if you could travel to any period of time to change something in science when would it be and why?

Question: if you could travel to any period of time to change something in science when would it be and why?
- Keywords:
  change,
  history,
  time,
  travel
Asked by anon-197617 to Matthew on 7 Mar 2019.
- Matthew Selwood answered on 7 Mar 2019:
  
  It is fairly recent history, but for me it would be to go back to America, Germany and Russia around the end of the Second World War, and tell them that the mind control experiments like MKUltra are never going to work, and please please please don’t subject your fellow humans to such horrifying torture in the name of science :/

Question: if you could travel to any period of time to change something in science when would it be and why?