Recent content by sub_zero

i'm not sure from your question, but you can prove this by analyzing a few simple/isolated systems such as an object hung to a string on a frictionless surface, a simple pendulum, and many others examples, those are simple, and you can further study about the conservation of energy for more...

theoretically, he will stuck for ever in that place, i recommend you to read physics for entertainment, author yakov Perelman, it's very popular and you can find it easily. in that book yakov discussed that very situation by details.

the energy that produces gravity is from the potential energy the planet Earth has, this energy is by nature come with all heavy mass objects, one evidence for that, that the gravity and the mass of the planet are direct proportional to each other, and otherwise you may think, this coincides...

first, the light does not require any type of a medium to propagate in, and the light experience time, but according to the theory of special relativity, the time it does experience is less than the time you (the observers on planet earth) think it.