Uncovering the Truth: Recording Lightspeed with a Trillion FPS Camera

[Mohd Abdullah]

Had anyone already watched this?
He said they successfully recorded the speed of light using a trillion fps camera that they had created. But isn't light already there even before someone started to record it? Not to mention that light is not actually accelerating.

Thoughts?

 

[BvU]

Hi,

But isn't light already there even before someone started to record it

No. The light is generated in the laser as a light pulse.

Not to mention that light is not actually accelerating

No one claims that it is accelerating.

 

[Mohd Abdullah]

Hi,
No. The light is generated in the laser as a light pulse.

No one claims that it is accelerating.

I see. So, is it really they successfully recorded the speed of light?

 

[BvU]

You can say that, yes. They managed to reconstruct light pulse movement through a scene.

 

[ZapperZ]

I see. So, is it really they successfully recorded the speed of light?

But was this what they wanted to do? All they stated in the video was to detect the motion the light pulse. They didn't say they wanted to actually measure the speed of light (which can be done in more accurate manner via other means).

BTW, in case anyone mistook this as actually observing the motion of ONE photon, this is not the case. Note the word "photons" being used. The laser is sending a light PULSE, not a single photon at a time.

Zz.

 

[Mohd Abdullah]

But was this what they wanted to do? All they stated in the video was to detect the motion the light pulse. They didn't say they wanted to actually measure the speed of light (which can be done in more accurate manner via other means).

BTW, in case anyone mistook this as actually observing the motion of ONE photon, this is not the case. Note the word "photons" being used. The laser is sending a light PULSE, not a single photon at a time.

Zz.

So if I understand you, they don't actually recorded the speed of light. Right?

What do you mean that it can be done in more accurate manner via other means?

 

[ZapperZ]

So if I understand you, they don't actually recorded the speed of light. Right?

Look at the video again. That wasn't the main purpose of the demo. If you really want to know what they were studying, you need to find the relevant papers that this group has published using this setup.

What do you mean that it can be done in more accurate manner via other means?

This is not the technique used to determine the book or reference value of "c" in vacuum that we all have been using. The CODATA standard describes the methodology on how c was determined.

Zz.

 

[Cutter Ketch]

There weren't measuring the speed of light. They were recording a scene at a high enough rate to discern the motion of a light pulse passing through the scene. They are saying the have slowed the action down so that you can witness things that happen at the speed of light. This is much much harder than merely measuring the speed of light. People have long used similar techniques to witness fast dynamics in chemical reactions for example (look up pump-probe experiments) but you have to be impressed that they can image like this.

 

[CWatters]

It's also clear that they use a lot of pulses to make the video. They explained how they use a mirror to scan the scene in one dimension but I wonder if they also use multiple pulses and a time delay to scan in the other dimension? So although they can apparently slow down a pulse its not the same pulse in each frame?

 

[Mohd Abdullah]

There are published papers regarding those experiments but it seems someone need to pay for it to read it. One of them is an article entitled 'Sequentially timed all-optical mapping photography' by K. Nakagawa and his other members that was published in 10 August 2014. It can be bought online at nature.com. The review is something like "High-speed photography is a powerful tool for studying fast dynamics in photochemistry, spintronics, phononics, fluidics, and plasma physics. Currently, the pump–probe method is the gold standard for time-resolved imaging, but it requires repetitive measurements for image construction and therefore falls short in probing non-repetitive or difficult-to-reproduce events. Here, we present a motion-picture camera that performs single-shot burst image acquisition without the need for repetitive measurements, yet with equally short frame intervals (4.4 trillion frames per second) and high pixel resolution (450 × 450 pixels). The principle of this method—‘motion picture femtophotography’—is all-optical mapping of the target's time-varying spatial profile onto a burst stream of sequentially timed photographs with spatial and temporal dispersion. To show the camera's broad utility we use it to capture plasma dynamics and lattice vibrational waves, both of which were previously difficult to observe with conventional methods in a single shot and in real time."

Thoughts?

 

[Doc Al]

You might want to check out this MIT news article from about 5 years ago: Trillion-frame-per-second video

 

[Cutter Ketch]

You might want to check out this MIT news article from about 5 years ago: Trillion-frame-per-second video

Ha! Trillion frames per second! Think how many hard drives it would take to video your grandma's 80th birthday party with that!

 

[Mohd Abdullah]

Are there something faster than light in the universe that even no matter how advanced the technology, no matter how fast the camera is, we will never be able to record a single frame of it?

 

[Drakkith]

Are there something faster than light in the universe that even no matter how advanced the technology, no matter how fast the camera is, we will never be able to record a single frame of it?

No, there is nothing that moves faster than light.

 

[CWatters]

No, there is nothing that moves faster than light.

...in a vacuum.

Light in other media can go a lot slower or even stopped..

 

[mfb]

The video is not even the record of a single pulse of light, but many pulses, merged with a computer afterwards (~1:30 in the video).

 

[Doc Al]

The video is not even the record of a single pulse of light, but many pulses, merged with a computer afterwards (~1:30 in the video).

Exactly. (That was my point in posting the link to the MIT news site earlier. It discusses such 'details'.)

 

[Mohd Abdullah]

...in a vacuum.

Light in other media can go a lot slower or even stopped..

But can we stop light in a vacuum?

 

[Mohd Abdullah]

The video is not even the record of a single pulse of light, but many pulses, merged with a computer afterwards (~1:30 in the video).

What is the difference if they record a single pulse of light compare to many pulses of light? Does it mean they didn't really record something moving at the speed of light?

 

[ZapperZ]

What is the difference if they record a single pulse of light compare to many pulses of light? Does it mean they didn't really record something moving at the speed of light?

They are taking a snapshot of many different pulses. How do you think this is a measurement of the speed of each light pulse?

I take many photos of the vehicles moving in front of my house at various times. Does that mean that I had recorded the speed of each of these vehicles?

Zz.

 

[A.T.]

Does it mean they didn't really record something moving at the speed of light?

Every video camera records light, which moves at the speed of light. And if you move far away enough, the propagation of a light pulse across the field of view can look arbitrarily slow, even on a real time video.

 

[Nugatory]

But can we stop light in a vacuum?

No.

 

[Cutter Ketch]

They are taking a snapshot of many different pulses. How do you think this is a measurement of the speed of each light pulse?

I take many photos of the vehicles moving in front of my house at various times. Does that mean that I had recorded the speed of each of these vehicles?

Zz.

I will say again that the point here was not to measure the speed of light. However in reply to Zz ...

A snapshot certainly doesn't show EACH cars speed. However if you can believe all of the cars are going the exact same speed, and you trigger a timer when they cross a particular point in the road and you take each of your photographs at precise delay intervals after the trigger then yes the photographs are a precise measure of the shared constant speed of the cars. Constant speed and fixed motion are not required. As long as the cars each perform the exact same movements as they pass, a montage of your photographs ordered by their respective time delays is a precise record of the motion of one and all of them.

The only trick is in believing that they will all do the exact same thing, and with light pulses that is a very good assumption. So even though this is composited from many pulses it is nevertheless a precise record of what each and every pulse did in real time.

 

[ZapperZ]

I will say again that the point here was not to measure the speed of light. However in reply to Zz ...

A snapshot certainly doesn't show EACH cars speed. However if you can believe all of the cars are going the exact same speed, and you trigger a timer when they cross a particular point in the road and you take each of your photographs at precise delay intervals after the trigger then yes the photographs are a precise measure of the shared constant speed of the cars. Constant speed and fixed motion are not required. As long as the cars each perform the exact same movements as they pass, a montage of your photographs ordered by their respective time delays is a precise record of the motion of one and all of them.

The only trick is in believing that they will all do the exact same thing, and with light pulses that is a very good assumption. So even though this is composited from many pulses it is nevertheless a precise record of what each and every pulse did in real time.

Believe me, I know it CAN be done if this is the goal. I measure the speed of electron bunch trains, so this is something I know how to do.

But I am replying to the OP in this context based on what has already been done in this report, not what they can or what is possible to be done. Somehow the OP seems to think that simply having the various snapshots of the different pulses can easily be translated to measuring the speed of these pulses.

Zz.