10 ms·
Video filmed at four trillion frames per second captures light in a flash
- deleted 7y ago[deleted]
- MattSteelblade 7y agoI'm blown away by this. If I'm understanding this correctly, this picture[1] is light traveling for a distance of about 3/8ths of an inch. [1] https://media.nature.com/w800/magazine-assets/d41586-019-01625-5/d41586-019-01625-5_16737810.gif https://media.nature.com/w800/magazine-assets/d41586-019-016...
- jolmg 7y agoDid you see measurements somewhere or are you just estimating from the time counter and the speed of light?
- MattSteelblade 7y agoEstimating based on the time counter.
- SilasX 7y agoWait, the light is all incoherent before it passes the dotted line, then coherent until it bounces and passes back through? What's going on?
- aflag 7y agoYou have to remember that's scattered light.
- improv32 7y agoI believe the area between the dotted and solid lines is a mirror. The blob of light is visible because it's passing through some medium that scatters it, then when it disappears it has been absorbed by the mirror, then we see it reemitted shortly after.
- hcs 7y agoThe solid line is the mirror, the dotted line is the edge of the scattering medium. I assume there is air or vacuum in between.
- Twirrim 7y agoCalTech films light at the speed of 10 trillion frames a second! The "Slow Mo Guys" went to caltech to take a look: https://www.youtube.com/watch?v=7Ys_yKGNFRQ https://www.youtube.com/watch?v=7Ys_yKGNFRQ
- newshorts 7y agoInteresting video, though I wish they would have explained more about what exactly we are seeing. Like the last video, is the flash in the middle of the frame the light as a particle?
- srcmap 7y agoI used to work on HP way back in 1991 on equipment that measure timing of signal to 7.9 pico second resolution. This is very cool. Love to see an ifixit tear down video on that CalTech camera. :-)
- tlb 7y agoThis is more impressive than previous claims of trillion FPS cameras, because it captures it all sequentially from a single event. Other such claims were based on capturing one frame at a time of a repeating event with different time delays.
- NullPrefix 7y agoYou could use an array of cameras and capture the same event at different times
- gugagore 7y agoThe change of perspective is undesirable. Unless you're filming the matrix: https://youtu.be/bKEcElcTUMk https://youtu.be/bKEcElcTUMk !
- totalZero 7y agoOr something really far away, like lightning.
- TheRealPomax 7y agoNot really - there is no way to synchronise the start of framecapture that finely by that many cameras. Using a single camera but clever optics to "temporally spread a tiny image over a large sensor" to effectively create a sprite sheet is kind of your only option.
- gridspy 7y agoYou see that light pulse that they captured? Your camera synchronization signal in the wire is traveling about 2/3 of that speed. Can you imagine all the cameras in your array receiving and interpreting that signal at the same time?
- kevin_thibedeau 7y agoYou pretrigger the cameras while accounting for the delay.
- ebg13 7y ago> The imaging system captures a light pulse (in a slowed video) I like that they remind us that the video is slowed down and that time doesn't actually move at 10 picoseconds per second.
- idlewords 7y agoIf it did move at 10 picoseconds per second, how would we know? Whoa. Stares at hand
- snowwrestler 7y agoMakes me think of those videos of house plants, which we normally think of as still objects. But with a time-lapse video, you can see them moving around a bunch during 24 hours. https://www.youtube.com/watch?v=z0I3174S8Xg https://www.youtube.com/watch?v=z0I3174S8Xg
- phyzome 7y agoHeck, with the right plants you can see them grow over the course of minutes: https://www.brainonfire.net/blog/2018/03/29/seeing-plants-move/ https://www.brainonfire.net/blog/2018/03/29/seeing-plants-mo...
- HeWhoLurksLate 7y agoHold up. Now we're saying it has acceleration!? Whoa. stares at the sun
- sdegutis 7y ago> The imaging system captures a light pulse (in a slowed video) Good to know that's not the actual speed of light! Anyway, it looks like the photons are "crawling" by their patterns of speed, rather than traveling at a fixed speed.
- jolmg 7y agoI would think that effect is due to impurities or lack of uniformity in the material which causes some spots to light up more than others.
- raziel2701 7y agoI wonder how the authors feel that their work is so good that the website for Nature has a piece on it but not good enough to be published in a Nature journal.
- busyant 7y agoMaybe the authors didn't want to submit to Nature? Also, not a physicist, but my understanding is that PRL is prestigious in its own right.
- makerofspoons 7y agoWhen I worked in a physics lab a PRL publication was seen as a big deal.
- theWheez 7y agoCan anybody comment on what is meant by a "frame" here? My intuition tells me that what we consider a "frame" in our daily experience (24 up through maybe 144) would be pretty different from what this "frame" would be, in terms of how it is captured and how it is subsequently rendered. Any ideas?
- thecatspaw 7y agoa frame is just a picture essentially. What you're refering here with 24 up to 144 are usually frames per second. Here we're talking about 4 trillion frames, so a frame would be 1/4 trillion seconds.
- jerf 7y agoWe do not usually consider a frame duration to measure a length, because for most of the durations we use the frame's size is absurdly large in practical terms, ranging from thousands of miles to larger than the diameter of the earth. So we can take a shortcut of identifying a frame as some area from the camera's point of view identifying an infinite, instantaneous volume in front of us, and don't consider the fact that light isn't instantaneous and in fact has a transmission time. Frames this short mean that there is a sort of volumetric aspect to what is being catured. From the point of the camera, when light collection begins an area sweeps out in front of the camera and back in time at the speed of light, and when the light collection stops, the end of the area sweeps out from the camera lens in the same direction. The result of this is a spherical shell volume travelling backwards in time that represents the spacetime locations that can emit light and appear in the frame [1]. The resulting picture is an integration of the photons emitted in this 4D spacetime volume, in the direction of the camera, projected onto a 2D image. (That's assuming a point-like camera and instantaneously turning the camera on and off; in reality it'll be fuzzier but the principle holds.) The difference is that at these incredible fast speeds, the resulting 4D spacetime volume is of human size in most directions in the places we care about [2], measured in human-sized measuring units like "centimeters" rather than "light-seconds". Normally we can neglect thinking about this volume because we simply spray so "much" out that we don't have to think much about capture exactly what we want, in much the same way that in normal day-to-day life we tend to act as if lightspeed is simply infinite. In this case, we actually have to think about it to get what we want. A similar effect can be seen in network equipment, for what it's worth; at the highest network speeds, we've now significantly passed the point where a given bit being transmitted is now a human-sized fraction of a wire. If you could "snapshot" a 100Gb network cable, you could see bits on the wire. If I'm getting my math right, each bit is on the order of 2-3 centimeters, give or take the medium not being fully light-speed. [1]: It may be more intuitive for a moment to instead imagine that the camera is starting to emit the shell at the time that it is turned on, and stops when turned off, forward in time, as that creates a more intuitive initial image of what-seems-to-be-cause preceding what-seems-to-be-effect. Imagine the camera emitting light instead of collecting it. It may be easier to then imagine this shell going out farther and farther, getting larger as it goes (and the light inside dimming as it has to fill that volume with the same amount of energy it started with), indefinitely out into the universe. But since the camera is receiving instead af transmitting photons, the reality is the same image, just with time reversed; as the time goes farther back, the shell is farther away from the camera and larger. [2]: Technically it extends all the way in the direction the camera is all the way out in space back to the Big Bang or the CMB or something, but unless you're deliberately photographing space, and why you'd do that with this camera I have no idea, you don't have to worry about that.
- hndamien 7y agoIs there any explanation for why it is so jerky?
- MattSteelblade 7y agoSampling rate isn't high enough is what I'd imagine, even at 4 trillion FPS.
- davesque 7y agoI'm confused how you could film a light pulse this way. It seems that the light pulse would itself have to be emitting light somehow. I'll assume it was travelling through a gas that scattered it.
- jerf 7y ago"The imaging system captures a light pulse (in a slowed video) as it passes through a material, exits the material (at the dashed yellow line) and bounces off a mirror (solid yellow line) back into the material."
- identicalgamer 7y agoIs this trying to imply that it is capturing the scattering off of the Frenel diffraction? I don't understand at first glance how this paper is capturing the light without having a sensor in the path of propagation.
- jerf 7y agoThe light is being put through a translucent medium, like shining a laser through milk or smoke or something, so you can see the scattered light. Conventional/non-QM-based light physics can handle this situation. If you mean, how are they seeing the non-scattered light, you are correct that they are not.
- HillaryBriss 7y ago> light is being put through a translucent medium at certain points, the light pulse seems to "leap ahead" in fits and starts on its journey. is that because of the way the medium scatters the light or something?
- mirimir 7y agoI think that it's because the speed of light inside the translucent medium (left side) is lower than in air (right side).
- cr0sh 7y agoI'd be curious to see the dual-slit experiment done using this camera as the "observer". I'm not sure it'd yield anything we don't already "know" - but it might be worth trying just because.
- lqet 7y agoI wondered exactly the same thing (see my other comment). However, I am not sure if they can actually film single photons. My school physics are a bit rusty, but iirc, quantum effects will not be relevant if you actually fire a light "impulse" consisting of many, many photons. However, as I have asked in my previous comment, it would be interesting if you could actually see the light impulse being "split up" and interfering with itself.
- rusk 7y agoIf you could do that then you could also know the fate of Schrödinger’s cat ...
- pathseeker 7y agoYou can only "film" something when the photons hit the "film" (a.k.a the image sensor). There's no way to record photons flying by.
- fastball 7y agoIs it not possible for the energy of a photon to to disrupt EM fields enough to be detectable, without the photon actually being incident on a sensor?
- pbhjpbhj 7y agoKinda, no. By observing a photon you perturb the system, you wouldn't get a result for what that photon would have done had it not been perturbed. AIUI if you detect the photon then it interacted with some part of your sensing apparatus, so it didn't then go on to do what it should have. Thus we're left to look at the aftermath and impute the situation that produced it.
- lqet 7y agoSo, looking at the video, I am curious: is there a video where they fire a light impulse against a double-slit experiment setup? Would it be possible to see the light being "split up" and interfering with itself?
- simias 7y agoYou can't see the light not going into the camera (obviously) so what you see is some light from the beam being reflected into the sensor. You can't take a picture of a photon, if that makes sense. So in the double slit experiment you could see the path the light took only if you allowed for a portion of that light to be reflected towards the camera. But then if you did that you wouldn't end up with anything particularly new or interesting as far as I can imagine.
- lqet 7y agoOf course, you are right! I intuitively thought of the light impulse emitting further photons in the direction of the camera, which makes no sense.
- deleted 7y ago[deleted]
- freedomben 7y agoThis article caused me to remember something I heard on a Youtube video and wanted to follow up on. Essentially, is there (and if so what is) the framerate of the universe? It makes logical sense to have a minimum bundle of time based on Planck's constant, so I did some googling and found the answer (I have not checked this math)[1]: > The Planck time is 5.39 × 10-44 seconds. No measurable time can be shorter than that according to quantum physics. Converting to FPS, that gives us: > One thousand eight hundred and fifty-five billion billion billion billion frames per second. 18.55 septillion FPS! So if like me you wondered if a trillion FPS is close to the maximum possible frame rate in the universe, the answer is nope! [1]: http://www.librador.com/2009/01/16/The-frame-rate-of-the-universe/ http://www.librador.com/2009/01/16/The-frame-rate-of-the-uni...
- klank 7y agoDon't confuse "our math breaks down at this point" with "it can't physically happen". Planck time is the time at which, if you want to do physics, you have to take into account quantum mechanics and gravity (i.e. understand quantum gravity). Something we don't know how to do. But it doesn't necessarily mean time is discrete. Maybe it is. Maybe it isn't. https://en.wikipedia.org/wiki/Planck_time#Physical_significance https://en.wikipedia.org/wiki/Planck_time#Physical_significa...
- freedomben 7y agoThanks for the link. I was referring to measurable time (since for frame rate we must have discrete intervals), but it sounds like that is still up for debate.
- pier25 7y agoDoes the same reasoning apply to the Plank length or is that one discreet?
- lodi 7y agoAs I understand it, currently everything points to space and time (really, spacetime) not being discrete. I'm copying and pasting a previous reply I made the last time this came up. --- I'm no physicist, but the layman explanation I've heard is that the concepts of Planck length and Planck time do not imply that spacetime is discretized into little "voxels"; instead these quantities are just limits on the uncertainty of any possible measurement. As I understand it there are two contributing facts: a) the Heisenberg uncertainty principle states that there's a tradeoff between certainty in position vs momentum, so if you're more certain in a particle's position you're less certain of its momentum. (For photons, momentum is proportional to frequency, i.e. wavelength, and frequency is proportional to energy.) b) By mass-energy equivalence, anything with energy has mass, therefore higher frequency photons are more "massive". A single photon of sufficiently high frequency would form a black hole. Putting those two together, to measure distances accurately you need higher and higher frequency photons with shorter and shorter wavelengths. For example, radar creates blurry images at ~5cm wavelengths, while ordinary photographs can be razor sharp with wavelengths of only ~500nm. The Planck length is just the wavelength at which the photon would have so much energy that it would collapse into a black hole and break our current mathematical models. That's why it's nonsensical--with current models--to talk about lengths smaller than a Planck length, but it doesn't mean that space itself is quantized. Similar argument for time. (Also, the same logic applies to other particles like electrons, protons, and even up to macroscopic items like baseballs; everything has a wavelength...)
- Causality1 7y agoThis technology could give us the opportunity to verify a ton of our physical and chemical models with direct observation. The demo may not be exciting but if they can scale it down you can expect a lot of exciting discoveries. I can't wait to see what we're wrong about.
- unseenbastiat 7y agoNature makes a perfect counter-ideal to technology for several reasons. Nature (that which is outside the power of the system) is the opposite of technology (which seeks to expand indefinitely the power of the system). Most people will agree that nature is beautiful; certainly it has tremendous popular appeal. The radical environmentalists ALREADY hold an ideology that exalts nature and opposes technology. [30] It is not necessary for the sake of nature to set up some chimerical utopia or any new kind of social order. Nature takes care of itself: It was a spontaneous creation that existed long before any human society, and for countless centuries many different kinds of human societies coexisted with nature without doing it an excessive amount of damage. Only with the Industrial Revolution did the effect of human society on nature become really devastating. To relieve the pressure on nature it is not necessary to create a special kind of social system, it is only necessary to get rid of industrial society. Granted, this will not solve all problems. Industrial society has already done tremendous damage to nature and it will take a very long time for the scars to heal. Besides, even pre-industrial societies can do significant damage to nature. Nevertheless, getting rid of industrial society will accomplish a great deal. It will relieve the worst of the pressure on nature so that the scars can begin to heal. It will remove the capacity of organized society to keep increasing its control over nature (including human nature). Whatever kind of society may exist after the demise of the industrial system, it is certain that most people will live close to nature, because in the absence of advanced technology there is no other way that people CAN live. To feed themselves they must be peasants or herdsmen or fishermen or hunters, etc. And, generally speaking, local autonomy should tend to increase, because lack of advanced technology and rapid communications will limit the capacity of governments or other large organizations to control local communities.
- korethr 7y agoI've had conversations with a guy who works at one of the companies that makes high-speed cameras. One of the interesting thing to come out of those conversations is that below a certain threshold of frame duration (which is related to, but not necessarily the recriprocal of the frame rate) a camera with that capability becomes subject to ITAR, because supposedly said camera could be used to develop nuclear weapons. My intuition is that the camera described in this article would be subject to ITAR were it developed in a western nation. But, I doubt China gives any fucks about that.
- tibyat 7y agoandroid had this 2 years ago
- objektif 7y agoLooks like a matplotlib chart turned into an animation.