There is a problem at the heart of all science.
We have two theories that describe the fundamental nature of the universe. General Relativity and Quantum Mechanics.
They do this by explaining the four fundamental forces. They are the laws of nature that determine how everything in the universe interacts with everything else. These laws include gravity, which draws together objects with mass, and the electromagnetic force that gives us electricity.
On their own, General Revativity and Quantum Mechanics are spectacular theories. Physicist Richard Feynman once said that Quantum Mechanics has been shown to be so precise, that it can make measurements equivalent to the width of North America accurately to within the width of one human hair. General Relativity on the other hand is Albert Einstein’s most lasting and well known contribution to physics.
But one of them is wrong.
When you put the equations of each one together, they produce impossible gibberish.
Fortunately for most practical tasks that scientists do, the gibberish doesn’t matter. General Relativity describes gravity in the world of huge objects, like the orbits of planets and stars. Quantum Mechanics describes the world inside the atom. It’s only in two special circumstances that scientists would want to combine the two theories and the gibberish becomes a problem;
- When studying black holes
- When studying the Big Bang
While both of these are pretty important, the bigger problem is that we don’t want two of our most important theories to be inconsistent. We have to work it out.
Enter the ‘Planck length’. The Planck length an incredibly tiny distance at which gravity starts to meld with the world of quantum mechanics. If there is an answer to how to make the theories consistent with each other, it happens at the Planck length.
The leading theory is called ‘String Theory‘. It proposes that the particles of Quantum Mechanics are like musical notes produced by tiny vibrating strings. The length of the string is supposed to be the Planck length.
The only problem is that it is really, really small. One of the smallest things that we have ever actually measured is the radius of the electron, which is about 10-22 meters. The Planck Length is estimated to be ten trillion times smaller at 10-35 meters.
Things this tiny are way beyond our ability to experiment on right now, and as a consequence, solving the inconsistency between two of our greatest theories in physics is likely to remain a mystery for some time.
But it’s nevertheless really interesting for physicists, as the Planck length is a distant new frontier for science. What we find there may effect everything that we thought we knew about the universe.