Don't understand Michelson–Morley experiment

[gen x]

I don't understand why people in Michelson-Morley experiment expect that light speed in direction in Earth motion would be light speed + earth speed, if they measure speed from earth frame?
Of course, we will get always light speed if we measure speed from Earth frame(as they did).
If car travel 100km/h and you trow a ball forward at 10km/h inside the car cabine, ball will always have 10km/h if we measure from car, but we need to measure from outside of car ("rest frame") to ball have 110km/h.

So to measure light speed+earth speed we would need somehow measure that speed from that is at rest in relation to earth, but that frame dont exist in universe..

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[Ibix]

Light was, at the time, believed to be a wave travelling in a medium called the ether. Its speed would always be $c$ relative to the medium, and would vary relative to Earth as Earth moved through the medium in different directions. This is exactly how other waves in media, such as sound waves, behave. Their speed is fixed relative to the medium but not the source.

You appear to have in mind a ballistic model where light is a series of little bullets launched by the source. In this case its speed would be fixed relative to the Earth and Michelson and Morley would also return a null result. However, it's ruled out by astronomical observations. If you observe a binary star, light coming from the component coming towards us would be slightly faster than light coming from the component moving away from us, which would cause them to appear to spend more time moving away than moving towards us. This is not observed, so the ballistic model is wrong.

 

[gen x]

Light was, at the time, believed to be a wave travelling in a medium called the ether. Its speed would always be $c$ relative to the medium, and would vary relative to Earth as Earth moved through the medium in different directions. This is exactly how other waves in media, such as sound waves, behave. Their speed is fixed relative to the medium but not the source.

You appear to have in mind a ballistic model where light is a series of little bullets launched by the source. In this case its speed would be fixed relative to the Earth and Michelson and Morley would also return a null result. However, it's ruled out by astronomical observations. If you observe a binary star, light coming from the component coming towards us would be slightly faster than light coming from the component moving away from us, which would cause them to appear to spend more time moving away than moving towards us. This is not observed, so the ballistic model is wrong.

I just want to say that is perfectly clear if you measure light speed from earth frame you will always get same speed.

If they assumed that ether is static, how they now in which direction is earth velocity if earth moves around itself, sun, milky way, other galaxyies, universes etc etc? What if all vectors of all this velocities sum up to zero? Highly unlikely but mathematically possible?

If light speed is not depend on source speed, my logic is because it is massless so source speed can not add "additional energy" to photons. Is that correct?

 

[Ibix]

If they assumed that ether is static, how they now in which direction is earth velocity if earth moves around itself, sun, milky way, other galaxyies, universes etc etc? What if all vectors of all this velocities sum up to zero? Highly unlikely but mathematically possible?

That's why they repeated the experiment multiple times over the course of a year. We could have a zero velocity relative to a static ether at one instant, but not throughout the year.

If light speed is not depend on source speed, my logic is because it is massless so source speed can not add "additional energy" to photons. Is that correct?

No. Light coming from a source approaching you will have higher energy than light from an identical source moving away from you. This is one interpretation of kinematic red and blue shifts. Light from both sources will have the same speed, however.

Photons are entities in relativistic quantum field theory and they do not behave very much like a naive idea of a particle at all. Our general advice is that it is a mistake to try to understand light behaviour in terms of photons until you can study what they actually are. There are times when fudging it with "light is made of particles" will kiind of work (Einstein's explanation of the photoelectric effect is an example) but many times when it won't. Think of light as a wave until you have a solid grasp of special relativity and non-relativistic quantum mechanics. Then you can start learning relativistic quantum mechanics and studying photons.

 

[gen x]

That's why they repeated the experiment multiple times over the course of a year. We could have a zero velocity relative to a static ether at one instant, but not throughout the year.

If source is accelerating toward you, light will comes to you again at speed c?

Our general advice is that it is a mistake to try to understand light behaviour in terms of photons until you can study what they actually are.

Who know what they actually are? They are just math constructions, but what they are?

Is this relative time ,space just math abstraction that somehow produce correct results or reality?
Does theory need to fit reality or only need to fit measurments results?

Why Tesla didnt accept relative time,space ?