The biggest question: why is there something rather than nothing?
Some physicists claim the universe sprang spontaneously out of nothing at all about 13.5 billion years ago
Theoretical physicist Albert Einstein in 1944: his theory of general relativity describes how the large-scale universe works in terms of space, time and gravity. Photograph: Popperfoto/Getty Images
Possibly the most fundamental of all philosophical questions was first asked by Gottfried Leibniz in 1697 – “Why is there something rather than nothing?” This question is usually considered to be unanswerable, but some physicists now claim to know the answer, believing they understand how our universe sprang spontaneously out of nothing at all (see A Universe from Nothing by Lawrence Kraus, 2013 ). I think they are mistaken, but, in any event buckle your seatbelts while we go on a lightning tour of their arguments.
These physicists hold that our universe suddenly popped into existence in a big explosion out of nothing at all about 13.5 billion years ago. This event was pretty much inevitable because nothing is an inherently unstable state and the sudden emergence of the universe follows naturally from the two most powerful theories in science – quantum mechanics and general relativity.
Quantum mechanics deals with the very small – atoms and smaller particles. It tells us that empty space cannot exist. Even a perfect vacuum seethes with particles and antiparticles that suddenly spring into existence from nowhere and then instantly annihilate each other before they can be noticed.
Einstein’s theory of general relativity describes how the large-scale universe works in terms of space, time and gravity. Attempts to combine quantum theory and general relativity have only had limited success, but when quantum theory is applied to space on the smallest scale, space and time break into space-time bubbles. Just as particles and antiparticles form and disappear again in the vacuum, so do space-time bubbles.
However, it is possible for a bubble to survive because of a phenomenon called cosmic inflation. We know our universe is expanding and, extrapolating backwards in time, physics believes the universe began with the big bang, when all matter and energy were condensed into one tiny point that exploded. Inflation theory says that, immediately after the big bang, the universe expanded much faster than it did later on, expanding the quantum sized bubble of space at an exponential rate before it could disappear, instantly ballooning it from a small fraction of an atom wide to the size of a grain of sand. The expansion then slowed down and the energy behind it transformed into the matter and energy that fill our universe.
This cosmic inflationary period explains several characteristics of our universe that would otherwise remain mysterious. In particular, it explains why the cosmic microwave background (CMB), a faint echo of the big bang that still whispers throughout the universe, is almost perfectly uniform across the sky. In the absence of inflation, we would expect to find a much lumpier CMB.
According to Einstein’s general theory of relativity, the geometry of space-time could be either flat (like a desktop), curved back on itself like a spherical surface, or curved out like a saddle. Measurements show our universe is flat and this is critically important because only a flat universe could have sprung from nothing.
Our universe contains billions of galaxies, which begs the question as to where all this energy came from if the universe arose from nothing. The answer is that our universe is still nothing because its net energy is zero – all the positive energy in the universe is balanced by an equal amount of negative energy. Every particle in the universe creates gravity, pulling other objects towards it. Gravity is negative energy, but only in a flat universe is the energy of matter exactly balanced by the energy of gravity. This is all explained nicely in more detail by Robert Adler in bbc.com, November 6th, 2014.
This is heady stuff, but has physics really explained how everything came from nothing? I’m afraid it hasn’t because the “nothing” from which the big bang arose was actually not nothing. It was a coherent something, operating according to scientific laws - a seething sea of virtual particles dancing in a quantum mechanical field.
Where did this field come from? Nobody knows and quantum theory says nothing about this. So, the argument that the big bang popped out of nothing is fatally flawed. The big bang popped out of something and the question now is - where did this initial something and its quantum mechanical laws come from?
William Reville is an emeritus professor of biochemistry at UCC