Knowledge, perhaps.
This question seems more like a riddle. Science is such a vast subject. There isn't one accomplishment that could be agreed upon to be best. You'd be hard pressed to do that for a single discipline.
The Best of Science Fiction was created in 1946.
experiment..........
The Best Thing was created in 2006.
Best Thing was created in 1972.
In science, a model should be made or created as similar as possible to the real thing.
The Best Science Fiction of Isaac Asimov was created in 1986.
The Best Thing About Me Is You was created on 2010-11-02.
The Best Bad Thing was created in 1997.
Terry Carr's Best Science Fiction of the Year was created in 1985.
The Next Best Thing was created on 2000-03-03.
Best Thing I Never Had was created on 2011-06-01.
Paddy the Next Best Thing was created on 1933-09-01.