New Moon

At New Moon, the Moon sits roughly between Earth and the Sun, with its illuminated hemisphere facing almost entirely away from us — so the side of the Moon facing Earth is essentially the Moon's own "night" side, dark to our eyes. It isn't literally invisible in the sky (it's still up there, tracking near the Sun), it's just that its lit face points the wrong way for us to see any of it reflected.

This is also, mechanically, the start of a new lunation — the roughly 29.53-day synodic month this site's astronomy core measures precisely by searching backward for the exact previous New Moon instant, rather than approximating from a fixed average, since the Moon's orbital speed genuinely varies enough through its elliptical path that a linear estimate would drift.

New Moon is also when solar eclipses become possible (though not guaranteed every month — see our eclipses guide) — because the Moon is between Earth and the Sun, if its orbital plane also happens to cross the Sun-Earth line closely enough that month, it can block sunlight for observers in a narrow path on Earth. Most months the Moon's slightly tilted orbit carries it just above or below the Sun's position, so no eclipse occurs.

In spiritual and reflective traditions across many cultures, the New Moon's dark, quiet start to the cycle is a commonly used marker for setting intentions or beginning something new — a genuine, widespread practice, though this site frames it plainly as tradition and personal reflection, not a claim about any measurable effect. Our dedicated new-moon-intentions guide covers the practice, and its honest evidence status, in full.

The exact moment of New Moon is defined astronomically as the instant the Moon's ecliptic longitude exactly matches the Sun's — a precise, computable point in time (to the minute), not a full day or a fuzzy window, even though the Moon looks essentially the same (invisible) for a day or two on either side of that exact instant to casual naked-eye observation.

Because the Moon and Sun share almost the same position in the sky at New Moon, the Moon rises and sets within minutes of the Sun each day during this phase — a genuinely useful fact for anyone trying to spot it, since it explains why New Moon is functionally invisible even during the day: it's too close to the Sun's glare for the unaided eye to pick out, even though it's technically above the horizon during daylight hours just like the Sun.

New Moon is also the reference point astronomers use to define the start of a lunation, and this site's own age-in-days figure (shown on the Today's Moon tool) counts forward from the most recent New Moon's exact instant, found by searching backward rather than approximated from a fixed average cycle length.