Can a photon attract another photon?

[sqljunkey]

I was thinking a group of photons traveling in a beam of light would create some gravity and attract to each other. But the field of gravity wouldn't be strong enough to affect each other unless it was a high energy group of photons. Is it possible for photons to want to stay together using some kind of field.

 

[trurle]

I was thinking a group of photons traveling in a beam of light would create some gravity and attract to each other. But the field of gravity wouldn't be strong enough to affect each other unless it was a high energy group of photons. Is it possible for photons to want to stay together using some kind of field.

Highly energetic photons (above 0.5 MEv each) will routinely interact with each other by producing virtual electron-positron pairs. This effect is much stronger than any gravity-mediated effects, and results in scattering rather than focusing of the beam (discovered in 1998). This mechanism is suppressed in collimated beam, although you still can create electron-positron pairs with the photons of thermal bath, at higher threshold of energy.
Longer wavelength beams will also diverge in general through multi-photon mechanisms - the gravity is too weak compared to the electromagnetic interaction. You may have influence of self-gravity overcoming self-scattering if energy of photons in beam is down to ~0.001 eV (millimeter waves) though.

 

[vanhees71]

Do you have a reference, where this effect of "Delbrück scattering" has been discoved?

To my knowledge "Delbrück scattering" has been observed for the first time by the ATLAS collaboration in this or the last year in ultraperipheral lead-lead collisions at the LHC.

 

[Dale]

I was thinking a group of photons traveling in a beam of light would create some gravity and attract to each other. But the field of gravity wouldn't be strong enough to affect each other unless it was a high energy group of photons. Is it possible for photons to want to stay together using some kind of field.

The Bonnor beam is a pp wave spacetime which describes the gravitational effect of light. Note, it is classical not quantum so it is “light” not “photons”. The beam of light modeled is incoherent.

 

[ErikPan]

What you seem to be describing is a 'geon', first investigated by Andrew Wheeler:

https://journals.aps.org/pr/abstract/10.1103/PhysRev.97.511

From the abstract:

"Associated with an electromagnetic disturbance is a mass, the gravitational attraction of which under appropriate circumstances is capable of holding the disturbance together for a time long in comparison with the characteristic periods of the system. Such gravitational-electromagnetic entities, or "geons"; are analyzed via classical relativity theory. They furnish for the first time a completely classical, divergence-free, self-consistent picture of the Newtonian concept of body over the range of masses from ∼10^39 g to ∼10^57 g. Smaller geons are quantum objects whose analysis would call for the treatment of characteristic new effects."

Though this appears to be a 'body', probably centred at the origin; I do not know if anyone has considered it as a 'beam', though I do know people are still working on geons (Jorma Louko is one I think).

 

[SWB123]

I was thinking a group of photons traveling in a beam of light would create some gravity and attract to each other. But the field of gravity wouldn't be strong enough to affect each other unless it was a high energy group of photons. Is it possible for photons to want to stay together using some kind of field.

,

Please correct me if I am wrong, but I am interpreting, and extrapolating the answer your question to be directly analogous to 'electronically steering a radar beam' by applying stronger excitation to the emitters opposite the direction you want the beam to be steered. Radar waves of stronger amplitude electromagnetically repel the weaker amplitudes and the whole beam is diverted relative to the differences in their strength. Light is just another strata of the 'electromagnetic spectrum'; so, I am certain that the same laws of electromagnetic 'attraction' and 'repulsion' are equally represented throughout the spectrum.

What was the light source you were thinking of when you asked the question? How the photons were emitted, their strength, and whether or not they were filtered, columnated, and or reflected may 'shed some light' on why you asked the question the way you did (pun intended).

 

[hutchphd]

'electronically steering a radar beam' by applying stronger excitation to the emitters opposite the direction you want the beam to be steered. Radar waves of stronger amplitude electromagnetically repel the weaker amplitudes and the whole beam is diverted relative to the differences in their strength.

Do you have a reference for this process?

 

[SWB123]

Do you have a reference for this process?

Here is a good one:
http://www.radartutorial.eu/06.antennas/Phased Array Antenna.en.html

A simple Google search on "3D Electronic Beem Steering" will bring up a wealth of information on the subject.

 

[hutchphd]

Here is a good one:
http://www.radartutorial.eu/06.antennas/Phased Array Antenna.en.html

A simple Google search on "3D Electronic Beem Steering" will bring up a wealth of information on the subject.

This describes a phased array and well known but your description of the physics is simply not correct.

Radar waves of stronger amplitude electromagnetically repel the weaker amplitudes and the whole beam is diverted

There is no repulsion of the waves...the result is simply the instantaneous sum giving rise to interference.

 

[SWB123]

I did ask to be corrected if I was wrong.

I had mistakenly thought that since the emissions were electromagnetic waves then their interaction/interference was a direct result of their electromagnetic properties.

A laser beam can be diverted by placing a permanent magnet near it. Is there no situation where the strength and polarity of EM waves or more specifically photons within a beam of light can affect each other in flight?

 

[hutchphd]

I did ask to be corrected if I was wrong.

I had mistakenly thought that since the emissions were electromagnetic waves then their interaction/interference was a direct result of their electromagnetic properties.

A laser beam can be diverted by placing a permanent magnet near it. Is there no situation where the strength and polarity of EM waves or more specifically photons within a beam of light can affect each other in flight?

Fair enough. Incidentally interaction and interference are not equivalent. Also I would be interested in a reference for the laser beam being diverted by a permanent magnet.
In the presence of other matter they can certainly interact indirectly. In vacuum I believe the answer is no at least for what we normally call light (very high energy gamma radiation may but I defer to experts here)

 

[SWB123]

This is still not the exact video I have seen in the past of a red laser being diverted, but it makes the point:

 

[hutchphd]

but it makes the point:

What point? Certainly not that a photon gets diverted by a magnet. This experiment shows that ferrofluid is affected by a magnet... hardly a startling concept. Please use more care.