Blackhole.
Why?
- It can't be seen. Yes! a blackhole cannot be detected neither with a telescope nor by any spacecraft, yet it is found to exist.
- It doesnot emit radiation. Being the most massive objects of the Universe ( an object of infinite mass ), it doesn't emit it's own radiation rather it is detected by the radiation given off by the body which is in it's acreetion disk. On the contrary, every body in this universe that has mass is found to emit radiation. An 'atom' ( basic structural unit of everything around us ) also emits radiation.
- If you wish to remain forever young, you should prefer going into a Blackhole. It's gravitational pull is so massive that even light cannot escape it's surface, time inside the blackhole stops.
- Even you can become a black hole. Theoretically,any object compressed to very high density has the potential of becoming a Blackhole.
- Despite being so massive, they can evaporate with time.
- Don't be surprised when a 5 ft 7′ guy suddenly looks like a 6 ft 4′ ! A phenomenon called 'spagehttification' takes place as your feet tend to get more closer to the center of Blackhole.
P.S.: No one is able to ascertain firmly the reason for all these phenomenon. The concept of Blackhole though discovered over a 100 years ago, still remains a matter of debate to the leading scientists of the World.