# Law of Conservation of Energy

I find it hard to comprehend the law of conservation of energy. Allow me to explain my confusion.

I understand that the law of conservation of energy states that energy is neither created nor destroyed. However, it has to come to a point in time where the origin of that energy is magically 'created'. How do we explain that?

For example, you can say that the energy in a falling ball comes from a human lifting and dropping it. Of course, that energy comes from food that we eat, and so on, all the way to the Sun. I know that some of you may be able to explain how the sun gets the energy, etc., but you get my point. I can go all the way back until a single point where you can no long go back.

• The law of energy conservation is a consequence of the time translation symmetry of spacetime. That, of course, breaks down at $T_{cosmological}=0$. At that point the math inevitably suggests that it has to be violated. – CuriousOne Dec 30 '14 at 15:25
• There are lots and lots of related questions on this site. At a quick glance I can't find an exact duplicate, but browsing the search I've linked would be worth while. The quick answer is that no-one knows what happened at the Big Bang because we have no theory of quantum gravity to describe it. Note also that conservation of energy can be a troublesome concept for expanding universes. It's fine at short length scales, but (probably) violated by the universe as a whole. – John Rennie Dec 30 '14 at 15:31
• I can sense that there may be more of an existential than a physical question here. Is it related to "Where did it all come from?". That's not a very good question to ask from physics because "where", "does", "it", "all" and "to come" are very hard to define words in cosmologically correct terms. There are toy models of pre-big-bang cosmology in which one can potentially talk about these things, but they require a well developed ability to drop implicit assumptions that are deeply rooted in western philosophical "common sense". – CuriousOne Dec 30 '14 at 20:41