suppose two rockets with a passenger are nearing speed of light velocities and are going opposite directions. Relative to eachother one rocket will seem stationary while the other rocket will look like it’s going almost twice the speed of light. What do both passengers see?

Question

I can’t wrap my head around it. But maybe it might be a very silly question with a simple answer.

In: Physics

Answer 1

You know that shit where people say “time is the 4th dimension”? This situation is why people say that.

Time does funky shit. From the perspective of one spacecraft, they observe the “head” of the other spacecraft to be “in the past” where it has not traveled that far, and the “tail” of the other spacecraft to be “in the future” where it has traveled even further.

The effect is that the other spacecraft “appears to” compress along its length. Because it’s shorter, it doesn’t travel as far per unit time as it would add its “true” length so it goes slower than the speed of light.