How can quantum gravity help explain the origin of the universe?

Answer 1

In the beginning, when the big bang (BB) supposedly went bang, the universe was very very hot. According to BB theory, essentially all the energy of the universe was a more or less uniform soup of heat energy.

But as the universe cooled, beginning immediately after the BB and continuing even today, the more or less uniform heat energy began to sort of congeal. Quarks, a basic mass particle that makes up protons and neutrons, for example, began to pop up among the primordial soup of heat. [See source.] Then photons, the basic electro-magnetic force particle, started to show up and...let there be light. (NB: The reason we can only see back 14 to 15 billion light years across our universe is because light has been around only 14 to 15 billion years.)

There are but four fundamental forces in our known universe: electro-magnetic (EM), gravity, and strong and weak atomic. The EM forces stem from photons, like the light that popped up 14 or so billion years ago. We have pretty good idea how all this light works as a particle with enegy E = hf and a group of particles forming waves that travel at the speed of light L/t = c. [h is Plank's constant, f is the particle frequency, L is the wavelength, t is the period, and c is light velocity.]

We have less insight on the strong and weak atomic forces, which keep all that positive charge from protons (hadrons made up of quarks) from blowing atomic nuclei apart. Like charges repel, even at the subatomic level. But we do have some experimental indicatiions of their existance as messenger particles called gluons and bosons.

But, and this is a big BUT, we have no experimental indication that gravitons, the quantum particle of gravity, exist. There are quantum gravity theories, like the string/M theory, predicting gravitons, but, thus far, none has been observed.

To date, prevailing theories have "unified" the EM, and strong and weak atomic forces. That is, a single set of equations can be used to "predict" the three quantum particles that create these three forces.

But there are four forces and if the BB theory explaining the origin of our known universe is correct, all the forces of the universe were once unified during the initial very short length of time after the bang. THEREFORE, until such time that a single set of equations unifies all four forces (and their messenger particles), including gravity, the BB theory, which says all four should be unifiable, remains suspect.

Thus, to answer your question directly, being able to observe gravitons, the gravity quantum, would go a long way in validating the big bang theory that explains the origin of our universe. That results because, at the time of origin and if the BB theory is valid, all four forces were in fact unified; so there has to be a unifiable gravity quantum particle if the BB theory is correct.

Answer 2

Stephen Hawking has drawn comparisons between the Big Bang Theory (which I believe was his theory to begin with) and the single point of infinite gravity and mass at the center of a black hole. Supposedly the universe started with such a point.

On the other hand, I really don't know much more about it than that. The only reason I know that is because there was a special on Stephen Hawking last night on the Science Channel.