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/sci/ - Science & Math

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2179335 No.2179335 [Reply] [Original]

Photons warp spacetime, yes?
Photons that travel "up" out of a gravitational well will be redshifted, yes?

Can someone do the math to show me that the galactic redshift we see is not due to photons constantly having to climb out of their own gravity well as they travel?

>> No.2179349

It should be obvious, the redshift we see increases with distance.

If what you say was the case, the shift would even out once the photons are far enough from gravity to no longer be affected.

>> No.2179367

>>2179349
But they are themselves the source of gravity, assuming photons warp spacetime. So its constantly with them.

>> No.2179393

Photons most certainly have wave properties, so they are ocillations of space-time. Gravity is a curve of 3-dimensional space into 4-dimensional space.

>> No.2179397

>>2179367

No, they are not. You might have noticed this by now, but if not, feel free to wander outside to check.

Photons have no rest mass. They can be manipulated BY gravity, but do not produce any themselves.

Even if they did, they would not be climbing out of the field, they would always be at the center of it, so they wouldn't redshift.

>> No.2179407

>>2179367
a photon is not a source of gravity, wtf please?

>> No.2179417
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2179417

>>2179367

>But they are themselves the source of gravity

>> No.2179418

>>2179397
>>2179407
I've asked a few times, and /sci/ seems to think photons warp spacetime. And what is a warp in spacetime if not gravity?

>> No.2179423

>>2179397
>Even if they did, they would not be climbing out of the field, they would always be at the center of it, so they wouldn't redshift.
Both photons and gravity travel at the same speed, so there would always be an area of less warped spacetime in front of the photon, where its gravity hasn't reached yet, right?

>> No.2179444

>>2179418
Any energy density warps spacetime. But photons are obviously not the mediating particle for the gravity force.

>> No.2179445

1. Energy and momentum (this includes photons) curve space time.
2. Photons are the quantization of the electromagnetic field. The oscillation of space time itself, the gravitational waves, are something completely different.
3. Read some basic books on the topic for gods sake.

>> No.2179446

>>2179418
Electromagnetism.

>> No.2179452

Yes, photons create a VEEERY small gravity well, since the have energy. However, since the gravity well co-moves with them, they don't have to climb up it. They are moving relative to their own gravitational potential. They are therefore not losing energy due to a change in gravitational potential relative to themselves, therefore there is no reason for there to be a redshift.

>> No.2179455

>>2179447
Some people like knowing how things work. You're on /sci/, BTW.

>> No.2179450

>>2179444
(cont)
Photons are the mediating particle for the electromagnetic force.

>> No.2179447

>>2179423
gravity travels at the speed of light? ... WHY WOULD THAT MATTER!?

What massive fuck off star is dense and big enough to give off a gravitational wave that travels (potently) that far!?

srsly, wtf.

>> No.2179459

>>2179335
>Photons warp spacetime, yes?

No, that doesn't sound right. Matter warps spacetime, and the more mass an object has, the more warping of spacetime will occur. Light waves that pass through a gravitational field will lose energy, causing the light waves to elongate. These longer waves produce the redshift of light

>> No.2179460

>>2179423
Even if there were, which I doubt, the photon isn't changing its position in the gravity well. It's staying in the same place. So it's no going "up-hill". It's not losing energy. It's not red shifting.

>> No.2179467

>>2179459
Energy warps spacetime. Matter is just the most obvious instance of this, because it contains a lot of energy.

>> No.2179473

>>2179447
The idea isn't that the gravity from the star is pulling on the photons that it emits, its that photons are emitting gravity.

>> No.2179474

>>2179455
sorry i shouldn't be a cunt. i am the same, i don't really know a fraction of what people talk about here.

bros?

>> No.2179478

>>2179474
lol sure

>> No.2179488

>>2179473
if X is moving in direction Y and the two forces acting on it are it's own emission of gravity and it's own acceleration, the only force acting on it is it's own acceleration.

>> No.2179492

>>2179467
>Matter is just the most obvious instance of this, because it contains a lot of energy

good point, but I was already aware of that. When I refer to energy, i talk about electromagnetism, radiation, electrical, and heat energy.

but it's cool though

>> No.2179504

>>2179492
dude E = mc^2

Never forget..

>> No.2179520

>http://van.physics.illinois.edu/qa/listing.php?id=1414
Well a physicist says photons have gravity.

>> No.2179595

>>2179460
But one second later, won't the photon be experiencing the gravitons that it emitted one second earlier?