Much ado about nothing

TODAY I will bounce off perhaps the most fundamental question ever asked, “Why is there something rather than nothing?”, which was posed by the German philosopher GW Leibniz (1646-1716). Leibniz conceived of nothing as a void or a complete absence of content.

He wasn't to know that, 300 years later, physics would say that a complete emptiness cannot exist and, even more surprisingly, that our entire universe popped spontaneously out of nothing, or as close to nothing as it is possible to get, 13.7 billion years ago in the Big Bang. As comic novelist Terry Pratchett put it: "In the beginning there was nothing, which exploded." You can pursue this matter in more depth in Issue No 2822, New Scientist,July 23rd, 2011.

What about entropy, you may ask? Entropy is a measure of the disorder of a system – the number of ways you can rearrange the components of a system without changing its overall appearance. Thus, the entropy of a gas, with its molecules moving randomly about at high speed, is high, whereas the entropy of a living cell is low – it will die even after a small rearrangement of its components. The Second Law of Thermodynamics forbids any closed system to spontaneously decrease in entropy.

Nothingness is the highest state of entropy – mix it up all you like and it remains identical; it remains nothing. Obviously, entropy decreases when nothing turns into a universe, but how is this possible? This is where the concept of symmetry comes in. Symmetry exerts a major influence on the universe.

Nothingness is totally symmetrical but physics has shown that this perfect symmetry is very unstable. States have been formed containing no quarks (quarks are the fundamental components of matter), but such states spontaneously form quark and antiquark pairs, which breaks the perfect symmetry of nothing. Something is the more natural state of nothing.

Try to think of a state of nothingness – a condition devoid of matter and radiation. Quantum physics tells us that such a “void” is not empty but seethes with activity as particles and their anti-particles spontaneously popping into existence and quickly disappearing again, before, as it were, the void has time to notice their existence. The greater the energy of the particles or fields that spontaneously appear, the shorter the time they can exist before they disappear, and vice versa. Hold this thought – we will return to it.

Physics tells us that the universe began about 13.7 billion years ago in a giant explosion in the void called the Big Bang, and it has been expanding outwards from that point ever since. Within a tiny fraction of a second after the initial explosion, the universe “boiled up”, going through a period of exponential expansion when it grew from a volume of diameter less than that of a proton to about the size of a grapefruit . Inflation then stopped and the universe continued to expand more sedately.

Inflation flooded the universe with energy but created the space-time of the expanding universe. Einstein’s general theory of relativity tells us that space-time means gravity. Gravity pulls matter together and represents negative energy that can cancel out the positive energy of inflation. In fact, when you add the negative energy of gravity to the positive energy of the expanding universe you arrive at an overall energy for the universe that is close to zero.

Now, if you think back on the longevity of the particle that spontaneously pops into existence in the vacuum, you will recall that the smaller its energy the longer it can last. This explains how our universe, with overall zero energy, has lasted, so far, for almost 14 billion years. The universe is, in fact, just a peculiar configuration of nothingness. This may sound like a fantasy to the non-physicist, but the scenario comes from mainline physics.

What came before the Big Bang? This is a meaningless question since space and time began with the Big Bang. Stephen Hawkings likens asking this question to asking what is north of the North Pole. Apparently nothing existed before the Big Bang – except, as I described, physics cannot deal with nothing. Physics can visualise the universe arising out of a quantum fluctuation in a vacuum but this means that the laws of quantum mechanics were already in existence. Where did these laws come from? From nowhere, I suppose.

William Reville is a UCC emeritus professor of biochemistry and public awareness of science officer at UCC. understandingscience.ucc.ie