Where did the universe come from?

Where did the universe come from? What will its fate ultimately be? How large is it and how is it structured? By what means did this structure come about? Is there life on other planets, in other solar systems, in other galaxies?

Questions like these have intrigued mankind for all of recorded history. The greatest thinkers of our species -- Aristotle, Copernicus, Galileo, Einstein -- have advanced our understanding over the centuries. Each one stood on the shoulders of the ones who came before. The pace of exploration and new learning has accelerated dramatically in the past century. Today we have an incredibly profound and detailed model of the universe and its evolution, yet we still have so much to learn.

There is compelling evidence that the universe began about 14 billion years ago in an enormous, extremely hot explosion out of a mysterious nothingness. The explosion, known as the 'big bang', created all the matter and energy that presently exist in the universe. Initially the matter and energy were in the form of hot plasma, but as the plasma cooled it turned into hydrogen, the simplest of all elements with one electron orbiting one proton. Over the subsequent millions of years, the force of gravity caused the hydrogen gas to clump together ever more tightly. Since the strength of the force of gravity grows exponentially with the amounts of mass involved, and with the inverse of the distance between distinct pieces of mass, the clumping process eventually led to enormously compressed hunks of mass. These hunks were, and are, the stars we see in the sky. Because they were so compressed (by the force of gravity), they became extremely hot (millions of degree centigrade). The heat permitted nuclear reactions to take place, accompanied by the emission of light and other forms of radiation. The reactions also transformed the hydrogen, step by step, into ever more complex elements, each with successively more electrons and protons in their atomic structures. The elements are, of course, those that were arranged in a periodic table by the Russian chemist Mendeleev in 1869, plus a few others that had not yet been discovered back then. So, all elements are created by the stars and it is in this sense that we are all, truly, stardust.

The force of gravity is what makes it all happen at the macro level (the forces of quantum mechanics, operating at the micro level, are quite another subject). Imagine what happens as clumps of mass get drawn closer to one another, eventually coming into contact. The resulting combination is much more tightly compressed than the pieces that made it up. If enough clumps combine, the resulting star can become gargantuan in size, vastly bigger than our star, the sun. The compression in such a case is incredibly great. So great, in fact, that it can cause the electrons and protons making up the matter to collapse inward upon themselves, squeezing the matter into a smaller and smaller space. If there is enough matter, making the force of gravity great enough, the matter collapses into a single, infinitesimally small point. Or so the available evidence indicates, anyway. A clump of matter this large -- and this small -- has become known as a 'black hole', so named because it is invisible. The force of gravity in the neighbourhood of such an entity is so enormous that even light radiation cannot escape. Most, if not all galaxies are believed to have black holes at their centres.

This is the wonder, and the puzzle, of the universe. It appears to have originated in an enormous explosion out of nothingness. Yet the matter emerging from that explosion is being drawn gradually together by gravity, and as it does so it shrinks back toward nothingness. So, are we to conclude that eventually, perhaps in many more billions of years, the entire universe will collapse into a single, enormous black hole? Will the 'big bang' eventually lead to the 'big crunch'? Perhaps. But perhaps not. The answer depends on how much matter is out there in the universe and how widely dispersed it is. Another possibility is that the universe will keep expanding forever, becoming cooler and cooler.

Modern technology, combined with the theories of modern science, allows mankind to understand the universe to an amazing extent . We can detect billions of stars out there, organized in clusters, galaxies, galaxy clusters and groups of galaxy clusters. In fact, all the stars we can see with our naked eyes are in our own galaxy, the Milky Way. Those outside our galaxy, in other galaxies, are too far away to be seen. The closest galaxy to our own is millions of light years away and while we can see it, we cannot distinguish individual stars inside it without help from powerful telescopes. However, we can plot an incredibly detailed three dimensional map of the universe. For the galaxies that are furthest away, it takes billions of years for their light to reach us here on earth. This means their light set off on its journey much closer to the time when the universe was born. As we gaze up into the sky, we are, quite literally, looking backward in time.

Philip Smith, March 2001.

Compiled, developed and maintained by Philip Smith