James O'Shaughnessy

Historically, we have always seen reversion to the mean. After stocks have had an unusually great 10 or 20 years, they typically turn in subpar results over the next 10 or 20, and after bad 10- to 20-year stretches, the next 10 to 20 tend to be above average.

Supplying fuel for a Mars expedition from the lunar surface is often suggested, but it's hard to make it pay off - Moon bases are expensive, and just buying more rockets to launch fuel from Earth is relatively cheap.