Reba said:
Where did the original elements come from? What caused "The Big Bang"?
Let's take a tour from the creation of the original elements to the Big Bang.
The original elements were mostly the usual kind of hydrogen, deuterium and helium. The helium and deuterium were created by fusion of the usual hydrogen nuclei, which are single protons, with each other and neutrons. This happened from one to three minutes after the Big Bang and the process is called the Big Bang's
nucleosynthesis.
Where did those protons and neutrons come from? The single protons and neutrons were made when quarks and gluons combined by 0.00001 second after the Big Bang. This process is called
baryogenesis because protons and neutrons belong to a class of particles called the baryons. There are three quarks in each baryon. Gluons are the particles that hold the quarks together.
Before baryogenesis, they existed in a soup called the
quark-gluon plasma. They think that they may have
created some of this in particle accelerators by accelerating particles and having them collide to make them as energetic as particles were soon after the Big Bang.
Where did the quark-gluon plasma come from? They are still working on that by accelerating particles to even higher energies and it could be a good idea to watch for very high energy cosmic ray particles from space that collide with air molecules, making showers of particles we can detect.
Before baryogenesis happened, they say that the universe increased in size very quickly for
various reasons you could read about if you want to.
They say that once they get down to small enough scales, they won't be able to go down any further because they'd reach the smallest possible units of space and time allowed by quantum mechanics. This is Planck length and Planck time. Planck length is 1.6x10^-35 meters and Planck time is 5.4x10^-44 seconds. Written out longhand, they would be 0.000000000000000000000000000000000016 meters and 0.000000000000000000000000000000000000000000054 seconds.
Planck time is the time light takes to travel Planck distance. On this scale, space and time are not smooth. For the
first Planck time after the Big Bang, the four forces of the universe were one force and there were no elementary particles. It's as if there was no room for any of those particles. Maybe it would be more meaningful to say that the Big Bang started at one Planck length and one Planck time.
To understand what's going on at those scales would require a theory of quantum gravity that does not exist yet unless you count superstring theories that people are working on. Those string theories say that particles are made of strings one Planck length long and they viberate in a number of dimensions in different ways, giving them different apperances. Those different modes of vibratation would be what we would see as different kinds of particles. They're still working on it now. Currently, it's a
protoscience, which means that they're thinking of ideas and models and preparing ways of collecting evidence.
Where did those strings or whatever particles are made of come from to make a Big Bang? Now they have some ideas about that. One idea, currently a protoscience, is
brane cosmology, which got some ideas from superstring theories. There are various versions of this. The idea is that our universe is contained by a thing called a brane that is moving though higher dimensions. Other branes could be moving around in those higher dimensions and affect our brane. Some people say that if branes hit each other, they would have Big Bangs.
Does this model make any testable predictions? Yes, they say that maybe the reason why gravity is much weaker than the other three forces of the universe is that gravity is the only force that could spread out in all dimensions, including the higher ones. They say that gravity would be much stronger than expected at sub millimeter scales because not as much of it had leaked away yet over the small distances like it would for distances over a millimeter. Now they're doing experiments to test the strength of gravity at sub millimeter distances to test the ideas of branes and higher dimensions that gravity leaks into loses strength to.
Where do those branes and higher dimensions come from? It could go on forever, but could there be anything at a top level that everything got created in or by? Some people could say that the brane stuff is what made everything. Others could say that a god did it. People could say that god made the brane stuff and made a Big Bang by causing branes to collide.
But we could ask what made the god and what made the maker of the god and go on forever. It's best to stick to things we have evidence for. They've thought of ways of testing the ideas of branes and higher dimensions and are doing it now. If we get evidence for the brane idea, we could say that it's possible that the branes had always existed and had always been colliding to make Big Bangs.
Why not put in a god? We could use
Occam's razor, which says "Do not multiply entities unless necessary." It means that we should make the least number of assumptions possible. It's also imporant for hypothesises to make testable predictions.
The branes ideas makes testable predictions about the strength of gravity at smaller scales that they are now working on measuring. Adding a god that made create the branes and make them collide or do whatever else to make the Big Bang happen adds another thing to our model, so it must be tested to see if there is any evidence of a god doing such a thing.
Nobody had shown me such evidence or a way to collect such evidence for such a god yet. So for now, the brane comoslogy is one of the possible ideas for what may be at the top level in scale and what caused the Big Bang that made our universe, without any assumptions about gods.