Loop Quantum Gravity Reveals What Came Before the Big Bang

The closest thing we have to an all-encompassing framework that explains all particles and forces is represented by the standard model of particle physics.

But I showed in a previous video this model is flawed because it does not explain gravity.

Gravity can only currently be modeled using Einstein's general theory of relativity.

A theory of everything has to be able to reconcile quantum mechanics with the general theory of relativity.

This reconciliation appears to be possible with a theory called loop quantum gravity, or LQG.

The core mathematics of LQG are super complicated, but I'm going to simplify it as much as I can.

According to Einstein, gravity is not a force, it is a geometric property of space-time itself.

The theory of LQG attempts to show that this geometric fabric of space-time is not continuous as Einstein presumed, but is itself quantum, made up of discrete quanta.

This is akin to the clothes or sweater you might be wearing right now.

Even though it looks smooth from far away, if you looked at it closely, you would see threads, nodes and loops woven together.

These are the quanta or bits that your clothing is made of.

Space-time is similarly not smooth at the smallest scale according to LQG.

Now this is different than every other theory including string theory because even in string theory space is the background or the canvas on which strings vibrate.

In LQG this space-time background is itself quantized like your clothing or your television.

So this means that distance has a minimum quantity about equivalent to the plank length or 10 to the negative 33 centimeters and volume has a minimum value of 10 to the negative 99 centimeters cubed below which it cannot go.

Now this is super tiny.

To give you an idea of the smallness of the scales we're talking about, LQG says that there are about 10 to the 99th quanta of volume every cubic centimeter of space.

This quantum value is so tiny that there are more such quanta in a cubic centimeter than there are cubic centimeters in the entire visible universe.

And time itself has a minimum quantity as well, which is 10 to the negative 43 seconds, or close to Planck time.

And what do these spacetime quanta look like? Well, you can't really visualize it, but conceptually, the clue is in the name loop quantum.

Spacetime is actually made up of finite loops.

The nodes that intersect is where the quanta volumes of space reside.

It has a volume that is a multiple of the Planck volume.

The loops in between the nodes represent two-dimensional areas, and large quantities of these loops and nodes are called spin networks.

Space is defined by the geometry of the spin networks.