How do we know dinosaurs existed? How do we know fossils are real? How do we know our dating methods are accurate?

Being a layperson, you can't really verify many things. You have to at least have quite a bit of knowledge in the matter. Those knowledge usually freely available if it's about science.

Taking physics as an example, before I get into physics major, I have no clue how to verify that elliptical orbit equation is correct. I just had to take Kepler's word on it. Now, in my 4th year, I at least can think of where to start and verify it myself.

Also, an expert in one field is a layperson in other field. A physicist usually don't know much about organic chemistry, so they either take chemists' words on it or try to gain the knowledge required to verify them.

/r/NoStupidQuestions Thread