How did the early scientists figure out all of these scientific facts (gravity, planetary motion, etc.) without the technology we have today, and how can we trust them?

Okay… bear with me here on this one. It’s kind of complicated, and I don’t know if it will come out right.

How is it that people readily believed (okay, for the most part, if they weren’t put in jail for being heretics or something) that what scientists said was true? For example, for Newton, he went and “discovered” gravity when the apple hit his head. How did he get from an apple to the planets? Why can we believe him?

I know that now we can figure it out with technology and everything, but how/why did we trust him? What if I was back in his time and decided that because a banana, for example, hit my head, that the planets (unlike the banana) stayed in orbit?

Does that make any sense, or did I completely confuse all of you?