COSMOLOGY has come a long way. Once upon a time it was akin to theology, and models in which the universe rested on the back of a giant turtle were as plausible as any other. Now we have a sophisticated mathematical model backed up by hard observations. The universe, it says, exploded into existence 13.7 billion years ago, and entities such as dark matter and dark energy are orchestrating its evolution.
Yet there remains something disquieting about this model. It contains a huge array of variables that can be changed pretty much at will. So flexible is it that some claim the model can be stretched to fit any observation. It also makes the highly unsatisfying prediction that only 4 per cent of all matter is accounted for by ordinary, familiar atoms. The rest is made up of utterly mysterious forms of dark matter and dark energy.
Cosmologists鈥� unease is increasing following a host of recent observations that are testing the standard model and, arguably, finding it wanting. Measurements from space experiments such as NASA鈥檚 Wilkinson Microwave Anisotropy Probe (WMAP) and the Spitzer infrared telescope are constraining the model, showing us where our thinking may be flawed and forcing us to ask new questions (see 鈥淓nd of the beginning鈥�). To accommodate the new findings, some scientists speculate that not just gravity but also electrical forces may play a role in shaping the universe at large scales. Others argue that Einstein鈥檚 theory of gravity is wrong. Some even suggest that the big bang never happened.
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Calling for a wholesale rethink of the big bang model is still an extreme view, but even mainstream cosmologists would accept that we may be missing a 鈥渂ig idea鈥�. They are just unwilling to venture what that idea might be.
This may all sound like bad news for cosmology 鈥� an indication that it is falling apart. Nothing could be further from the truth. These are exciting times, bursting with ideas that will be put to the test by the next generation of data-gathering instruments. The European Space Agency鈥檚 Planck probe will confirm or dispel some surprising anomalies in the WMAP鈥檚 readings of relic radiation from the big bang. And by observing how dark energy has evolved over time, NASA鈥檚 Supernova/Accelerator Probe (SNAP) may finally shed light on what exactly it is.
Cosmology has moved on from the realm of theological speculation. It is well and truly an experimental science, complete with its own turmoil of testable theories. It has entered a golden age.
