Scientists have observed the universe through many different lenses over the years, and
the models and theories have shifted, giving rise to new revolutionary concepts. Not all
of them turn out to be accurate, but no one should ever complain that physics is boring.
String theory is maybe one of the most fascinating, not to mention complex, notions to emerge
from theoretical physics. String theory is a framework to bring together
the two pillars of 20th Century physics, quantum mechanics and Albert Einstein’s theory of
relativity, into a single framework that can describe all of the reality of physics.
It attempts to do so by positing that particles are one-dimensional, string-like entities
whose vibrations determine their attributes, such as charge and mass.
According to a website on string theory created by the University of Oxford and the British
Royal Society, this counterintuitive hypothesis was first developed in the 1960s and 1970s,
when strings were used to simulate data pouring out of subatomic colliders in Europe.
Strings gave a classic mathematical way of explaining the strong force, which keeps atomic
nuclei together and is one of the four fundamental forces in the universe.
One of the four forces used by physicists to describe nature is gravity.
However, unlike the other three forces: strong force, weak force, and electromagnetism, gravity
is so weak that it cannot be observed or detected on a particle scale. However, its effects
are only significant on cosmic objects like the moons, planets, stars, and galaxies.
In addition, gravity does not exist as a particle of its own. Theorists can estimate the shape
of a gravity particle, but when they try to determine what happens when two of these gravity
particles collide, they get an endless amount of energy crammed into a small space.
One probable solution that theorists acquired from nuclear physicists in the 1970s was to
abandon the complex, point-like graviton particles. Strings are capable of colliding and rebounding
without implying physically impossible infinities. String theory rewrites the traditional universe
description by replacing all matter and force particles with only one element: small vibrating
strings that twist and turn in intricate ways that appear to us as particles.
A photon may be formed by a string of a specific length striking a specific note, and a quark
could be formed by a string folded and vibrating at a different frequency, and so on.
Besides taming gravity, string theory was appealing because it promised to explain supposed
fundamental constants like an electron’s mass.
Theorists hoped that the next step would be to find the appropriate way to explain the
folding and movement of strings, then everything else would follow.
However, that early simplicity came at the expense of unexpected complications; string
math didn’t operate in our four-dimensional world, that is, three of space and one of
time. It required a total of ten dimensions, six
of which were visible only from the perspective of the small strings, similar to how a powerline
appears as a 1D line to birds flying far overhead but looks like a 3D cylinder to an ant crawling
on the wire. Today’s string theory differs significantly
from that of the 1960s and 70s. Researchers are divided on whether it is still
the best candidate for a “theory of everything”, with adjustments, or whether theorists should
forsake it in favor of other subjects. There were several solid reasons to bring
a standstill on working on the string theory between 1973 and 1974.
It remained negligible for many years until the “string theory revolution” in 1984,
when theoreticians Michael Green and John Schwarz came up with equations showing how
strings avoided certain irregularities afflicting models that defined particles as point-like
objects. However, five different theories emerged from
the initial blooming, each describing how one-dimensional strings oscillated in a 10-dimensional
reality. In 1995, physicists demonstrated that these
different notions were all interconnected and could be coupled with another theory termed
supergravity, which worked in 11 dimensions. The current incarnation of string theory is
the result of this technique. The present challenges to string theory have
arisen from the framework itself, which predicts the existence of a potentially enormous number
of unique universes, as many as 10 to the power of 500.
String theorists suggest an almost infinite number of mathematical structures with no
known reference to observation. Other scientists believe that string theory will produce findings
one day.