• Welcome to Phoenix Rising!

    Created in 2008, Phoenix Rising is the largest and oldest forum dedicated to furthering the understanding of and finding treatments for complex chronic illnesses such as chronic fatigue syndrome (ME/CFS), fibromyalgia (FM), long COVID, postural orthostatic tachycardia syndrome (POTS), mast cell activation syndrome (MCAS), and allied diseases.

    To become a member, simply click the Register button at the top right.

Real time video of light moving: applications for biomedical science

Cheesus

Senior Member
Messages
1,292
Location
UK
According to the abstract, this will be super helpful in biomedical science. I don't know much about that, really I just wanted to show you guys this ridiculously awesome video of light moving. It is filmed at 100 billion frames per second

https://i.imgur.com/gKfHroL.gifv

Here is the corresponding abstract:

Ultrafast video recording of spatiotemporal light distribution in a scattering medium has a significant impact in biomedicine. Although many simulation tools have been implemented to model light propagation in scattering media, existing experimental instruments still lack sufficient imaging speed to record transient light-scattering events in real time. We report single-shot ultrafast video recording of a light-induced photonic Mach cone propagating in an engineered scattering plate assembly. This dynamic light-scattering event was captured in a single camera exposure by lossless-encoding compressed ultrafast photography at 100 billion frames per second. Our experimental results are in excellent agreement with theoretical predictions by time-resolved Monte Carlo simulation. This technology holds great promise for next-generation biomedical imaging instrumentation.

https://www.researchgate.net/public..._Mach_cone_induced_by_a_scattered_light_pulse
 

Hip

Senior Member
Messages
17,824
It is filmed at 100 billion frames per second

That's pretty amazing that we have cameras that can film at that speed.

By my calculation, in a 100 billionth of a second, a light particle will move 3 mm.
 

Jonathan Edwards

"Gibberish"
Messages
5,256
That's pretty amazing that we have cameras that can film at that speed.

By my calculation, in a 100 billionth of a second, a light particle will move 3 mm.

It is a very clever piece of filming but light does not actually move. Nor is it made of particles. The weird thing about a photon of light is that it is a connection between one place at one time with another place at a later time but it takes no time to get from one place to the other. Once the connection has started it has also finished.

What the video shows is lots of photons being scattered out from a path that if they were not scattered would bounce back near to where they started. I assume there is a short burst of photons, which means that photons that get scattered out of the path later connect to the camera later. You cannot see or detect with a camera a photon that is following a path that is not to the camera so the apparent movement in the video is just like the apparent movement on a TV screen or a neon sign or Christmas lights. It seems to move because light is coming from a different place as time goes by.

Imaging using scattered light has been going on for a couple of decades. It is used to study infant brains. Surprisingly you can shine a light straight through a baby's brain and get a picture of what the internal structure is. It is just that you have to clean up the image hugely. I guess this fast tracking camera might help in calibrating such techniques.
 

Cheesus

Senior Member
Messages
1,292
Location
UK
The weird thing about a photon of light is that it is a connection between one place at one time with another place at a later time but it takes no time to get from one place to the other. Once the connection has started it has also finished.

Physics is so cool.
 

Jonathan Edwards

"Gibberish"
Messages
5,256
@Jonathan Edwards

So would it be correct to say that it is a video of light travelling, rather than to say it is a video of light moving?

No I don't think it travels either, and the apparent movement or travel in the picture is not 'light travelling' any more than the 'movement' of a bright spot in a neon display is anything travelling. Light comes in units called photons but these are not particles. They are never in one place or another. They are causal connections between two places in spacetime. And they are not even strings, just causal connections.
 

sb4

Senior Member
Messages
1,654
Location
United Kingdom
It is a very clever piece of filming but light does not actually move. Nor is it made of particles. The weird thing about a photon of light is that it is a connection between one place at one time with another place at a later time but it takes no time to get from one place to the other. Once the connection has started it has also finished.

Wouldn't this be true only in a vacuum, gravity and other things slow down light meaning it's not travelling at c meaning it experiences time?
 

Jonathan Edwards

"Gibberish"
Messages
5,256
Wouldn't this be true only in a vacuum, gravity and other things slow down light meaning it's not travelling at c meaning it experiences time?

No, it has nothing to do with general relativity. It is a basic feature of quantum theory - confirmed by the Aspect experiments that tested Bell's theorem. Light does not travel any more than anything travels in QM. There are no trajectories. It is basic to the theory. As Bohr pointed out, the dynamic connection that is a quantum system cannot be divided into a 'particle' being in one place at one time and another place at another.
 

sb4

Senior Member
Messages
1,654
Location
United Kingdom
No, it has nothing to do with general relativity. It is a basic feature of quantum theory - confirmed by the Aspect experiments that tested Bell's theorem. Light does not travel any more than anything travels in QM. There are no trajectories. It is basic to the theory. As Bohr pointed out, the dynamic connection that is a quantum system cannot be divided into a 'particle' being in one place at one time and another place at another.
So the photon is a wave (in a super position?) but why does the wave not experience time when slowed down(in gravity for example )?
 

Jonathan Edwards

"Gibberish"
Messages
5,256
So the photon is a wave (in a super position?) but why does the wave not experience time when slowed down(in gravity for example )?

No a photon is not a wave. That is a trivial analogy often used but it is unhelpful. I am not sure that anything experiences time, in the sense of time in physics as a component of spacetime. We have an experience of 'time' that is a sign created by parts of our brains to indicate to other parts of the brain a story about the world. As pointed out by Newton that is not time in the sense used in physics. Time is never slowed down or speeded up. Again that is a misinterpretation of SR. All these myths are ways of trying to make physics seem like our experiences, but 300 years ago the people who invented physics, like Descartes, Newton and Leibniz understand that this is a pointless exercise.

It's a long story.