String theory

Today our guest is Dr. John Schwarz.

He is one of the pioneers of super string theory and who played a major role, you know, in the first super string revolution and with his work with Michael Green.

His research mostly focuses on string theory, quantum gravity and theoretical particle physics.

So Dr. Schwartz, welcome to the podcast.

Nice to have you.

He didn't discuss interactions.

But he had a stringy generalization of the Dirac equation, which I think is a fair way of saying what he did.

And a month or two after that, Andre Neveu and I wrote down a second formula for bosons which the second string theory for bosons in which the critical dimension turned out to be 10 rather than 26.

Gravity is not like the other forces and nobody has been able to figure out how it is related to the other forces.

String theory attempts to do just that.

And if it can, it would unite the large and the small worlds of our universe into one set of equations and would explain all particles and forces in the universe.

This could be the theory of everything.

It could answer one of the biggest questions in cosmology.

Why do we exist? What is it and what does it have to say about reality? That's coming up right now.

String theory dispenses with the idea that the tiniest particles in nature are points.

Rather, string theory hypothesizes that at the smallest scales, nature is made of tiny vibrating bits of energy in the shape of filaments or strings.

This is analogous to the way an exchange of photons results in electromagnetic attraction between two oppositely charged particles.

String theory attempts to do something like this.

More about that in a moment.

The second way is to attempt to quantize space-time itself.

So Klein's small dimension idea was generally put on the back burner.

especially since it didn't include the strong and weak force.

It's only later, in the 1960s, that his ideas were resurrected when scientists started working with the extra dimensions of string theory.

So now I want to touch on two popular approaches to finding a quantum theory of gravity.

We truly are multidimensional.

And, you know, string theory is debatable.

But if you're to understand, you know, the way string theory is described, it's very interesting and it helps support this theory.

And how is the timeline created in the first place? It's important to first understand the basics of string theory and how making one choice over here on this timeline doesn't necessarily mean that the other choice couldn't exist at the same time in another timeline.

In each of our decisions, each action we take creates another world.

So we're creating these worlds, which effectively means there are infinite realities with infinite versions of us creating infinite possibilities.

The interesting thing is that if you treat the universe as strings vibrating in nine dimensions, a particular closed string vibration results in a unique graviton particle.

This appears naturally in the mathematics of string theory.

If the graviton exists as predicted by string theory, then gravity could be treated as a force, where virtual gravitons act as the mediating particle which transmits the force of gravity between two objects.

The mathematics of this force could be then put into the quantum field theory framework and be treated similarly to the mathematics of, for example, the electromagnetic force, where virtual photons act as the mediating particles between two electrically charged objects.

Unlike electromagnetism though, where only electrically charged particles are affected by the force of electromagnetism, in the case of the graviton, anything with mass or energy would be affected by the force of gravity.

It is possible that either the theory is wrong or our instruments are not sensitive enough.

Quantum gravity forces us to rethink what space-time itself is.

String theory suggests gravity emerges from quantum strings.

There you go.

And it says here, your research includes the geometry and particle phenomenology in string theory.

Yes, it does.

Duh.

i mean actually what you just described there this this question of like you know where's this going am i going to make a breakthrough is it worthwhile that's something that researchers in any form of research really have to ask right you're trying to solve a hard problem and you have to ask am i making progress you know what's this going to deliver and on what time scale is it worth the trip And I would say, you know, comparing this to Einstein's theory, Einstein's theory, amazing brilliance, you know, yes, general relativity, you know, one of the greatest intellectual accomplishments of the 20th century.

But also in terms of testability, we had a lot of data and measurements ready to go on gravitational physics on the scale of our solar system or nearby solar systems, stars, planets, galaxies that we could try and compare to very rapidly.

The hard part about what string theory is trying to do and where I would argue that this progress is sort of innately on a different time scale is we're trying to describe quantum gravity.

And that involves physics from the very, very smallest distance scales all the way up to the large scale structure and history of the universe.

But they could be different, and in other pockets, they could be completely different.

Now, let's leave the bubbles alone and take a look at another cosmological approach to the concept of a multiverse, which is usually called the string theory landscape, and this one is based on what is called string theory.

We enter the realm of physics that becomes impossible to visualize, to picture, because it is very theoretical.

But let's keep things simple.

What is string theory? String theory tries to explain everything in the universe by assuming or starting with tiny strings that vibrate in different ways to make particles and forces.

We don't need to elaborate on string theory.

What matters is that this theory is a theoretical framework that aims to unify, to reconcile quantum mechanics, which describes the very small, like particles and general relativity, which is about the very large scale, like gravity and the universe.

String theory proposes that the fundamental building blocks of reality are not particles, which would be like tiny little points, but instead tiny vibrating one-dimensional strings.