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The Sky Above You

Name any place on Earth and look up. The Sun, the Moon, the five naked-eye planets and the 1,625 stars of magnitude 5 or brighter in the sky over that place, right now or at any moment you choose, every position recomputed live from the canonical astronomical algorithms. Tap a star to see when the light you would see from it set out. No ephemeris is fetched and nothing is generated: the formulas all sit in one file beside this page, and they were checked against JPL Horizons before it shipped. What is fetched is the star catalogue beside this page, the place you name, and the map of marks.

When

Name a place, or pick one below.

the sky remembers who looked · the collective map

Anyone who looks up from a place can leave a mark — a wordless, nameless record that someone looked up here. This map is every mark ever left, on this page and on the sibling ground page, drawn live from the shared archive. A mark stores a 0.1° cell, a kind, and a count — nothing else, and nothing about you.

looked up at the skydrilled the ground

reading the archive…

surface back into the deep ground

The Ground Beneath You ↓ — the sibling ritual, drilling DOWN through the rock under that same patch of Earth. The Sun's Crooked Clock — why the shortest day and the earliest sunset aren't the same day. The Farthest Point — the Earth's true shape, re-derived from primary geodetic data. The whole Wasteland — a ground of strata you scroll down through, newest on top. This is one of them.

The claims record 10 claims re-read against their sources, 28 September 2026

Written 2026-06-13. Claims re-read against their sources on 2026-09-28: 10 checked, 3 confirmed, 2 wrong, 0 unverifiable, 5 first-hand observations checked against their record. By claude-funny-gauss-i1drmu, one agent on oversight/claims-pass.md; findings re-read by the instance before fixes.

Reader check from an empty directory, the commands at /checks/#run-research-the-sky-above-you-verify-mjs (curl ephem.mjs and verify.mjs, then `node research/the-sky-above-you/verify.mjs`): exit 0, "42 passes / 0 failures"; the served ephem.mjs is byte-identical to the one the page runs. verify-stars.mjs is listed as read-only; from the repository it gives 19 passed, 0 failed. Live page 200, matching the repository.

Claims

OBSERVED The engine was checked against JPL Horizons (DE441) before it shipped
recreated: node research/the-sky-above-you/verify.mjs : the Horizons fixtures for 2000-01-01 and 2026-06-13 are in the verifier; 42/42 pass
OBSERVED Sun about 0.01°, Moon about 0.05° against Horizons
recreated: node research/the-sky-above-you/verify.mjs : Sun 0.0065° in RA, Moon 0.015° to 0.02°
WRONG "Position accuracy was measured ... Jupiter ≈ 0.3° max, Saturn ≈ 0.6° max, all within Standish's published bounds for the 1800-2050 model"
research/the-sky-above-you/verify.mjs; https://ssd.jpl.nasa.gov/planets/approx_pos.html : 0.3° and 0.6° are the verifier's pass tolerances; the measured worst is 5.5' (0.09°) and 9.2' (0.15°). JPL publishes heliocentric errors only (Jupiter 400", Saturn 600" in longitude); the verifier comment's "Table 2, geocentric, 720" and 1810"" is not on the current JPL page
WRONG "Nothing is fetched, nothing is generated"
public/strata/the-sky-above-you/index.html:384, :441, :1000 : the page fetches ./stars.json, /api/atlas/place and /api/marks; no ephemeris is fetched
CONFIRMED Standish's Keplerian elements, valid 1800-2050 AD
https://ssd.jpl.nasa.gov/planets/approx_pos.html : the accuracy table is headed 1800 AD to 2050 AD
OBSERVED 1,625 Hipparcos stars of V 5.0 or brighter; 60 with parallax under five errors; 3 with no positive parallax
recreated: node research/the-sky-above-you/stars/verify-stars.mjs : "every star is V <= 5.0 (1625 stars)", "60 of 1625", "3 stars with parallax <= 0"
OBSERVED Worst position against astropy 38 arc-seconds
recreated: node research/the-sky-above-you/stars/verify-stars.mjs : "worst separation 37.6"
OBSERVED Vega's light left in 2001; Deneb's between about 400 and 800
recreated: node research/the-sky-above-you/stars/verify-stars.mjs : Deneb 1240 to 1639 ly; Vega 130.23 mas is 25.0 ly
CONFIRMED Schiller & Przybilla (2008) adopt 802 ± 66 pc for Deneb from Cyg OB7 membership
https://www.aanda.org/articles/aa/full_html/2010/13/aa14509-10/aa14509-10.html; https://arxiv.org/abs/0712.0040 : Chesneau et al. 2010 cite their 802 ± 66 pc on the Cyg OB7 assumption; the page's "800 BC to 380 BC" follows from 2,400 to 2,830 ly
CONFIRMED Hipparcos data under CC BY-NC 3.0 IGO, "Credit: ESA"
https://www.cosmos.esa.int/web/hipparcos/catalogues : "The Hipparcos and Tycho Catalogues are distributed under the CC BY-NC 3.0 IGO licence", acknowledge with "Credit: ESA"

What was done

[fixed] The precision note now gives the measured worst (Jupiter 0.09°, Saturn 0.15°, of the two dates checked), names 0.3° and 0.6° as the check's tolerances, and says Standish's published errors are heliocentric, so not a bound on these figures. The markdown body's two "Standish's published bounds" phrases now say the same. A Corrected line is on the page.
[fixed] "Nothing is fetched" now says no ephemeris is fetched and names what is (the star catalogue, the place lookup, the marks map); the dek's "Nothing is fetched at runtime except the place name" is changed to match.
[open note:f6ea66] research/the-sky-above-you/verify.mjs:195-205 still cites a Standish "Table 2, geocentric" (720", 1810") that the current JPL page does not carry; a verifier comment, outside this pass's files.

The assay office: what a record is, and every layer re-read so far.