God, the Big Bang … next please …

Is another cosmic beginning just beyond the horizon? evanlane.com

“In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep.”

These words, the Biblical creation of the universe, are quite dramatic, with the richness of the heavens carved from a nothingness several thousand years ago.

While our modern cosmological view has dispensed with the hand of God, and expanded the timescale from thousands to billions of years, it appears to share some uncanny similarities to the Biblical view.

As the textbooks tell us, roughly 13.7 billion years ago the universe was born, exploding into existence from an unimaginable nothingness, a nothingness of no space and no time. Before its birth, there was no universe to talk about.

These words are unsettling, and are often thrown in our faces by those who seek to undermine modern cosmology. It is often claimed that the spontaneous birth of the universe is “illogical”, and the hand of someone, maybe God, was needed to light the touch paper of the Big Bang.

Get back

The truth of the matter is that most modern cosmologists would agree with the above sentiments: the idea the universe sprang from nothing cannot be correct (although modern cosmologists might not necessarily call on supernatural powers to kick-start the universe).

To understand this, it must be remembered that modern cosmology is built upon two key components. The first is the observation that other galaxies in the universe are moving away from us, driven by the cosmic expansion.

The second is the mathematical framework, given to us by Einstein’s theory of relativity, which allows us to interpret these observations.

With our cosmological equations, it is simple to run the universe backwards and ask what it was like in the past.

What we find is that galaxies were closer together in the
past, and the further back we wind the clock, the closer they were.

The density of galaxies grows as we look further into the past, until 13.7 billion years ago when the distance between galaxies becomes zero, and the density diverges to infinity. We have arrived at “Singularity”, the birth of the universe.

Within general relativity, we cannot wind the clock back any further. We’re stuck. It’s like trying to head north when you are already at the North Pole.

Being unable to follow a path of time and space through the singularity means we conclude that before the Big Bang, there was no space; there was no time.

Singularity

The singularity at the Big Bang, like the singularity at the heart of a black hole, has achieved mythical, almost magical, status, especially through the writings of the popularisers of science.

But science is replete with singularities, such as the ultraviolet catastrophe which guided us to quantum mechanics, and all physicists know the presence of singularities means one thing above all else: you have pushed your scientific theory too far, and something has gone horribly wrong.

So what has gone wrong here? We know that the dynamics and evolution of the present-day universe are governed overwhelmingly by the action of gravity, as expressed in general relativity, and we can safely ignore the forces that dominate the quantum world of the very small: electromagnetism and the strong and weak forces.

The long and winding road

As we wind our cosmic clock backwards, watching galaxies disassemble themselves and stars disperse into gas clouds, gravity reigns supreme. Further back, electrons leave atoms, then nuclei dissociate to give the plasma soup at the initial stages of the cosmos. Again, gravity is king.

But pushing back further, the density increases, back through the time when the density of the universe is many times greater than that of an atomic nucleus today.

The quantum forces, which we could safely ignore, steadily grow in importance.

And then we hit the wall that has stymied physics since Einstein’s time: how can we make quantum forces and relativistic gravity work together?

While we can attempt to beat the problem with various approximations, we eventually have to throw up our hands and declare we can move no further without a major leap in physics, a leap for which we have been waiting many decades, with only glimpses and suggestions we will ever see it.

With this leap, we will erase the singularity of the Big Bang and be able to move further north than the North Pole. What should be expect to find in the universe’s past?

Cosmic parents

In truth, we don’t know, but it’s expected that the featureless void of the purely general relativistic picture was not our cosmic parent.

Speculation abounds, with the idea that our universe is just the next step in a infinitely long sequence of universes that have born and died, or is the daughter universe that has budded off a parent, or it is just one universe in a hyper-dimensional sea of universes.

At best these are speculation and guesswork, and without our next leap in physics, they may remain this way. But, if and when we make this leap, we could potentially reveal a cosmic history richer and more bizarre than we currently imagine.

What is certain is that the beginning, as we think of it now, is unlikely to have been the beginning.

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