If an observer is observing from his own frame of reference on a road, a car coming His relativity =paralax?

Question

Assume that car moving at a relativistic speed his lenght is shrinking relativisticaly but the observer sees the car getting bigger as it approaches him and the time it takes to appoach him is getting shorter. How does Relativity theory apply?

Is relativity an observational effect?

Answer 1

If we imagine this all happening on in 1 dimension, a line, (i.e. no up/down or side to side movement possible), then the only way something can travel is toward or away from the observer.
Even if this is not the exact case as in your example, this effect is easily done by merely turning one's head in order to align one's reference frame to the direction of the car's motion and thus would have the same effect.

In this case, our observer sitting at some location on the line and in his reference frame, everything else is moving either toward him or away from around him.
In his reference frame, he sees a car heading Straight towards him at relativistic speeds in the opposite direction he is facing.

A length contraction occurs only in the direction of motion as observed by the observer. In other words, if the car is moving toward/away from the observer, the car's length shortens, not its width or height.
The length contraction is in the same direction as the relativistic motion. Since we defined this to be a single dimensional system with only one direction of travel possible, the approaching car would not get thinner or shorter (less tall), but rather, its length would contract.

The effects of the car appearing wider and taller as it got closer and closer would still apply as normal since the car is not traveling in either of those directions.


In your own frame of reference, taking a measurement and finding that the car has experienced a length contracting still makes that measurement every bit as real and valid as a measurement taken from the other car's frame of reference (v = 0) where there is no length contraction.

Answer 2

The car is not getting bigger. Its getting closer.

Parallax does not apply - its an observational effect due to separation of objects/observers and angles of observation.