Isaac Newton’s third law of motion is one of the most useful rules in all of physics: every force creates an equal and opposite force. If you push on something, it pushes back on you just as hard. If you fire a bullet from a gun, the gun kicks backward against you with the same force the bullet flies forward.
This rule explains a surprising number of everyday things. Right now, gravity is pulling you down toward Earth. The floor is pushing back up against your feet with the exact same force, which is why you’re not falling through. When you walk, you push your foot backward against the ground - and the ground pushes you forward in response, sending you taking a step.
It’s how rockets work, too. A rocket engine throws hot exhaust gases out the back at high speed. By Newton’s third law, the gases push the rocket forward with the same force the rocket pushed them backward. No atmosphere, no spinning wheels, just a pure action-reaction trade. It’s the same principle that lets an octopus jet through water by squirting water out, and a balloon zip across a room when you let it go.
