- What phase is the moon in tonight?
- The moon's phase tonight depends on where it is in its 29.53-day synodic cycle relative to the sun as seen from Earth. The eight named phases — new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent — describe how much of the moon's lit hemisphere faces us. This page shows the live phase, illumination percentage, and lunar age (days since the last new moon) computed from your device's clock, so it updates wherever you are in the world.
- When is the next full moon?
- Full moons occur roughly every 29.5 days, when the moon is on the opposite side of Earth from the sun and its entire near-side is illuminated. The exact instant varies by a few hours from month to month, and the calendar date depends on your timezone — a full moon at 23:30 UTC may fall on different dates for viewers in Tokyo and Los Angeles. The 'Next full moon' card above always shows the next one in your local time.
- How long is a lunar cycle?
- The synodic month — the time from one new moon to the next — averages 29.530588 days, or about 29 days, 12 hours, and 44 minutes. That is slightly longer than the sidereal month (27.32 days, the moon's actual orbital period) because Earth itself moves around the sun during a lunar orbit, so the moon has to travel a little further each cycle to catch up to the same sun-Earth-moon alignment.
- What's the difference between a full moon and a supermoon?
- A supermoon is a full moon (or, less commonly, a new moon) that happens near perigee — the point in the moon's elliptical orbit where it is closest to Earth. Definitions vary, but a common rule is that the moon must be within ~10% of its closest approach. Supermoons appear about 7% larger and 15% brighter than an average full moon, which is noticeable but subtle to the naked eye. The dramatic 'huge moon' photographs you see online are usually due to telephoto compression, not the supermoon effect.
- What is a blue moon?
- There are two definitions. The 'monthly blue moon' is the second full moon in a single calendar month — a quirk of the calendar rather than astronomy, since 12 lunar cycles add up to 354 days, leaving roughly 11 spare days a year. The older 'seasonal blue moon' is the third full moon in an astronomical season that contains four full moons. Despite the name, blue moons are not actually blue; the term just means 'rare,' as in the phrase 'once in a blue moon.'
- Why does the moon look bigger near the horizon?
- This is the moon illusion, an optical effect that has puzzled astronomers since antiquity. The moon is the same physical size — and almost exactly the same angular size — whether it is on the horizon or overhead; you can confirm this by photographing both and overlaying them. The leading explanations involve the brain's depth perception: nearby reference objects (trees, buildings, hills) cue the visual system to interpret a low moon as 'far' and therefore 'large,' while a high moon against featureless sky reads as closer and smaller.
