There's no such thing as a free lunch, or so the saying goes, but that may not be true on the grandest, cosmic scale. Many physicists now believe that the universe arose out of nothingness during the Big Bang which means that nothing must have somehow turned into something. How could that be possible?
Due to the weirdness of quantum mechanics, nothing transforms into something all the time. Heisenberg's uncertainty principle states that a system can never have precisely zero energy and since energy and mass are equivalent, pairs of particles can form spontaneously as long as they annihilate one another very quickly.
The less energy such a system has, the longer it can stick around. Thanks to gravity – the only force that always attracts – the net energy balance of the universe may be as close to zero as you can get. This makes its lifespan of almost 14 billion years plausible.
If you take inflation into account, which physicists think caused rapid expansion in the early universe, we begin to see why MIT physicist Alan Guth calls the universe the "ultimate free lunch."
You can read the full story here or check out the rest of our Existence special.
In our previous animated explainers, you can find out why free will is an illusion or how animals shaped the human mind.
MacGregor Campbell, consultant
10:22 28 July 2011