Every phenomenon, side by side
Every event this tracker follows, side by side — how it forms, what you actually see, how often, and where. The sharpest difference between them is how far ahead you can plan: eclipses run like clockwork centuries out; a sardine run might not show at all.
Can you plan for it? — the predictability spectrum
Astronomical
Driven by the geometry of Earth, Sun and Moon, or by the wider solar system — predictable centuries out because it's orbital mechanics, not weather.
Atmospheric (weather)
Optical or electrical effects made by light, ice or charge moving through the sky itself — governed by weather and season, not orbits.
Biological (animal)
A living population's seasonal behaviour — migration, spawning, overwintering — timed by instinct, temperature and moonlight rather than a fixed calendar.
Oceanic
Phenomena made by moving water itself — tides, currents and blooms — distinct from the animal life the ocean also carries.
Geological
The land or its underground processes doing something visibly strange — mineral, thermal or mechanical, with no living or orbital cause.
Light Alignments
The sun (rarely, the moon) lines up with a specific fixed point on the ground — a peak, an arch, a waterfall — on a narrow, named window each year.
Calculated, live-monitored, or no date at all
Computed from an engine or a published authority — exact day, correct years in advance.
Only appears when a real-time feed currently flags it — no forecast, just present conditions.
Real and season-accurate, but no specific day is claimed — the geometry or schedule isn't known precisely enough to compute one honestly.
Surveyed, or approximate
Coordinates, altitudes and thresholds either come from a survey or publication that can be checked — or they're this project's best inference from photos, tour operator descriptions and secondary sources. Both are used. Only one is stated as fact. The atlas entries carry this distinction in their own words:
- Diamond Fuji's viewpoint coordinates are third-party, not GSI-surveyed
- Biševo's Blue Cave position is rounded, not surveyed
- Victoria Falls' viewing spot is inferred from tour descriptions, not confirmed
- Keyhole Arch shows no specific date — the arch's true opening height is unknown
Where the data comes from
Eclipses
NASA GSFC's five-millennium catalogs (Fred Espenak), cross-checked against timeanddate. Lunar-eclipse markers sit at the antisolar point at greatest eclipse — computed here, not tabulated. Where sources disagree on a duration, NASA's figure wins. Confirm exact paths at eclipsewise.com before booking travel.
Meteor showers & coral spawning
Shower peaks repeat on close to the same calendar date every year, but exact hour and moon interference shift — check the IMO calendar close to the date. Coral spawning windows are computed from an approximate ±1-day full-moon calculator, not official Reef Authority predictions.
Live feeds
Kp-index data comes from NOAA's SWPC, fetched client-side with an automatic fallback through this site's own allowlisted proxy (NOAA, USGS, Open-Meteo geocoding and forecast — nothing else). Volcanic alerts blend the USGS HANS feed (U.S. only, updates through the day) with the Smithsonian/USGS Weekly Volcanic Activity Report (worldwide, but only weekly) — which is why global entries carry no alert level: no harmonised international scale exists to assign one.
Globe layers
The light-pollution overlay is David Lorenz's Light Pollution Atlas — his recalculation of Pierantonio Cinzano's original world atlas of artificial night-sky brightness from 2025 VIIRS satellite data — fetched directly as map tiles from his own site (djlorenz.github.io). It is a modelled estimate of sky brightness (atmospheric light-transfer from satellite radiance), not a direct measurement. It carries no stated license of its own; a third-party project (a Windy.com plugin) already embeds the same tiles, and this site follows that precedent with visible attribution rather than an explicit grant. Stated plainly rather than glossed over. The cloud-cover overlay is Open-Meteo's forecast API, sampled on a fixed grid of points in one batched request rather than per-pixel tiles — a coarse, honest approximation rather than a smooth satellite product, chosen because this site has no backend to render real tiles from.
The basemap
MapLibre GL rendering a self-hosted Protomaps vector tileset, built from OpenStreetMap data and served as PMTiles byte ranges out of this site's own R2 storage — no CARTO, no third-party tile host, no API key to go missing. OpenStreetMap's ODbL license requires attribution wherever the map is shown; that credit lives in the map source's own attribution string and renders through MapLibre's attribution control.
Photos & summaries
Every banner photo is curated by hand for all 46 phenomena, freely licensed, sourced from Wikimedia Commons or the ESO archive, and served from this site with its own credit. The "what it is" summary is fetched live from Wikipedia's public REST API and cached for the session — all of it refetches every time the page loads.