GUEST,PMB

I think we're getting to quibbles about what the word "believe" means.

On the contrary, "belief" is the fundamental difference between religion and science.

You can believe in scientific theories, and you do; to the extent that you are prepared to bet your life on it.

A scientific theory is a hypothesis that has been tested against the observed facts and found to correspond to the limits of experimental accuracy. That doesn't make it true, just your best bet.

Don't fly or go climbing if you don't believe in gravity.

Gravity isn't a scientific theory, it is an observed physical phenomenon which we experience in our everyday lives (unless you are in the International Space Station). People climbed trees and apples fell out of them and the planets followed their orbits perfectly happily before Newton came along with his theory which merely describes what they do.

Interestingly, it is the crew of the International Space Station who are staking their lives on the correctness of Newton's theory to do the calculations that allow the space shuttle to meet them at the right time and place. They don't need to worry that it isn't actually "true" because it is good enough for that purpose. In other areas, such as calculating the orbit of Mercury, it gives the wrong answer.

You can bet your life on Newton's theory but you can't "believe" it because it isn't true. Relativity isn't "true" either; it's just a better fit to the observations.