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Nothing. Nil, naught, zilch. The absence of anything. It's easy to think that ‘nothing' is insignificant, but far from it; the concept of ‘nothing' is fundamental to our Universe.
What is 'nothing' though? It's a difficult question to answer, because wherever we look around us, there always seems to be something there. Just trying to imagine absolute nothingness is tricky.
Consider a simple area of space, let's say the contents of this jar pictured. Now remove everything we possibly can from inside of it: all the air, molecules, particles, every single atom... until there are no things left in it. Now what still exists inside the box? It is really nothing? Or is there something still in it?
This is an important question because such 'emptiness' makes up most of the Universe; the atoms that make up everything, including us, are mostly empty space.
Studying this nothingness has revealed nature's deepest secrets and helped us to explain why we exist.
For over a thousand years our understanding of nothingness was through the ideas of the Greek philosopher Aristotle who believed that nature would always oppose the existence of true nothingness. This all changed in the 17th Century due to work by Torricelli who created the first sustained vacuum and Pascal who furthered the work. Their experiments revealed a profound truth - that nothing is everywhere.
Cause and effect. Action and reaction. This is how our everyday classical world behaves: sensible, predictable, and understandable. But the microscopic quantum world is very different. It's strange and based on uncertainty and probabilities. You can never be sure of what's going to happen, not because the experiments and measurements aren't good enough, but simply because of the inherant uncertainty present.
Heisenberg's Uncertainty Principle states that there is a fundamental limit to the precision with which two physical properties of a particle can be simultaneously known. The common interpretation of this is that it means the more precisely we know where a particle is, the less we know about its movement. Unfortunately there's no way around this, it's an inescapable feature of reality at this scale. So what has this quantum weirdness got to do with the concept of nothingness? Well this theory can take a different form, in terms of energy and time. Let's think again about that ‘empty' jar...
If we examined a very small volume of space inside the jar, we could in principle know precisely how much energy it contains. But if we could slow down time and look at it over a very short time interval, things start to get strange. According to the Uncertainty Principle, because we're looking at that bit of space over a small interval of time, we've lost the ability to know exactly the amount of energy present there. If we could examine an even smaller volume of space inside the jar over an even smaller interval of time, then something weird can happen. How much energy there is in that part of the box will be so uncertain that there is a chance it could contain enough energy to create particles literally out of nowhere.
Heisenberg's Uncertainty Principle suggests that in extremely tiny amounts of space and time, something can come from nothing.
But how? Surely this makes no sense? Well this seemingly empty space, contrary to what we would intuitively expect, is teeming with what physicists call quantum fluctuations, little packets of energy that appear and disappear very quickly. This is perfectly allowed by the laws of physics, with the Uncertainty Principle telling us it is possible to borrow energy from nothing as long as it is ‘paid back' quickly enough. This concept, strange though it seems, is fundamental. This theory of quantum mechanics explains physical phenomena at the microscopic scale, and is the most accurate and powerful description we have of our Universe.
There is a much more dramatic way that this idea and the effects of quantum fluctuations can be seen rather than just inside that arbitrary jar. The ‘Big Bang' theory, our best take on explaining how the Universe began and how we came into existence, says that the entire universe appeared nearly 14 billion years ago out of nothing. Tiny quantum fluctuations suddenly produced the energy that led to the rapid expansion of space and the mass that then continued to grow and develop into the stars, galaxies, and everything else we see around us today. The strange truth is the profound connection between our infinite Universe and the nothingness from which it originated; nothing really has led to everything.
Image credits:
Jar of Nothing: Heshmista
