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Filming the Speed of Light at 10 Trillion FPS

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Mar 27, 2019

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Filming the Speed of Light at 10 Trillion FPS
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  • Today, we're at CalTech,
  • because in a building over there
  • is a camera that absolutely blows my mind.
  • Now, we've filmed at some very high frame rates.
  • We're talking up to about half a million, which is...
  • - Not to be sniffed at. - ...serious frame rates.
  • Their camera puts ours to shame
  • and does 10 trillion frames per second.
  • That's 13 zeroes.
  • For reference, that is 20 million times faster
  • than the fastest we've ever filmed on this channel.
  • And there's not much you can't film
  • with half a million frames a second,
  • but one of those things is the speed of light.
  • - Not a bad subject. - No.
  • - Let's get in there. - All right.
  • Even the shoe cover technology is cool.
  • I kind of want one of these at home, actually.
  • - Just for people. - All right, let's go in,
  • see what this CUP is all about.
  • - Nice to meet you. - Man: Nice to see you.
  • - How's it going? - Good.
  • So, what's actually--
  • what are we doing here? This looks all very complicated.
  • Oh, this is the world's fastest camera.
  • Oh, okay. Yeah. This is the world's fastest camera.
  • There you go. Just as easy as that.
  • How big is the actual camera part?
  • I can show you.
  • That big box is the camera itself.
  • And here is the optics that we designed
  • - to make the thing work. - Very cool.
  • A lot of times in our YouTube comments,
  • we get asked to film the speed of light.
  • And I have to always reply to people
  • letting them know that the speed of light,
  • it's almost incomprehensibly fast,
  • and even our cameras, under a million frames a second,
  • will never see anything like that.
  • Is this camera capable of filming the speed of light?
  • Yeah, that's basically what we are gonna see.
  • For the example I'm going to show, the light will move
  • about the length of this bottle.
  • In time, how long does it take for light to start here and end here?
  • It takes about 2,000 picoseconds.
  • - That's pretty quick. Yeah. - Pretty quick.
  • So for the audience, it goes milliseconds, microseconds...
  • - Is it nano-- - ...nanoseconds,
  • - picoseconds, femtoseconds. - Yes.
  • So we're on the sort of pico/femto scale with this stuff.
  • - We've never done that before, for sure. - Yeah, no.
  • This is completely on another level.
  • Shall we set up the first experiment?
  • - Sure, yeah. - Start with the bottle?
  • - Everyone should wear laser goggles. - Goggles?
  • - Okay. - Peng: We have some.
  • - Do I look good? - You've got side panels in your glasses.
  • - You look like you're about to-- - You look bad-ass.
  • It looks like you're about to go skiing with a welding torch.
  • It's just...
  • So, I assume because we're trying to film light,
  • it'll be useful to turn all the lights off in here, right?
  • - Yes. - Otherwise, we'll just get...
  • All the ambient light comes, yeah.
  • Right. Okay.
  • Let's get ready for lights off.
  • Yeah.
  • - Can you hold this for me? - I'll hold this.
  • - Yeah, thank you. - I'm excited.
  • I get giddy by this frame rate stuff.
  • We want to see the light propagation from the side,
  • so we need to make sure that the light is scattered out of the plane of view
  • through the milk molecules inside,
  • then you can see light scatter from the side.
  • So, this is a bottle full of water with a bit of milk in?
  • So, I am going to turn on the laser.
  • So all you do is just move mirrors and lenses around
  • and then it goes to different areas?
  • We use that to move the laser. The laser's too big.
  • See, the light hits the bottom of the bottle.
  • So it goes through the bottle.
  • - Is it a powerful laser? - It's very powerful.
  • It can basically burn any, like, papers.
  • - I will stay away from that. - Yeah.
  • - Whoa, that's cool. - You can see its glow.
  • The first thing I'm going to capture
  • is the static image
  • as our reference.
  • For today, I'm going to try...
  • - Excellent. - Yeah, yeah.
  • I mean, I remember when I was excited
  • when we started shooting,
  • we moved from 1,000 frames a second
  • - to 28,000 frames a second. - That was a big jump.
  • Okay, we're pretty much done with the water bottle.
  • I'd like to take a photo of this.
  • As you can see, we can only see the light.
  • We cannot see the bottle and the label on it.
  • - Yeah. - So, finally, in the movie, we may want to overlap
  • both the bottle itself and the light.
  • - Like, composite a real picture. - Yeah, yeah.
  • So you just take a photo on your phone and that can-- you can do that?
  • Yeah, you can just use software to overlap these two things.
  • - Gav: Neat. - Dan: You're in the photograph.
  • Just photo-bombing the bottle.
  • Okay, let's watch back our bottle.
  • This took eight hours to process,
  • during which time I grew a slightly longer beard.
  • I had a haircut as well.
  • All right, here we go.
  • Dan: Okay, so what we're seeing here
  • is the bottle's just been comped in, basically.
  • Gav: Yeah, this camera only detects the light itself,
  • which is like a blue-ish laser light,
  • which is why you don't really see anything else
  • other than the light looking like that.
  • And then we comp in the picture of the bottle.
  • In the room with my actual eye,
  • it looked like it was constantly lit up,
  • but here we're able to follow
  • the light moving through the bottle.
  • It may not look like it, but this is actually real.
  • Dan: It's refracting the photons and that's why you can see it.
  • But when it's just going through the air,
  • there's nothing to actually reflect the light.
  • Gav: Yeah, it's only showing up in the bottle.
  • It is interesting. It almost looks like sort of an '80s film effect.
  • It does, doesn't it? It looks like--
  • Like some sort of ghost flying into the room.
  • But actually, that is light.
  • Gav: Isn't that weird? Look at the scale.
  • Every frame seems to be ten picoseconds.
  • And we're just sort of casually
  • watching this light go left to right
  • through the bottle, but in reality,
  • the light is moving a million times faster
  • than a bullet.
  • - Dan: What a mental subject. - Yeah.
  • Gav: Okay, so we've shot light through milk.
  • - Next experiment? - Yep.
  • For this experiment, we designed a special cavity.
  • We call it a chaotic cavity.
  • When light comes in the cavity,
  • it will bounce back and forth multiple times
  • by the mirrors surrounding in the cavity.
  • - You're almost trapping light inside the-- - Yeah. Yeah, exactly.
  • What's the purpose of this? This egg thing?
  • This is to create a water vapor
  • surrounding the environment so that light scatters out.
  • - The same thing, like-- - Oh, so you can sort of see a little bit.
  • - Makes sense. - Yeah, so this is how the system works.
  • - Turn it on. - All right, let's go do the "experimon."
  • How long did it take you to learn to use this?
  • Uh, maybe a few months to get used--
  • - A few months to get used to it. - Yeah.
  • Because it's a really complicated system.
  • It's really complicated, is it? I hadn't noticed.
  • ( both muttering )
  • Okay, so this is the chaotic cavity
  • at 100 billion frames a second.
  • Just like nothing.
  • Gav: Once again, the duration of this video is--
  • you can't even get your head around
  • how short an amount of time it is.
  • Dan: That is amazing.
  • Gav: When we were in the room,
  • it looked like the whole thing was glowing,
  • but now we can see the individual pulse of light
  • bouncing around this thing.
  • Looks like a weird version of "Pong."
  • This is one femtosecond of laser pulse,
  • so it's as if you just went like...
  • - with a laser. - A femtosecond pulse.
  • Gav: And if you pause it, you can see it's just a dot of light.
  • Dan: And it's comped in the shape of the mirrors.
  • I wonder if you could actually build,
  • like, a big maze to get it around.
  • Do, like, a little maze and try to get it in.
  • - World's fastest maze completion. - Yeah.
  • - ( trills ) - Light.
  • Dan: Oh, it almost went in the corner there.
  • Gav: It is. It's like the DVD screensaver, isn't it?
  • You just want it to go straight in the corner.
  • Dan: Nearly.
  • - So this one's 100 billion? - Yeah.
  • Should we see what 500 billion looks like?
  • - All right, so the area is quite small. - Yes.
  • So there's no way that we can stand in and be filmed by this camera.
  • But alternative solution-- little mini-figurines of us.
  • Wait, why is mine-- oh, for goodness sake.
  • - Again, every time. - So we'll put them on there.
  • - Flipping heck. - All right.
  • So, in this experiment, instead of shooting light from the side,
  • I've changed the beam path to bounce back this mirror,
  • this mirror, and use a concave lens
  • to expand the beam to shoot at an angle.
  • So this is more about scattering light
  • on the surface of the figurines?
  • Yes, you're sweeping across the surface of the figures.
  • Because we're obviously not see-through, so...
  • Yeah.
  • This is the static image of the two figures.
  • Now I'm doing 500 billion frames a second
  • with two by two coding.
  • So two by two and a casual half trill.
  • - ( both laugh ) - Peng: Yeah.
  • I think we're pretty much done with this one.
  • This is 500 billion frames a second
  • of our little figurines,
  • with a resolution
  • of 549 by 439.
  • The footage is played back
  • at 20 frames a second,
  • therefore it's slowed down by
  • a factor of 25 billion times.
  • I do like that I was able
  • to successfully photobomb this picture.
  • Dan: I like how it shows up on your nose so much.
  • Gav: All right, I knew you'd say something about that.
  • It does-- it does get caught by my nose, doesn't it?
  • - Dan: Yeah. - Gav: It is interesting to see the light scatter
  • on the surface of something
  • as opposed to go through our body.
  • Dan: So again, all they've done here is pretty much
  • comp in our bodies with the light.
  • So the camera would have got this blue light
  • and they've just taken a picture and comped in us
  • and matched it up to where the light hit.
  • Gav: You look miserable in that.
  • Dan: You look like I've just said something awkward,
  • and you're like, "Ooh."
  • - Should we do these poses? - Yeah, sure.
  • Gav: And you can see on the time scale
  • it's a much slower progression of picoseconds.
  • as opposed to half a trillion frames a second.
  • All right, that's 500 billion done.
  • - Child's play. - Child's play.
  • - Let's crank it up. - All the way?
  • - Yep. - All right.
  • Let's do 10 trillion frames a second.
  • So, Peng, we're at a different camera now.
  • - Is that correct? - Yeah.
  • And this one can do up to 10 trillion frames a second?
  • Yeah, yeah. This is the 10 trillion frames a second.
  • That's the maximum speed that we can do.
  • Here we have a sample which contains diluted milk,
  • about a few millimeters long.
  • That's all that the camera's looking at, is a few millimeters long?
  • Yeah, that's how long the light propagates within 30 picoseconds.
  • Dan: Okay, wow.
  • Here is the same software
  • that we use to capture the image.
  • So for this one we're allowed to keep the lights on?
  • Because we are doing ultra fast images within a very narrow time scale
  • there's a minimum amount of light that comes through the ambient light.
  • - In comparison to the powerful laser. - Laser, yeah.
  • - It's all relative, I suppose. - Yeah, much brighter.
  • - All right, cool. - Yeah, this is how it works.
  • Dan: So this is a much smaller scale
  • 'cause we're using a higher frame rate
  • capturing a very much smaller amount
  • of space and time, essentially.
  • - Yes. - Gav: All right.
  • This is the light traveling through the milk vial
  • at 10 trillion frames a second.
  • - This is the reason we came here. - Yeah.
  • - Gav: So cool. - So on the bottle video,
  • the light seemed to have gained the same speed.
  • But then you gotta remember that the scale of this
  • is much smaller. So this is one millimeter,
  • it says here, is the distance,
  • whereas before, it was an entire bottle.
  • Which shows you that we're actually recording
  • light traveling through such a small amount of space.
  • Gav: And it's so slow now that our picosecond
  • has a decimal place to the hundredth femtosecond.
  • Dan: That's blowing my mind for a start.
  • Gav: When Peng turned on the laser,
  • I didn't see anything at all.
  • But now we can actually see how it moves.
  • On this scale of time,
  • if we fired a bullet through this frame,
  • it would take years
  • to go from one side to the other.
  • Dan: And the light is just going, blip.
  • That really puts it into perspective as well, doesn't it?
  • I just feel like no human should ever have seen this.
  • It's like looking at the base of the universe.
  • I've heard that in the future,
  • the CalTech team actually intends to increase the speed
  • up to one quadrillion frames per second.
  • It's a bit mind-blowing, to be honest.
  • Gav: We have to leave now and go back to our old
  • measly hundreds of thousands of frames a second.
  • Measly, pathetic hundreds of thousands.
  • Thank you very much, Peng, for showing us your amazing kit.
  • - Thank you. - Yeah, thanks.
  • - Thank you. - Learned a lot.
  • Yeah.
  • Well, to me, that's some of the most
  • mind-blowing footage ever.
  • I mean, visually, it's just a blob
  • going from left to right.
  • But to know that that's light--
  • Dan: I would say it was actually one of the most
  • mind-blowing things that we've seen.
  • Well, I feel very accomplished.
  • Hopefully, you enjoyed watching
  • light move through the air in slow-mo.
  • Feel free to check out other episodes
  • from "Planet Slow Mo," and join us in part two,
  • where we'll be learning a lot more
  • about how this camera works.
  • You can subscribe, too, if you want.
  • We'd appreciate it.
  • Still not sure I'll be able to understand it after part two.
  • - We'll do our best. - All right.

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What is the fastest thing we as the human race know of? Gav and Dan try and film that.