- Patrick Farla

# String Theory, is it still relevant?

*This Article was written by Patrick Farla, Year 8*

To ask this question you first have to understand the basic concept of what string theory is. String theory is a concept that states the universe is constructed by tiny vibrating strings smaller than the smallest subatomic particles. As these fundamental strings twist, fold and vibrate, they create matter, energy, gravity, etc. You can think of it as a guitar string, when moved at different speeds, the sound it produces is at a different pitch and for string theory, different vibrations create different particles.

###### How do we know?

Well, we don't really, but you might ask why we don't use a very good microscope. Well to see a single atom is incredibly hard and you need a very good electron microscope. An atom is made of protons, electrons, and neutrons, which can be split up into quarks. Quarks are the smallest thing we can ever see (physically possible), this is because, to see something, the light has to reflect off of it and this is where the problem is. At this point, anything is too small for light waves to reflect off, so the particles just move around it with no reflections; a stronger ray of light will just push it to the side more. There is no way to see these particles of this size.

###### How did we figure this out?

In the summer of 1968, while a visitor was in CERN's theory division, Gabriele Veneziano wrote a paper titled, ‘Construction of a crossing-symmetric, Regge behaved amplitude for linearly-rising trajectories’. He was trying to explain the strong interaction, but his paper wound up marking the beginning of string theory.

###### What does this mean?

If string theory is true, this means that there are different dimensions all around us and this would solve a lot of quantum physics problems. If string theory is verified, strings would be the most fundamental units as the building blocks of everything.

###### Why hasn't string theory been proven yet?

Even in the low-energy limit, string theory requires a significantly higher degree of symmetry than this, therefore a low-energy prediction of superpartners should materialise. It is a huge disappointment for string theory because we have found exactly 0 supersymmetric particles, even at LHC strengths. Furthermore, because the strings are so tiny, it’s nearly impossible to check the validity by experimenting with the theory or the mathematics explained by it.

###### What current problems are in string theory?

The famous words of Wolfgang Pauli, "It's not even wrong," best capture it. Not only does string theory not predict any physical phenomena at experimentally accessible energies, but it also does not offer any predictions at all. Another reason is that if details are seen, string theory might not be able to explain them. One way to rule out the idea is if we can prove that it does not predict an essential feature of the universe, also string theory isn’t complete yet, it doesn't exist. We only have approximations that we hope come close to the actual theory, but we have no idea how right or wrong we are.

###### What are our next steps?

A “solution” in string theory would mean that there would have to be a spacetime vacuum that is regulated by Einstein’s theory of gravity in conjunction with the quantum field theory. With its own collection of particles, fundamental forces, and other defining characteristics, each solution defines a distinct.

We might never prove that String theory is true, Or possibly in our lifetimes, not now, or tomorrow, But for now, we don't have the instrumentation necessary to prove this theory, hopefully, one day, we will prove this.

(if you want to learn more about string theory in finer detail, read this university page)

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