patrick.net

Here's my take.

What is nothing? Empty space, even if it were truly empty, i.e. no quantum fluctuations or virtual particles, is not nothing because space and time are things. They are not material things. They are ethereal things, but they are still things. A thing is defined by its properties. To have properties is to be a thing and thus not nothing. Time and space have properties that can be measured: distance, dimensionality, curvature. Therefore, they are things. An empty void is not nothingness because the void itself is a thing.

OK, so nothing is the lack of time and space, then? Well, that's not sufficient either. A spaceless, timeless system with no matter and no energy would be close to nothingness, but not quite. If such a system had any laws of nature, any patterns, then it would not be nothing because laws of nature are properties. The system would have to follow no laws and be indescribable by laws, and thus would not be a system in any sense of the word.

OK, so nothing must also lack any laws of nature and must have no patterns to describe because patterns or laws of nature are things. As such is nothingness logically consistent? Well, logical consistency is a property. It is a thing and it assumes other things, specifically mathematics which is essentially patterns and laws. Logical consistency is a very thing. It's an ethereal thing, but its definitely a thing with lots of properties. True nothingness would have to have no properties.

The lack of any properties cannot, by definition, be expressed. You can define a symbol like the null set to refer to the lack of properties but the lack of any properties itself cannot be expressed because any expression would be an assertion of properties. Put simply, there is something rather than nothing precisely because it is impossible for nothingness to exist for merely existing would make nothingness a thing.

The closest thing to nothingness one can express is something that does not exist like a perpetual motion machine. Such a thing doesn't exist and so is as much nothingness as can be. Possible universes that don't actual exist are as like nothingness as can be as well.

Another topic of interest brought up by the first video and briefly touched on by Tyson is the question, given the premise that our universe is a part of a multiverse, do other multiverses exist that are completely separated from our multiverse. More fundamentally, is that question even meaningful?

What does existence mean at this scale? What does it mean to say that a multiverse, not separated from us by event horizons, but rather completely separated from our multiverse with no connection, exists? If we say that such a multiverse has laws of nature or is logically consistent, then we are assuming a large framework in which such laws and mathematics operate and thus we violate the premise that the multiverse is truly separate from our own. If we accept the premise that the second multiverse is completely separated from our own then why should it obey mathematics and be logically consistent? And since there can be no interaction between our multiverse and that one, and mathematical and logical consistency does not apply, then what is the difference between that second multiverse existing and simply being an imagined possibility?

Such a distinct multiverse unbounded by mathematical and logical properties could never be interacted with by any means. Nor could the properties of such a multiverse be described. So what would existence even be defined as in this scope? Within the universe or the multiverse, to exist means to have properties and to interact with other things. At least the later does not apply to parallel multiverses, and the former might not be meaningful.

Parallel multiverses would in effect be supernatural entities, and supernatural entities can never, even in principle, interact with nature. Of course, such supernatural entities would have nothing to do with the "spiritual" beliefs and religions of any human being in history precisely because such supernatural entities cannot interact with our universe and no message, nonetheless moral code, could be transmitted. And nothing in a parallel multiverse could know of our existence.

So perhaps the cosmos -- a word I am commandeering to mean everything, the set of all systems, regardless of how big that is or how disconnected the components of that are -- is composed of an infinite number of logically consistent and maybe also not logically consistent possibilities separated by nothingness so they can never interact or contradict each other. The question then becomes does the cosmos have a unified set of laws, a unified math, or is composed of parts with completely different and incompatible laws that cannot be subsumed into a coherent whole, or is there only one universe or only one multiverse and nothing else exists?