WHERE NEXT FOR US?
Our latest estimate for the age of the universe, based on examining the distance away from us of the oldest stars and then extrapolating back based on the known expansion rate of the universe, is around 13.8 billion years. What we know as The Big Bang happened at this time; not so much an explosion in the conventional sense, where matter spreads out evenly from a central source, but instead an explosion everywhere at the same time. There then went on a long period of cooling during which, to begin with, electrons, positrons, neutrinos and photons (light particles) dominated along with smaller numbers of protons and neutrons. As the temperature dropped to around thirty thousand million degrees centigrade, the electrons and positrons began to annihilate each other at a faster rate than they could be created. As the universe cooled further atom nuclei of heavy hydrogen and helium formed and then later, after another period of cooling, hydrogen and helium atoms began to form by combining with the small number of electrons which had survived the earlier positron-electron annihilation. The resulting gas then began to clump together due to gravity, finally forming our stars and galaxies we see today. Our own solar system was formed in this way around 4.5 billion years ago with Jupiter being the first planet to form. Not long after the earth’s own formation, around 100 million years later, water appeared (most likely following a strike by a water laden meteorite) and the oceans began to take shape, leading to, in another one to five hundred million years, the first signs of life. It was to be almost another 4 billion years later (five to seven million years ago) that our own first primitive ancestors began to appear in Africa.
So, what have we been doing since? Not surprisingly, all we need to do is to look at the world around us today to see the answer to this question. By simply looking, we in fact see the evolution of our world in that we only see the continued existence of our ‘good ideas’ much in the same way that only the fittest species have survived. Much of what we see then, such as agriculture and our ability to make and use tools, has simply got better. Technology is now the main driver of where we go next, developing small digital devices with the power of a super computer from only a few years ago to developing an effective virus for a world pandemic in a matter of months. It is certainly the case that places such as CERN have helped to drive our technological advances as well as trying to uncover the mysteries of the universe and the quantum world. The discovery of the Higgs particle in July 2012 was the confirmation of a theory put forward almost half a century before and helped confirm the validity of the Standard Model; the theory describing all elementary particles and three of the four known forces. The fact is that we still know very little of how our world, and indeed universe, works. The quantum world is still baffling (beyond baffling to most of us!) and we only have an understanding of a small fraction (5%) of what makes up the universe. The rest is in the form of dark matter – around 27% - which holds our galaxies together and prevents them flying apart and dark energy – around 68% - whose effects can be seen in the way that the expansion of the universe is accelerating rather than, as previously, thought, slowing down.
And so, life will go on, continually advancing at an ever-quicker pace and discoveries will come about that will tell us about things we don’t even know exist at the moment – at least that is what will happen for a while! The reality is that the Sun only has so much hydrogen fuel (when two hydrogen atoms fuse together to form a helium atom, excess mass is converted into energy and by Einstein’s equation, E = mc2 , this means a lot of energy is released even from a relatively small amount of mass) with which to supply us, and the rest of our solar system, with its life giving light and heat. Eventually the Sun will become unstable (in around 4 to 5 billion years – so no need to worry yet!), as the density of its core can no longer resist its own crushing gravitational force. At this point the Sun will begin to shrink, until it is yet again dense enough to re-start nuclear fusion. This time nuclear fusion takes place nearer to the Sun’s surface, resulting in an outward expansion which overcomes the Sun’s weaker gravitational force. This is where we, or at least Earth, disappears forever, as the Sun expands outwards into the solar system, engulfing each planet in turn. The Sun’s final act is to explode and as it does so, it leaves behind the building blocks (dust, debris, new heavy atoms) for the formation of a new star and new planets.
So, what about us I hear you ask? Well at the moment our main problem is the distance to other potentially life-saving stars and planets. If it was possible to reach another star then common-sense dictate that you head for the nearest – Proxima Centauri. Proxima Centauri could be a good candidate as it is a red dwarf star. For the human race this means that the fate that befell the Sun will not happen to Proxima Centauri since its size (one seventh of the Sun) means its rate of fusion is much, much slower – the rule is, the bigger the star the shorter its life span. Although there doesn’t seem to be any planets orbiting Proxima Centauri, there may be something similar nearby – red dwarfs are not as bright as other stars so are difficult to spot. The final requirement for our interstellar ancestors will be to find a planet with water. This means not too far or else not too close to a star, a zone known as the Goldilocks Zone.
So, what else is out there? The answer is countless galaxies like our own. In fact, if possible, we should be able to continue on through galaxy after galaxy in search of our new home and the odds are stacked heavily in our favour that somewhere out there, we find a replica of the Earth we left behind. But a note of caution! The universe doesn’t go on forever: at least this is the case for light. As you reach 13.5 billion light years from Earth you now notice that there is a lot less light; you have now entered the Cosmic Dark Ages. Eventually you come to a point, a wall, where light can no longer penetrate. The wall is opaque and made from pure energy. This is as far as we can see, as far as light can travel, the end of the visible universe.