How many spaces after a period, one or two?

Quote: Wizard

We learned on the IBM Selectric and were damn grateful to have them

I took typing in HS in 1963 and we had Selectrics.
2 years after they came out. They were always
breaking down. Issac Asimov had 4 Selectrics.
2 were always in for repair and he had an extra
for when the one he was using broke, which it
always did. He said it was a constant stream of
repairmen in and out of his house. At one time
he had more books in print than any other author
in history. Over 200, I believe. 95% were science
books. He was a very good typist and very fast.
Hugely high IQ, he said he never really thought
about what he was typing, it seemed to come over
his left shoulder and out his fingers.

He said the science books went fast, it was the fiction
that was hard. Typically took him 30 hours to write
a science fiction book. poor guy.

Face, I probably saw it on facebook. I know it isn't the first time I saw it. These things go around in cycles.

I thought I'd post about it here because of the smaller audience.