Under the Microscope: Humans have always wondered how the world began. The Christian tradition pictures God creating the world out of nothing, writes Prof William Reville.
The Indian Hindu tradition believes the universe is infinite, having no beginning and destined for no end. The conventional scientific explanation harmonises more with the Christian tradition and postulates that the universe began 15 to 20 billion years ago in a massive explosion called the big bang.
The universe that emerged was filled with particles and radiation of almost infinite density and temperature. After an initial period of extraordinarily rapid expansion (inflation) the universe has since been expanding at a more sedate pace. Recent measurements have indicated that the rate of expansion of the universe is now accelerating under the influence of a mysterious form of energy called dark energy, whose fundamental nature remains unknown. There is much observational evidence to back up this big bang/inflationary picture and until recently most cosmologists regarded the basic cosmic story as settled.
A new theory of cosmology was recently unveiled and is attracting a lot of attention. This theory describes a cyclical universe that was not born in one big bang but a universe that has been passing though cycles of creation and annihilation forever. The new cyclical model, proposed by Neil Turok of Cambridge University, and Paul Steinhardt of Princeton University, is based on string theory. String theory proposes that the fundamental building blocks of space and time are tiny vibrating strings. This new model is based on new mathematics and, although most cosmologists are interested in it, they are also sceptical.
String theory proposes that the universe contains nine to 11 dimensions, all but three of which are hidden because they are curled up in a complex manifold of microscopic size. When string theory is applied on a large scale, for example cosmology, it invokes esoteric mathematical bodies called membranes, branes for short. The cyclical model proposes that there are two branes, one containing our own universe and the other containing a parallel universe that is a mirror image of our own universe.
The cyclical theory proposes that the two branes periodically collide, releasing a massive amount of energy. This last happened about 15 billion years ago causing what conventional cosmology calls the big bang. And, just as in the big bang theory, the new theory proposes that the energy released in the collision made all the matter and radiation that fills our universe.
After a collision, the two branes spring apart and the universe on each brane swells outwards over billions of years, with matter and energy becoming ever thinner and more diluted. Each brane is four-dimensional, but a fifth dimension bridges the two. We can neither see nor traverse this fifth dimension. The expansion energy in each brane is eventually overcome by the spring-like fifth dimension, which drags the two branes together again in a massive collision and the whole process repeats itself.
One significant problem with the conventional big bang/inflation theory of cosmology is that it cannot explain what happened before the big bang. Indeed, big bang theory says that to ask this question makes no sense, since time and space were created in the big bang and simply didn't exist before that event. Before the big bang there was nothing.
This raises the deep philosophical question as to how something can arise from nothing. One clever explanation of this conundrum describes the universe as being "the ultimate free lunch". The idea is that the big bang created positive and negative energy in exactly equal amounts and, if you do the sums, the entire content of the universe adds up to zero.
Although the positive and negative energy explanation is clever, one is turned off intuitively by the idea of something springing from nothing. The cyclical model of the universe overcomes this problem because at no stage do we have to deal with something arising from nothing - the universe is eternal. The cyclical model also explains other problems that the conventional theory cannot deal with. For example, the universe should contain more energy than we can measure in it and we have no explanation for this. The cyclical model suggests that the energy of the universe is less than it should be because energy, in the form of gravity, leaks through the fifth dimension that connects our brane to the complementary brane.
In the fourth century A.D., in his Confessions, St Augustine pondered the question of what God was doing before he created the world. Agustine was a clever fellow and he produced a very modern answer - before God created the world there was no time and therefore there was no "before". If the cyclical theory takes over from the big bang/inflation theory, St Augustine's answer will look much less impressive, and possibly be reduced to the status of a "no-braner".
I will now leave you to stuff these ideas into your respective pipes and smoke them. If you wish to delve more deeply into this matter you could consult an excellent article by Gabriel Veneziano in the May 2004 edition of Scientific American. William Reville is associate professor of biochemistry and director of microscopy at University College Cork.