Though the universe is 3-D, what I don't get is how it expands equally without having a centre. I have seen the raisin bread analogy, isn't there a centre to that raisin bread? The univserse is expanding equally in all directions, how is there no centre?
I've seen the example when people say the universe is expanding like the surface of a balloon. You have dots on that balloon which are galaxies and as you blow up that balloon they grow further away from each other. If the universe is expanding equally isn't there a centre which is constantly...
If I am correct, no law of physics says traveling back in time is impossible? Einstein's theory of special relativity dictates that an object gains mass as it accelerates. The faster it goes, the more massive it becomes. The more massive it becomes, the more thrust or push it requires in order...
The Multiple universes hypothesis states that there are infinite number of universes, collectively known as the "multiverse". If a person is about to travel back in time, he will create his own parallel universe upon arrival in the past. So if he kills "his" grandfather, a paradox would not...