December 3, 2021

I, Science

The science magazine of Imperial College

How thinking about nothing has led us to theories about everything...

What is nothing? It’s a very difficult question to answer, because wherever we look around us, there always seems to be something there. Even just trying to imagine absolute nothingness is tricky.

Let’s think of a box:


Now let’s 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?

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 explain why we exist. This is because our best theories say that the entire universe appeared nearly 14 billion years ago out of nothing.

For over a thousand years, our understanding of nothingness was though 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 this work. These experiments revealed a profound truth – that nothing is everywhere. Our Earth is just a tiny point floating through in an enormous void.



Newton’s balls. Action and reaction. Cause and effect. 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. 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 fundamental uncertainty.

Heisenberg’s uncertainty principle (HUP) states that there is a fundamental limit to the precision with which two physical properties of a particle can be simultaneously known. This 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, the HUP can take a different form, in terms of energy and time. Let’s think again about that ‘empty’ box:



If we examined a small volume of the space inside the box, we could in principle know very precisely how much energy it contains. But, if we could slow down time and look carefully at a very short interval, things start to get strange. According to HUP, because we’re looking at a small interval of time we’ve lost the precise information about the exact energy in that part of the box.

If we could examine an even smaller volume of space inside the box over an even smaller interval of time, then HUP suggests 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.

The uncertainty principle suggests that in extremely tiny amounts of space and time, something could come from nothing. But how?

The void, 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 HUP telling us it is possible to borrow energy from nothing as long as it’s paid back quickly enough. This concept, strange though it seems, is fundamental to our universe. 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.

But there is a much more dramatic way idea that we can see the effects of these quantum fluctuations than envisaging an empty box. The ‘Big Bang,’ our best theory of how the Universe began, says it appeared from nothingness and expanded very rapidly. So the rules of the quantum world contributed to the large scale structure we see today. Tiny quantum fluctuations suddenly expanded, and continued to grow into stars, galaxies, and everything else in the universe. The strange truth about reality is the profound connection between our infinite universe and the nothingness from which it originated – nothing really has led to everything.

IMAGE: Anderson Mancini, flickr.