Misc: From where does the expression "thin as a rail" originate?

Questions

Which musical term denotes that the pitch of a note is lowered by a semitone?

Oneirology is a study and interpretation of what?

The Nuffield Radio Astronomy Laboratories are more usually known by what name?

What, on an Italian menu, is 'zuppa inglese'?

Which actor won an Oscar for his portrayal of Gauguin in the film Lust For Life?