Space expands. So we are told. But why only intergalactic space? I asked Stephen Hawking once (I happen to live in the same town), and he replied 'gravitationally bound systems (such as the Local Group of galaxies) do not expand'. Why not? Does gravity have a limited range? An expansion rate of 1 part in 13.7 billion per year would surely show up on the solar-system scale. It doesn't. How can Space expand, but only if the distances involved are vast? There would seem to be a discontinuity. Not happy.