Around 13.7 billion years ago, a hot, dense and infinitesimally small point started to expand rapidly in an event known as the 'Big Bang'. As it inflated, the matter within it cooled, condensing into galaxies and stars until it became the Universe we see today.
Ironically, the man who coined the term 'Big Bang' was not one of the founders of the theory, but one of its opponents. Sir Fred Hoyle was an astrophysicist at the Institute of Astronomy in Cambridge and is possibly better known for his naming of the theory he did not believe than for his ground breaking work on stellar nucleosynthesis; the mechanism by which stars form the heavy elements such as carbon and oxygen. Hoyle favoured a 'Steady State' cosmological model, whereby matter is continuously created as the Universe expands, so there is no absolute beginning. In 1949, he used the term 'Big Bang' (some claim derisively) while discussing his research on the radio, and the striking image this conjoured caused the name to stick for both its supporters and opponents alike. Since then, the Big Bang theory has become accepted as part of the standard model for cosmology and very little is heard of alternative theories outside historical reviews of the field.
For me, the first time I head anyone talk on a different model was this semester when Professor Jayant Narlikar was invited to speak at McMaster, giving talks both at the Origins Institute and in the Astronomy department. Professor Narlikar worked with Fred Hoyle while he was at Cambridge in the 1960s and, like his mentor, is a proponent of steady state theories. His affiliation with Hoyle and subsequent astrophysical career would have made him a speaker not to be missed, but I was also intrigued and (I admit) skeptical. Few people nowadays questioned the Big Bang theory, so was it not time for Hoyle's old team to drop their searches for an alternative explanation?
With this in mind, I listened as Professor Narlikar began his talk by explaining what had driven himself and his colleagues to seek out a new cosmological model. He explained that in 1948, the Armenian scientist, Viktor Ambartsumian, raised ideas about astronomical objects known active galactic nuclei (AGN). These highly compact regions were seen to be pumping energy into space, suggesting that they were violating two of the sacred rules in physics; the conservation of energy and momentum.
To explain these systems, Narlikar, Hoyle and a third astrophysicist, Geoffrey Burbidge, developed a variation on Hoyle's original Steady State theory which become known as the 'Quasi-steady State’ theory in 1993. Like the standard picture, Narlikar's universe contains dark energy that permeates all of space. In the Big Bang theory, however, the presence of dark energy causes the Universe to expand, whereas here it has the opposite effect, pulling the Universe in on itself. To off-set this, Narlikar introduces a second energy type called the "C-field". When the C-field energy gets very high, it creates both matter and space via Einstein's equation for the equivalence of matter and energy, E = mc2, thereby continuing to conserve energy.
The C-field's strength increases around very compact, massive objects (such as AGN), causing a mass production of particles such as what Ambartsumian described. The standard picture of AGN is that they are black holes that are accreting mass that radiates furiously as it is accelerates. In Narlikar's model, black holes do not exist in the traditional sense, but are places where the C-field is exceptionally strong, producing explosive creation events of matter and space.
The resultant creation of space dilutes the C-field, eventually causing it to become much weaker than the dark energy which takes over and starts to pull the Universe back in. As space collapses, the C-field density rises until it once again dominates the dark energy and forces the Universe to perform another change of direction. It is a giant heart beat, lasting billions of years.
So can this be tested? Professor Narlikar's idea was straight forward; while most of the galaxies and stars would be destroyed as the Universe contracts, a few would survive into the next heart beat. Therefore, if we could find stars older than the Big Bang model gives for the age of the Universe (that is 13.7 billion years), it is possible that they came from a previous expansion phase in a universe that is better fitted by Narlikar's model.
Professor Narlikar's team conjectured that such surviving stars were likely to be ejected away from our galaxy during the turmoil caused in the contraction and expansion of the Universe. They therefore searched for old stars near one of our Milky Way's satellite galaxies, the Large Magellanic Cloud. Examining data from the Hubble Space Telescope, the astronomers found a number of candidates that appeared to be abnormally old. However, Narlikar's group were cautious; could there be alternative theories as to why these stars might appear much older than they really were? For instance, if the star was really not a single object, but two stars orbiting one another closely in a binary, it would be redder (and therefore seem older) than either twin actually was. Alternatively, their candidate might be not very old, but very young, too young to be accurately dated by the techniques they were employing. Finally, they might have made incorrect assumptions about the composition of the star, causing the age estimates to be off.
After considering all these points, Professor Narlikar concluded that, while they had possibilities for stars whose age exceeded 13.7 billion years, it was impossible to prove conclusively at this time.
I continued to think about Jayant Narlikar's talk for the rest of that day. It stayed in my mind not because he had convinced me that the Big Bang theory was wrong, or even because the talk had been well presented and interesting (although it had been). It was because it reminded me strongly why I became a scientist; to question all and every idea in the search for the truth.
In the 17th century, Galileo Galilei was condemned for his support of the Copernican model of the Solar System which placed the Sun, not the Earth, at its centre. (Amusingly, the Catholic Church only publicly vindicated him in 1992). This history is evidence for how easy it is to become complacent with established theories and loose track of what science is about. After listening to Professor Narlikar's talk, the direction my own research could go in seemed to double and triple before my eyes. I remembered that I should not be be confined by what people had done before, but rather use the ideas as stepping stones to go in any number of directions.