Nothing means no spacetime and no information but it cannot mean no mathematics or no laws of physics
Two weeks ago, Inspiring Philosophy posted a YouTube video claiming "A Universe From Nothing, Therefore God Exists!"
It starts with a bizarre quote of Lee Smolin who said that the information is important – one could have achieved the same thing by quoting people like John Wheeler, you don't need to spend one of the most glorious crackpots in the present world. Then it criticizes Lawrence Krauss and sort of endorses William Lane Craig, an Evangelical ideologue.
Inspiring philosophy seems to understand that one may create matter out of the "empty space", the vacuum state in a quantum field theory or its generalization. For example, during the cosmic inflation, the space becomes basically empty and exponentially increasingly empty. But at the end of the inflationary epoch, the energy carried by the oscillations of the inflaton field around the minimum gets converted to oscillations of all other fields that exist. And those are manifested as particles.
At the end of inflation, matter as we know it is created out of pure energy. And the initial energy needed to create all the matter of the visible Universe is really tiny. Why is it tiny? Because during the inflation, the total energy \(E(t)=\rho V(t)\) of the visible patch of the Universe exponentially increases. It increases because the energy density \(\rho\) is basically constant (much like the cosmological constant today but vastly greater) while the volume \(V\) is exponentially expanding.
OK, Inspiring Philosophy is probably OK with that but he and William Lane Craig say that the vacuum state of the inflating quantum field theory is not what a layman would consider "nothing". But a funny problem with this criticism is that I agree – and I am confident that Lawrence Krauss agrees, too.
Instead, physical mechanisms are known (at least at some preliminary level) that create the initial Universe out of nothing that also contains no space and time. One may describe such creation in terms of instantons. Imagine some Euclideanized, topologically \(S^4\) instanton solution of the field equations of motion. When you Wick-rotate this instanton to the Minkowski signature, it will really be interpreted as the tunneling from nothing – which contains no space and time – to something – which includes a spacetime, and an expanding one.
The Neverending Story only showed a modest version of the "nothing" where the Earth and other environmental details have been removed. What was the English name of the dog dubbed by Mr Cupák?
So physicists – I think including Lawrence Krauss – do mean that in physics, we may really describe creation of some spacetime out of something that has "no spacetime"! So this initial state has no fields in the spacetime or their fluctuations, either. Hartle and Hawking have made this proposal more detailed. They believe that the \(S^4\) instanton also predicts the "initial state of the Universe" and if you knew how to rigorously apply this formalism in string/M-theory, it would also predict which compactifications are much more likely than others.
Yes, quantum gravity does imply that a spacetime may arise from the initial state with no spacetime. Note that we can't describe the creation of the Universe out of no spacetime in terms of the rate \(\Gamma = dP/dt\) because there is no time and therefore \(dt\) in the initial state. If something, the final theory predicts the probabilities \(P\) – or probability densities per initial state \(\rho\) – with no "per unit time" qualification.
Inspiring Philosophy is perhaps unsatisfied. The initial nothing should be more nothing-like, we hear. At 3:00, it is being required that a true nothing contains
no spacetime, no matter, no quantum states, no laws of physics, no information.Because physics doesn't obey all these conditions – I agree it doesn't – it doesn't describe the creation of the Universe out of true nothing, and God is therefore needed, Inspiring Philosophy reasons. Well, as you may imagine, I disagree.
Let's look at the conditions one by one and a bit more carefully. I've said that even inflation creates matter out of "no matter" – the vacuum state of a quantum field theory. Nonperturbative quantum gravity goes further and there's really no spacetime – and not even time (some axis on which you could chronologically order many events) – in the initial state.
Now, a misunderstanding of Inspiring Philosophy is the information. He believes that there's still "information" when the nothing state tunnels to a spacetime state. But that's not true. The information of the initial spacetime-free state is exactly zero. There is no information there. It's meaningless to talk about the information (in the physical sense) in a state without time because the information is what comes out of measurements and those always take place while chronologically ordered. You can't get any information without the structure that allows the chronological ordering of measurements. Because the information only exists to the extent to which observers measure something, there's no information in the spacetime-less regime!
The information in the world around us is a huge amount of bits – and this number is an increasing function of the size of the Universe. The information was growing together with the Universe itself. And the initial tunneling event that created the spacetime out of the spacetime-less initial state created information out of no information, too.
So the frequently repeated assertion that the information must always be there is simply not true. In quantum gravity, the information may arise from no information.
One might object that such a creation of information is "non-unitary". Well, it would be if one could parameterize the Hilbert space in some way both in the initial and final state. But a funny fact about the spacetime-less initial state is that one can't really identify the individual pure vectors at all. The whole spacetime algebras of observables – like the effective quantum fields in the spacetime – are created along with the spacetime, too.
So I may be willing to say that before the event that creates the spacetime out of nothing, there are no quantum states. It's a bit problematic discussion here because the particular states in the Hilbert space are at least meaningless if there's no algebra of observables that an observer could be interested in.
But what I am certainly admitting is that the initial "nothing" cannot achieve to throw away all "laws of physics". If you want a physical explanation of anything, including nothing :-), you obviously need some laws of physics. Physics is unable to describe anything, not even nothing, with no laws of physics, but that's not a limitation of physics. This "inability" is because the desire for physics to do thing without physics is self-contradictory. It is exactly as silly as the complaint that God is impotent and incapable of creating the world without God.
It's the whole point of the pride of physics that when it explains something, including nothing, it may keep on assuming that the laws of physics are always valid. If they weren't valid, it would be a defect of physics, not a victory! So I think that Inspiring Philosophy and William Lane Craig get this point completely upside down.
"What was when there were no laws of physics" is obviously a question that doesn't belong to physics, much like the research of planets without animals doesn't belong to zoology. Pure logic and linguistics is enough to see that it doesn't. I think that this question is meaningless, too. I don't believe that it makes any sense to seriously talk about anything physics-related while assuming that no laws of physics are applicable at some moment. The laws may be unknown or probabilistic or effective or limited in some way but there have to be some laws, otherwise you're simply not doing science.
I think that there doesn't exist and there can't exist any sensible justification of the opinion that "something about Nature must be studied while assuming that no laws of Nature exist". For this reason, I also think that there can't be any sensible justification similar to one in this video that there should exist God. The laws of physics are at the top – and they stand above the initial "nothing", too. I understand that a religious person may want to preserve his belief that God simply has to be the ultimate boss of something, at least the ultimate boss of nothing ;-), but indeed, quantum gravity builds on the exactly opposite assumption. The laws of physics are placed above nothing or God – and they seem to work OK.
To complain that physics still uses the "laws of physics" that exist, so the set of things that exist isn't really "nothing", is both logically nonsensical and fully comparable to the complaint that God didn't achieve the creation out of nothing, either, because if God exists, it's also more than nothing. So at the end, with the very same logic, He is just another worker who turns one something into another something – e.g. a rib (or penile bone) of His son into a woman.
By the way, the second part of the YouTube video talks a lot and sort of uncontrollably about the need for observers, the importance of information, and even shows the crazy debate where some people were saying we live in a simulation. I agree with something but not everything and I won't respond to that because I don't think that the video has made any better case for such things.