Can a photon become stationary (like a proton)?

[0]

Okay, at CERN, they accelerate protons up to near light speed. Is it possible to slow down a photon from light speed? What happens then? Can a photon become stationary?

 

[f95toli]

No, photons always travel at the speed of light (c).
Light that passes through e.g. water is of course "slower" than light in vaccum (or air), but the difference is due to the photons interacting with the atoms in the medium, "internally" they are still traveling at c.

 

[QuixoticOne]

In the laboratory frame photons always travel at (c), for any possible laboratory.
You could have a photon packet of more than one photon moving together as in a laser beam
or just a hypothetical frame that is co-moving with the photon, i.e. the photon's rest FRAME.

You can't really slow / stop light in the laboratory except in the types of experiments they do that relate to phase velocity as distinct from group velocity for instance in passing a laser pulse through an excited gas at a wavelength corresponding to a critical position near the absorbtion edge of that gas. Google slowing / stopping light for those kinds of experiments.

 

[QuixoticOne]

http://en.wikipedia.org/wiki/Slow_light
http://www.hno.harvard.edu/gaz.../1999/02.18/light.html

 

[0]

Originally posted by: QuixoticOne
In the laboratory frame photons always travel at (c), for any possible laboratory.
You could have a photon packet of more than one photon moving together as in a laser beam
or just a hypothetical frame that is co-moving with the photon, i.e. the photon's rest FRAME.

You can't really slow / stop light in the laboratory except in the types of experiments they do that relate to phase velocity as distinct from group velocity for instance in passing a laser pulse through an excited gas at a wavelength corresponding to a critical position near the absorbtion edge of that gas. Google slowing / stopping light for those kinds of experiments.

So if light travels slower through a material, does that also mean that time has "sped up" for the light in accordance to Relativity?

 

[f95toli]

Originally posted by: 0

So if light travels slower through a material, does that also mean that time has "sped up" for the light in accordance to Relativity?

No, because as I pointed out above the photons aren't really "slowing down", the fact that the light beam is "slowed down" does not change the fact that the photons are not; they always travel at c (regardless of frame)

One (somewhat inaccurate) way of thinking about it is to imagine the photons being absorbed/re-emited and scattered many time as they pass through the medium which effectively slows down the beam because these processes take time, but inbetween these events the photons are still traveling at c.

In reality it is of course more complicated than this (you need to quantum electrodynamics in order to give a more accurate desciption); but this simplified picture should still give you some idea of what is going on.

 

[silverpig]

Originally posted by: f95toli

Originally posted by: 0

So if light travels slower through a material, does that also mean that time has "sped up" for the light in accordance to Relativity?

No, because as I pointed out above the photons aren't really "slowing down", the fact that the light beam is "slowed down" does not change the fact that the photons are not; they always travel at c (regardless of frame)

One (somewhat inaccurate) way of thinking about it is to imagine the photons being absorbed/re-emited and scattered many time as they pass through the medium which effectively slows down the beam because these processes take time, but inbetween these events the photons are still traveling at c.

In reality it is of course more complicated than this (you need to quantum electrodynamics in order to give a more accurate desciption); but this simplified picture should still give you some idea of what is going on.

Think of it as a runner always running at the same speed, but when he hits a treadmill he appears to be going slower to observers, despite the fact he's still running at the same speed on the treadmill.

 

[Peter]

Does photon-emitting stationery count?

 

[Onceler]

Maybe it moves slower than c overall but in between molecules at c like electrons do(almost)

 

[Aberforth]

http://edition.cnn.com/2008/TE...dex.html?eref=rss_tech

 

[Draquuis]

While I'm pretty sure you can't slow a photon in a lab. Theoretically if the white hole theory is proven, then should a photon be travelling directly toward the singularity, or where it were, then at the reverse event horizon the photon would be stationary, before turning back

 

[ThatBuzzkiller]

Talk about necrobumping ...

No, photons can not become stationary according to the theory of special relativity.

 

[KWiklund]

Maxwell's theory would also forbid it (which is how Einstein came to his conclusion).