General relativity, will we learn otherwise?

[Mac]

I looked at the linked page, now please explain it for me(in laymans terms), I am not a physicist, but interested in theory....

 

To keep it simple and not to explain why according to the theory behind it:

 

A symmetrical test mass which had a hole through it's center was used.

 

That geometry meant that neither the total mass nor the center of mass changed yet the magnitude of gravity varied depending on how it was viewed relative to the torsion arm.

 

Newton for example F = G * m1 * m2 / r^2. In this case NONE of the mathematical factors used to calculate F have changed but F in fact does change depending on the viewing angle.

 

GR also functions in a simular fashion. That is it calculates as a function of the center of mass, total mass, etc.

 

The test shows that the force of gravity is not an inherent property of mass nor of curved space by mass but is a function of mass and it's geometry subjected to an external energy field.

 

The port being open or closed acted like a ball valve and actual throttled a streaming component of the total field involved in the generated force.

 

Did you view the test equipment photographs?

[paultrr]

The gravitational field outside a uniform sphere is GM/r^ 2 towards the center. The field inside a uniform sphere is F=mgr/r_e. Around a ring of mass it is F=-GMx/(x^2+a^2)^3/2. The equations are a bit different for each situation.

[Guest Zanket]

General relativity is most likely here to stay. It may be extended (kind of how Einstine extended, but did not refute, Newton's mathematical descriptions of space and time and gravity) but it's not likely to be flat out proven wrong.

General relativity (GR) does not extend Newtonian mechanics. GR contradicts the predictions of Newtonian mechanics. Only one of those theories can be valid. Newtonian mechanics works good in weak gravity because it closely approximates GR there. The predictions of the theories diverge as gravity strengthens.

 

In my opinion, general relativty is here to stay. The only real problem that I know it faces is being merged with quantum mechanics for special cases such as things described as singularities, but string theory offers a possible way out of that dilemma.

GR is also incompatible with quantum mechanics (QM) near a central singularity theorized by GR. Only one of those theories can be valid. I think if one of them is valid, it's likely QM.

[DryLab]

The data shows that gravity is not a function of curved time-space which functions from the center of mass.

Hi Mac; I share your view that GR might not be the final answer even though it does pretty much predict observations.

 

I think Lorentz had a better take on it than Einstein did. He developed the equations first, and formulated a theory that didn't require warped space-time. H. Ziegler discussed this with Einstein in 1909.

[DougF]

I said proven wrong but thats a littel harsh. I also meant replaced by something better.

[DryLab]

I also meant replaced by something better.

That is a much better option. We know GR predicts well. We don't yet realize what is the underlying seat of the phenomena it predicts.

[Guest Zanket]

A theory could be better than GR only if it predicted differently. Of two theories that predict differently, only one can be valid. Then a truly better theory would necessarily invalidate GR.

 

For example, GR is better than Newtonian mechanics. GR predicts things, like the relativistic orbital precession of Mercury, that we observe and that Newtonian mechanics does not predict. Thus Newtonian mechanics is wrong even though NASA uses it. It would be wrong even if GR had not been invented.

[InfiniteNow]

A theory could be better than GR only if it predicted differently. Of two theories that predict differently, only one can be valid. Then a truly better theory would necessarily invalidate GR.

 

For example, GR is better than Newtonian mechanics. GR predicts things, like the relativistic orbital precession of Mercury, that we observe and that Newtonian mechanics does not predict. Thus Newtonian mechanics is wrong even though NASA uses it. It would be wrong even if GR had not been invented.

 

Zankie, I believe you struggle due to your word choice. New theories don't necessarily invalidate old ones, they're often just better. Further, Newtoninan mechanics are not wrong, they simply don't apply to all reference frames or relatvistic speeds.

 

You clearly have a solid understanding of the subject matter, but your mind is so made up that GR is wrong that you spend all of your time looking for ways it's invalid instead of using it where it's validitiy is unquestioned or describing an improved model.

[Guest Zanket]

Zankie, I believe you struggle due to your word choice. New theories don't necessarily invalidate old ones, they're often just better. Further, Newtoninan mechanics are not wrong, they simply don't apply to all reference frames or relatvistic speeds.

Newtonian mechanics does apply to relativistic speeds. It gives incorrect answers at those speeds.

 

You clearly have a solid understanding of the subject matter, but your mind is so made up that GR is wrong that you spend all of your time looking for ways it's invalid instead of using it where it's validitiy is unquestioned or describing an improved model.

You clearly have a poor understanding of the way science is done. I suggest you focus on the scientific method instead of guessing what I do with my time.

[InfiniteNow]

You clearly have a poor understanding of the way science is done. I suggest you focus on the scientific method instead of guessing what I do with my time.

 

Okay. Sure. Just trying to help you out, mate. Feel free to carry on. :zip:

[Natural]

"General relativity is a geometrical theory which postulates that the presence of mass and energy "curves" spacetime, and this curvature affects the path of free particles (and even the path of light)."

 

Sorry, I just thought I would ask. I don't like the above statement, it seems to fit the present research, but I find it hard to believe.........Sorry, I am not smart enough to come up with a new/better provable theory, but I don't have to like the old ones either.

 

I know the feeling, I don't like it either.

My main problem with curved space is that the "models" are all 2 dimensional. (along with the thinking):bdayhappy_balloons:

Instead of all of the images and drawings that you've ever seen, imagine something that curves from a point outward IN ALL DIRECTIONS. (ALL) ;)

So now describe a path along which something could travel.

Sorry there is no such thing as a path when you curve in all directions.

I know... I know... rotational orbit makes a difference but gravity is still working in ALL directions simultaneously. So which way is the curve?

There in lies my problem with this theory.

:D

[HydrogenBond]

Here is General Relativity consideration. If gravity equals GR, than stars should show some degree of time dilation. What this means is the rate of nuclear reactions, in the sun's core for example, relative to our reference, should appear to slow. In other words, if there was no gravity, but the sun's core was nuke burning at its current rate, it would last X years. If we add GR time dilation to the sun, in our reference the rate should appear to slow down, such that the sun should be cooler than Newtonian.

 

Let me give a time dilation analogy with SR, if a space ship had controlled fusion and burnt 100 nuclei per sec, in its reference, and was traveling fast enough where time dilation becomes apparent, in our reference, it may appear like its fusion rate is 99 per/sec due to time dilation. Or the apparent joules/sec in our reference would appear like 99% theoretical energy output. GR should make the sun appear to burn cooler, in our reference.

 

Cooler is sort of relative, with its current heat output the final result. But the point is if the energy output is lagging due to time dilation than maybe some of the energy transfer assumptions are not totally valid. If it was a better conductor of less heat we would get the same energy output.

[freeztar]

Here is General Relativity consideration.

 

Ok.

 

If gravity equals GR,

 

Which of course, it is not. GR provides an explanation for gravitation.

 

than stars should show some degree of time dilation.

 

And indeed they do.

 

What this means is the rate of nuclear reactions, in the sun's core for example, relative to our reference, should appear to slow.

 

This is not really correct as I understand GR. The reactions do not slow, but the photons emitted from the reactions are red shifted for bodies moving away from each other.

 

In other words, if there was no gravity, but the sun's core was nuke burning at its current rate, it would last X years. If we add GR time dilation to the sun, in our reference the rate should appear to slow down, such that the sun should be cooler than Newtonian.

 

What?

 

Let me give a time dilation analogy with SR, if a space ship had controlled fusion and burnt 100 nuclei per sec, in its reference, and was traveling fast enough where time dilation becomes apparent, in our reference, it may appear like its fusion rate is 99 per/sec due to time dilation. Or the apparent joules/sec in our reference would appear like 99% theoretical energy output.

 

Ok.

 

GR should make the sun appear to burn cooler, in our reference.

I see what you are getting at, but I don't think that it is quite accurate.

 

Cooler is sort of relative, with its current heat output the final result. But the point is if the energy output is lagging due to time dilation than maybe some of the energy transfer assumptions are not totally valid.

 

The energy is not "lagging". Light still travels at c.

 

If it was a better conductor of less heat we would get the same energy output.

 

I'm not quite sure what you mean by this but it seems, overall, that you are putting too much emphasis on hot/cold and not enough on here-now/there-then.

 

Time Dilation can be quite un-intuitive at times. Nonetheless, notice that the link above makes no mention of temperature as a basis of time dilation.

[sanctus]

I know the feeling, I don't like it either.

My main problem with curved space is that the "models" are all 2 dimensional. (along with the thinking):hyper:

Instead of all of the images and drawings that you've ever seen, imagine something that curves from a point outward IN ALL DIRECTIONS. (ALL)

So now describe a path along which something could travel.

Sorry there is no such thing as a path when you curve in all directions.

I know... I know... rotational orbit makes a difference but gravity is still working in ALL directions simultaneously. So which way is the curve?

There in lies my problem with this theory.

:)

Welcome then! No one claims to be able to imagine without the 2D analogy the curvature, but does this make the theory wrong just because you see it as too abstract?

[HydrogenBond]

Maybe I didn't explain myself well enough. If we assume Newtonian gravity, without any GR considerations, such as time dilation, the calculated Newtonian mass-gravitational-pressures-temperatures and density in the sun's core results in a certain nuke reaction rate. This reaction rate will be directly related to the energy output from the core.

 

If we add GR to the blend, and therefore some time dilation, because the reaction rates have a time element, these reaction rates should dilate. Or the reactions rates should appear to slow in our earth reference relative to the Newtonian predictions. If there is no change there is no time dilation affect coming from the GR relative to the Newtonian prediction.

 

Let me use a easier example. If one fell into a black hole, from the earth reference they would appear to fall forever. If we had a flashlight with a battery that last 24 hours on earth, it would now appear to last longer near the black hole. Or the energy output from the flashlight slows to trickle.

 

If we assume GR is valid, the slower nuke reaction rate in stars, should get proportionally slower with increasing star mass, since increasing mass implies increasing GR. If it doesn't, then GR time dilation is not valid or the assumptions of star innards need work.

[CraigD]

If we assume GR is valid, the slower nuke reaction rate in stars, should get proportionally slower with increasing star mass, since increasing mass implies increasing GR. If it doesn't, then GR time dilation is not valid or the assumptions of star innards need work.

This is a good thought, but I believe HydrogenBond fails to consider how many and complicated are the factors affecting the rate of stellar fusion, and how gravitational field strength varies within stars and other gravity-contained objects, such as planets.

 

The primary factors determining rate of stellar fusion is the temperature and pressure in the stellar core (by definition, where fusion occurs), and the abundance of elements there. The fusion rate changes significantly on a long time scale over the life of the star, and on the short term, as stars oscillate and vary (which, observation makes increasingly clear, even “non-variable” stars like Sol do, to some extent).

 

Like an Earth-like planet’s, the gravitational field strength that determines the gravitational time dilation factor actually decreases at some point as it approaches the center of the star, to nearly zero at the center. So the time dilation factor in the core may be less than in a star’s outer layers, and the time dilation in the core of a more massive star may be less than that of a less massive one. A good and succinct, if necessarily ideal description of this can be read in the “outside and inside a non rotating sphere” section of the wikipedia article “gravitational time dilation”.

 

Combined, I think these factors result in a situation where the effect on the rate of stellar fusion due to gravitational time dilation is so small relative to the other factors that it is, for all practical purposes, “lost in the noise”. So observing the bolometric magnitude of stars of different masses isn’t a good test of relativity.

 

From what I’m able to gather, the most precise tests of General Relativity, such as the Pound-Rebka experiment (a redshift, not time dilation, experiment), have been performed using very precise clocks to and very small differences in gravitational field strength.

[HydrogenBond]

From what I’m able to gather, the most precise tests of General Relativity, such as the Pound-Rebka experiment (a redshift, not time dilation, experiment), have been performed using very precise clocks to and very small differences in gravitational field strength.

 

The experiment demonstrates that even subtle gravity differences can exhibit a GR affect. All I was saying was in comparison to Newtonian predictions, with a slower GR time dilated reaction rate relative to the classical Newtonian prediction.

 

You brought up an interesting point about the center of gravity mathematically causing vector canceling. Although the directional force vectors cancel, the gravity scalar is at a maximum in the center. Does that scalar addition correspond to GR? The reason I ask that is the GR of a planet is often explained, in simple terms, as analogous to a bowling ball making a well in the fabric of space-time. If the vector addition is important than the bottom of that well should contain a peak since the gravity vector addition decreases toward the center. But it is never explained with a peak in the center, but appears to assume scalar addition for only a well.

 

This leads to two possible stellar reaction rate dilation scenarios. If the GR well is deepest in the center, no vector canceling peak, than the reaction rates are slower in the center and increase toward the perimeter, relative to classical gravity. If there is a peak in the center due to vector canceling, the rate in the center is slowest and increases outward. This can be understood with red or blue shift coming from the center. The first scenario implies blue shift into the perimeter for hotter reaction energy. The second scenario implies red shift into the perimeter for cooler reaction energy, relative to Newtonian.