What did Newton understand that was such a revolution? Can someone just... explain gravity to me? Let's start with a ...

planets, asteroids and comets to orbit the Sun; moons to orbit planets; artificial satellites to orbit planets; a dropped mobile phone to fall to the ground. Back in 1687, Sir Isaac Newton ...

Isaac Newton - isn't he the guy who discovered gravity? Great! So, what's gravity? Aaaah, gravity is the force that makes objects fall towards the ground. And, without gravity, we'd all float!