Physics you can see.

More equations, waiting their turn.

Ideas for future pages, in the same three groups — each one an equation you can feel by dragging a slider, not just read.

Everyday maths

• Compound interest — why the last decade earns more than the first three put togetherA = P(1 + r/n)^ntidea
• Two 12-inch pizzas, or one 18 — the everyday area question almost everyone gets wrongA = πr²idea
• Miles per gallon is a trap — why 15→20 mpg saves far more fuel than 40→50fuel ∝ 1/mpgidea
• Why computers count in sixteens — flip eight bits and watch a number, a hex pair and a letter appear togethern = Σb_i2ⁱidea
• The birthday paradox — how 23 people in a room turn into a coin flipP = 1 − 365!/(365−n)!365ⁿidea
• Why the big roast takes so long — the ratio that also decides which animals can keep themselves warmA/V = 6/Lidea
• Decibels are logarithmic — why “twice as loud” isn't what you'd guessdB = 10log₁₀(I/I₀)idea

Discoveries

• Why the grid runs at 400,000 volts — the same power down the same wire, a hundredth of the lossP = I²Ridea
• Earth's temperature from first principles — sunlight in, heat out, and the 33° gap that is the greenhouse effectT = (S(1−α)/4σ)^1/4idea
• Squeeze the Earth into a black hole — the whole planet, nine millimetres acrossr = 2GM/c²idea
• Moving clocks run slow — small enough to ignore, until GPS has to correct for it every dayγ = 1/√(1 − v²/c²)idea
• The 99%-accurate test — why most positive results for a rare disease are still wrongP(A|B) = P(B|A)P(A)/P(B)idea
• A square wave built from sine waves — add harmonics one at a time and watch the overshoot refuse to leavef = (4/π)Σsin(kωt)/kidea
• Escape velocity — why the Moon lost its atmosphere and Earth kept its ownv = √(2GM/r)idea
• Radioactive half-life — how carbon dating reads a bone's age off its isotope ratioN = N₀e^-λtidea
• Doppler shift — why a passing siren drops in pitch, driven by a car you can steerf′ = f(v±v_o)/(v±v_s)idea

Fun physics

• The ten-metre ceiling — no pump on Earth can suck water higher, however hard it pullsh = P₀/ρgidea
• Milk now, or milk later — the coffee argument has a definite answerT = T_a + (T₀−T_a)e^−ktidea
• Resonance — sweep past a bridge's own frequency and watch a small push become a large oneA ∝ 1/(ω₀² − ω²)idea
• A string you can actually hear — change length and tension, and the note moves with themf = (1/2L)√(T/μ)idea
• Measure light speed with chocolate — melted spots half a wavelength apart, in a 2.45 GHz microwavec = fλidea
• The slinky that hangs in mid-air — the bottom doesn't know it's falling until the news arrivesv = √(kL/m)idea
• Why the sky is blue — and why sunsets turn red through the same scatteringI ∝ 1/λ⁴idea
• Why ships float — and exactly how much cargo it takes to sink oneF = ρVgidea
• The weight of all animal life — humans, livestock, and wild mammals stacked by total mass, not headcountM = Σ(n·m)idea