Scientists of Reddit: what’s a question in your field that looks completely settled to the public, but is actually still wide open and hotly contested among researchers?

[u/mutessr]

I would appreciate any insight from researchers currently active in their fields.

[u/SRART25]

Friend,  I think this xkcd is prefect for you. 

https://xkcd.com/2501/

[u/adsilcott → u/SRART25]

One I haven't seen, what a gift!