The other day Alexey emailed me, wondering why physics textbooks never explain why the laws of physics are the way they are. They give us these mathematical expressions but why those as opposed to something else? It all seems so arbitrary.
In computer simulations, the code is written by a programmer who determines the rules for how things behave. The universe works differently. Its code is embedded and runs within the fabric of space-time. The properties of this fabric determines the “code” and rules for how things behave in that that universe.
Space-time seems to be a fabric composed of tiny vibrating pieces of energy “strings” which extend into multiple dimensions. Depending on how this fabric is curled and scrunched up, energy will “pulse” through it differently, giving rise to different forces, types of particles, and all the laws which run that universe. This fabric is very pliable and it is capable of producing nearly an infinite number of different universes.
Stanford professor Dr. Leonard Susskind compares this fabric and how it’s curled up to DNA. In biology, different DNA sequences give rise to different types of organisms. Within each cell of a living organism’s body, you can find a copy of their DNA code. In the same way, if you examine the properties of super tiny patches of this space-time fabric, its bending and folding is a sort of DNA sequence for that universe.
This fabric contains a lot more than just our universe. It contains many other universes as well. They’re all tied together in this common fabric, just like bubbles are in a champagne bottle. Unfortunately the scale of these bubbles is so massive, there’s no way we could travel between them.
So Alexey’s question gets more complex. If this fabric can bend and fold in all these different ways, why is each area of space-time within our universe so uniform in every direction? If the bending and scrunching was different throughout our universe, you’d have different laws of physics within different areas of space and time. Time would flow differently, different types of particles with different masses would exist in different areas of space, some areas would have stars and galaxies, other areas would not, etc. The “laws” could also change over time as well. How come this doesn’t happen?
It turns out that our entire universe originates from a very tiny patch of this space-time fabric which was blown into a huge bubble. Since it all originates from a small uniform patch, our universe is pretty uniform overall. If you look at all the stars and galaxies from a “birds-eye” perspective, they’re spread throughout space very evenly. The fabric is bent, curled, and scrunched in pretty much the same way throughout our universe, hence the “laws” of physics are the same everywhere.
There’s a lot more to say about this sort of thing, but I better stop now before I get way over my head. I still have a lot to learn about this stuff myself.