The Island Universe Debate

Abstract

We still accept the picture of our Milky Way system that Harlow Shapley developed towards the end of the First World War, even if some corrections have to be made, primarily because of the effects of dust clouds in weakening the light from distant stars. Qualitatively, Shapley was right. The centre of the halo and the centre of the disk are one and the same. We, and our Solar System, are not, however, located at the point round which everything else is rotating. We are certainly inside the disk, but about l0kpc from the centre — more or less on the outside. The disk itself is not just full of stars. The masses of dust within it weaken the light from distant disk stars and make them appear even more remote. They fool us into believing that beyond a certain distance space is almost empty. In fact, the dust weakens the light from distant stars so greatly that we are no longer able to observe them.