Because that's not true: Velikofsky's claims are quite impossible in
many ways: "Manna" as described in Exodus appeared on the ground in the
mornings as was nutricious: anything falling from the sky would be very
different. The parting of the Red Sea (another Velikofsky claim) does
not follow any laws of gravity or fluid dynamics. The timing of the
passes of Venus does not comport with any reasonable stretch of the law
of gravity.
But beyond all that, Velikofsky deserves ridicule not for merely being
wrong--as many good scientists, including Sagan, have been--but for
doing the exact opposite of science itself: by taking the conclusions
first, and stretching the facts to fit them, rather than starting with
observations, postulating ideas that fit the facts, then testing them
to reach conclusions. Velikofsky is not merely a bad scientist, or
even a non-scientist; he's an anti-scientist, and an apologist for
theists.
I lost a lot of respect for Sagan when he sued Apple for making fun
of him, but despite that, he's always maintained at least a modicum
of epistemological integrity and scientific honesty--even his "nuclear
winter" work was an honest possibility arising from observed phenomena
and reasonable guesses about unknowns. As it happened, his guesses
were wrong, but he never tried to hide them, and he always used the
known facts as they were. Like Velikofsky, his guesses were perhaps
motivated by religious prejudice--in Sagan's case his environmental
beliefs, so Sagan loses another point on that, but he's still so far
above Velikofsky on the scale that it's hardly worth noting.
> BTW, is the Paul Ehrlich who co-authored 'The cold and the dark' the same
> one who was predicting mass starvation in the seventies? If so, Sagan
> could clearly have picked better people to work with on his models.
Yes, and he deserves to be put closer to the Velikofsky camp, as you say.
Maybe we should evaluate scientists on a scale of integrity and rigor:
We'll make Richard Feynmann a 10.0, L. Ron Hubbard a 0.0. That puts
Velikofsky in the 0.5 range, Sagan probably around 7.0.