This is a common misconception. In fact modern science, meaning since the middle ages, is about believing only what you can see or measure, taking nothing on faith. Of course no one individual has the time or resources to discover everything, which is why we rely on previous discoveries to make new ones. However, we can verify old discoveries. For example, when I teach physics, my students do lab measurements that verify F=ma, V=iR, and other previously known results. The reason we make them do the lab is so that they can see for themselves that the laws we teach are based on observation, not authority. I tell my students "Don't believe me or the book; find out for yourself."
One reason people have a problem with science is that we can never truly get to the bottom of a "why?" question. Physics goes all the way back to the Big Bang but no one has any clue whatsoever why the Big Bang happened, or what was before. Does that mean physics is worthless? No, it just means we don't have the complete answer yet, and maybe/probably never will.
Another reason people distrust science is because there's so much you have to know these days to be able to learn more. Here, Feynman explains why it's so hard to explain magnetism to someone who hasn't studied physics already:
As for gravity, the attraction between any two bodies has been demonstrated in the laboratory, using a torsion balance (look up the Cavendish experiment if you are curious). You have personally observed some of the effects of gravity: a thrown object falls in an arc, a lot of water is heavier than just a little water, etc. Newton's laws explain all that and more. If it seems hard to believe, fine. Lots of physics is hard to believe. Physicists accept it because it explains an awful lot of observations people have made over the centuries, including the orbits of the planets, motion of projectiles, why transistors work, the colors of hot objects, etc.
Are all science theories correct? Of course not. Often theories have to be modified because new observations are made that don't match the theory. For example, Newton's theory of gravity is good enough for most purposes but not for the precision time-keeping needed for GPS. For that you need Einstein's theory of gravity (commonly called "general relativity"), which says matter warps space and time. It sounds crazy...and yet your GPS wouldn't work if the people who designed it did not believe the theory. For that matter, none of the components of your car would work if the people who designed them did not accept the laws of physics.
By the way, religion does exactly what science doesn't do: it gets to the bottom of the "why" questions. However, it's not based on evidence but on faith. There's no inherent conflict between religion and science. The conflict only comes up when some fool scientist claims to prove God does or doesn't exist, or some fool theologian tries to explain the laws of nature by making up stories about God doing stuff when we can clearly see that nature follows the theories discovered by scientists (evolution for example). If you choose to believe in a Creator, it should be OK to believe that She made the laws of physics and let nature do the rest. You don't need to make up stories about firmaments.
Next time you're at the beach, watch a container ship sail away. Does it just get smaller, or does the bottom disappear before the top? Look carefully and you'll see that the ship is going around a vertical curve. That's gravity making the ocean round.
Some will say I'm wasting my time responding on this thread, but AJ has helped me more than once and I think I owe it to him.
