactly the same length. And the way this
Speaker 1: works is that kind of behind the crux, you've got
Speaker 1: a laser that shoots out a beam of light to
Speaker 1: a beam splitter. The splitter does exactly what it sounds like.
Speaker 1: It does. It splits the beam into two separate beams
Speaker 1: with alternating canceling wavelengths. I guess I should say, so
Speaker 1: the troughs and peaks on one match up with the
Speaker 1: peaks and troughs of the other. That's really important when
Speaker 1: we get a little further down the line here. So
Speaker 1: one of those two beams goes down one branch of
Speaker 1: this L shaped detector. The other beam goes down the
Speaker 1: other branch. And keep in mind, like I said, both
Speaker 1: of these branches are exactly the same length. Two and
Speaker 1: a half miles or four kilometers. When the laser gets
Speaker 1: to the end, they hit a mirror. Each beam hits
Speaker 1: a mirror, they come back to the point of origin,
Speaker 1: and because the two laser beams have these counteracting wavelengths,
Speaker 1: they cancel each other out, so the peaks on one
Speaker 1: cancel out the troughs of the other, and vice versa.
Speaker 1: That means that no light gets emitted through this system.
Speaker 1: And that's important because there's actually a light detector that's
Speaker 1: part of this system as well. It's looking for any
Speaker 1: sign of laser light, because a sign of laser light
Speaker 1: would say that something has changed somehow the distances between
Speaker 1: these or the distances represented by these two vacuum tubes
Speaker 1: has changed, and that would be indicative of an event
Speaker 1: like a gravitational wave moving through. So if any light
Speaker 1: shines through, you know something has happened. Essentially, it says
Speaker 1: that there's a mismatch in the lengths of the vacuum
Speaker 1: tubes themselves. So when a gravitational wave passes through, one
Speaker 1: vacuum tube will get shorter while the other gets longer.
Speaker 1: And that's because the two tubes are offset by ninety degrees,
Speaker 1: so one is going to be along one side of
Speaker 1: the wave and that will lengthen the other will be
Speaker 1: along will be perpendicular to that, and will shorten as
Speaker 1: a result. And this means that the lasers will have
Speaker 1: different distances to travel down, So the laser traveling the
Speaker 1: shorter distance takes less time to get back to the crux.
Speaker 1: The laser going down the longer distance takes more time.
Speaker 1: And even though this is only happening within a fraction
Speaker 1: of a second, it's long enough for us to be
Speaker 1: able to detect the difference. And it also means that
Speaker 1: those wavelengths don't match up anymore, they don't cancel each
Speaker 1: other out anymore. So some of that laser light gets
Speaker 1: emitted to the light detector, which then indicates what's going on.
Speaker 1: It knows which one of the branches was short versus long,
Speaker 1: and knows how long it happened. It knows how much
Speaker 1: it oscillated back and forth, because obviously this is continuing
Speaker 1: as these as the gravitational wave moves through, So you
Speaker 1: collect a lot of data in a short amount of time.
Speaker 1: And we're talking like teeny tiny slices of a second.
Speaker 1: As we're getting all this information, which is pretty incredible.
Speaker 1: We're almost done with our discussion about LEGO, but before
Speaker 1: we can do that, we need to take one more
Speaker 1: quick break. So once you get all that data, you
Speaker 1: can then analyze it. Actually, more importantly, before you analyze it,
Speaker 1: you have to verify it. Now. This is why it's
Speaker 1: important that there are two detectors, and it's also important
Speaker 1: that they are so far apart, like three thousand kilometers
Speaker 1: apart from each other. That's because if you get a
Speaker 1: blip on one of them, if it's a true gravitational wave,
Speaker 1: you should also get a blip on the other one.
Speaker 1: And because gravitational waves move at the speed of light,
Speaker 1: there should be a slight difference in time when both
Speaker 1: detectors pick up on this gravitational wave, somewhere right around
Speaker 1: ten milliseconds or less. In the case of the one
Speaker 1: that was detected back in the fall of twenty fifteen
Speaker 1: but not announced until twenty sixteen, it hit the Louisiana
Speaker 1: detector first, and seven milliseconds later it hit the Washington detector,
Speaker 1: So that is indicative of something like a gravitational wave
Speaker 1: as opposed to some local event that would have caused
Speaker 1: interference and created a false positive. If an earthquake had
Speaker 1: happened in Washington, then the facility may may have picked
Speaker 1: something up, but you wouldn't expect to see it in
Speaker 1: Louisiana because it was a localized event. Same thing is
Speaker 1: true if something had happened in Louisiana. So by seeing
Speaker 1: it happen at both within this ten millisecond timeframe meant
Speaker 1: that it was a very good candidate for a gravitational
Speaker 1: wave passing through. And that's exactly what happened. It was
Speaker 1: a home run in the first ending of the game,
Speaker 1: or even really the first at bat of the game.
Speaker 1: It's like your first player steps up on the first
Speaker 1: day of baseball and knocks a home run and that
Speaker 1: defines the moment the season. Really, that's that's the equivalent
Speaker 1: of what we saw here on a scientific basis. So
Speaker 1: the other thing I want to talk about was how
Speaker 1: LEGO tries to minimize the possibility of detecting a false
Speaker 1: positive in the first place. So, yeah, false positives are
Speaker 1: something that they worry about, and the fact that there
Speaker 1: are two detectors helps minimize that. But even so, you
Speaker 1: want to eliminate the possibility of a false positive so
Speaker 1: that you're not constantly sifting through noise looking for a signal.
Speaker 1: Do you want to minimize noise as much as possible.
Speaker 1: So Lego does this through using combinations of active and
Speaker 1: passive vibration reduction systems. One thing that they do is
Speaker 1: they remove the air from the tubes. That is why
Speaker 1: they're vacuum tubes. They remove the air for two reasons. One,
Speaker 1: they don't want any sound passing through the chambers. Sound
Speaker 1: could possibly interfere with the measurements. Sound would impact the mirrors,
Speaker 1: and even a small impact would be enough to cause
Speaker 1: a problem when you're measuring this laser. For one thing,
Speaker 1: they're looking at distances when they're measuring the changes between
Speaker 1: the two branches. You know, I mentioned that one's getting longer,
Speaker 1: one's getting smaller. The distances they're looking at are very
Speaker 1: very tiny. We're talking ten to the negative nineteenth power meters.
Speaker 1: So again, you take the number ten, you move a
Speaker 1: decimal place nineteen times to the left of that, and
Speaker 1: you put meters at the end. That's the distance that
Speaker 1: these lasers are are measuring the distortion and distance. So
Speaker 1: it's very very very tiny, and something as simple as
Speaker 1: sound could change that. So you can't have any sound
Speaker 1: in these vacuum tubes, you've got to get the air out. Also,
Speaker 1: air can absorb and scatter laser light, which would interfere
Speaker 1: with the experiment as well, so you've got to get
Speaker 1: air out. Now down to the vibration reduction systems. So
Speaker 1: the active isolation system is meant to weed out the
Speaker 1: majority of vibration, and it's active because it is actively
Speaker 1: working against any vibration it encounters. You've got sensors that
Speaker 1: detect vibration, they send commands to force actuators that move
Speaker 1: in opposition to the vibration. So it's kind of like
Speaker 1: noise canceling headphones. If you put on a pair of
Speaker 1: noise canceling headphones, what they're supposed to do is pick
Speaker 1: up any incoming sound and then generate sound waves that
Speaker 1: are in direct opposition of the incoming sound, so that
Speaker 1: you get a cancelation effect. That's the same thing that
Speaker 1: these active systems are trying to do at LIGO, except
Speaker 1: instead of it just being sound, it's really any vibration.
Speaker 1: Although I guess you could argue that any vibration really
Speaker 1: is sound, so it's kind of a moot point. But anyway,
Speaker 1: they're actively trying to counteract that vibration. But then you've
Speaker 1: got the passive system. This is the suspension system for
Speaker 1: the mirrors, and this is the next step. So you've
Speaker 1: eliminated a huge percentage of the vibration at this point,
Speaker 1: but that's not good enough. You need to eliminate as
Speaker 1: much as close to one hundred percent of the vibration
Speaker 1: as you possibly can. So next we look at the
Speaker 1: suspension system of Ligo's mirrors, and they are at the
Speaker 1: base of a four pendulum system. Meaning imagine you've got
Speaker 1: a string and it ends in a pendulum. A weight
Speaker 1: a mass of some sort, and it has to be
Speaker 1: a mass of significant size so that it will it'll
Speaker 1: resist moving. It's the law of inertia. You know, an
Speaker 1: object at rest tends to stay at rest, so it
Speaker 1: will end up absorbing a lot of vibration and minimizing
Speaker 1: it on the other end. So you've got that first pendulum,
Speaker 1: that's pendulum number one. From that you suspend pendulum number two.
Speaker 1: So already you're getting fewer vibrations because pendulum number one
Speaker 1: is picking them up. What vibrations do manage to pass
Speaker 1: through start to get picked up by pendulum number two,
Speaker 1: and again the law of inertia means that it will
Speaker 1: dampen a lot of that vibration. Then you've got pendulum
Speaker 1: number three, and then beneath that you finally have the mirror,
Speaker 1: which is forty kilograms or about eighty eight pounds worth
Speaker 1: of mirror. And hopefully, after the active impassive systems have
Speaker 1: all taken care of the vibration, nothing else is getting
Speaker 1: to that mirror. By the way, you can actually test
Speaker 1: this out yourself, if you like, by getting four strings
Speaker 1: that are all equal length, and some washers, some nice
Speaker 1: heavy washers. Tie a washer at the end of the
Speaker 1: string of the first string. Then tie a washer so
Speaker 1: that one end of the string connects to washer number one,
Speaker 1: one end of the string connects to washer number two,
Speaker 1: and so on and so forth. And if you hold
Speaker 1: it up and you start shaking your hand holding the string,
Speaker 1: notice that the washer at the top moves more than
Speaker 1: the second washer, which moves more than the third, And
Speaker 1: by the time you get down to the fourth one,
Speaker 1: it's not moving much at all because it's been the
Speaker 1: vibrations have been dampened by the previous pendulums. That's the
Speaker 1: principle of this passive system. So that helps eliminate a
Speaker 1: lot of that vibration. Without those dampening systems in place,
Speaker 1: the two LIGO detectors would be picking up a lot
Speaker 1: of noise, and since we're still not really sure how
Speaker 1: often gravitational waves pass through the Earth, that would be
Speaker 1: a problem now. Between two thousand and two and twenty
Speaker 1: and ten, with the early version of LEGO, they didn't
Speaker 1: pick up any gravitational waves at all, which we think
Speaker 1: is because the detectors weren't sensitive enough. We think that's
Speaker 1: the reason, but an alternative reason could be that gravitational
Speaker 1: waves aren't as frequent as we think they are, that
Speaker 1: they don't pass through the Earth as frequently as we
Speaker 1: otherwise believe. However, the opposite could be true. We could
Speaker 1: have way more gravitational waves passing through Earth than we
Speaker 1: had anticipated. Some of them may be so faint that
Speaker 1: even this advanced LIGO system cannot pick it up. There
Speaker 1: are already plans to upgrade LIGO again, and there are
Speaker 1: other LIGO observatory systems that will that are in development
Speaker 1: now that will also listen in for gravitational waves. And
Speaker 1: listen tends to be the way most people refer to it,
Speaker 1: like you're listening for this universal vibration moving through the Earth.
Speaker 1: So because it was only a few days after they
Speaker 1: came online, a lot of people are thinking that gravitational
Speaker 1: waves are probably fairly common. Otherwise, it was just extraordinarily
Speaker 1: lucky that we picked it up just days after the
Speaker 1: observatory was online. Again, the one that we did pick
Speaker 1: up one point three billion light years away, which means
Speaker 1: that the event happened one point three billion years ago.
Speaker 1: That event being two black holes colliding with one another
Speaker 1: to form a solitary black hole mass. In the process,
Speaker 1: it vaporized about three solar masses worth of mass I guess,
Speaker 1: which is a huge amount to think about being converted
Speaker 1: into energy, and the gravitational waves emanated from there at
Speaker 1: the speed of light. So one point three billion years later, Earth,
Speaker 1: which was one point three billion light years away, picked
Speaker 1: them up. So in a way, it was incredibly lucky.
Speaker 1: But if this happens more frequently than we originally believed,
Speaker 1: we might see that this is not an uncommon event.
Speaker 1: It's very possible that there are things we cannot see
Speaker 1: in the universe that create gravitational waves. So in other words,
Speaker 1: it's off that does not give off electromagnetic radiation at all,
Speaker 1: but it does create gravitational waves, meaning that we now
Speaker 1: have the capacity to detect things that otherwise would have
Speaker 1: remained completely undetectable by us. So one of the many
Speaker 1: reasons why this discovery is so exciting, it opens up
Speaker 1: brand new science. It creates a new discipline of science,
Speaker 1: gravitational astronomy, which can really get going now because it's
Speaker 1: not that different from when the telescope was invented. Before
Speaker 1: the telescope, astronomy was pretty limited. You could map out
Speaker 1: astrological bodies when you were way back in the day
Speaker 1: before the science of astronomy had really gotten going. Once
Speaker 1: you started figuring out the difference between mythology and science,
Speaker 1: then astronomy really takes over. You could map out where
Speaker 1: these different bodies go. You could figure out which ones
Speaker 1: are must be planets versus stars, but you couldn't really
Speaker 1: gather a lot more information than that. You could still
Speaker 1: get an impressive amount of data just from observing with
Speaker 1: the naked eye, but the telescope opened up a whole
Speaker 1: new world of study, and this gravitational wave detector system
Speaker 1: has opened up a similar, all new world that was
Speaker 1: not accessible by us until this year really late last year,
Speaker 1: late twenty fifteen, So we might end up discovering things
Speaker 1: that we've never been able to observe before. Will also
Speaker 1: likely be able to study all sorts of cool stuff,
Speaker 1: like how fast is the universe expanding, how much dark
Speaker 1: energy is in our universe. We might learn more about
Speaker 1: black holes already. The gravitational wave detected by LIGO has
Speaker 1: given us the strongest direct evidence of black holes. I
Speaker 1: guess I should say indirect evidence because it's the gravity
Speaker 1: waves generated by the black holes. But not that we
Speaker 1: ever doubted the existence of black holes, but this is
Speaker 1: yet more evidence in support of them. So it's really
Speaker 1: an exciting time. We could end up learning all sorts
Speaker 1: of stuff, stuff that we can't even anticipate right now,
Speaker 1: and that's why it's such a big deal. I also
Speaker 1: think that LEGO is just an incredibly elegant way of
Speaker 1: detecting something that otherwise is impossible for us to see
Speaker 1: or feel or experience, and it's incredibly simple, at least
Speaker 1: on the principle of it. The technology itself is very
Speaker 1: complicated because it has to be so sensitive to detect
Speaker 1: these very tiny changes in distance and time. But the
Speaker 1: principle behind it is elegant, and I mean, you don't
Speaker 1: get much more simple than a ninety degree angle. That's
Speaker 1: pretty bare bones there, but a very clever way of
Speaker 1: detecting something that Einstein believed was going to be beyond
Speaker 1: our ability to ever experience. So now we have a
Speaker 1: revolutionary new way to examine the universe. We have no
Speaker 1: way of knowing what sort of stuff we might learn
Speaker 1: as a result, which is incredibly exciting. And it's all
Speaker 1: due to some lasers, some beam splitters, and some mirrors.
Speaker 1: And since we're already looking at lots of different organizations
Speaker 1: building their own LIGO observatories and also increasing the capacity
Speaker 1: or at least the sensitivity of the current LEGO system,
Speaker 1: who knows what we're going to see next. I hope
Speaker 1: you enjoyed that classic episode on HOWLEGO works way back
Speaker 1: in twenty sixteen. I should definitely do an update on
Speaker 1: that and talk more about the sort of things we've
Speaker 1: learned since the detection of gravitational waves and how that
Speaker 1: has affected science. But if you have suggestions for things
Speaker 1: I should cover in future episodes of tech Stuff, I'd
Speaker 1: love to hear. There are a couple of different ways
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Speaker 1: It's free to downloads free to us. You can just
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Speaker 1: You'll see a little microphone icon. If you click on that,
Speaker 1: you can leave a voice message up thirty seconds in length,
Speaker 1: and I love hearing from y'all, so feel free to
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Speaker 1: of tech Stuff and I'll talk to you again really soon.
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