Einstein constructed general theory of relativity to uphold "all coordinate systems are equal".
Can't we summarize the final result like this: All coordinate systems are equal; some coordinate systems are more equal (at the vicinity of an event).
General relativity is valid for virtually all coordinate systems. But for local Minkowskian reference frame even the special relativity is valid.
The most important point is how the observers feel the spacetime. We think the observers age in local Minkowskian reference frame, if we bring a ruler or clock to somewhere in spacetime it will run same way in the LMRF. Practically, the speed of light is constant (1) in the LMRF which is a crucial parameter to model the universe.
Einstein assumed that the speed of light was constant, so the theory of relativity appeared. Then we now assume that the speed of sound wave transmission is unchanged, but also can establish a "sound speed of relativity". Using the logic of relativity, you will find that the speed of sound is also constant, and the air does not exist.
Relativity is wrong, which is quite obvious. Because we can also build a "sound wave relativity" by assuming that "the sound wave speed is constant", which, as we all know, is absurd. So why is Albert Einstein's theory of relativity right?
Hi Duan Xian Xiang,
I think you've missed the point. Maxwell equations (ectromagnetism) are not compatible with Newtonian mechanics and Galilean transformations. One example is that according to Maxwell equations the speed of light is a constant.
Einstein fixed this by finding the coordinate transformation that keeps both mechanics and electromagnetics valid. He did not arbitrarily choose the speed of light.
There was no issue with the speed of sound in the beginning because acoustics was always compatible with Newtonian mechanics.
Thamalu Maliththa Piyadigama
You can assume that "the speed of sound does not change," and that it is incompatible with Newtonian mechanics. Using the logic of relativity, you can perfectly deduce a "sound wave relativity theory", and it also has a lot of experiments and observations now matching it.
Why should you "assume" aacoustics is incompatible with Newtonian mechanics when it is actually compatible. Electromagnetics was never compatible with it. Einstein didn't just "assumed" it.
Thamalu Maliththa Piyadigama
You now know that acoustics and Newtonian mechanics are compatible, so you are already preconceived and reluctant to make this assumption. But what if a civilization doesn't know that acoustics is compatible with Newtonian mechanics? Can they assume that acoustic and Newtonian mechanics are incompatible? Is it possible to assume that the speed of sound does not change "? Humans now assume that "the speed of light does not change", I'm afraid that on distant foreign planets, where the aliens think that we don't know that the speed of light can change, and we actually assume that "the speed of light doesn't change."
Thamalu Maliththa Piyadigama
If a civilization lives in a vacuum and they never feel the air, can they do an experiment proving that air does not exist, then say "the speed of sound does not change," and then propose a theory of relativity? We just didn't find the medium of the light wave, and we don't mean it really doesn't exist. The Michelson-Morley experiment does not negate the existence of the aether. I would mention a new aether model that could not be measured with Michelson-Morley experiment.
The aether is like the atmosphere of a planet or like a gravitational field, (maybe it is a gravitational field). Every planet and a mass object has an ether, such as around the Earth and the sun. The Earth's aether moves with the Earth in the solar system, It is relatively stationary with the earth. The aether around the sun and the sun are relatively static, It's like a gravitational field from the sun itself. Because Earth's ether and Earth are relatively stationary, the Michelson-Morley experiment did not detect ether.
Yes, in theory you can assume speed of sound is constant to the every observer. But it doesn't solve any problem rather introducing one. Simply you are marking new set of space and time coordinates in a way that sound travels same speed. But you don't know what are the physical laws working in your CS. Niether Maxwell laws nor Newtonian mechanics works for that CS. You have to invent those laws.
(It is not hard now. You can deduce the equations from General Relativity which is coordinate independent.)
That is just some fancy work. Einstein's time there was the dire need for reconciling electromagnetism. Yea, later he converted his solution coordinate system independent (speed of light is not a constant in general relativity e.g. for Rindler's coordinates).
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