Black books

It is amazing that scientists have managed to capture an image of M87, the supermassive black hole 55 million light years away, which is larger than our entire solar system.

Twenty years ago, black holes seemed more science fiction than science fact. Now we have good reason to think that there is a black hole at the centre of every galaxy, including our own, the Milky Way.

Likewise, astronomers now realise that ordinary visible matter accounts for only a tiny proportion of all the matter of the universe. The shape of galaxies and their rotational speed has led them to conclude that dark matter is vastly more abundant than

ordinary matter. What black holes and dark matter have in common is gravitational power. It pulls galaxies into the shapes we observe and it can pull stars out of sight if they disappear into a black hole.

It may also be responsible for the red shift in light from distant galaxies – the red shift which first led astronomers to think that all those galaxies are receding from us.

If it is gravity, not recession, which has caused the red shift, then the whole idea of an expanding universe which began with a Big Bang may collapse. An older cosmology which depicts stars and galaxies coalescing out of gas and dust, persisting for a time, then dispersing, only to coalesce again elsewhere, is on its way back.

So, it seems that supermassive black holes may swallow up not only stars and planets, but also heaps of astronomy books which assumed that Big Bang had proved its case. The poor black holes may find the latter far harder to digest!

LES REID Morton Street, Edinburgh