Fred Hoyle

Fred Hoyle was a British astronomer famous for being very right about stellar fusion and being very wrong about the origins of the cosmos. His most enduring contribution to science is his work on explaining stellar fusion; according to many, he should have been a co-recipient of the 1983 Nobel Prize for Physics. He was also a passionate defender of the Steady State theory of the universe, even long after the evidence pointing to the big bang (a sarcastic term coined by Hoyle which stuck) model was overwhelming.

Steady state
The steady state model was as valid as any scientific hypothesis; but evidence stacked up against it in the 1960s, and has been disproved beyond any reasonable doubt since the 1980s. Fred Hoyle (as well as some others, such as Halton Arp) continued to cling to the steady-state model, though, which got increasingly silly as time went on.

It's a good example of how even the very intelligent and knowledgeable can be fooled by cognitive bias — many of the steady state proponents considered an eternal ever-continuing universe to be more elegant and desirable (they're not wrong, reality unfortunately disagrees).

Fred Hoyle actually coined the term Big Bang; many say it was done in jest to ridicule the theory, although he always denied this was his intention. At any rate, it's not a particularly accurate description since there was no "bang" or "explosion" involved (no matter how fancy Discovery Channel's animations look).

It came from outer space!
About his incursions into theoretical biology and evolutionary theory, the less said the better. He was also noted for some rather strange ideas on the subject of evolution and infectious diseases, including a version of panspermia. In his book Evolution from Space: A Theory of Cosmic Creationism (co-written with Chandra Wickramasinghe), it is hypothesised that the Earth is somehow bombarded by a steady stream of extra-terrestrial life, and that this contribution to the planet's gene-pool is fundamental in evolution. In Lifecloud, Diseases from Space (also co-written with Chandra Wickramasinghe), this idea is taken a step further, where it's claimed that certain infectious diseases, such as the black death or Spanish flu, were actually caused by this extra-terrestrial life. In a letter to the Daily Telegraph on December 1 1986, Wickramasinghe and Hoyle deepened their insanity "eccentricity" by also claiming that AIDS,, and  came from outer space. (Specifically, from comets that somehow infected rainwater, which according to Hoyle then entered "lesions in feet in the mainly barefoot populations of the Third World".) Otherwise respectable historian Norman Cantor devotes a chapter to this nonsense idea in his book In the Wake of the Plague: The Black Death and the World It Made for some reason.

Science fiction
Hoyle had a taste for science fiction, and found time to write some himself. His first two novels, The Black Cloud (1957) and Ossian's Ride (1959) are generally considered to be quite good. Especially The Black Cloud is considered to be something of a classic; it explored the same topics as the better known Carl Sagan's Contact and Stanisław Lem's Solaris, so if you liked those, you'll probably like The Black Cloud.

His television series A for Andromeda (1961) received mixed responses; we'd give our own judgement here, but like  the BBC chucked out the tapes after it was broadcast, and most of it is considered lost. There's a 2006 remake which is, of course, shit.

His other ventures into science fiction have been met with lukewarm responses at best.