An old schoolmate recently asked an interesting question:
Most people don't really understand science. They are only repeating what they heard at school or in the media. So aren't they just taking science on faith, as if it were another religion?
Short answer: No.
Long answer: First of all, professional scientists don't understand most of science. How could it be otherwise? The totality of science is the work of thousands if not millions of people, over hundreds of years. It's far more than one human being could learn in a lifetime.
So the question isn't why the ordinary person in the street should believe what scientists say. Why should anyone believe them?
One good reason is that any given part of science is open to being observed and understood by a newcomer. Here is an example from my personal experience.