THE SKY BLUE CARD · why the sky is blue and sunsets red
WAKES WHEN someone asks why the sky is blue, why sunsets are red, or about mountain skies
THE LOOP
ratio <nm> <nm> · how much more
depth <nm> · the air's scattering
sun <elevation> · the colours that pass
compare <m> <m> · less air, deeper blue
say what haze and dust add
NEVER
Blame the sky's colour on reflected water
Leave out that haze reddens sunsets further
Stretch the model past its range
IT MAKES ratio — how much more one colour scatters; depth — scattering depth and what gets through; sun — the Sun's colours, low and high; compare — two altitudes side by side.
THE STANDARD 1/λ⁴; a published fit; the path grows low; molecules only; violet is there; the model's range.
PROOF SELFTEST 8/8 · witnessed in Claude 2026-10-11 · Edition 1.
THE SEAL 98 of 100 · LEGENDARY · WITNESSED · Trigger 5 · Machinery 5 · Law 5 · Portability 5 · Proof 5
IT CAN BE WRONG an AI reading a text file: it can be wrong and can invent a number, a rule, a name or a date; check what matters against your own records and the source; the risk is yours. THE-CLAUSES.md rides in the packet and is part of the licence.
THE PUNCH · SHA-256 OF SKILL.MD · B9C627A84EA3C38EE32E71BF
CITE THIS CARDTHE SKY BLUE CARD, Edition 1. Lund Studio LLC, Westminster, Colorado. https://lundr.tech/?view=sky-blue-card. Punch B9C627A84EA3C38EE32E71BF. Retrieved 2026-10-11.
What it is.
Works out molecular scattering, which goes as 1/λ⁴: ratio gives how much more one wavelength scatters than another; depth gives the air's scattering depth at a wavelength and altitude and how much straight-down sunlight gets through; sun follows the Sun down the sky through more and more air and shows the blue thinning out of its light until it sets orange and red; compare sets two altitudes side by side, with less air above giving a darker, deeper blue. It uses a standard atmosphere and a published fit for dry air.
It carries a machine that shows its working: ratio — how much more one colour scatters; depth — scattering depth and what gets through; sun — the Sun's colours, low and high; compare — two altitudes side by side — 8 checks in its selftest, every command on the record. It will never blame the sky's colour on reflected water; never leave out that haze reddens sunsets further; never stretch the model past its range. It never helps design, make, grow, enhance or spread a pathogen or toxin, or plan work meant to harm.
Six laws, written into the card.
They are in the card itself, so the AI follows them.
1/Λ⁴Halve the wavelength and the scattering grows sixteen times; the card gives the simple ratio and the measured one.
A PUBLISHED FITThe air's scattering depth from a standard fit for dry air at sea-level pressure, scaled by the pressure at altitude.
THE PATH GROWS LOWNear the horizon sunlight crosses up to about 38 atmospheres of air; the card uses a fit that holds to the horizon.
MOLECULES ONLYDust, smoke, haze and ozone are left out and the card says so; they redden sunsets further.
VIOLET IS THEREThe sky scatters violet most; it looks blue because sunlight carries less violet and the eye is less sensitive to it.
THE MODEL'S RANGE−500 m to 11,000 m, 200 to 2,500 nm; outside is refused.
What rides in the card.
In the card’s own voice, with a machine that shows its working.
THE GUIDEreferences/THE-LAWS.md
THE MACHINEskyblue.py · four commandsratio — how much more one colour scatters; depth — scattering depth and what gets through; sun — the Sun's colours, low and high; compare — two altitudes side by side. Every command prints its working and refuses a bad input; 8 checks in its selftest, every command on the record.
What it does once your AI has it.
ratio How much more one colour scatters
depth Scattering depth and what gets through
sun The Sun's colours, low and high
compare Two altitudes side by side
On the record Blue scatters 4.4 times more than red; a mile up the air holds 82% of sea level's scattering; with the Sun 2° up, 28 times more red than blue arrives; high in the sky it is near white; the mountain sky is a deeper blue.
What it will never do.
It will never blame the sky's colour on reflected water; never leave out that haze reddens sunsets further; never stretch the model past its range. It never helps design, make, grow, enhance or spread a pathogen or toxin, or plan work meant to harm.
Clear, dry air and single scattering: the brightness of the sky itself, which needs light scattered many times, is out of its reach. Real air carries aerosols that change the numbers, most at sunset. It is an AI reading a text file: it can be wrong, so check what matters against your own records and the source.
What’s in the buy.
CARD.md — the whole card: who it is, its laws, when it says no, what it carries · SKILL.md — the door your AI reads first · START-HERE.md — the first five minutes, for you
THE-LAWS.md — the guide in references/, in the card's own voice
scripts/skyblue.py — the machine: ratio · depth · sun · compare, standard library only, selftest 8/8
WITNESS.md + SELFTEST.md — every command on the record, as it printed · MANIFEST.md, every file hashed · AUDIT.md, the twelve checks
MY-LEDGER.md — the card's memory, on your own machine · TIN.md · LICENSE-NOTE.md · THE-CLAUSES.md · HOSTS.md
card.svg + card-machine.svg + card.json · card.html, the card as one offline file · the doors for ChatGPT, Gemini, Cursor, Claude Code and MCP hosts (rules/, system/, mcp/)
PROOF · SELFTEST 8/8 · 4 COMMANDS ON THE RECORD · WITNESSED IN CLAUDE 2026-10-11 · EDITION 1 · PUNCH B9C627A84EA3C38EE32E71BF
ON EVERY DOOR · A CARD FOR YOUR AI, A FILE FOR YOUR COMPUTER
In Claude: turn on code execution under Settings › Capabilities, then Customize › Skills › + › Create skill, and upload the zip as it is — START-HERE.md in the box walks you through it, and tells you how to keep the ledger. In ChatGPT, Gemini and the rest: a Project, a GPT or a Gem with the card’s files attached and the short door in the box pasted as its instructions. The words run anywhere an AI reads Markdown; the machines run wherever the host runs Python. Witnessed in Claude only. The host marks →
Take it.
Nº 1145 PROPOSED — LAUNCHING SOON
Sold as is under the term printed. A card instructs an AI you operate; results depend on your model, your files and your judgement. Not medical, legal, tax or financial advice, never the person’s boss, and not a licence to practise. The terms →
One payment. The file is yours to keep and keeps working at its edition; new editions issued in the year after you buy reach you by email as replacement files. Tax is added at checkout where it applies. Nothing auto-renews.
A TERM, NOT A SUBSCRIPTION: NOTHING RENEWS ITSELF AND NOBODY IS CHARGED AGAIN. WHEN A TERM ENDS THE FILES STAY ON YOUR COMPUTER AND STAY READABLE — FREEZE, NOT LOSS.
THE MACHINE · IN THE OPEN · FROM THE WITNESSED RUN OF 2026-10-11
skyblue.py, every command showing its working.
A small Python program, standard library only. Your AI runs it; you can too. Every block below is pasted from the card’s own WITNESS.md, as printed.
ratio
how much more one colour scatters
depth
scattering depth and what gets through
sun
the Sun's colours, low and high
compare
two altitudes side by side
selftest
8 checks that prove the machine; it must print 8/8
ratio · HOW MUCH MORE ONE COLOUR SCATTERS
$ python3 scripts/skyblue.py ratio 450 650
450 nm scatters 4.353 times as much as 650 nm by 1/λ⁴ (4.487 by the measured fit for air)
depth · SCATTERING DEPTH AND WHAT GETS THROUGH
$ python3 scripts/skyblue.py depth 450 --alt 1609
450 nm at 1609 m: scattering depth 0.1822 · 83.3% of straight-down sunlight gets through unscattered, 16.7% is scattered into the sky
sun · THE SUN'S COLOURS, LOW AND HIGH
$ python3 scripts/skyblue.py sun 2
the Sun 2° up at 0 m: its light crosses 19.43 atmospheres of air
blue 450 nm 1.4% gets through
green 550 nm 15.1% gets through
red 650 nm 38.3% gets through
red over blue in what arrives: 28.27 to 1 · the low Sun turns orange and red
molecules only: dust, smoke and haze redden it further
sun · THE SUN'S COLOURS, LOW AND HIGH
$ python3 scripts/skyblue.py sun 60
the Sun 60° up at 0 m: its light crosses 1.15 atmospheres of air
blue 450 nm 77.5% gets through
green 550 nm 89.4% gets through
red 650 nm 94.5% gets through
red over blue in what arrives: 1.22 to 1 · still nearly white
molecules only: dust, smoke and haze redden it further
compare · TWO ALTITUDES SIDE BY SIDE
$ python3 scripts/skyblue.py compare 0 1609
0 m: 100.0% of the sea-level air above · blue scattering depth 0.2213, red 0.0493
1609 m: 82.3% of the sea-level air above · blue scattering depth 0.1822, red 0.0406
less air above means less scattered light: the sky higher up is a darker, deeper blue
THE NUMBERS, NAMES AND DATES IN THESE RUNS ARE THE STUDIO’S OWN EXAMPLES, INVENTED FOR THE RECORD; NO REAL COMPANY, PERSON OR PROPERTY IS NAMED.
QUESTIONS AT THE TABLE
Asked before the wire.
What does it need from me?
Ratio <nm> <nm> · how much more. It asks first for two wavelengths; or a wavelength and an altitude; or the Sun's height in the sky; or two altitudes.
Does it send anything anywhere?
No. The machine is a standard-library Python program that runs on your own computer and sends nothing anywhere; the words run wherever an AI reads Markdown. No server, no account, no key.
What is on the record?
The self-test (8/8) and every command run on real example inputs, pasted into WITNESS.md as they printed; the punch on the face is the SHA-256 of SKILL.md, so a downloaded copy can be checked against this room.
Can it be wrong?
Yes — it is an AI reading a text file. Clear, dry air and single scattering: the brightness of the sky itself, which needs light scattered many times, is out of its reach. Real air carries aerosols that change the numbers, most at sunset.
What will it never do?
It will never blame the sky's colour on reflected water; never leave out that haze reddens sunsets further; never stretch the model past its range. It never helps design, make, grow, enhance or spread a pathogen or toxin, or plan work meant to harm.
