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Author Topic: Does light curves space and time?  (Read 14047 times)

Offline yor_on

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Does light curves space and time?
« Reply #25 on: 10/09/2010 12:08:20 »
LeeE I think you're perfectly correct, even though light and matter are convertible, they are not the exact same. Take a look here for a definition.
 

Offline Farsight

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Does light curves space and time?
« Reply #26 on: 10/09/2010 13:49:57 »
I think it might be a bit of a stretch to infer that this is proof that light interacts with light.
Then take a look at photon-photon pair production. Read this and this.

Quote from: JP
You're right. It's a light-matter interaction, Geezer. It also doesn't have anything to do with general relativity.
See above. Light interacts with light, and the connection with general relativity is that light is energy, and energy causes gravity. Like I said, see The Foundation of the General Theory of Relativity and look at page 185 where Einstein says "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". It’s energy that causes gravity, not matter per se. Matter only causes gravity because of the energy content. So whatever we might discuss re curved space and curved spacetime, the answer to the OP is yes.
 

Offline Geezer

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Does light curves space and time?
« Reply #27 on: 10/09/2010 23:43:33 »
I think it might be a bit of a stretch to infer that this is proof that light interacts with light.

Then take a look at photon-photon pair production. Read this and this.


Farsight,

I'm merely pointing out that the particular reference does not demonstrate direct light-light interaction. Do you disagree?
« Last Edit: 10/09/2010 23:53:16 by Geezer »
 

Offline Farsight

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Does light curves space and time?
« Reply #28 on: 11/09/2010 18:00:52 »
I'm not sure. I take your point, but the title does say Like Magnets, Light Can Attract and Repel Itself, and the abstract for the paper says interacting lightwaves. Sure, matter is involved, but the article talks about the need for small scale rather than light interacting with matter. Take a look at that  two-photon physics which "is a branch of particle physics for the interactions between two photons". That sounds unambiguous enough. But lower down it says "A photon can, within the bounds of the uncertainty principle, fluctuate into a charged fermion-antifermion pair, to either of which the other photon can couple". That's pair production wherein matter is made from light, and relates to vacuum polarization wherein virtual particles are the QED description of the evanescent wave. That's a light wave in the wider sense, but it's a standing wave rather than one travelling at c.
 

Offline Geezer

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Does light curves space and time?
« Reply #29 on: 12/09/2010 03:39:04 »
The author of the piece got a bit carried away in the title. The abstract seems to indicate that there is other matter involved in the interaction.

I understand it's possible to cause two lasers to interact by using a single rubidium atom as a sort of switch, but one atom is still other matter.

Perhaps JP can tell us if he knows of any experiments where light interacts with light without the presence of some other matter.
 

Offline Farsight

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Does light curves space and time?
« Reply #30 on: 12/09/2010 14:51:56 »
Maybe he can. JP, have a look at two-photon physics. Here's the paper for reference anyhow: Tunable bipolar optical interactions between guided lightwaves. My take on it is that the medium is more dieletric than vacuum and thus magnifies the effect.

But anyway, as regards the OP, light does curve spacetime because energy curves spacetime rather than just matter. I hope everybody can agree with that, because it is what Einstein said.
 

Offline JP

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Does light curves space and time?
« Reply #31 on: 12/09/2010 16:15:17 »
Skimming the paper, it looks like a classical effect of light interacting with matter:

Quote
The optically excited dipoles in one waveguide interact with the evanescent field of
the other waveguide and generate a force which is dependent on the separation of the
waveguides and the relative phase of optical modes.

In other words, the light polarizes the waveguides and this polarized matter can interact with the field in the other waveguide.  It is not due to the photons themselves interacting.  Without the matter, you would not see this effect.  (You might get tiny QED effects, but they're produced by different mechanisms.)

I agree that light should curve spacetime just by virtue of having energy, but that's a totally different effect than what's in this paper and than pair production and other QED effects.  I'd also be surprised if this was ever actually observed, since the energy involved would have to be huge to produce a measurable gravitational effect.
 

Offline Farsight

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Does light curves space and time?
« Reply #32 on: 12/09/2010 18:11:12 »
JP: good stuff re light curving spacetime by virtue of energy but that it's not practically measurable. I'd say that's the OP settled. 

Re what I said about the paper and magnifying the effect, have a look at vacuum polarization and two-photon physics. But maybe we need another thread for that.

 

 

Offline JP

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Does light curves space and time?
« Reply #33 on: 13/09/2010 03:11:41 »
I don't think that paper is about magnifying the vacuum polarization.  Both seem to involve polarization, but this paper talks about real matter being polarized and its a classical effect.  Vacuum polarization is a separate effect that needs quantum field theory in order to be described.
 

Offline kenhikage

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Does light curves space and time?
« Reply #34 on: 14/09/2010 14:58:11 »
I don't know about the math at all, but could the high energy of light be bending (or "straightening") space into allowing the "straightest possible path" and thus making it the fastest thing on the block?
 

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Does light curves space and time?
« Reply #34 on: 14/09/2010 14:58:11 »

 

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