Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jeffreyH on 04/11/2015 22:15:05

Title: Can a photon be length contracted?
Post by: jeffreyH on 04/11/2015 22:15:05
Can the concept of length contraction be applied to photons? If not then why not?
Title: Re: Can a photon be length contracted?
Post by: alancalverd on 04/11/2015 22:31:04
If an object has no existence at rest, it cannot contract from its rest length.
Title: Re: Can a photon be length contracted?
Post by: jeffreyH on 04/11/2015 22:35:07
That's a very good point.
Title: Re: Can a photon be length contracted?
Post by: evan_au on 05/11/2015 01:44:05
Quote from: jeffreyH
Can the concept of length contraction be applied to photons?

Yes. This works with photons (light) as well as phonons (sound).

But it is a Doppler contraction of the wavelength (or it's relativistic equivalent at very high relative velocities between source and receiver).

Unlike relativity, you can also get wavelength expansion, if the source is moving away from you.
Title: Re: Can a photon be length contracted?
Post by: PmbPhy on 05/11/2015 13:53:14
Quote from: jeffreyH
Can the concept of length contraction be applied to photons? If not then why not?
In addition to the above comments you should also take note that no elementary particle that has a non-zero proper mass undergoes Lorentz contraction because it has no dimensions because its radius is zero and L/gamma = L for all point particles having non-zero proper mass.
Title: Re: Can a photon be length contracted?
Post by: Bill S on 06/11/2015 21:34:08
Quote from: evan_au
This works with photons (light) as well as phonons (sound).

My understanding is that phonons are excitations in (for example) a crystal lattice, and that only very long wavelength phonons are associated with sound.  Have I got that right?