The honest answer is that scientists don't fully understand this yet. We have good models that make accurate predictions, but the 'why' underneath is still an active area of research. Anyone who tells you they have the complete answer is oversimplifying.

Carl Sagan's 'Cosmos' explains stuff like this better than any textbook. If you can find the old TV series or the book, watch or read it. He had a gift for making the universe make sense without dumbing it down. Highly recommend.

I'd recommend the book 'A Brief History of Time' by Stephen Hawking, or for the math side, 'The Joy of x.' Your library has them. They're written for curious regular people. You don't need a degree to understand the big ideas.

There's a great explanation of this on the HowStuffWorks website, and the NASA site has good material too if it's space-related. Both are written for normal people, not scientists, so you won't get lost in jargon.

The math looks scary but it's mostly just a precise way of saying something you can understand in plain English. Once you get the concept, the equations are just bookkeeping. Focus on the idea first, the symbols second.

Great question! The math behind this is complex but the concept is actually straightforward once you see it the right way. Forget what you learned in school for a moment and think about it from first principles.