# Spaghettification and gravity in theory of relativity?

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1. Oct 7, 2015

### Pejeu

Per my layman's understanding, the apparent force of gravity, as explained by the general theory of relativity, is actually the result of rectilinear motion at uniform speed through warped spacetime.

1. If that's the case, what actually causes gravity for objects at rest with respect to the black hole? What is it about the difference of what a metre, in the direction defined by the black hole and the object, is nearer and farther away from the black hole that causes the object to accelerate towards the black hole?

2. How can we know a know a metre closer to a black hole along the direction defined by the position of the black hole and the object is different in length? Doesn't this require or imply the need for an absolute reference frame for us to know can be the case?

3. To my mind, the spacetime deformation would simply only warp the shape and size of objects with respect to the absolute reference frame rather than cause any acceleration. At least for objects which are stationary with respect to one another and which are not rotating about any of their own or each other's axis. It would not cause acceleration with respect to the warped spacetime.

4. How can spaghettification occur? Spaghettification implies and requires a difference in the force of gravity. How can this arise simply from a part of the object being in one place with respect to the warped space-time continuum and another part of the object being in a different place?

To my mind all this would do would be to warp the object with respect to some hypothetical absolute reference frame although in the warped spacetime continuum the object actually resides in the object would actually not experience any deformation.

If I'm permitted this crude analogy, similar to how blowing up a balloon with a drawing on it causes the drawing to become warped and deformed in the absolute reference frame in which we, the observers residing in that absolute reference frame outside the universe that is the balloon, see the balloon is indeed being inflated with respect to our reference frame and its surface is indeed being warped but this would cause no internal stresses for the drawing itself, which is embedded on the balloon's surface and not in the absolute reference frame we reside in.

As far as the drawing is concerned, it would have the exact same dimensions between any two points on its surface as it did before the balloon was inflated. Within the context / reference frame of the balloon - which is the simulacrum of deformed spacetime of its universe rather than the absolute reference frame with respect to which the balloon - and the drawing along with it - is indeed being deformed.

And this can be proven by drawing a uniform grid on the surface of the balloon along with the drawing itself, before the balloon is inflated. (Let's place the grid on top of the drawing and use a different colour so we can see it)

After the balloon is inflated, the drawing can be seen to be completely the same dimensions, with respect to the spacetime of the universe that is the balloon, as before it was inflated.

Which brings me to point 5.

How can expansion of the universe cause / account for the redshifting of light from other stars with respect to the distance from them and cause expansion of the distances between star / star systems / galaxy, with the reference frame of our spacetime continuum?

This likewise implies and requires belief in an absolute reference frame and that light actually travels along this absolute frame rather than through the spacetime continuum of our universe. But then, why would there exist gravitational lensing? Why would the path that light takes conform to our deformed spacetime continuum? If it did, there'd be no redshift because of the expansion of the universe.

Thoughts (I fully expect to be pilloried for this post but please don't simply delete it rather than addressing the points)?

2. Oct 7, 2015

### Chronos

Lorentz transformations are a well understood and validated principle in physics. I think it is safe to assume professional scientists are unlikely to have misinterpretted or misapplied it to cosmology. The 'absolute reference frame' idea as conceived by Newton went the way of the dodo about a century ago.

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