How is it possible that time can be relative?


I might be rambling here, but how is it even possible that the faster you go you perception of time becomes different. Why would going at light speed affect how much time passes for you? It’s weird how time, distance, and space can all be relative, but the speed of light can’t.

In: Physics

As I understand your perception of time doesn’t change at all. You perceive the time just as normal as someone not moving at near lightspeed. But given enough time you will say you spend a day in space and someone on earth will say you’ve been gone a week. By no means are my words precise but theyre descriptive.

There is also the famous light trapped inside two mirrors concept, I recommend checking that out. It helped me greatly increase my understanding of this.

I have one advise: look up a good course on special relativity (there is a chapter on it in the feyman lectures if you don’t know were to start). Although it is hard to really understant, it follows from the statement that any observer sees light moving at the same velocity (comes from experiment) and some basic math.

We think it’s weird because we are not used to it. We live in a world were everything we can see moves at slow velocities (compared to light). It is hard to give an eli5 besides every experiment we have done afterwards says it is this way.

In an ELI5 explanation:

Imagine a magic car. This car is a special car that can’t go faster or slower than it’s top speed. No one has ever seen it go a faster or slower speed. It is built so it cannot ever go a different speed, no matter when you look at it, it is always travelling at this speed.

Now imagine a huge aircraft carrier. This is a much larger boat than normal, with a large space for driving on it. This is a special boat that is very fast. It can travel at 90% the speed of the car.

Now imagine the car is driving sideways on the boat, while the boat drives forwards. You are standing on the boat. You see the car drive past at it’s set speed. That is good.

Now this is the confusing part. Imagine you are sitting outside of the boat. You see the boat drive past with the car driving on it. From your perspective, the car would be travelling at about 1.35x the max car speed. This is not allowed – the magic car always travels precisely at its top speed.

The solution to this is time appears to go much more slowly for the people on the boat from the outside (about 2.3x in this case) that way the car looks like it is driving at the correct speed for onlookers, but feels like it is moving the correct speed for people on the boat (who don’t feel any difference).

In the real world, the car is light (actually all EM waves, but light is the ELI5 version). Light cannot go a different speed, so when someone is travelling close to the speed of light (on whatever their aircraft carrier might be – a super fast rocket for instance) time passes normally for them, but someone watching will see them living life more slowly, so that the light is travelling at the correct speed.