Perceptense

Perception+sense

Perception meets sense.

A course for building real intuition.

The idea

Facts are easy. Sense is hard.

You know a marathon is long and Picasso was important. But how long? Important compared to whom? Perceptense covers the things you should have a feel for: weight and distance, but also art, history, technology, wellness, and the everyday systems around you. Here's the kind of question a module might open with.

Module 01 · Weight & Mass
Which is heavier?
vs
How a module works

A small toolkit, mixed differently.

Every module reaches for the same set of ingredients. Click each one to see a working example.

Anchors are real-world reference points your brain can latch onto. Once you know a few solid ones, every other number snaps into place by comparison.

1 second A heartbeat. Roughly one full breath in or out.
1 minute Boiling an egg for a soft yolk. A single song chorus.
1 hour A lecture. A short film. About 3,600 heartbeats.
1 day Earth turns once. You sleep for ≈ a third of it.

Calculators let you plug in your own numbers. The point isn't the math — it's seeing how the answer changes when you tweak the inputs.

You save $30.00 — final price $90.00.

Visual scale turns abstract numbers into things you can see. Bars, maps, and side-by-side layouts make orders of magnitude obvious instead of theoretical.

Mouse heart 600 bpm
Hummingbird 1,200 bpm
Human (rest) 70 bpm
Blue whale 8 bpm

Heart rate vs. body size. The smaller the animal, the harder its heart works.

Q&A reveals are quick estimation prompts. Form a guess in your head, then tap to see what's actually true. The gap between guess and truth is where intuition gets built.

If you stacked every person alive today head-to-toe, how tall would the stack be?

About 13.7 million km — tall enough to wrap around Earth's equator 340 times, or reach the Moon 35 times over.

How many seconds are in a human lifetime (80 years)?

About 2.5 billion seconds. We typically think in years, but per-second it's a strikingly finite number.

Interactive games turn classic puzzles into something you can actually play. The Monty Hall problem only really clicks once you've felt the math by tapping a few times — switching wins ~2/3 of the time.

Pick a door. There's a car behind one, goats behind the other two.
Stayed
0/0 —
Switched
0/0 —

Animations show what static text can't. A wave isn't a number — it's something that moves. Modules use small live visuals to make ideas like interference, orbits, and feedback loops feel concrete.

Two-source wave interference, simplified. Where the rings meet in step, the wave reinforces; where they meet out of step, they cancel — the heart of the double-slit experiment in Module 43.

By the numbers

The course, in its own units.

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Modules, each self-contained and standalone.
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Categories: from numbers and scale to mind and meaning.
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Interactive elements: calculators, games, animations, reveals.
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Questions designed to provoke estimation, not memorisation.
Who made this

Hi... I'm Kia!

Kiarash Farajzadehahary
Kiarash Farajzadehahary
Scientist · developer · designer · curious engineer

I built Perceptense because I kept catching myself nodding along at numbers I didn't really understand, gigatons of CO2, light-years, basis points, GDP. The internet is great at facts and bad at feel. This is my attempt at a small antidote: short, playful modules you can poke at, instead of long articles you skim.

Everything here is hand-built, single-file HTML, and free forever. If a module clicks for you, or breaks, I'd love to hear about it.

Currently curious about how trees move water 100 m straight up

Perceptense is free — no ads, no paywalls, just curiosity; if a module left you a little sharper than it found you, a coffee helps keep the next one coming.

Ready to build some intuition?
Pick any module. They're standalone — no order, no prerequisites, no scoreboard.