I think that's it. A recent discussion on reddit[1] mentioned that energy actually weighs something (because of e=mc^2), so the energy required to lift "1kg" o

I think that's it. A recent discussion on reddit[1] mentioned that energy actually weighs something (because of e=mc^2), so the energy required to lift "1kg" of energy would be exactly equal to the amount of energy that dropping it would produce. [1] http://www.reddit.com/r/AskReddit/comments/awi5k/what_is_the_craziest_fact_you_know_that_most/c0jrlxs http://www.reddit.com/r/AskReddit/comments/awi5k/what_is_the...