Not yet reviewed.

These pages are built and working, but haven't been through a final accuracy-and-polish pass yet — treat them as drafts. The homepage only lists pages once that review is done; this is everything still waiting its turn.

Everyday maths

Eleven pages

02 / Sound

How far away was that lightning?

Time the gap between the flash and the boom, multiply by the speed of sound, and measure a storm without any instrument.

03 / Motion

Why speed quadruples your stopping distance

Drag the speed slider and watch braking distance grow with the square of speed — and see reaction distance stack on top.

04 / Gearing

Same legs, different gear

Pick a chainring and a sprocket, hold your cadence steady, and watch one pedal stroke buy either speed or a hill you can actually climb.

05 / Bending

A shelf that sags

Load the middle of a plank and watch it bow — then turn the same board on its edge and see one cubed term erase almost all of it.

06 / Growth

The last decade earns more

Watch a fixed interest rate compound year after year, until the dollars added in the final decade outweigh the first three decades combined.

07 / Geometry

One big pizza, or two smaller ones?

Compare a single pizza against two smaller ones sized to true relative area — the diameter that sounds smaller usually wins.

08 / Rates

Miles per gallon is a trap

Drag two mpg values and see how much fuel each gain actually saves — the same 5 mpg jump can save six times more gas depending on where you start.

09 / Number systems

Why computers count in sixteens

Flip eight bit switches and watch a decimal number, a two-digit hex code, and sometimes a letter appear together.

10 / Probability

23 people, a coin flip

Slide the size of a room and watch the odds that two people share a birthday cross fifty-fifty at just 23.

11 / Scaling

Why the big roast takes so long

Resize a cube from a chicken breast to an elephant and watch the ratio of surface to volume decide both cooking time and body heat.

12 / Logarithms

Decibels don't add up

Drag the decibel slider and watch actual sound intensity and perceived loudness pull apart onto two very different curves.

Discoveries

Nineteen pages

14 / Light and distance

You are seeing the past

Choose a planet and compare where its light began with where that planet is now.

15 / Mass and energy

How much energy is in matter?

Turn an ordinary amount of mass into the energy hidden in E = mc².

16 / Gravity

The pull between worlds

Change mass and distance to feel Newton’s inverse-square law take effect.

17 / Geometry

Two sticks measure a planet

Compare shadow angles at two cities a known distance apart, the way Eratosthenes sized up the Earth around 240 BC.

18 / Optics

Why the straw looks bent

Bend a ray of light across the boundary into water or glass, then reverse it and watch the same equation cut the light off entirely.

19 / Propulsion

Why one more passenger costs so much fuel

See why required propellant grows exponentially, not linearly, with the speed change a rocket needs.

20 / Orbits

Why Mercury's year is 88 days

Slide a planet's distance from the Sun outward and watch its orbital period grow even faster than its distance.

21 / Circuits

Why the grid runs at 400,000 volts

Slide the transmission voltage up through real grid standards and watch resistive loss fall with the square of the increase.

22 / Climate

Sunlight in, heat out

Tune Earth's reflectivity and watch the balance settle on a temperature — then see how far the real 33° greenhouse gap sits above it.

23 / Relativity

Squeeze the Earth into a black hole

Pick a real mass, from a mountain to the Sun, and see how small you'd need to crush it before it became a black hole.

24 / Relativity

Moving clocks run slow

Drag a clock's speed toward light itself and watch two ticking dials — one stationary, one moving — pull apart.

25 / Probability

Why a 99%-accurate test can still be wrong

Set a disease's rarity and a test's accuracy, then watch a grid of a hundred people show how many positive results are actually real.

26 / Signals

The overshoot that refuses to leave

Add sine waves one harmonic at a time and watch a square wave emerge — with an overshoot that never quite goes away.

27 / Gravity

Why the Moon lost its atmosphere

Launch something from a real world's surface and see whether your speed clears its escape velocity or falls back down.

28 / Nuclear physics

Reading a bone's age off its isotopes

Pick a real isotope and slide elapsed time in half-lives to see how carbon dating reads a bone's remaining atoms.

29 / Waves

Why a passing siren drops in pitch

Steer a car's speed past a fixed listener and watch the pitch drop the instant it passes.

46 / Spectroscopy

Starlight has a barcode

Drag a hydrogen electron's jump to emit one exact colour, then pick a real star and see which elements' dark lines show up in its light.

47 / Orbital mechanics

Orbit isn't up. It's sideways.

Fire Newton's cannonball harder and harder from a mountain and watch it go from crashing, to orbiting, to leaving Earth for good.

48 / Rotating frames

Straight lines that don't stay straight

Watch a ball roll dead straight across a spinning disc and still look like it curves — then see why it's real for artillery but invisible in your bathtub.

Fun physics

Fourteen pages

31 / Oscillation

A swing keeps its own time

Pull a pendulum back further and watch its rhythm barely change — until you push past the angle where that stops being true.

32 / Falling

Falling as fast as the air allows

Change body position and mass and watch a skydiver's fixed top speed shift — then open a canopy and watch the same equation slow it to a walk.

33 / Scale

All the salt in the sea

Evaporate every ocean, spread the leftover salt over dry land, and see how deep the pile gets.

34 / Fluid pressure

The ten-metre ceiling

However hard a pump pulls, no vacuum on Earth can lift water past one fixed, unbeatable height.

35 / Heat

Milk now, or milk later?

Add cold milk right away or wait until you're ready to drink — the same physics gives a different final temperature either way.

36 / Oscillation

A small push, badly timed

Sweep a driving frequency past a system's own, and watch a small push turn into a dangerously large swing.

37 / Sound

A string you can actually hear

Change a string's length, tension, and thickness, then press play and actually hear the pitch move.

38 / Waves

Measuring light speed with chocolate

Measure the gap between two melted spots in a microwaved chocolate bar and turn it into an estimate of the speed of light.

39 / Waves

The bottom hasn't heard yet

Let go of a stretched slinky's top and watch the bottom hang motionless until the news of the drop reaches it.

40 / Optics

Why the sky is blue

Slide through the visible spectrum and see why short wavelengths paint the sky blue and long ones paint sunsets red.

41 / Fluids

Why ships float

Load cargo onto a steel hull and watch it settle lower in the water, until it finally floods and sinks.

42 / Scale

All animal life, by weight

Stack humans, livestock, and every wild mammal on Earth by total weight, not headcount.

43 / Scale

Closer to the smallest thing, or the biggest?

Slide from the Planck length to the observable universe on one logarithmic ruler and see where anything — including you — actually falls.

44 / Collisions

Count the bounces

Drop a real ball onto a real surface and watch each rebound keep the same fraction of the last one's height — then turn on a balloon drum and keep counting after your eyes give up.

These pages follow the same format as the rest of the site — one question, real numbers, a figure you move yourself — but haven't yet had the accuracy-and-polish review pass the homepage's pages have. Some may already be fine; treat all of them as provisional until they move to the homepage.