What if one is in 1905 and debating foundational fundamentals?

[sandip4]

Einstein's theories are accepted since 100+ years. Modern science built on it somehow provides a proof of truth of his theories but what if one is living when Einstein proposed his theories and debating its merit?

Einstein did two things:
1. He declared velocity of light as invariant c for all observers.
2. He removed vacuum as the preferred frame of reference and introduced relativity.

I like to know:
(a) How many experiments actually measure speed of light in other frames? Local frame will always measure c.
(b) What's wrong to have a preferred frame of reference? In Twin Paradox, is not the earth preferred frame of reference?

As a side note:
Assume that a man named Adam is all alone in vast space. Now can Adam take a step and walk? I am sure this question is commonly asked and I can guess the answer but issue is NOT about whether it is possible to measure distance traveled by Adam or his velocity. Issue is, is motion without any reference possible in space?

 

[Ibix]

(a) How many experiments actually measure speed of light in other frames? Local frame will always measure c.

What do you mean by "measure speed of light in other frames"?

What's wrong to have a preferred frame of reference?

There's no known theory with a preferred frame that is consistent with experiment. To put it another way, what's wrong with a preferred frame is that there doesn't seem to be one in reality.

Now can Adam take a step and walk?

He has nothing to push against, so no. He can wave his legs around. Or he can build a rocket and move.

 

[Orodruin]

2. He removed vacuum as the preferred frame of reference and introduced relativity.

This is incorrect. Relativity as such was not invented by Einstein. It is an integral part of Newtonian mechanics as well. “Vacuum” was never a preferred frame, nor was there any preferred frame in Newtonian mechanics.

What there was before Einstein was a belief in a medium called the ether, which was supposed to be the medium in which electromagnetic waves would travel and Maxwell’s equations would hold exactly in its rest frame. Declaring the speed of light invariant removed the need for such a medium.

 

[sandip4]

Thank you for making the post clearer.
Once ether was removed, why was vacuum or space not taken as stationary reference frame?

 

[sandip4]

What do you mean by "measure speed of light in other frames"?

There's no known theory with a preferred frame that is consistent with experiment. To put it another way, what's wrong with a preferred frame is that there doesn't seem to be one in reality.

He has nothing to push against, so no. He can wave his legs around. Or he can build a rocket and move.

I like to know how do they know speed of light is c in other frames of reference -nonlocal frames - without measuring it?

Can Adam move using a rocket? I carelessly said step thinking it is self explanatory that I am interested to know motion without any reference frame. Sorry.

 

[Ibix]

Once ether was removed, why was vacuum or space not taken as stationary reference frame?

How would you measure the speed of vacuum in order to know if you were at rest?

I like to know how do they know speed of light is c in other frames of reference -nonlocal frames - without measuring it?

What do you mean by a nonlocal frame? You seem to have invented the term, but you haven't defined it.

Can Adam move using a rocket?

Adam can certainly accelerate using a rocket and can measure his changing speed with respect to his exhaust plume.

 

[berkeman]

Can Adam move using a rocket? I carelessly said step thinking it is self explanatory that I am interested to know motion without any reference frame.

Adam doesn't need to build a rocket. As he is floating in space flailing his legs, he can just take off his space helmet and throw it hard in one direction to propel himself in the other direction (conservation of momentum).

Poor Adam.

 

[PeterDonis]

The OP question has been answered. Thread closed.