One theory to bind them all
- By Kanina Foss
Theoretical physicists like Professor Robert De Mello Koch have spent the last decade trying to come up with a theory to explain why the ludicrous is true.
It’s like trying to explain why oranges are blue, except that in this case oranges really are blue and if De Mello Koch and his colleagues can understand how, humanity could be jet propelled into a world of applications we can’t yet imagine.
The Wits physicist recently gave an inaugural lecture on the problem, which can be briefly framed as follows:
There are two very different ways of thinking about forces. The first – Einstein’s Theory of General Relativity – describes how forces act over long distances. This theory does away with Newton’s explanation of gravity and uses the curvature of space-time to describe why, if you drop a pen, it falls to the ground. General relativity challenges everyday intuition: ‘gravity as a force’ is replaced by ‘gravity as geometry’.
Apart from gravity, we have three other forces in nature: electromagnetic, and strong and weak nuclear forces. We use quantum field theory (the standard model) to describe these remaining three forces. Under this theory, which is used to describe forces acting over very short distances, force arises through an exchange of particles. For example, one electron can interact with another by giving it a photon, thus producing the electric repulsion between like charges.
The shocking, unimaginable thing which has been accepted as true and which De Mello Koch is trying to understand is that these theories must be equivalent – in other words, they are different ways of describing the same thing.
This means that the force which is keeping your body on the planet is secretly, the same as the force which is pushing electrons around in your computer.
A modern day Newton, sitting under an apple tree would not be wondering why apples fall to the ground. Instead, he would be wondering how the force pulling the apple downwards could be explained in the same terms as the exchange of particles happening as photons bounced off the apple and into his eye.
When physicists manage tobind general relativity and quantum field theoryinto one, unified theory, we will understand space-time on a whole new level. It will be possible to answer questions like how did the universe begin? How do black holes evaporate?
Furthermore, the applications which will arise may be limitless – as difficult to conceive of as the theory itself. It’s like a trying to imagine a washing machine before the understanding of Maxwell’s equations which enabled the discovery of electricity.
There are about 2 000 people in the world working on the theory and they are in constant contact with one another, sharing papers and discussions. The first thing De Mello Koch does when he switches on his computer in the mornings is to check the shared forum.
This problem is 80 years old and although there has been progress, we are still just coming up with the language to describe it.
How much longer will it take? De Mello Koch smiles. ‘I don’t know.’