Robert Adler has a nice article with the title Why is there something rather than nothing?explaining what our best theories say about why the universe exists at all and why it has the properties it does, such as being so flat and uniform.
He starts out with the idea that according to quantum field theory, a vacuum is not nothing in the classical sense but consists of quantum fields and is unstable. At small scales it consists of a foam of particle-antiparticle creation and annihilation and that in some cases inflation causes one of the bubbles to expand to macroscopic scales, creating all the matter we see in our universe and that as long as the universe if flat, the positive energy required for matter creation is exactly balanced by negative gravitational energy. Thus the creation of the universe does not require a net energy creation.
This explanation seems to presume that the existence of relativistic quantum fields even in a vacuum is a given and some have asked why that should be the case, and that a true ‘nothing’ would not contain these fields at all. In that case, the question raised by Adler shifts from how we get the material universe from a vacuum containing only quantum fields to how we get a vacuum of quantum fields from a vacuum of nothing. Whether this is a meaningful question is a contentious issue that I addressed last year in my post Much ado about ‘nothing’.
The bolded part: I’m afraid this is one of my pet peeves, especially since it’s ubiquitous in pop science articles and even some text books. In my years of studying quantum field theory, I’ve never seen the basis for this view, other than handwaving for things like vacuum polarization* and the Casimir effect. The closest thing to this picture in the formalism is vacuum Feynman diagrams. But these are static contributions to the vacuum energy, not stuff popping in and out of existence, with the implied time dependence. If someone can actually justify the ‘bubbling’ picture, I’d appreciate it.
If it’s used only in discussions of the early universe, that’s another matter. That’s all a pretty dodgy/speculative marriage of quantum physics and gravity. But the author clearly attributes it to quantum mechanics, even without gravity.
*I like Steven Weinberg’s term “so-called vacuum polarization”.
“and even some text books” should be “and even shows up in some text books”.
Ethan Siegel would be annoyed that Adler repeats the idea that cosmic inflation came after the Big Bang rather than before the Big Bang.
https://proxy.freethought.online/singham/2013/03/16/much-ado-about-nothing/
Damn. Wrong copy/paste link. This is the correct one:
https://medium.com/starts-with-a-bang/all-about-cosmic-inflation-211a64441ddd
Good try but no, it doesn’t help. You can’t get from an is to a why.
Science does not explain why there is something rather than nothing. And nor does religion neither.
I think I agree with Phillip if I understand him correctly. Unless the universe was created, there is no “why” it exists. And if it was created there’s the equally unanswerable question of why there is a god, gods or impersonal creator rather than not.
Sometimes in casual speech, the word why is used similarly to”how” or “by what process.” But even then, I’m not sure I see the meaning of asking for an explanation of the fundamental starting point of existence as such. Asking how that original state developed into what we recognise as a universe is very worthwhile and is usually what scientists are really investigating even if the word “why” is used.
In a non-universe where nothing existed, there would be no one to ask “why all this nothingness.” It seems like this line of reasoning can easily lead to teleological thinking.
Once I got into a brief debate with a (non-fundamentalist, very intellectual) Christian while waiting for a business meeting to start and he rattled off all of these criteria that had to exist for human life to be possible and thought that proved some anthropic principle.
By my reaction was basically, yes if things had been different enough then we wouldn’t be here Being non-existent, we wouldn’t know or care and if this imaginary alternate setup produced radically different intelligent beings they might be having a similar conversation.
One thing I don’t think I have ever seen is anyone explain why ‘nothingness’ should even be the null state. The Laws of Thermodynamics state that energy can be changed, but not destroyed. And E=MC^2 says that all matter is really energy. So why did there have to be a time when all this energy didn’t exist?
moarscienceplz @7:
One scenario is that the total energy of the universe is zero, with gravitational energy being negative, and balanced by dark energy, matter and radiation. But the concept of energy in general relativity is kind of dodgy. Theorists get into scraps about whether energy is conserved in our spacetime, or even whether an unambiguous definition of energy in the context of GR exists. See here and here.
To follow up on Rob’s comment, Sean Carroll has a nice explanation of what is going on in GeneralRelativity with respect to energy conservation and why it is possible to have two different interpretations of the same thing, one in which energy is conserved and one in which energy is not conserved, depending on how you treat the energy stored in the gravitational field.
But in any event, something called energy-momentum is always conserved.
Why is there something rather than nothing?
It’s revealing about human psychology that Leibniz seems to have been the first person to ask the question.