I watched new documentary made by smartest man
I suppose you're talking about Stephen Hawking.
when you are close to huge object like black hole
Not quite. What black holes do to space-time is that they bend the fabric to some outer confines beyond our current comprehension. It's like taking a fabric of stretched cloth and "
inching" a part of it towards yourself.
oh and btw, it is true that if you would go at the speed of light...you would get younger by a few seconds.
Nope, that is absolutely impossible. You cannot get younger. Time "relatively" slows down for you quite significantly. What Tnymeh has stated is a valid instance of the event.
Time travel
To be honest, I don't think time travel is possible. I have three reasons to believe so,
1. The TT paradox
2. Even if you do go back in time what probability exists that you or this so-called "your-past-self" would perform the same actions as you did. This, more-or-less, implies that you might not even have time traveled. However, you still came back in time to observe this sequence of events and that is absolutely ludicrous.
3. Time travel also brings into effect the argument of freezing time. Consider that I could time travel and/or freeze time. On one of my "frozen-time" excursions I see a mugger robbing an old lady. I immediately move the old lady away from the robber and "
lace" the robber in the jail.
However, when time "resumes" (from my perspective) it should be resuming from the very same moment as I had left it. Which means that even though I moved the robber and the lady, but, in confines of reality, they are still there, that event of robbery is still occurring (or will still occur) because time was frozen "relative" to ME and not to the man or to the lady.
It is a tad bit complicated to put my above argument in sane yet proper words. But I tried.
Although, sci-fi, fantasy and various sub-genres of novels, movies, etc., have banked upon and heavily advocated the use of time travel, but as it is I believe time travel is impossible and will (rather, must) remain so.