The special theory of relativity seems to depend on the assumption that observer can have a velocity. Is this assumption correct?

Here is excellent animation of what happens in an electric field when a charge accelerates.

http://www.tapir.caltech.edu/~teviet/Waves/empulse.html

This acceleration causes a disturbance in the electric field that travels at the speed of light.

When we look at this animation, the viewpoint is covering the whole extent of motion without moving itself.

Therefore, isn't the "velocity of observer" an arbitrary assumption?

Question

The special theory of relativity seems to depend on the assumption that observer can have a velocity. Is this assumption correct?

Here is excellent animation of what happens in an electric field when a charge accelerates.

http://www.tapir.caltech.edu/~teviet/Waves/empulse.html

This acceleration causes a disturbance in the electric field that travels at the speed of light.

When we look at this animation, the viewpoint is covering the whole extent of motion without moving itself. 

Therefore, isn't the "velocity of observer" an arbitrary assumption?

primeralph · Answer

It all depends on the reference frame. In a moving observer's frame, he/she is stationary, so no velocity.
So, it depends on where you're looking from.

anonymous · Answer

Can we say that in the Theory of Relativity, the viewpoint of the observer is permanently tied to the body of the observer, because it is the body that has a velocity, and it is being identified as the observer's frame of reference.

But when we expand the viewpoint to the size of the universe then no “velocity of the observer” is necessary.

I need to understand the significance of the "frame of reference" better.

anonymous · Answer

Shall we be trying to understand the universe from the viewpoint of the universe, or from the viewpoint attached to a tiny body?

primeralph · Answer

Here's the story: yes the viewpoint of the observer is tied to the observer essentially. But of course on a large scale such as the universe, you might want to be more specific since there can also be parts of the universe in motion.

primeralph · Answer

A standard example of a frame of reference: you're in a car that's moving. In your frame of reference, the car is stationary and someone by the roadside would be moving. But from the perspective of someone standing by the roadside, your car is in motion. 
Here's another thing to it: say you're in a moving car and you flip a coin; the coin has been detached from you while it's in the air, so it will appear to have moved backward (since the car is moving forward). In your frame of reference, the coin moved back even though in reality, you were the one who moved forwards.