Hello skeptics and other lurkers,
Today’s post again comes courtesy of a tweeter, who asked a question along the lines of this post’s title. This is a question which I have wanted to deal with for a while now, and I think that tonight is as good a time as ever for me to deal with it.
The laws of nature (as you should all know by now) are the laws which define the four fundamental forces we observe (gravity, strong nuclear, weak nuclear, electromagnetism) and the mathematical equations which describe these four forces. Most of the plight of modern particle physics is to find out as much as we can about these forces and equations, and see how it works out for the universe now, in the past and in the future, hoping to discover as much about our universe as possible, with the ultimate goal being to finish with one sum which describes all of these forces, the Theory of Everything (TOE). Last night I talked about string theory and the TOE, and this is one of the important parts in answering tonight’s question.
One of the most important ideas in particle physics is that, under extremely high energies, three of the fundamental forces (electromagnetism, strong nuclear, weak nuclear) can be united by one Grand Unified Theory (GUT) which describes all three forces. This theory has survived mathematical attempts at disproof and appears strong mathematically. This Grand Unified Theory is very important to particle physics. The hope is that, under EVEN higher temperatures and energies, this Grand Unified Theory can be combined with gravity to create the Theory of Everything. Gravity has always been a thorn in the side of physicists, and is actually the least understood and proven of all the fundamental forces, despite its obviousness in everyday life.
The hope and expectations are that gravity and the other three forces can be combined under higher temperatures to form one Theory of Everything. If it is true, as predicted by modern physics, then this has surprising implications for the four fundamental forces.
When the universe was born in the big bang, it was in a state of extreme heat, pressure and energy. Then it went under a process called ‘inflation’, where the universe expanded extremely rapidly (faster than the speed of light) and cooled extremely rapidly. There are two factors which are important in answering our question. 1. At the start, the universe was in a state of very high energy and heat, and 2. The universe expanded faster than the speed of light. Now, if there was ever a time in the history of the universe where the four fundamental forces would be combined, it would be right at the start.
Now, one hypothesis of a multiverse is extrapolated from this. If the universe went under rapid expansion while the four fundamental forces were combined, it could be true that, due to different parts of the universe being cut off from each other because of the speed of light, in different places, the universe could have cooled at different rates, meaning that the four fundamental forces could be different in those universes. Due to this hypothesis, it could be true that from one big bang, multiple universes could have been created. The definition of a universe is all of the things which can be observed, and seeing that these places are cut off from each other due to the speed of light, you have your self a multiverse, with different laws of physics.
This idea, like all multiverse hypotheses, has ramifications for the fine-tuning of the universe. It is one which is also hypothesized by accepted physics models, and is one if the easiest to accept, seeing that we know there must be much more out there than the observable universe.