When I was growing up in the 1950s, the most difficult job that one could imagine was that of a brain surgeon. This gave rise to a popular expression of incredulity directed at someone’s inability to understand a relatively mundane concept:
“It’s not brain surgery!”
However, sometime during the 1970s, probably in response to what would have been seen as the marvel of space exploration, brain surgery went out of fashion as a basis for comparison. In its place, the new remonstration:
“It’s not rocket science!”
The term ‘rocket scientist’ even made it into Shania Twain’s 1998 hit That Don’t Impress Me Much as a proxy for a smart-arse. But did you notice the ‘dumbing down’ that this change in popular usage implies?
Ask yourself: what, exactly, is rocket science? For every action, there is an equal and opposite reaction. That’s it. The whole of rocket science can be expressed in ten words.
It’s not brain surgery.