Back when I was a callow teenager, thousands of years ago, I wrote a science fiction story called The Fist of God in which a gigantic intergalactic spaceship was on a never-ending journey through the cosmos, seeking a new home for the human race.
This is, of course, not exactly an original trope, nor was my further plot development. Predictably enough, the crew and presumptive colonists lost sight of their main purpose, over time, and disintegrated into squabbling, mutually hostile tribes engaged in low-intensity civil war, where those castes which controlled the air, waste retreatment centres, and hydroponic farms held the balance of power over the rest.
The story even had a heroine, a young, restless girl who refused to be content with her future prospects as a (privileged) worker tending the hydroponic gardens, and who was the cause of much consternation among her teachers, who were afraid she’d get into trouble. There were also – and for the life of me I can’t remember why I put them in – gorilla/human hybrids called “Gormans” who were genetically engineered to be a low-intelligence, high-strength slave labour class, and who by the beginning of the tale had already gone extinct.
It was a very bad story.
Anyway, at what I intended to be the climax of the piece, the heroine had finally got herself into serious trouble over something or other, and the silly little chit had been dragged to the Ultimate Authority – the Control Room itself – for suitable punishment. But just before the awful judgement, whatever it was, could be handed down, the Big Bang ended. The Universe, having reached the limit of its expansion, began to collapse on itself. The Big Crunch was on.
And, in my fictional spaceship, time went into reverse. People began to unsay things, unthink thoughts (I confess that I typed sentences back to front to show that they were doing this), unlive their lives; and, as the galaxies fell back towards each other, the “fist of God closed in.”
Yes, that was how I ended the damned tale. The Fist of God closed in.
It was a very, very, very bad story. Not as bad as the one in which a demon-haunted house turned anyone who entered into a gourmet meal (that one was called Sous-Chef, can you imagine?) but still, extremely putrid. I offer no excuses for it, nor shall it ever see the light of day.
So why do I bring it up at all?
This: there is a question which many people ponder, without finding an answer; “if one could reach the edge of the universe, what would be on the other side?”
This article, by the author of The Fist Of God, is an attempt to answer that question.
Now, before we go any further, let me state right away that I will – with the scientific evidence firmly on my side – assume that the reader is aware of, or willing to accept, the following facts:
First, that the Universe, which comprises thousands of millions of galaxies, each comprising millions of stars, is not a mere six thousand years old; and that naked apes crawling on the surface of a ball of rock rotating round an inconspicuous star in an undistinguished outer fringe of one such galaxy have no particular reason to think themselves as the centre of all creation.
Second, that the Universe started at a finite point in the past, albeit many aeons ago, in a quantum event called the Big Bang, the background radiation of which is detectable to this day. This Big Bang, furthermore, caused a rapid and continuing expansion of the Universe, an expansion which can be observed to be still continuing, and is still accelerating. Obviously, by measuring the rate of expansion and the acceleration, one can calculate roughly how long ago the Big Bang must have occurred.
Third, that – as per Einstein – space and time are part of a single unified quantity, called spacetime, and that one cannot have one without the other. Also, again as per Einstein, gravity has a significant effect on spacetime...it curves it. The stronger the gravitational field, the more it curves spacetime, until when the gravitational field reaches a sufficient level, spacetime is completely curved in on itself in a sphere. Such a sphere of closed spacetime is called...anyone willing to hazard a guess? No? Well, it goes by the name of a black hole, from which nothing – not even light – can ever escape.
Incidentally, for anyone inclined to doubt its existence, the curvature of spacetime was proved as long ago as 1919 by observation. It is not “just a theory”, as people who don’t know the scientific definition of the word “theory” are so fond of saying. So there.
Fourth, that the speed of light is a universal constant, which cannot be exceeded, or even matched by anything except light itself. Also, as one gets closer to the speed of light, time slows down – and comes to a complete halt at light speed itself. If you went faster than light, you’d go backwards in time. Again, it’s been proved (by experiments with ultra-accurate clocks on aeroplanes) that the faster you go, the slower time moves. This is proven, scientific fact.
Since all good stories should begin at the beginning – though most avant garde ones begin somewhere at the halfway mark and begin crawling back and forth like a demented earthworm – let’s start with the Big Bang. Now, we can’t say just why the Big Bang happened.
One possibility is that it could have been, as in my awful story, due to the gravitational collapse of a pre-existing universe. As the post-Big Bang expansion of the universe continues, it will, according to this idea, ultimately begin to slow down as the mutual gravitational attraction of the galaxies begin to counter the expansion. Finally, the gravitational attraction will cause the expansion to halt, and then fall in on itself. As it does, it will begin to accelerate inwards towards a common centre, moving four times faster for each halving of the distance, as per a very well known fact of physics called the Inverse Square Law. Ultimately, moving at a terrific velocity, it will all come together in one colossal smash, annihilating anything and everything. And then, the energy released will cause it to blow outwards again, in a successor Big Bang. A neat idea, with an endlessly repeating cycle of universes.
There’s just one problem, a rather big problem, with this idea. It requires the Universe to have enough mass to possess the necessary gravitational attraction to cause the galaxies to collapse together. And, as far as can be detected, the Universe doesn’t – not by a long chalk.
The commonest explanation of this “missing mass” is that it exists as “dark matter” which is not directly detectable by currently available means. However, the existence of “dark matter,” and its counterpart, “dark energy”, which together comprise over 84% of the Universe, is wholly hypothetical (a different kettle of fish from theoretical). At the moment, it’s only conjectured to exist. It might well not.
If dark matter does not exist, then, the Universe will not slow its expansion and ultimately fall in on itself, to be reborn in another Big Bang. It will, instead, expand forever, until and beyond the time when the last forlorn star burns out. Obviously, in that case, the Universe wasn’t created by the expansion of a pre-existing universe (otherwise it would, you know, have the mass to collapse in its turn). And in that case, this Universe came into being in a quantum event, where any one of a literal infinity of possibilities can occur.
Before I go any further, this might be the time for a brief discussion of the word “infinity”. It does not mean “a very, very large number, larger than anything you can even imagine even if you get yourself blind drunk and then try to think of a really huge, enormous, gigantic number.” A million billion trillion gazillion isn’t infinity; a zillion times that isn’t infinity, either. Infinity means a literally endless quantity. If you subtract a quinquasesquillion from infinity, you still end up with infinity. If you subtract infinity from infinity, you still end up with infinity. Fine?
OK, maybe not so fine. Never mind, for the moment. I’ll get back to this again, though. It is kind of important.
To get back to that quantum event – in it, any one of an infinite number of possibilities can occur. Obviously, at least one of that infinite number of possibilities is the Big Bang. We know this because, you know, the Big Bang actually occurred, which is why you’re in a position to read these words now. The advantage of the quantum Big Bang is that we don’t need any hypothetical dark matter; we don’t need a collapsing earlier universe; and we don’t need some kind of creator to start things off, either. All we need is for something to be possible, and it will exist.
Now, I am going to say something extremely important. It is so important that without it the whole question of the edge of the Universe, which we’re, you know, discussing in this article, becomes unanswerable. It is this:
Whatever the origin of the Universe, it did not come into being at a certain point in the empty voids of space. There were no voids of space. Space, or to be more accurate, spacetime, came into being at the same instant as the Big Bang. Before that there was literally nothing. After that there was everything.
This holds true even in case this Universe came into being in the heat death of the previous one. Because, as I said, spacetime is curved by gravity, as the galaxies collapse inward and their mutual gravitational attraction grows, they will curve the space around them more and more tightly. Spacetime will contract around them, like a protective sheath, until at the moment of the Big Crunch the gravitational attraction will be infinite (that word again!) and the curvature of spacetime will also be infinite. Spacetime will, in effect, cease to exist until it comes into being again with the next cycle of expansion.
What this means, in plain words, is this: Spacetime exists only as long as the Universe does. It expands, or contracts, along with the Universe expanding, or contracting.
Does this also answer the initial question? Since spacetime is expanding at the same rate as the Universe, it’s absolutely impossible to reach the edge of it, let alone go beyond that edge. We are in the position of someone trying to walk off a cliff’s edge, where the cliff is enlarging itself at the same rate at which we’re walking. We can never step off, no matter how hard we try.
If you want a demonstration of what I’m talking about, take a rubber balloon. With a pen, draw dots at fixed intervals on its surface. Now, blow up that balloon. What happens? The dots stretch apart, don’t they? If a dot wanted to jump off the surface, it couldn’t, could it?
Want to know what it’s like at the edge of the Universe? Look around you.
Now, let’s assume that we’re one of the dots on the surface of the balloon. If we look at the other dots, along the surface, we can see them receding from us as the balloon expands. Of course, we’ll see them because of the light they emit, which in turn means (since the speed of light is finite, a matter of 300000 kilometres per second) that we’re not seeing them as they are, but as they were. And if we were to look at the centre of the balloon, we’d only be able to see the dots on the other side of the void where we used to be. We can’t go to the centre from here, no matter how hard we try.
Suppose, now, we were to try and set out along the expanding surface of the balloon, to try and find its edge. Of course, we would not find its edge, because there is no edge to find. If we could walk far enough, we’d end up back at our starting point. Isn’t that so?
Similarly, if we were to try and reach the edge of space, we’d – assuming we could survive long enough, and supposing the universe were to survive long enough – end up where we were. If an astronaut in orbit were to shoot a sufficiently powerful bullet into space, and if he could wait long enough, the bullet would end up hitting him in the back of the head after circumnavigating the curve of the Universe. The same thing would happen with a sufficiently powerful laser beam, or a pebble, or anything at all.
Therefore the question of what lies beyond the edge of space is as meaningless as asking what colour a unicorn’s horn is – because there isn’t one.
At this moment, though, one might want to examine a slightly more hypothetical question – the possibility of the existence of other Universes. Now, if the Big Bang was a quantum event, there was an infinity of possibilities of what might happen. So, there might be an infinity of other Universes, in parallel realities to our own. But they would be in their own closed curves of space – we could not even detect them, nor they us, far less visit them from where we are. Their existence can only be, and remain, hypothetical. Also, since the possibilities are infinite, there is no reason why they should share the same fundamental physical laws as our Universe. They could be literally unimaginably different. But we would never know.
There is a tendency to confuse these putative universes with universes in another dimension. This, basically, is because a lot of people are confused about just what a dimension is. Let’s clear up a couple of misconceptions here.
Listen: time is not a dimension. It’s common to speak of time as the “fourth dimension”, but that is completely incorrect. Each dimension is at right angles to the others. The second is at right angles to the first, and the third to the second. A fourth dimension would be at right angles to the three we know. And a fifth dimension would be at right angles to that. And so on and on.
There is an interesting and entertaining construct called Flatland, about a hypothetical two-dimensional world, in which everything has only length and breadth, but no height. To such a world, we would, of course, be in an unimaginable “third dimension”. Flatland mathematicians could speculate about us, but they could not actually detect us. All right so far?
Now, of course, time does not cease to flow in Flatland. So, suppose Flatlanders called time the next higher dimension to them – the third dimension. That would make one of the three dimensions in the world we live in time. But it isn’t, is it?
Time isn’t the fourth dimension. Instead, as part of spacetime, it is part of all the three dimensions; just as it is part of any of the higher dimensions. And all these dimensions, being at right angles to each other, are part of our universe. Just as they are part of any other universe.
Any other universes can’t be at right angles to ours, but in parallel. They occupy not other dimensions, but other realities.
It’s entirely possible that...in an infinity of unknowable other realities...other Big Bangs are occurring at this very moment in our spacetime. But we can never know them, never detect them, never cross the boundary of the rubber balloon.
But there’s more than enough to explore in our universe. And a long, long time to do it in.
As long as we don’t kill each other over lines on a map or the shape of one’s place of worship, first.