‘Nothing’ is a tricky concept to think about and it is as much a philosophical problem as it is a scientific problem. The question “Why is there something rather than nothing?” has been tackled by different philosophers in different ways. Parmenides, the ancient Greek philosopher, stated that “nothing comes from nothing” which means for something to come into existence, there must be something else in existence first. You cannot, according to Parmenides, have nothing and then have something. So in a sense, the reason that there is something rather than nothing is that existence is something eternal – things have always existed.
The German philosopher Gottfried Leibniz points out that there is this fact, namely that “there is something instead of nothing”, and from this said that we need a sufficient reason to explain this fact. This is based on his principle of sufficient reason, which says that everything has a reason or a cause behind it. His explanation, then, for something existing instead of nothing is God. God, for Leibniz, is a necessary being (meaning it has to exist) – the reason or explanation for its existence is found within itself.
But with arguments like this, it is vital to define the terms that are used. It may seem like common sense to think of ‘something’ as a material object existing at a point in space-time, and ‘nothing’ as the absence of that object – or just void and emptiness – but is that really nothingness in a true and meaningful sense? The ancient Greek philosopher, Leucippus (who believed that all matter was made of “atoms”), maintained that ‘nothing’ was the void of space, but this void was still something that exists between material objects. This sort of went against the common-sense notion of ‘nothing’ being the absence of existence, or a state of non-existence.
Philosophers and scientists have been struggling with the question of whether space is empty, and even if it is, whether this means that empty space is nothing or not. If space is empty, does it still not exist? When we talk about ‘empty space’, do those words not refer to something real, or are we just referring to the absence of something real and tangible? Some logicians might say that since concepts are things, the concept of ‘nothing’ exists, even if that term does not refer to anything in reality.
In the world of physics, a lot of effort has gone towards pinning down what ‘nothing’ actually means. In the 2013 annual Isaac Asimov Memorial Debate (which can be watched here) a group of scientists and intellectuals discuss the definition of ‘nothing’. When empty space is suggested as a possible candidate, the philosopher Jim Holt rebuts by saying that even empty space “…has a topology, it has a shape, it’s a physical object” – the shape of empty space, by the way, is flat. Even if we eradicate empty space from the picture, the moderator of this debate, Neil deGrasse Tyson, still points out that we are left with something: “If [the] laws of physics still apply, the laws of physics are not nothing.”
The theoretical physicist Lawrence Krauss was also present at the discussion, and in that same year, he had published his book, A Universe from Nothing. In it, he details how modern physics shows how the universe could emerge from ‘nothing’, although he defines ‘nothing’ defined in a very specific, technical sense. Krauss argues that the closest we can get to nothing – and so the only meaningful thing that ‘nothing’ can refer to – is if we removed all the matter, radiation, and fields from space. There is now nothing in this empty space, but Krauss says that there is still activity going on.
Apparently, there are virtual particles popping in and out of existence on time scales so small that we would never be able to notice it going on. Furthermore, this kind of ‘nothing’ is unstable, and it is through this instability that real particles and radiation can come into existence. We know that these virtual particles exist because of the effect that they have on the properties of atoms. Also, even though we cannot measure them directly, if we take them out of calculations and predictions, then a wrong answer comes up; whereas if they are included the predictions then become incredibly accurate. This suggests that these virtual particles are a part of the fabric of empty space.
So, in empty space, there may not be any signs of ‘something’ on the large scale, but at the Planck scale space-time isn’t flat at all – there are vibrations and curvature, and a fundamental uncertainty in regards to the energy content. The Planck scale, by the way, is a value of energy at which the quantum effects of gravity take place, and it is a scale in which our present theory of sub-atomic particles breaks down (since we do not have a grand theory that has unified Einstein’s theory of gravity and quantum theory). In this quantum vacuum pairs of particles and anti-particles pop into existence for very short amounts of time.
Experiments have confirmed the existence of these particle/anti-particle pairs through the creation of an artificial vacuum. For example, in an artificial vacuum, you can place two uncharged metal plates facing each other, and the quantum fluctuations actually cause these two plates to attract each other. Quantum fluctuations could take place and could get stretched due to the expansion of empty space. Essentially, all material objects (both small and large) and radiation would be the result of quantum fluctuations being stretched. Galaxies, stars, and planets are areas where stretched quantum fluctuations have been affected by the force of gravity. This, Krauss believes, is how a universe could come from nothing.
It seems then that a distinction should be made between a philosophical and a scientific definition of nothing, although the philosophical definition of nothing is debatable. The philosophical definition of nothing may vary depending on which branch of philosophy is studying it: Eastern/mystical, existential, metaphysical, logical, etc. Krauss says that we have the answer to the question, “Why is there something rather than nothing?” from a scientific point of view; but he seems to have discounted the more baffling philosophical question, “Why is there something rather than the absence of existence?”
Why does a quantum vacuum with virtual particles exist in the first place? Perhaps the answer is that this kind of empty space has always existed and that some philosophical definitions of ‘nothing’ refer to something which is physically impossible. It may not be logically impossible for non-existence or the absence of everything to be (if that even makes sense), but such a state of affairs may be physically impossible if empty space were eternal, for example. But then you could always ask: Why is empty space eternal? There are clearly some mysteries yet to be solved when it comes to the concept of ‘nothing’.