Is time constant?
No, time is not constant. There is no absolute time, where time passes at the same rate for everyone everywhere. Einstein prove that back in 1905 with his publication of Special Relativity. How fast time appears to pass is dependent on how fast you’re traveling and how strong the gravitational force is pulling on you. What this means is that if you’re moving very very fast, like close to the speed of light, then time passes very slow for you. Similarly, if you’re very close to a very strong gravitational field, like near a blackhole, time will passes very slow for you too. And if you’ve fallen into a blackhole, time will have appear to have stop for you when you reach the blackhole’s event horizon (that is where gravity is so strong that not even light can escape).
