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

Over the wall.
On the mark.

Set your angle, speed, and launch height. Clear the wall and land within 2 meters of the flag to light up the sky. Fewer attempts and closer landings earn more points.

Best miss
CourseChallenge 01
Attempts this course0
Targets cleared0
Session points0
42 m target · 6 m wall
Clear the wall. Land within 2 m.
Wall clearanceTake a shot
Landing error
The maths behind your shot

x = v₀ cos(θ)t0.0 m

y = h₀ + v₀ sin(θ)t − ½gt²0.0 m

Flight time t0.00 s

? Uniform Earth gravity · no air resistance · the ball is modeled as a point. Touching the wall stops the shot. The flag marks the ground target; a landing error of 2.00 m or less wins.

Scoring & model notes

Each cleared course awards up to 1,000 points. Landing error costs 150 points per meter and each retry costs 60, with a minimum of 100 for a successful shot. A course can be scored once before moving on. Points and cleared targets last for this page session. A blocked shot earns no points, even if its unobstructed trajectory would have reached the flag.

The launch platform sets the initial ball height h₀. The wall is an ideal thin vertical obstacle at a known horizontal position. Collision time and landing time are calculated exactly, so frame rate and pauses cannot change the result. The ball, flag, and fireworks are enlarged for visibility. Reduced-motion mode replaces moving fireworks with a still celebration. At equal launch and landing heights, 45° maximizes range for a fixed speed; elevated launches can have a different optimum.

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