What is the biggest discovery you have ever made?

Question: What is the biggest discovery you have ever made?
- Keywords:
  discovery,
  research
Asked by anon-207475 to Oliver on 7 Mar 2019. This question was also asked by anon-207744.
- Oliver Andrews answered on 7 Mar 2019:
  
  The biggest scientific discovery I have made is that the amount of oxygen in the ocean (which marine animals need to breathe just like us) has reduced because of climate change. This means that the oceans are already feeling the effects of global warming

Question: What is the biggest discovery you have ever made?