As we saw in the previous video, Inflation explains the bang in the big bang, as the expansion it represents was far more extreme than the expansion predicted by the traditional big bang theory of general relativity.
. However, for our theoretical models of inflation to make sense, the initial state of the universe had to be set up in a special and highly improbable way.
The traditional inflation theory resolves a set of issues, but creates another - the need for a very special initial state.
The Einstein's theory of general relativity should be replaced with a more accurate theory, if we are to explain the origin of universe.
This is because, with energy concentrations so high, and matter compressed to microscopically small scales, one should expect the laws of quantum theory to come into play.
For practical calculations involving the everyday world, we continue to use classical theories.
But back when the universe was as small as the Planck size, one billion-trillion-trillionth of a centimeter, is the scale at which we should take quantum theory into account.
We don't yet have a complete quantum theory of gravity, but we do know that the origin of the universe was a quantum event.
So if we want to go back even further and understand the origin of the universe, we must combine what we know about general relativity with quantum theory.
First, we need to understand the concept that gravity warps space and time.
Imagine universe as a trampoline with edges held high in the air by long poles.
When we drop a heavy rock, it stretches the trampoline's center downward a great distance.
Now imagine yourself as a small ant living on the surface of this trampoline.
Though you can't step out of the sheet and observe the warpage, what you can do is march around it and measure the circumference.
You then discover that the circumference is shorter than the diameter itself.
Same with the warpage in our universe - it stretches or compresses distance between points of space, changing its geometry, in a way that is measurable from within the universe.
Warpage of time stretches or compresses time intervals in a similar way.