Does Velocity Affect Gravitational Red Shift in Light Signals?

[jostpuur]

Sorry about being tempted to take part in the relativistic mass stuff.

But I was also interested in the OP. Unfortunately I don't know GR enough to understand what you are talking about, but did I understand correctly, that the duordi's original question is not simple enough to be answered yes or no?

 

[duordi]

Is relativistic mass not usable?

I have always considered all mass to be relativistic.

It was found the atom was made of smaller particles with velocity, electrons protons and neutrons.
The velocity of the proton and electron would be partly energy of motion and therefore relativistic mass.
As it is discovered that atomic particles can be divided into smaller and smaller parts all of which have motion allowing another portion of the rest mass to be redefined as relativistic mass.
The question then becomes where will this end?
Eventually everything may be made of photons which have no rest mass at all.

If this is the case would it be smart to do away with the idea of relativistic mass altogether just for the sake of ease of use of current theory?

 

[jostpuur]

I have always considered all mass to be relativistic.

It was found the atom was made of smaller particles with velocity, electrons protons and neutrons.
The velocity of the proton and electron would be partly energy of motion and therefore relativistic mass.
As it is discovered that atomic particles can be divided into smaller and smaller parts all of which have motion allowing another portion of the rest mass to be redefined as relativistic mass.
The question then becomes where will this end?
Eventually everything may be made of photons which have no rest mass at all.

If this is the case would it be smart to do away with the idea of relativistic mass altogether just for the sake of ease of use of current theory?

In fact you probably don't want a fine thread to start moving in this direction. That matter is not directly related to your OP here, and it would be a pity if this thread ended in a mass concept debate.

 

[pervect]

but did I understand correctly, that the duordi's original question is not simple enough to be answered yes or no?

Correct, the original question isn't quite clear enough to have a definite answer. (Unfortunately it takes specifying a lot of details to make the question really clear.)

A clear enough question to answer that I can come up with that seems similar to the original woud be "Imagine a massive body. An observer stationary relative to the massive body and an observer moving directly away from the massive body both measure the redshift of a previously emitted light signal or photon while both observers and the photon are all at the exact same location in space. What do the observers measure, how do their results compare?"

I think I've answered that version of the question in my last posts.

If you are interested in the general question of the gravity of moving objects, very similar questions have been addressed in the past, see for instance:

https://www.physicsforums.com/showpost.php?p=1352227&postcount=6
https://www.physicsforums.com/showpost.php?p=1347429&postcount=10
https://www.physicsforums.com/showthread.php?t=177014

some of the answers may be a bit technical.

A paper that addresses some of the issues (bu8t is also rather technical) is http://arxiv.org/abs/gr-qc/0612140

which compares the tidal force of gravity with the tidal force of electromagnetism.

Comparing tidal forces is the best way to go, because it allows exact quantitative comparisons. Very general "intuitive" comparisons can be made by comparing the force of a moving charge with the force of a moving mass. But to even do this requires that one understand how the electric field of a moving charge transforms. (Coulomb's law does not work for a moving charge, the third link above talks about the problem.)

 

[rbj]

In fact you probably don't want a fine thread to start moving in this direction. That matter is not directly related to your OP here, and it would be a pity if this thread ended in a mass concept debate.

i've been staying dahell outa it. even though i was tempted to reply in such a manner that would move the thread in that direction (being a believer in the usefulness of the concept of "relativistic mass").

 

[duordi]

Sorry, I won't mention phyosophical opnions again.
I would like to thank Pervect for the referances.

Duane

 

[mendocino]

I agree. These are two different ways of looking at the same thing. Deciding that other one is wrong, doesn't seem a sign of deeper understanding to me. Although it could be true, that the approach that uses merely distances and time, uses in some sense simpler concepts, than the approach that uses also energy.

The use of relativistic mass is based on heuristic grounds and is not a fundamental part of the theory. Why employ an unnecessary concept that is furthering confusion?

Is this what you call "deeper understanding" of relativity theory ?

 

[mendocino]

If you go too fast do you become a black hole?

If someone believe in "relativistic mass", then how to answer this question?

According to relativity the following are true facts:

1> As an object approaches the speed of light, its kinetic energy increases without limit.
2> Energy is related to mass by the formula E = mc2.
3> As an object approaches the speed of light, its length contracts towards zero.
4> If enough mass is squeezed into a sufficiently small space it will form a black hole

Put these facts together and it looks like we should be able to conclude that an object which moves at a speed sufficiently close to the speed of light should collapse to form a black hole.

True or not?

 

[meopemuk]

2> Energy is related to mass by the formula E = mc2.

This is not correct. The correct relativistic relationship between energy and mass is

E= \sqrt{m^2c^4 + p^2c^2}

where p is system's momentum and mass m is an invariant (i.e., m doesn't depend on system's velocity). The formula you wrote is a particular case of this general relationship when the system is at rest, i.e., p=0

Eugene.