ELI5: Why does gravity mean that the universe came into being "for free"? explainlikeimfive

Modern physics seems to suggest that universes are created constantly, because when we look at our universe, all the positive energy (matter and movement) perfectly cancels out with the negative energy (gravitational potential energy). Therefore, since there is always a net energy of zero, there is nothing stopping universes from coming into being, hence, universes always are coming into being.

This is my understanding from what I've read, but this explanation, in my opinion, has some huge problems.

So, am I understanding this incorrectly?

First of all, why is gravity considered negative energy? In entry level physics, gravity is considered positive potential energy. Why is it considered as negative energy in this context?

Second, and more importantly, consider a refrigerator. Through coils and gases, it creates an area of cold inside the fridge and releases heat outside of the fridge. Therefore, if we get this balanced enough, the process will net zero thermal energy, and we can run our fridge all day every day for free!

But even a trivial understanding of physics knows that isn't true. In this case, we are neglecting that, to create that temperature gradient, we run compressors and expanders that require power to keep running. So, while we began with 0 and ended with a net of 0, it took work to make (15 and -15) out of that 0.

Perhaps a more lofty yet still easy to understand example is matter and antimatter. Being polar opposites, these two are said to "cancel out". It has been noted that the two could be created "from the vacuum", and when you do so, it would always create the same number of matter atoms as antimatter atoms. This experiment, however, would require some pretty impressive electromagnetic fields, but you'd be able to take free space and "separate it" into matter and antimatter, which makes perfect sense to me.

But, do notice the qualifying clause. We would need some serious magnetic fields to do so.

So, even if matter plus antimatter equals 0, it takes work to turn 0 into matter and antimatter.

If gravity as negative energy makes sense, I'm fine with that, but wouldn't it take some seriously cosmic-level yet-unexplained ignition energy to separate 0 into positive energy and gravity?

I'm assuming I'm missing something. I think the multiverse is plausible, and even likely, but this explanation still feels lacking. Can anyone explain this in layman's terms?

Submitted May 06, 2015 at 09:00PM by dillionmcrich http://ift.tt/1KM3qMS explainlikeimfive