Vacuum-ether and spacetime

Question

in the past you could not give an explanation for various phenomena in which was an action at a distance like magnetism or gravity that occurred in a vacuum; For this reason, it was hypothesized ether as something that would by connecting to bring the information of the positive charge to the negative charge (remaining in the field of magnetism), in short, was inconceivable that this attractive force could exist in empty. At a later stage it was thought to .......... Then with General Relativity about gravity is thought to a deformation of the space-time, for which (for example) the Earth has a fixed course in its turn around the sun Now excuse me if my question to the introduction I wrote inaccuracies, but did not know how to explain otherwise ........ I come to the question whether in the past had broken into the ether because it was inconceivable that a force could be transmitted in a vacuum, now why it can deform according to the General Relativity? If it is empty what deform? Then I have to re-introduce the ether for something to deform? I hope that no one gets a laugh for this my silly question, but instead to help me understand a little better as far as possible. Luca

Answer 1

Welcome to physics.se .

The luminiferus aether was postulated because of the existence of light as electromagnetic waves. Physicists at the time had studied waves in various media and could not conceive of a wave existing without a medium to carry it, similar to water for waves on the sea, or air for sound waves. So this hypothesized medium was an inertial frame against which everything had some velocity.

There exists the Michelson Morley experiment which first disproved the existence of the luminiferous aether and several later and recent ones. The disproof says that there is no basic inertial frame for electromagnetic waves, since they always move with velocity c in any frame.

The behaviour of matter and electromagnetic waves is consistent with this when described in terms of special relativity which ensures that the velocity of light is c. Any physics model that is Lorenz invariant assures that this is true. In fact field theoretical models for particle physics populate the vacuum with virtual pairs of particles, BUT, the whole model is Lorenz invariant so this teeming population of the vacuum is not the luminiferous aether of old.

General relativity equations also respect Lorenz invariance so even if it is hard to visualize space as an underlying dynamical system, since it is Lorenz invariant it cannot be thought as a substitute of the ancient luminiferous aether, either.

It is Lorenz invariance found to be always validated experimentally that disproved the existence of ether .

Answer 2

In general relativity, it is the geometry of the space itself which is dynamic.

• The metric determines the shape of spacetime we live in.
• This metric includes time and space, and thus can tell us: if you're moving forward in time (which we all are), standing still is "that way"; around a massive body, this happens to be towards the center of the body, thus, if we want to be at a static position, a force must be exerted to do so.
• The metric is dynamic, and thus the space we live in is changing all the time. The evolution of this metric is determined by Einstein's equations. One can show that wiggles and changes to the metric governed by Einstein's equations propagate at the speed of light.

These points illustrate why the introduction of ether is unnecessary. I think 'deform' is not the best word to use when thinking of General Relativity. A better way to think of it is in terms of a geometry of space and time which is non-euclidean.