An introduction to physics

The universe is always in motion.

Physics is our way of asking why. Why do planets orbit, light bend, and tiny particles behave like waves? Start with the big ideas, then put one to the test.

Four ways to see the world

One universe. Different scales.

No single model explains everything. Each theory is a lens, sharpened for a different part of nature.

Newton's playground

Can you hit the target?

Choose a launch angle and speed. Gravity handles the rest—no air resistance, just a beautifully simple arc.

Best miss
Adjust your launch, then fire!

? Try 45° first. On level ground, it gives the greatest range for a fixed launch speed.

Keep wondering

Every answer opens another question.

What happens when gravity is not a force, but curved spacetime? Or when a path loops through a surface with only one side?

Continue into topology