How long are the days on the Moon? Science answers!

A day on Earth is very different from a day on Jupiter, Saturn, or any other celestial body in the Solar System. What about the Moon? Because it is so close to us, many people believe that day and night cycle here. The same or very similar to Earth’s, but its duration is much longer than thought.

First of all, it is important to understand what a sidereal day and a synodic (solar) day are. Sidereal days take into account the time it takes for the planet to complete its full rotation relative to a fixed star in the sky; Duration is approximately 23 hours 56 minutes.

On the other hand, The reference of the synod day is something that is constantly moving in space, like the Sun. The difference arises because the Earth is also advancing in its orbit as it rotates, requiring extra time for the Sun to return to the same position in the sky; this causes a difference of 4 minutes, so we count 24 hours.

If there was a telescope that could observe all sides of the Moon, you could follow the celestial body for at least a month to understand how a full lunar day works.

It doesn’t look like that However, the day and night cycle on the Moon lasts approximately one Earth month.. If it were possible to carry out the experiment in question, you would notice that half of this period is illuminated by the Sun (lunar day), while the other half is marked by the darkness of the lunar night.

“Because the Moon is gravitationally locked to the Earth, it always shows the same side to our planet. This also means that its rotation occurs at the same speed as in Earth’s orbit. The US National Aeronautics and Space Administration (NASA) states in an official publication that a lunar day has the same duration as a full orbit relative to the Sun.

How long is a lunar day?

One lunar day lasts approximately 29.5 Earth days, each phase of day and night lasting just over 14 days. For example, NASA sent the Lunar Reconnaissance Orbiter (LRO) to collect data on the Moon for 100 lunar days; This is equivalent to a much longer period when we count Earth days.

Considering the sidereal day, it takes approximately 27.3 days for the Moon to complete its rotation around the Earth.. However, in the synodic the period is 29.5 Earth days, precisely because of the apparent ‘delay’ of the Sun.

In earthly time, 100 days of observation by LRO is equivalent to approximately 2,950 days on Earth. Therefore, the period observed by the probe corresponds to approximately 8 Earth years. In an article about the mission, NASA explains that one lunar day is equivalent to one synodic month.

We can say this The Moon is gravitationally locked to the Earth, which is exactly why it always remains on the same side facing us.

It takes a natural satellite the same amount of time to complete one rotation around its axis as it does to make a complete orbit around the Earth. This motion, known as synchronous rotation, is what causes the phenomenon known as the far side of the Moon; Only probes and spacecraft can observe what is happening in this region.

It’s worth noting that this ‘dark side’ isn’t exactly dark, it’s just not visible from Earth due to synchronous rotation.

“A lunar day takes the same time as a complete orbit around the Sun. A lunar day also corresponds to a complete cycle of Earth’s visible phases, so a lunar day is the same as a synodic month,” NASA adds.

This was very important in the Apollo missions Consider the phases of the lunar day to ensure a successful landing and avoid possible problems. All landings on the satellite occurred shortly after sunrise, when shadows cast on the lunar surface made navigation easier for astronauts.

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