The Moon is waning, already loosening its alignment with Earth
A lua de maio de 2025 atravessa seus últimos dias de plenitude — 89% iluminada em 16 de maio, ela já inicia sua lenta retirada do céu noturno. O ciclo lunar, registrado pelo Instituto Nacional de Meteorologia do Brasil, é um dos ritmos mais antigos que a humanidade aprendeu a ler: 29,5 dias de transformação contínua, da invisibilidade à completude e de volta ao silêncio. Observar essas fases é, em certa medida, observar o próprio tempo em sua forma mais visível e recorrente.
- Em 16 de maio, a Lua Cheia já não está em seu auge — ela atingiu a plenitude em 12 de maio e agora declina, com 89% do disco ainda visível mas diminuindo a cada noite.
- Em apenas quatro dias, no dia 20 de maio, a fase Minguante Crescente se instala oficialmente, marcando a entrada da Lua em seu período final antes do reinício do ciclo.
- O calendário lunar de maio traça uma progressão precisa: Crescente em 4 de maio, Lua Cheia em 12, Minguante em 20, e Lua Nova em 27 — cada fase com hora exata registrada pelo INMET.
- A lunação não é um ciclo fixo, mas uma média de 29,5 dias que varia mês a mês, com fases intermediárias como a Gibosa Crescente e a Gibosa Minguante que tornam a transformação mais gradual do que o modelo de quatro fases sugere.
- Para observadores do céu, os próximos quatro dias representam a última janela para ver a Lua em sua quase-completude antes que o disco comece a encolher visivelmente pelo lado direito.
Na manhã de 16 de maio de 2025, a Lua aparece quase inteira no céu — 89% de seu rosto iluminado, mas já em declínio. A Lua Cheia atingiu seu momento de plenitude absoluta quatro dias antes, em 12 de maio, às 13h59. Agora, ela está na fase final de sua completude, a quatro dias de entrar oficialmente na fase Minguante.
O calendário lunar de maio conta uma história de progressão constante. O ciclo começou em 4 de maio, com a chegada da Lua Crescente — a Lua emergindo da invisibilidade e começando a crescer. Oito dias depois veio a Lua Cheia. Em 20 de maio, às 9h, a Minguante se instala. E em 27 de maio, à meia-noite e quatro minutos, a Lua Nova encerra o ciclo e tudo recomeça.
Essas datas e horários são fornecidos pelo Instituto Nacional de Meteorologia do Brasil. A precisão importa porque o ciclo lunar — chamado de lunação — não é fixo: dura em média 29,5 dias, mas varia ligeiramente a cada mês. Além das quatro fases principais, existem fases intermediárias como a Gibosa Crescente e a Gibosa Minguante, que tornam a transformação da Lua mais gradual e texturizada do que o modelo simplificado sugere.
Para quem observa o céu, os próximos dias oferecem uma última chance de ver a Lua em sua quase-plenitude. Após o dia 20, o disco visível começará a encolher de forma notável. Em 27 de maio, a Lua estará completamente invisível — posicionada entre a Terra e o Sol, com sua face iluminada voltada inteiramente para longe de nós. Então, o ciclo recomeça.
On the morning of May 16, 2025, the Moon hangs nearly complete in the sky—89 percent of its face illuminated and already beginning its slow fade. It is a Full Moon in its final days of fullness, four days away from the moment it tips into the Waning Crescent phase. For anyone watching the night sky, this is the tail end of a lunar moment that peaked just four days earlier, on May 12 at 1:59 p.m., when the Moon reached its absolute fullness.
The lunar calendar for May tells a story of steady progression. The month began its cycle on May 4 at 10:53 a.m., when the Waxing Crescent phase arrived—the Moon emerging from invisibility and beginning to grow. Eight days later came the Full Moon, that moment of perfect illumination. Now, on the 16th, the Moon is already in decline, though still nearly complete. In four more days, on May 20 at 9:00 a.m., the Waning Crescent will officially begin, marking the Moon's entry into its final phase before the cycle closes. That conclusion comes on May 27 at 12:04 a.m., when the New Moon arrives and the entire cycle begins again.
These dates and times come from Brazil's National Meteorology Institute, the official tracker of lunar phases for the country. The precision matters because the Moon's cycle is not fixed—it is what astronomers call a lunation, a period that averages 29.5 days but varies slightly from month to month. During each lunation, the Moon passes through four primary phases: new, waxing, full, and waning. But there are also intermediate phases, the ones most people never name. Between the new and full phases sits the Waxing Gibbous. Between full and waning sits the Waning Gibbous. These interfases extend the visible transformation, giving the Moon's journey a more granular texture than the simple four-phase model suggests.
Each of the four main phases lasts roughly seven days, though the exact duration shifts slightly depending on where Earth sits in its own orbit around the Sun. The Full Moon phase—the one the Moon occupies today—is the moment when Earth sits directly between the Sun and Moon, allowing the Sun to illuminate the Moon's entire face as seen from our vantage point. By May 16, that alignment is already loosening. The Moon is waning, meaning it is moving toward a position where less and less of its lit face will be visible from Earth.
For those tracking the sky or planning observations, the next four days offer a window to see the Full Moon in its final hours of near-completeness. After May 20, the visible disk will begin to shrink noticeably, the right edge darkening first as the Moon moves deeper into its waning phase. By May 27, when the New Moon arrives, the Moon will be invisible—positioned between Earth and Sun, its lit face turned entirely away from us. Then the cycle begins again, and the Waxing Crescent will emerge once more.
Citas Notables
A lunation or cycle lunar averages 29.5 days, during which the Moon passes through four main phases: new, waxing, full, and waning— National Meteorology Institute (Inmet)
La Conversación del Hearth Otra perspectiva de la historia
Why does the Moon's cycle matter to anyone who isn't an astronomer?
Because it's one of the few natural rhythms that still governs human life—tides, sleep patterns, the way light falls at night. Knowing where the Moon is in its cycle helps you understand what you're seeing in the sky, and it connects you to something older than electricity.
The source says the Full Moon is 89% visible, not 100%. Why isn't it completely full on May 12?
The peak fullness on May 12 is the moment of perfect alignment—when Earth is exactly between the Sun and Moon. But the Moon's disk appears nearly full for several days around that moment. By May 16, the alignment has shifted slightly, so technically a tiny sliver is already darkening, even though your eye can barely detect it.
What's the difference between a lunation and just calling it a month?
A lunation is the Moon's actual cycle—29.5 days on average. A calendar month is arbitrary, a human invention. They don't line up perfectly, which is why lunar calendars exist separately from the ones we use for work and appointments.
You mention interfases—the Waxing Gibbous and Waning Gibbous. Does anyone actually use those terms?
Astronomers do, and people who watch the sky carefully. Most people just say "almost full" or "almost new." But the terms exist because the Moon's transformation is continuous, not sudden. There are real visual differences between a quarter moon and a gibbous moon.
If the cycle is 29.5 days, how do you track it precisely to the minute?
The National Meteorology Institute uses astronomical calculations based on the Moon's orbital mechanics. The exact moment of each phase—when the Moon reaches a specific geometric relationship to Earth and Sun—can be calculated years in advance. That's why you get times like 1:59 p.m. on May 12, not just "sometime in the afternoon."