Quantum gravity

A sensor capable of resolving the lens-thurring effect on a tabletop is actually sensitive enough to bridge the gap into the most elusive domain in modern physics.

Quantum gravity.

Yes.

The researchers have calculated that the extreme phase sensitivity of the supercooled helium could reveal extraordinarily tiny differences in how time passes along different paths around the sensor's loop.

And quantum mechanics perfectly dictates the micro universe, subatomic particles, wave functions, superfluids.

But the math of one falls apart when applied to the other.

We know a unifying framework, a theory of quantum gravity, must exist.

The universe operates as a singular entity.

So there are now people, not people, the great physicists that argue like Stephen Hawking being one and Gerardo Tuft and Lenny Susskind and others that said, ah, What if what happened with, you know, with real magnets, by analogy, there's something quantum.

What quantum? Quantum gravity.

There's something to do with gravity being a quantum, having a quantum effect.

What if that... would jump in and save the day.

If you actually can see a magnetic field line with these ion filings, you see that it's concentrated in a tube.

like a magnetic tube.

Well, what loop quantum gravity is saying is that imagine that you can make tubes of gravitational fields and sort of loop them around like like chains, like, you know, like a chain.

But I can have a

And this is the key to uniting the large and the small worlds of physics.

Thus, string theory can model quantum gravity similar to the way loop quantum gravity also models quantum gravity.

Ok, so if we can model gravity at the quantum scale, then our work should be done.

We should have a theory of everything, right? Well, not exactly.

I've had a weird path.

You know, I really want to become, you know, a professor in theoretical physics and figure out quantum gravity.

Um, but maybe, you know, and I ended up getting into theoretical physics for, for college and for my master's.

So I, I did, um, math and physics at McGill.

I was part of this collaboration where we were trying to view all the universe as like one big giant computer.

It's the it from qubit school of thought.

basically every information theory has a unifying lens to view everything in the world so already that was that got me into information theory and like viewing the universe as a computer and so this duality between computation and the universe and them being one in the same is basically the theme of like the past 10 years for me and so um yeah so essentially got to a certain level in theoretical physics, did my thesis, but then I kind of had like, you know, ever since I was a kid, I wanted to be the one to figure out quantum gravity, many such cases.

How as a kid, did you know about quantum gravity? Like, was there a moment in which it turned on for you so young?

That's a huge problem, but also an open frontier, and it's arguably the biggest puzzle in fundamental physics.

Theorists are working on potential candidates like string theory and loop quantum gravity, and observatories like the Event Horizon Telescope and LIGO are watching black holes and gravitational waves for tiny cracks in Einstein's theory that could point the way forward with new breakthroughs.

Here's another long-standing mystery.

All the stuff I talk about – atoms, forces, light, planets, people – accounts for only about 5% of the universe's content.

We can predict eclipses, land robots on Mars, and map the universe's age.

But some of the biggest questions remain open.

Dark matter, dark energy, quantum gravity.

Each is both a mystery and an opportunity.

Hey, it's Professor Dave.

Let's talk about quantum gravity.

He knows a lot about the science stuff.

Professor Dave explains.

But that leaves one more step to go.

We have not, as of the time of the writing of this course, been able to verify the existence of the graviton, the hypothetical particle that should mediate the gravitational force.

Being able to describe such a quantum field theory for gravity, called quantum gravity, could allow us to show how for the briefest instant after the Big Bang, all four fundamental forces were actually one singular force, and the theory that governs this force would therefore be a theory of everything, a theory from which all the forces and all the particles could be derived.

This is obviously an area of great interest in physics today, and there are many competing theories attempting to succeed in this monolithic task.