Cosmic Bubbles
February 29, 2016
A few days ago I was chatting with some physics students online, as I often do, and one of the students asked me if there were any well motivated theories for why the laws of physics in our Universe should happen to be just right to support life. In fact there are many very good theories on this point, ranging from landscape theories in the multiverse, to a Universe that evolves baby Universes through the formation of black holes, and through to very speculative ideas that have been put forth in the last few years on self-collapsing wavefunctions in quantum physics.And while any one of those would make for a fascinating article on modern physics theories, I am not going to discuss anything so speculative today.
What I am going to discuss is an idea that is almost universally accepted as being proven by experimental physics, and yet is not often discussed or thought about by the physics community. In my discussion with these students, I made an offhand remark about different parts of our Universe having different laws of physics. The students were understandably shocked and assumed that I meant there was speculation that such a thing might be possible. But they were wrong - it is actually a lesser known prediction of the Higgs model, which was confirmed at the Large Hadron Collider less than four years ago. Since the LHC has shown us that the Higgs model is correct, it follows that the Higgs model's predictions for variable laws of physics must also be assumed to be true.
According to the simplest form of the Higgs model, which is consistent with what has been detected at the LHC, there are two types of Higgs field. For this article I will call them H1 and H2. At the Big Bang, neither field existed in the Universe. However this empty state is unstable, and both H1 and H2 spontaneously appear in bubbles throughout the early Universe. These bubbles then started to expand until they meet with each other and form common boundaries (which may or may not be stable - it is possible that many of the bubbles just merge at their boundaries). As the Universe inflates and expands, these bubbles grow to be enormous - the one that we are living in is believed to be at least one hundred billion lightyears across!
That alone would be an interesting piece of astrophysical trivia, but the properties of these Higgs bubbles are perhaps even more interesting. The relative amount of H1 and H2 in each bubble is randomly formed a fraction of a second after the Big Bang, and while it is constant across each bubble, it is different in different bubbles. And from particle physics, we know that this relative abundance determines the strength of the electromagnetic force and of the weak nuclear force. (It is possible that the strength of the strong nuclear force is affected by a similar field, however this has not yet been proven in either experiments or accepted theories).
And so in each bubble, at least two of the four fundamental forces of nature will have different properties. Our bubble has the right mixture of H1 and H2 to allow molecules to form and interact in such a way that planets can form and evolve life. Another bubble might have a different mixture in which the electromagnetic forces are too weak to form atoms or molecules, and the weak nuclear force is so strong that all heavier nuclei decay away quickly to hydrogen. Yet another bubble might have a stronger electromagnetic force and weaker weak nuclear force, in which case heavier nuclei are more stable but the electrons might be too tightly bound to their nuclei to create certain molecules.
At present the two Higgs fields are the only experimentally confirmed fields that create different physical properties in different bubbles, but in theory there could be many more. More speculative theories also allow for variations in the strong nuclear force which holds protons and neutrons together, in the masses of the fundamental particles themselves, and even slight variations in the speed of light.
Given that there is an unimaginably large number of such bubbles - possibly even an infinite number - it follows that we can be certain that a significant number of them will have the right properties to evolve planets and life forms. The Universe is filled with bubbles, each of which possesses different properties, and we just happen to live in one that happens to have the right properties to support life.
And so without getting too deep into philosophy, the answer to the original question then becomes obvious: the laws of physics in our cosmic bubble support life, because only a cosmic bubble that supports life would support an observer who could ask the question!
What I am going to discuss is an idea that is almost universally accepted as being proven by experimental physics, and yet is not often discussed or thought about by the physics community. In my discussion with these students, I made an offhand remark about different parts of our Universe having different laws of physics. The students were understandably shocked and assumed that I meant there was speculation that such a thing might be possible. But they were wrong - it is actually a lesser known prediction of the Higgs model, which was confirmed at the Large Hadron Collider less than four years ago. Since the LHC has shown us that the Higgs model is correct, it follows that the Higgs model's predictions for variable laws of physics must also be assumed to be true.
According to the simplest form of the Higgs model, which is consistent with what has been detected at the LHC, there are two types of Higgs field. For this article I will call them H1 and H2. At the Big Bang, neither field existed in the Universe. However this empty state is unstable, and both H1 and H2 spontaneously appear in bubbles throughout the early Universe. These bubbles then started to expand until they meet with each other and form common boundaries (which may or may not be stable - it is possible that many of the bubbles just merge at their boundaries). As the Universe inflates and expands, these bubbles grow to be enormous - the one that we are living in is believed to be at least one hundred billion lightyears across!
That alone would be an interesting piece of astrophysical trivia, but the properties of these Higgs bubbles are perhaps even more interesting. The relative amount of H1 and H2 in each bubble is randomly formed a fraction of a second after the Big Bang, and while it is constant across each bubble, it is different in different bubbles. And from particle physics, we know that this relative abundance determines the strength of the electromagnetic force and of the weak nuclear force. (It is possible that the strength of the strong nuclear force is affected by a similar field, however this has not yet been proven in either experiments or accepted theories).
And so in each bubble, at least two of the four fundamental forces of nature will have different properties. Our bubble has the right mixture of H1 and H2 to allow molecules to form and interact in such a way that planets can form and evolve life. Another bubble might have a different mixture in which the electromagnetic forces are too weak to form atoms or molecules, and the weak nuclear force is so strong that all heavier nuclei decay away quickly to hydrogen. Yet another bubble might have a stronger electromagnetic force and weaker weak nuclear force, in which case heavier nuclei are more stable but the electrons might be too tightly bound to their nuclei to create certain molecules.
At present the two Higgs fields are the only experimentally confirmed fields that create different physical properties in different bubbles, but in theory there could be many more. More speculative theories also allow for variations in the strong nuclear force which holds protons and neutrons together, in the masses of the fundamental particles themselves, and even slight variations in the speed of light.
Given that there is an unimaginably large number of such bubbles - possibly even an infinite number - it follows that we can be certain that a significant number of them will have the right properties to evolve planets and life forms. The Universe is filled with bubbles, each of which possesses different properties, and we just happen to live in one that happens to have the right properties to support life.
And so without getting too deep into philosophy, the answer to the original question then becomes obvious: the laws of physics in our cosmic bubble support life, because only a cosmic bubble that supports life would support an observer who could ask the question!
I am a theoretical physicist & mathematician, with training in electronics, programming, robotics, and a number of other related fields.
