SPRING AND NEAP TIDES

the Earth–moon–sun geometry that makes the tides swing — after NOAA

Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.

Three sizes in one archive — from a sheet on the fridge to a poster on the wall.

Formats: A4 · A3 · A2
What you get: Print-ready PDFs, one per size, with every letterform converted to outlines — nothing to install, nothing to shift.
Subject: astronomy · everyone · memo · study

The geometry, the seven-day step, “about half” and 390³ ≈ 59 million are from the NOAA Ocean Service (“What are spring and neap tides?”) and the NOAA Tides & Currents tutorial (after Thurman, 1994). Sun and moon masses — NASA planetary fact sheets. The water bulge in the diagrams is exaggerated. Checked 2026-08-13.

NOT THE SEASON

The name has nothing to do with the season: it is the tide that “springs forth”. That is why spring tides come twice each lunar month all year long — in winter just the same.

And it is the moon that wins this pair: the sun is 27 million times heavier, but 390 times farther away, and tide-generating force falls with the cube of distance — 390³ is about 59 million. What remains is roughly half of the moon’s pull.

On the sheet

The geometry, the seven-day step, “about half” and 390³ ≈ 59 million are from the NOAA Ocean Service (“What are spring and neap tides?”) and the NOAA Tides & Currents tutorial (after Thurman, 1994). Sun and moon masses — NASA planetary fact sheets. The water bulge in the diagrams is exaggerated. Checked 2026-08-13.
Colour carries meaning, but meaning never rests on colour alone — the sheet reads in black and white.
Nothing about how it was made: the sheet carries only what the reader needs.

Printing

Three sizes in the archive: A4 — 210×297 mm, A3 — 297×420 mm, A2 — 420×594 mm.
All text is converted to outlines. No fonts to install, and nothing shifts on another machine.
White background and sparing fills — it prints on a home printer without draining the cartridge.
Margins of at least 10 mm: a home printer cannot print to the edge.
No stroke thinner than 0.3 mm, so nothing disappears in print.

Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 8 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.

SPRING AND NEAP TIDES

NOT THE SEASON

On the sheet

Printing

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