What is string theory and how can it further our understanding of gravity and space around us?
String theory is a concept in theoretical physics, that states that reality consists of infinitely tiny vibrating strings that are smaller than atoms, electrons, or quarks. According to this theory, when a string vibrates, twists, and folds, it produces effects in many small dimensions that humans can interpret, from particle physics to large-scale phenomena such as gravity. String theory has been thought of as a possible “theory of everything”, a single theory that can unite general relativity and quantum mechanics. These are the two theories that underlie almost everything in modern physics. Quantum mechanics is very good at explaining the behavior of very small things, and general relativity works well to explain how very big things happen in the universe, but when they are together, they don’t work well. Some scientists believe (or believed) that string theory could solve the mystery between the two and
overcome one of the biggest remaining unsolved problems in physics. However, after string theory gained attention in the late 1960s and 1970s, its popularity among theoretical physicists diminished, according to a lecture by California Institute of Technology physicist John Schwarz. After countless papers, conferences and dry-erase markers, the breathtaking breakthrough many once hoped for seems further away than ever. So how can String theory help us understand space around us?
In Albert Einstein’s theory of general relativity, gravity is a force that warps space-time around massive objects. It’s one of the four forces that physicists use to describe nature. But unlike the other forces, gravity is so weak that it can’t be detected on the scale of a particle. Its effects are only noticeable on the scale of moons, planets, stars and galaxies. Theorists can predict what a gravity particle should look like, but when they try to calculate what happens when two such “gravitons” smash together, they get an infinite amount of energy packed into a small space which is a sure sign that the math is missing something, meaning that gravity cannot exist as a particle. One possible solution, is to get rid of the idea of the problematic, point-like graviton particles and use strings. Only strings, can collide and rebound without making physically impossible infinities.
In addition to helping us understand gravity better, string theory was great for its potential to explain so-called fundamental constants like the mass of an electron. The next step that theorists hoped for would be to find the right way to describe the folding and movement of the strings. But that simplicity turned out to come with some unexpected complexity. The math used for string theory didn’t work in our four dimensions (three of space and one of time). It needed a total of 10 dimensions, with six visible only to those little strings, much as a powerline looks like a 1 dimensional line to birds flying far overhead but becomes a 3 dimensional cylinder to an ant crawling on that same powerline.
Citations
https://www.space.com/41947-gravitational-waves-reveal-no-extra-dimensions.html