[Dark Tofu]

Does anyone know anything about general relativity, if so, I understand it generally, but have some objections to it and would like to know what you think.

1) Light is not the fastest possible propogation speed.

Consider the relationship between the earth and the sun. It takes 8 minutes for the light from the sun to reach our planet. Therefore, when we look at the sun, we are seeing it as it was 8 minutes ago. We travel in an (albeit slight) ellipse around the sun. Therefore, the sun is at one of the two focal points in our orbit. It appears to be in a place slightly off from that position. Therefore, it appears to be in a place other than at the focal point in our orbit. If gravity propogates at or slower than the speed of light, we would feels the effects of the sun's gravity, not from the focal point, but from a position slightly off of that focal point. That position would be slightly ahead of where the sun really is (consider a diagram of the sun and where we see its light from and where it would seem to be). Thus, our orbit would continue to expand, because the focal point would be continually moving away from the other focal point. Therefore, because our orbit is not growing (in fact it is shrinking) gravity must propogate much faster than light.

Also consider a binary star system where one star is a black hole. According to general relativity, the black hole would warp space so that it would be an infinitely deep hole (with respect to the warped 5th dimension), with the singularity residing at the bottom. There is therefore an infinite distance that must be traversed for the black hole to communicate with the star next to it. Therefore, according to general relativity, gravity (or gravitational waves in spacetime, I suppose) would have to propogate at an instantaneous rate, much faster than light!

Therefore, gravity must propogate faster than light and black holes as described by general relativity cannot exist.

2) An accelerated frame of reference is not the physical equivalent to a graviational frame of reference.

Consider first two skydivers that are a few thousand feet in the air, and are several hundred feet apart. When they reach the ground they will be closer together than they were at the beginning. This is because they would both be pulled toward the center of the earth, not in a parallel straight down. In empty space, two people floating at a certain distance apart would always remain at that same distance. These are called tidal forces. (Einstein tried to account for them, but it seems to me that he used circular reasoning. Anyway, there is more than this of course.)

Secondly, in a gravitational frame of reference, the strength of the acceleration gets weaker as you move away from the center of gravity (i.e. the higher you get above sea level the less you weigh), while in an accelerated frame of reference, your weight would stay the same at all distances from the flat floor. The floor would remain flat no matter how far you walked, while on earth it curves because gravity acts toward the single center of gravity (usually), while acceleration acts in the same direction for all points.

Thirdly, although the observer within cannot measure this, I think it is worth noting, that in all know accelerating reference frames, a force is required to cause this acceleration. If I want my car to go faster, I need to give it more gas. All except for gravity. Gravity has no force that causes objects to have a higher force. Gravity is the only reaction acceleration that has no force action according to GR, although it claims that it acts in exactly the same way as an acceleration.

Therefore, the equivalence principle from general relativity must be wrong.


These are just some thoughts I have been considering. Tell me what you think. Am I right, or am I horribly mistaken. Food for thought. I'd be interested to hear your responses.

[JerryLove]

I'm pretty sure they conduced experiments last year to measure the speed of gravity, and found it at c. I'll have to go look.

[Nate]

Originally Posted by JerryLove

I'm pretty sure they conduced experiments last year to measure the speed of gravity, and found it at c.

Now that's cool.

[nate95366]

If gravity propogates at or slower than the speed of light, we would feels the effects of the sun's gravity, not from the focal point, but from a position slightly off of that focal point. That position would be slightly ahead of where the sun really is (consider a diagram of the sun and where we see its light from and where it would seem to be). Thus, our orbit would continue to expand, because the focal point would be continually moving away from the other focal point. Therefore, because our orbit is not growing (in fact it is shrinking) gravity must propogate much faster than light.

What you're saying about the focal point of the gravitationally bound elliptical orbit isn't making sense to me. I'm having a hard time jumping from "time delay in the gravitational effect" to "ever expanding orbit" even after sketching the diagrams.

Nate

[JerryLove]

Agreed, and my bad for not reading more of the post.

Whether the sun actually exists at the epicenter of the gravity well we orbit, or whether it's slightly off, doesn't seem to create the effect you assert.

[Dark Tofu]

See if these pictures help you to understand what I was saying (they may not be in the right order, but you can figure the order out, it's pretty simple). What do you think?

Order is 1, 4, 5, 2, 3

[nate95366]

I think I can understand the diagrams well enough, but I still do not see how your conclusion follows, if indeed Earth does actually revolve around the sun and does not just travel on a line tangent to the sun.

Nate

[Nate]

Originally Posted by nate95366

if indeed Earth does actually revolve around the sun and does not just travel on a line tangent to the sun.

I have absolutely no clue what this thread is about, but isn't "traveling on a line tangent to the sun" basically what an orbit (revolving around) is? I mean, the earth travels in that line, sure, but it's gravity that keeps it in orbit, right? If it were traveling in the circular direction of the orbit to begin with, then gravity would cause it to start spiraling in towards the sun, right?

[Dark Tofu]

Originally Posted by nate95366

I think I can understand the diagrams well enough, but I still do not see how your conclusion follows, if indeed Earth does actually revolve around the sun and does not just travel on a line tangent to the sun.

Nate

That is exactly what I'm saying, though. Earth really does revolve around the sun, but general relativity says that gravity traverses at or less than the speed of light. I'm saying that according to GR, the earth would not workingly orbit around the sun. Therefore, because GR predicts something other than the way reality works, it is not right.
What do you make of my other thoughts?

[nate95366]

Originally Posted by Nate

I have absolutely no clue what this thread is about, but isn't "traveling on a line tangent to the sun" basically what an orbit (revolving around) is? I mean, the earth travels in that line, sure, but it's gravity that keeps it in orbit, right? If it were traveling in the circular direction of the orbit to begin with, then gravity would cause it to start spiraling in towards the sun, right?

I suppose I wasn't clear enough. Perhaps to be more clear, I should just say that the sketches don't help the position (that if gravity operates at the speed of light, the Earth's orbit should be ever-expanding) make any more sense to me.

Nate

[JerryLove]

Originally Posted by Dark Tofu

That is exactly what I'm saying, though. Earth really does revolve around the sun, but general relativity says that gravity traverses at or less than the speed of light. I'm saying that according to GR, the earth would not workingly orbit around the sun. Therefore, because GR predicts something other than the way reality works, it is not right.
What do you make of my other thoughts?

Actually: The Earth and the sun orbit a shared center of gravity... just like the Earth and the moon do.

now you have an issue with relaitivity. Relative to the Earth, the sun is pretty stationary (putting its gravity pretty much in the same spot it is). Since the sun is stationary, there's no movement to adjust for... though the pull of the Earth on the Sun will be where the Earth was 4 minutes ago.

If it makes it simpler, just remove the real Earth and Sun from the equasion and look only at the apparent gravity centers from one point or another), and you'll see how it works.