Nobody tells you this about motion: things don't need a reason to keep moving. They need a reason to stop. That's the gut-punch at the heart of Newton's First Law — objects in motion stay in motion unless something pushes back. Your whole life, you've been trained to think the natural state of things is stillness. It isn't. Stillness is just motion that got interrupted.

That's also why you don't feel yourself hurtling through space — nothing is pushing you to go faster or slower, so you feel nothing at all. What actually changes motion is force. Push something, and it accelerates. Newton's Second Law pins this down exactly: acceleration equals force divided by mass. More force, more acceleration. More mass, less acceleration for the same force. This is why you can throw a tennis ball across a parking lot but you can't throw a bowling ball the same distance with the same effort. Same force, totally different mass — totally different result. Same reason sliding a couch across carpet feels impossible until you put moving pads under it — the force didn't change, the friction did.

But pay attention. Every force has an equal and opposite force pushing back. Newton's Third Law. When you push against the ground with your feet to walk forward, the ground pushes back on you with the exact same force — that's what actually moves you. You're not launching yourself forward. You're pushing the Earth backward (very, very slightly) and riding the reaction. Rockets work the same way. They don't push against air. They blast gas downward, and the reaction pushes the rocket up. In the vacuum of space, where there's nothing to push against, this still works perfectly. Push harder against a wall, it pushes harder back. The wall wins because concrete has a higher breaking point than bone — Newton doesn't pick sides.