which do you think has been the greatest discovery in history?

Question: which do you think has been the greatest discovery in history?
- Keywords:
  discovery,
  history
Asked by anon-228775 to Sophie, Jolel, Emily, Amber, Alex on 20 Nov 2019. This question was also asked by anon-228762, anon-228757.
- Jolel Miah answered on 20 Nov 2019:
  
  for me there is water can be found on the outer world of our solar system!

Question: which do you think has been the greatest discovery in history?