As we learn more about the nature of the universe, so too we achieve a greater understanding of what we do not know. Scientists now believe that baryonic matter – those atoms that we know comprise our own planet, the Sun, the stars and whole galaxies – makes up perhaps no more than 5 per cent of the universe. It is widely postulated that the rest (and to be clear, that is a lot of universe to account for) is comprised of some 27 per cent dark matter – a mysterious, non-light-emitting material – and 68 per cent dark energy.
Although dark matter is now widely accepted among the scientific community, since astronomer Fritz Zwicky first suggested its existence in 1933, there are currently no devices that allow for it to be observed. Not only is it invisible, it does not emit any known type of electromagnetic energy. However, while dark matter appears to impose a gravitational effect on galaxies, dark energy (which was only putatively discovered in the 1990s) is thought to contribute to the accelerating expansion of the universe in apparent contravention of the expected effect of gravity.
Some scientists argue that dark matter consists of an as yet unknown type of particle, and others suggest that it is better understood if we accept a fundamental revision of traditional gravity. As to what dark energy is, there is even less consensus, although one suggestion is that it is a type of hitherto unknown force filling the universe in the manner of a fluid.
While scientists literally flail around in the dark, the prospect of bettering our understanding of dark energy and matter is an exciting one, opening up vast swathes of the universe that have until now been intellectually off-limits. As Stephen Hawking has observed: ‘The missing link in cosmology is the nature of dark matter and dark energy.’