Filming the Speed of Light at 10 Trillion FPS

Today we are at CalTech, because in a building there there is a camera that leaves me absolutely speechless. We have now filmed at very high frame rates. We're talking about half a million, which is... - It should not be despised. - ...frame rate important. Their camera puts ours to shame and produces 10 billion frames per second. There are 13 zeros. For reference, that's 20 million times faster than the fastest we've ever filmed on this channel. And there's not much you can't film at half a million frames per second, but one of those things is the

speed

of

light

. - It's not a bad topic. - No. - Let's go in there. - Alright.

Even the shoe cover technology is cool. In fact, I want one of these at home. - Only for people. - Very good, let's go see what this CUP is about. - Nice to meet you. - Man: Nice to see you. - How are you? - Good. So what is it really... what are we doing here? This all seems very complicated. Oh, this is the fastest camera in the world. Ah OK. Yes. This is the fastest camera in the world. There you go. As easy as that. How big is the actual camera part? Can i show you.

That big box is the camera itself. And here is the optics we designed: to make it work. - Very cool. Many times, in our YouTube comments, we are asked to film the

speed

of

light

. And I always have to respond to people by letting them know that the speed of light is almost incomprehensibly fast, and even our cameras, at less than a million frames per second, will never see anything like that. Is this camera capable of

filming

the speed of light? Yes, that's basically what we're going to see. In the example I'm going to show, the light will move along this bottle.

Over time, how long does it take for light to start here and end here? It takes about 2,000 picoseconds. - That's pretty fast. Yes. - Pretty fast. So, for the audience, it's milliseconds, microseconds... - Are it nano-- - ...nanoseconds, - picoseconds, femtoseconds? - Yeah. So we're on sort of a pico/femto scale with this. - We've never done that before, for sure. - But. This is completely on another level. Shall we organize the first experiment? - Of course yes. - Start with the bottle? - Everyone should use laser glasses. - Safety glasses? - Well. - Peng: We have some. - I look good? - You have side panels on your glasses. - It looks like you're about to... - You look really bad.

You look like you're about to go skiing with a blowtorch. It's just... So, I guess since we're trying to film the light, it'll be helpful to turn off all the lights here, right? - Yes. - Otherwise, we'll just have... All the ambient light will come in, yes. Good. Well. Let's get ready to turn off the lights. Yes. - Can you hold this for me? - I will hold this. - Yes, thanks. - I'm excited. This frame rate thing makes me dizzy. We want to see the spread of light from one side, so we need to make sure that the light is scattered outside the plane of view through the milk molecules inside, then the scattered light can be seen from one side.

So this is a bottle full of water with some milk in it? Then I'm going to turn on the laser. So all you do is move mirrors and lenses and then it goes to different areas? We use it to move the laser. The laser is too big. Look, the light hits the bottom of the bottle. Then go through the bottle. - Is it a powerful laser? - Is very powerful. It can basically burn any type of paper. - I'll stay away from that. - Yeah. - Wow, that's great. - You can see its shine. The first thing I'm going to capture is the static image for reference.

For today I'm going to try... - Excellent. - Yes Yes. I mean, I remember being excited when we started

filming

, we went from 1,000 frames per second to 28,000 frames per second. - That was a big jump. Okay, we're almost done with the water bottle. I would like to take a photo of this. As you can see, we can only see the light. We cannot see the bottle or the label. - Yes. - So finally, in the movie, we might want to overlay both the bottle and the light. - Like, composing a real image. - Yes Yes. So you just take a photo with your phone and that can... can you do that?

Yes, you can use software to overlay these two things. - Gav: Great. - Dan: You are in the photograph. Simply photobombing the bottle. Well, let's keep an eye on our bottle. It took me eight hours to process, during which time I grew a slightly longer beard. I also cut my hair. Alright, here we go. Dan: Okay, so what we're seeing here is that the bottle has just been prepared, basically. Gav: Yes, this camera only detects the light itself, which is like a bluish laser light, so you don't actually see anything other than the light that looks like that.

And then we compile the bottle image. In the room with my real eye, it looked like it was constantly lit, but here we can follow the light moving through the bottle. It may not seem like it, but this is actually real. Dan: It's refracting the photons and that's why you can see it. But when it simply passes through air, there is nothing to really reflect the light. Gav: Yes, it only appears on the bottle. It's interesting. It almost looks like some kind of 80s movie effect. It does, doesn't it? It seems... Like some kind of ghost flying into the room.

But actually that is light. Gav: Isn't that weird? Look at the scale. Each frame appears to last ten picoseconds. And we're just casually watching this light pass from left to right through the bottle, but in reality, the light is moving a million times faster than a bullet. - Dan: What a mental topic. - Yes. Gav: Well, then we have shot light through the milk. - Next experiment? - Yes. For this experiment, we designed a special cavity. We call it chaotic cavity. When light enters the cavity, it will bounce back and forth several times by the mirrors surrounding the cavity. - You're almost trapping light inside the... - Yes.

Yes, exactly. What is the purpose of this? This egg thing? This is to create water vapor surrounding the environment so that light is dispersed. - Same thing, like... - Oh, then you can see a little bit. - Makes sense. - Yes, that's how the system works. - Turn it on. - Very well, let's do the "experiment". How long did it take you to learn how to use this? Uh, maybe a few months to get used to it... - A few months to get used to it. - Yes. Because it is a really complicated system. It's really complicated, right?

I had not noticed. (both murmur) Okay, so this is the chaotic cavity at 100 billion frames per second. Like nothing. Gav: Again, the length of this video is... you can't even imagine how short it is. Dan: That's amazing. Gav: When we were in the room, it seemed like everything was glowing, but now we can see the individual light pulse bouncing around this thing. It sounds like a weird version of "Pong." This is a femtosecond laser pulse, so it's like you just do something like... - with a laser. - A femtosecond pulse. Gav: And if you pause it, you can see that it's just a point of light.

Dan: And it's shaped like mirrors. I wonder if you could actually build a big maze to navigate through it. Make a small maze and try to enter. - Complete the fastest maze in the world. - Yes. - (trills) - Light. Dan: Oh, he almost fell in the corner. Gav: It is. It's like the DVD screensaver, right? You just want him to go straight to the corner. Dan: Almost. - So this is 100 billion? - Yes. Should we see what 500 billion looks like? - Okay, so the area is quite small. - Yes. So there is no way we can stand and be filmed by this camera.

But an alternative solution: small minifigures of us. Wait, why is mine...? Oh, for God's sake. - Once again, every time. - Then we'll put them there. - Devils! - Alright. So in this experiment, instead of shooting light from the side, I changed the beam path to bounce this mirror, this mirror, and used a concave lens to expand the beam and shoot at an angle. So, is it more about dispersing the light over the surface of the figures? Yes, you are sweeping the surface of the figures. Because obviously we're not transparent, so... Yes. This is the static image of the two figures.

Now I'm doing 500 billion frames per second with two-by-two encoding. So two by two and a casual half-trill. - (both laugh) - Peng: Yeah. I think we're done with this one. This is 500 billion frames per second of our figurines, with a resolution of 549 by 439. The footage is played at 20 frames per second, so it is slowed down 25 billion times. I like that I was able to successfully photograph this image. Dan: I really like how it shows up on your nose. Gav: Okay, I knew you'd say something about that. It gets stuck in my nose, doesn't it? - Dan: Yes. - Gav: It's interesting to see light disperse on the surface of something instead of passing through our body.

Dan: Again, all they've done here is basically compare our bodies to light. So the camera would have picked up this blue light and they just took a picture and compared it to us and compared it to where the light hits. Gav: You look miserable with that. Dan: It sounds like I just said something awkward and you're like, "Ooh." - Should we do these poses? - Yes, sure. Gav: And you can see on the time scale that it's a much slower progression of picoseconds. as opposed to half a billion frames per second. Very good, that's 500 billion now. - Child's play. - Child's play. - Let's get it going. - All the way? - Yes that's fine.

Let's do 10

trillion

frames per second. So, Peng, we're facing a different camera now. - Is that correct? - Yes. And this one can generate up to 10 billion frames per second? Yes Yes. These are the 10 billion frames per second. That is the maximum speed we can do. Here we have a sample containing diluted milk, a few millimeters long. That's all the camera looks at, is it a few millimeters long? Yes, that's how long light travels in 30 picoseconds. Dan: Okay, wow. Here is the same software we used to capture the image. So in this case can we keep the lights on?

Because we are doing ultra-fast imaging on a very narrow time scale, there is a minimal amount of light passing through ambient light. - Compared to the powerful laser. - Laser, yes. - Everything is relative, I guess. - Yes, much brighter. - It's good, awesome. - Yes, that's how it works. Dan: This is a much smaller scale because we're using a higher frame rate to capture a much smaller amount of space and time, essentially. - Yes. - Gav: Okay. This is the light traveling through the milk vial at 10

trillion

frames per second. - This is the reason we came here. - Yes. - Gav: How great. - So, in the bottle video, the light seemed to have gained the same speed.

But then you have to remember that the scale of this is much smaller. So this is a millimeter, it says here, it's the distance, whereas before it was a whole bottle. Which shows that we are actually recording light traveling through such a small amount of space. Gav: And it's so slow now that our picosecond has a decimal to the hundredth femtosecond. Dan: First of all, that blows my mind. Gav: When Peng turned on the laser, I didn't see anything at all. But now we can see how it moves. On this time scale, if we were to shoot a bullet through this frame, it would take years to get from one side to the other.

Dan: And the light is just going out. That puts it into perspective too, right? I feel like no human should have seen this. It's like looking at the base of the universe. I heard that in the future, the CalTech team intends to increase the speed up to a quadrillion frames per second. It's a little mind-blowing, to be honest. Gav: We have to go now and go back to our miserable old hundreds of thousands of frames per second. Hundreds of thousands miserable and pathetic. Thank you very much, Peng, for showing us your amazing kit. - Thank you. - Yes, thanks. - Thank you. - He learned a lot.

Yes. Well, to me, it's one of the most amazing images ever seen. I mean, visually, it's just a mass going from left to right. But knowing that's light... Dan: I'd say it was actually one of the most mind-blowing things we've ever seen. Well, I feel very accomplished. Hopefully, you enjoyed watching the light move through the air in slow motion. Feel free to watch other episodes of "Planet Slow Mo" and join us for part two, where we will learn a lot more about how this camera works. You can also subscribe if you want. We would appreciate it.

I'm still not sure I can understand it after the second part. - We will do our best. - Alright.