Phases and cycles
The Moon is humanity's oldest clock. Its phases, the return of the crescent after the days of darkness, the eclipses that switch off the Sun or tinge the full disc with copper marked the time of farmers, priests and sailors long before written calendars. This section explains precisely the phenomena that govern the lunar sky: the synodic and sidereal months, the nodes and their slow regression, the Saros and Metonic cycles, libration, earthshine, tides, the supermoon and the blue moon. Alongside the astronomy it tells how these rhythms have been read through history, from the tablets of Babylon to the Antikythera mechanism, from Herodotus to Leonardo, and which symbolic meaning tradition has given to each of them. Myths and beliefs are presented for what they are: witnesses of an ancient way of looking at the sky.
The lunar phases: why the Moon changes its face every night
From new moon to full moon: how the eight lunar phases arise, what the terminator and the quarters are, and which symbols tradition attached to them.
02 · 3 min readSynodic and sidereal month: the two measures of lunar time
Why the month of phases lasts 29.53 days and the month of the stars only 27.32: the difference explained, with the calendars and lunar mansions it shaped.
03 · 3 min readAnomalistic and draconic month: the hidden rhythms of the Moon
Perigee, apogee and nodes: what the anomalistic and draconic months measure, where their names come from and why they hold the key to eclipses.
04 · 3 min readThe lunar nodes: Head and Tail of the Dragon in astronomy and myth
What the lunar nodes are, why they regress in 18.6 years and how they became Rahu and Ketu in India and caput and cauda draconis in medieval Europe.
05 · 3 min readLunar eclipses: why our satellite turns red
Umbra, penumbra and light bent by the atmosphere: how a lunar eclipse happens, what the Danjon scale measures and how the ancients interpreted it.
06 · 3 min readSolar eclipses: the coincidence that switches off the day
Total, annular and hybrid: how a solar eclipse happens, what can be seen during totality and which scientific discoveries it has made possible in history.
07 · 3 min readThe Saros cycle: how the Babylonians predicted eclipses
223 lunations, 18 years and a handful of days: how the Saros cycle works, what the Babylonians knew and why its name was born of a misunderstanding.
08 · 3 min readThe Metonic cycle: nineteen years to tune the Sun and the Moon
Why 235 lunations almost equal 19 solar years: Meton, the Babylonians, Callippus, the golden number of Easter and the Hebrew calendar.
09 · 3 min readThe supermoon: how much larger the Moon really is at perigee
Where the word supermoon comes from, the real figures behind it, the Moon illusion explained by Ibn al-Haytham and its modest effect on the tides.
10 · 3 min readBlue moon: the story of an expression born of a mistake
Second full moon in a month or third in a season with four? The two definitions of blue moon, the 1946 error and the rare moons that really look blue.
11 · 3 min readLibration: how we see 59 per cent of the lunar surface
Synchronous rotation, Cassini's laws and three apparent wobbles: why from Earth we see more than half the Moon, and how its far side was first photographed.
12 · 3 min readEarthshine: Leonardo and the glow of the Earth on the Moon
Why the rest of the lunar disc glows grey beside the thin crescent: the explanation in the Codex Leicester, Mästlin, Galileo and Danjon's measurements.
13 · 3 min readTides: how the Moon lifts the oceans
Two bulges, spring and neap tides, the role of the Sun, the theories of Galileo and Newton and the Strait of Messina currents behind Scylla and Charybdis.
14 · 3 min readThe neomenia: the first thread of Moon that opens the month
From the Greek noumenia to the Roman kalends, from Rosh Chodesh to the Islamic hilal: how sighting the first crescent founded the month in many cultures.
15 · 3 min readWaxing and waning moon: the calendar of the fields in tradition
From Hesiod to Cato, from Pliny to popular almanacs such as the Barbanera: the history of the lunar rules of farming and how to read them today.
16 · 3 min readThe Antikythera mechanism: a Greek calculator of lunar cycles
Gear wheels, spiral dials for Meton and Saros and the irregular Moon of Hipparchus: how the Antikythera mechanism was built and what it calculated.
17 · 3 min readEclipses and history: from Thales to Christopher Columbus
The battle halted in 585 BC, the ruin of Nicias at Syracuse, Columbus's ruse in Jamaica: the eclipses that have left their mark on history.
18 · 3 min readHarvest moon and hunter's moon: the full moons of autumn
Why around the autumn equinox the full moon rises at almost the same time for several evenings, and where the traditional names of the full moons come from.
19 · 3 min readThe Moon that drifts away: 3.8 centimetres a year
How tides push the Moon away and lengthen the Earth's day: the Apollo laser reflectors, ancient eclipses, fossil corals and the future of eclipses.
20 · 3 min readThe major lunar standstill: the extreme Moon every 18.6 years
What a lunar standstill is, why it returns every 18.6 years, what happened in 2024-2025 and which ancient monuments have been linked to this cycle.