# A relative confusion

1. Jun 15, 2015

### ag048744

There is no such thing as absolute motion or rest. This is because one can record the speed of an object moving relative to it and find that it is in motion. The same holds for the object in motion. An observer on the object will observe the other observer moving relative to him. The measured velocity of the observer will be equal to the measured velocity of the other. So, am I right in saying whichever observer I choose to be with, I will witness equal relativistic effects in the object undergoing relative motion?

2. Jun 15, 2015

### RyanH42

Yeah,the motion will be same in relativity equations.If you see an object moves a velocity v other observer will see -v.
Can you be more spesific like giving an example ?

3. Jun 15, 2015

### A.T.

Only in flat space-time if both are inertial.

4. Jun 15, 2015

### harrylin

That is a positivist claim which cannot be validated. What we can say, is that according to current knowledge, no such thing as absolute motion or rest can be observed.
One could just as well conclude that it is the other object that is in motion. Thus we only find that the objects are in relative motion; for uniform motion we cannot determine which is moving, or if both are moving.
Yes indeed, as long as you mean with "whichever observer", that you set up a standard inertial reference system.

5. Jun 15, 2015

### ag048744

Wow, very fascinating. Could this mean that this could give rise to different universes?

6. Jun 15, 2015

### Mentz114

Er, I think not. The replies you've had would suggest that every inertial observer experiences the same universe viewed from a different perspective ( Weyl refers to relativistic effects as 'velocity perspective').

7. Jun 15, 2015

### ag048744

8. Jun 15, 2015

### ag048744

Hmm that is so strange. Is it possible for the observers with different perspectives to communicate to each other simultaneously?

9. Jun 15, 2015

### Mentz114

What do you mean by 'communicate simultaneously' ? It has a number of different interpretations.