Make knowledge come alive.

Stand on a rotating planet and watch sunlight sweep through a day.

Plot geometric day length against latitude and find the polar-day and polar-night boundaries.

Bring two points together and discover the slope at one point.

Move a curve and understand each parameter in its formula.

Stack rectangles under a curve and watch the sum approach the exact area.

Watch a point turn on a circle and trace its height as a sine curve against time.

Change the damping and see when the oscillation dies away — and when it stops oscillating altogether.

Drive a damped spring with a sinusoidal force and see why one frequency builds a large amplitude.

Change the voltage and the resistance of one loop and read the current and the power.

Change a string's length and explore what sets the period.

Close one loop with a source, a resistor and a capacitor, and watch the capacitor voltage approach the source EMF at a rate set by τ = RC.

Change the incidence angle and the two refractive indices to see how a ray bends at a plane interface, and when it cannot enter the second medium at all.

Compare one series and one parallel two-resistor circuit that share the same source.

Change mass, stiffness and amplitude to see what sets the period.

Send two equal waves in opposite directions along a string with fixed ends and see why some points never move.

Move an object and watch a convex lens form real or virtual images.

Add two waves travelling the same way and see when they reinforce or cancel.