ELIF: how is time relative?
In: Physics
The place to start is here: the universe has some kind of underlying set of fundamental rules. We know about 30% of those rules. In the past when I have posted a statement like that I received a huge number of replies saying that’s absurd and we know so much less, or that there is no way to know how much we know, etc. etc. etc. That’s why I like to do it. If we knew 90%+ of the rules we would feel pretty confident about things. If we knew <10% we wouldn’t even be able to make a sensible guess. We do OK. There is a ton we don’t understand, probably we mostly don’t understand, but we have definitely identified a bunch of basic particles, we definitely understand at least a few fundamental forces, and we have enough understanding that often our guesses and deductions about how things should work based on what we have seen prove to be true.
That’s a lot of setup for the actual answer.
The answer is we don’t really know. Time is slippery at the moment. Some people think it doesn’t even really exist. I have a very hard time accepting that proposition. What we do know is that the structure of the universe can be bent by gravity and time bends with both gravity and speed.
Lets take two examples. First. If I built a huge rocketship that could travel at just under the speed of light, I could point it at a distant galaxy a billion light years away, climb in, step on the gas, and I would be able to get to that other galaxy and still be alive. To me it would take a few months. Anyone watching me do it from Earth it would look like I was frozen in time inside the rocketship. The ship would be moving ahead at near the speed of light, but I would be frozen in time.
Second. Lets turn it around, if I could watch the people on Earth running around it would look as though they had been sped up. Is time going slower for me, or faster for them? Its harder to say than you might think.
The point is that time is really relative to the observer.
Latest Answers