String theory is probably one of the wildest theories that has ever come out of science.
But to verify any theory, we need to design and run experiments. At the beginning of modern science, a person like Galileo could build their own instruments by hand and discover new things about the universe. He discovered the moons of Jupiter that led to confirming the theory of heliocentrism, which is the theory that the Sun is at the centre of the solar system.
But as science has advanced, and the deeper and further that we peer into the universe, the more sophisticated equipment we’ve had to build. At the cutting edge right now is the Large Hadron Collider, or LHC. It’s a facility so expensive (at $4.75 billion USD to build and $1 billion per year in running costs) that it requires the collaboration and funding from over 100 countries to keep it running.
Enter string theory. It arose from an entirely theoretical basis in an attempt to bridge the gap between the theory of relativity with quantum mechanics. It’s based on the idea that all subatomic particles are made up of tiny, vibrating strings. The strings are predicted to be so tiny that if a quark was blown up to the size of the sun, a string would be smaller than a human hair on its surface.
You can barely see the Earth next to the sun, let alone a human hair.
This colossal distance between the smallest thing that we can see right now and a string is why string theory is not confirmed. We aren’t even close. To see strings, we need either a particle accelerator the size of the galaxy (really), or a new approach.
Fortunately, there may be another way. Some scientists think that a fraction of a second after the Big Bang, where the universe expanded rapidly from an infitesimally tiny point, the universe must have been about the size of a string. So we may find ‘shadows’ of strings in the overall shape of the universe. The idea goes that building a telescope powerful enough to see them is probably going to be easier than building a galaxy-sized particle accelerator.
From the perspective of physicists string theory is a really elegant theory, and it could be the solution to one of the biggest unsolved problems in physics: why general relativity and quantum mechanics seem incompatible.
But there’s a problem.
But even though string theory is so far away from being verified, our bias towards it is strong. There could be other theories out there that are not getting any attention because string theory hogs the limelight.
Many careers and huge amounts of financing have been invested into the research and development of string theory, and it is becoming increasingly entrenched in the scientific community. Academia, because of a limited number of resources and tenure positions, is regularly a zero-sum game. This may mean that alternative theories may not be getting the time that they deserve.
In any case, right now there are no competing theories that come close to string theory when it comes to explaining the deepest layers of the universe.