A question about gravity and photons

Imagine you are in a sealed room. The room could be sitting motionless on a space ship. The space ship could have a soundless, vibration-less rocket that we cannot tell if it is firing or not. If it is firing it is accelerating the room at 9.8 m/s^2. Is there any experiment that we can do that will allow you to figure out if the room is sitting on the earth or accelerating through space at 9.8 m/s^2? NO, there is no possible experiment we can do to tell the difference, so then there is no difference. Gravity is not a force but acceleration that manifests itself as a warping (curving) of Space-Time.*

*(Hence the issue with the standard model and quantum mechanics)

ANYONE I know who has taken any undergraduate level class that covers relativity would trace the path of Einstein. And he DISCOVERED relativity with a similar thought experiment. So everyone gets told acceleration is the same as gravity. Its just something we say, all the time.

"Acceleration doesn't cause gravity"
For all intensive purposes, im sorry. It does.

reply to post by ubeenhad


But the issue is, acceleration isn't dependent upon mass at all. It would have to be exactly as you stated, a closed system at a constant acceleration to mimic gravity on behalf of the observer. If the room were to stop accelerating, the effect would be lost. However, since gravity is based upon mass and the distance from that mass, it isn't going to change due to the lack of movement, it only changes if the mass or the distance changes.
Therefore, acceleration and gravity are not the same thing at all. Acceleration can mimic gravity in a controlled environment for a given experiment, but they are not the same.

reply to post by PurpleChiten



Re-read my original post. I think we are now in agreement.

Originally posted by ubeenhad
reply to post by PurpleChiten

 

Re-read my original post. I think we are now in agreement.

So you agree that gravity and acceleration are not the same thing.

reply to post by PurpleChiten


Your using a very rudimentary argument, im not sure how to proceed. I feel I've made my point to an acceptable degree.

Originally posted by PurpleChiten
Acceleration can be caused by gravity, but gravity cannot be caused by acceleration

Gravity, no, but the feeling of weight, yes. In a spaceship accelerating at 1g, you'll feel just like on Earth. The effect of gravity is the same as effect of acceleration.

reply to post by PurpleChiten


Acceleration is dependent on motion, but motion is relative. If you're in a sealed blind spaceship travelling at a uniform speed, and then it starts to deccelerate, it will feel like you started accelerating in the opposite direction.

Acceleration is measured in g's. 1g is the acceleration we experience when standing on Earth.

but the point is, acceleration and gravity, although similar when measured or used in calculations, are not the same thing

They can produce similar effects, but are still two different things, different concepts, different origins

Originally posted by ubeenhad
reply to post by PurpleChiten

 

Your using a very rudimentary argument, im not sure how to proceed. I feel I've made my point to an acceptable degree.

Actually, since you are simplifying both into one, the rudimentary description would be more accurate on your end. (not insulting or attacking, just clarifying). You're looking only at the end product, not the parts that make up the whole. It's only in breaking apart the pieces that we see what's really at work

reply to post by PurpleChiten


Come on, this is the problem with forums. The nit picking of arguments. In the context I used it, I am absolutely correct*. My very first physics block as a freshman in college touched on relativity, and the first thing we learn after the photoelectric effect, is inertial reference frames.

*As I will now show The effects of gravity are indistinguishable from the effects of acceleration. Not just in trivial thought experiments.

Equivalence principle

(Inertial mass) * (acceleration) = (intensity of the gravitational field) * (gravitational mass).

DONE.

simplistic interpretation of the equivalence principle is that “gravitation is acceleration.”
-Dr. Robert Heaston

Originally posted by wildespace
reply to post by PurpleChiten

 

Acceleration is dependent on motion, but motion is relative. If you're in a sealed blind spaceship travelling at a uniform speed, and then it starts to deccelerate, it will feel like you started accelerating in the opposite direction.

Acceleration is measured in g's. 1g is the acceleration we experience when standing on Earth.

Or as I said accelerating at 9.8 m/s^2 or we use the constant little 'g'.

Originally posted by beezzer

If a photon has no mass and falls into a black hole due to the curvature of space-time, then is there anything than can puncture space-time and simply travel in a straight line regardless of outside influence?

No.

In particular, when you have space-time with a curvature, the straight lines followed by photons are as straight as straight can get. In this space-time they are going straight.

More philosphically, the assertion that gravitation changes spacetime is the most important insight of Einstein, because it means that gravity must necessarily affect everything, and no physics is outside of it.

It is unlike the rest of physics in this way---it is a rule which all the other physics known or unknown must follow. Observation of something which did not follow this would refute the fundamental principle of relativity. There has never been any experimental evidence suggestive of this.

Originally posted by PurpleChiten
reply to post by ubeenhad

 

But the issue is, acceleration isn't dependent upon mass at all. It would have to be exactly as you stated, a closed system at a constant acceleration to mimic gravity on behalf of the observer. If the room were to stop accelerating, the effect would be lost. However, since gravity is based upon mass and the distance from that mass, it isn't going to change due to the lack of movement, it only changes if the mass or the distance changes.
Therefore, acceleration and gravity are not the same thing at all. Acceleration can mimic gravity in a controlled environment for a given experiment, but they are not the same.

It's convenient to divide gravitation into the effect (space time warping) and the cause (the stuff which is the source of the warping differential equation).

Locally, the effect of gravitation is indistinguishable from the effect of acceleration.

Globally the source terms creating gravitational warping arise from the combination of matter and the energy (including kinetic) of all particles, with mass or without. The motion caused by acceleration can add to this, but it isn't an exclusive term, because rest mass also is the dominant source of gravitational warping.

Originally posted by ubeenhad
Imagine you are in a sealed room. The room could be sitting motionless on a space ship. The space ship could have a soundless, vibration-less rocket that we cannot tell if it is firing or not. If it is firing it is accelerating the room at 9.8 m/s^2. Is there any experiment that we can do that will allow you to figure out if the room is sitting on the earth or accelerating through space at 9.8 m/s^2? NO, there is no possible experiment we can do to tell the difference, so then there is no difference. Gravity is not a force but acceleration that manifests itself as a warping (curving) of Space-Time.*

*(Hence the issue with the standard model and quantum mechanics)

ANYONE I know who has taken any undergraduate level class that covers relativity would trace the path of Einstein. And he DISCOVERED relativity with a similar thought experiment. So everyone gets told acceleration is the same as gravity. Its just something we say, all the time.

"Acceleration doesn't cause gravity"
For all intensive purposes, im sorry. It does.

edit on 3-11-2012 by ubeenhad because: (no reason given)

edit on 3-11-2012 by ubeenhad because: (no reason given)

edit on 3-11-2012 by ubeenhad because: (no reason given)

I believe what Einstein proposed in his "Elevator" thought experiment was that the force created by acceleration was indistinguishable from the force created by gravity to an observer with no other frame of reference but themselves (ie: enclosed in an elevator).

This does not equate to acceleration and gravity being the same thing.

Originally posted by chr0naut

Originally posted by ubeenhad
Imagine you are in a sealed room. The room could be sitting motionless on a space ship. The space ship could have a soundless, vibration-less rocket that we cannot tell if it is firing or not. If it is firing it is accelerating the room at 9.8 m/s^2. Is there any experiment that we can do that will allow you to figure out if the room is sitting on the earth or accelerating through space at 9.8 m/s^2? NO, there is no possible experiment we can do to tell the difference, so then there is no difference. Gravity is not a force but acceleration that manifests itself as a warping (curving) of Space-Time.*

*(Hence the issue with the standard model and quantum mechanics)

ANYONE I know who has taken any undergraduate level class that covers relativity would trace the path of Einstein. And he DISCOVERED relativity with a similar thought experiment. So everyone gets told acceleration is the same as gravity. Its just something we say, all the time.

"Acceleration doesn't cause gravity"
For all intensive purposes, im sorry. It does.

edit on 3-11-2012 by ubeenhad because: (no reason given)

edit on 3-11-2012 by ubeenhad because: (no reason given)

edit on 3-11-2012 by ubeenhad because: (no reason given)

I believe what Einstein proposed in his "Elevator" thought experiment was that the force created by acceleration was indistinguishable from the force created by gravity to an observer with no other frame of reference but themselves (ie: enclosed in an elevator).

This does not equate to acceleration and gravity being the same thing.

if a mass like the earth was motionless,, would it have gravity?

Originally posted by chr0naut

This does not equate to acceleration and gravity being the same thing.

I've already made the point of inertial reference frames.

If you read the topic, I refuted the same claim in a simpler manor.

Here it is again. Your being overly facetious.

reply to post by ImaFungi


Yes, it would still have gravity. It's a result of it's mass, not a result of it's motion.

Originally posted by ubeenhad

Originally posted by chr0naut

This does not equate to acceleration and gravity being the same thing.

I've already made the point of inertial reference frames.

If you read the topic, I refuted the same claim in a simpler manor.

Here it is again. Your being overly facetious.

No, you claimed acceleration and gravity were the same thing and were refuted.....

Originally posted by PurpleChiten
reply to post by ImaFungi

 

Yes, it would still have gravity. It's a result of it's mass, not a result of it's motion.

To be technical the motion of the Earth such as its rotation also contributes to the term which is the source of gravity, but it is quantitatively much, much smaller than the effect from the rest mass of the Earth.

As the regular "warping" is a perturbation to what Newtonian gravity would show, this effect is a perturbation to a perturbation in magnitude.

And yes, it was experimentally measured and confirmed by an extraordinary and heroic experiment called Gravity Probe B, a space mission which took 40 years to plan and execute.

Originally posted by ubeenhad
Acceleration is the same as gravity. So, speeding up gives you mass. Any object, no matter how big/small experiences this. You guys are arguing over semantics. Photons have no rest mass. Thats the answer. To go any deeper requires a much longer explanation than can be given on a forum.

Thats what I said.

Yes. Acceleration and Gravity are different. They are spelled differently.
But in the context of the above post, it is entirely accurate and creates NO conflicting ideas or notions.

I also went on to clarify, shortly there after.

Originally posted by ubeenhad

 

More semantics.
The effects of gravity is indistinguishable from the effects of acceleration.

Which is all besides the point. I was simply trying to give the idea of relativistic mass in a more laymen friendly way.