# What are the lunar phases

One of the recurring questions in Natural Science exams in Primary Education is what are the lunar phases.

Just as no student is usually confused with the full moon and the new moon, the same does not happen when our satellite is in the first quarter or last quarter.

And not only are children wrong, but many adults are incapable of distinguishing them, even though, in their day, they approved the old EGB. Which shows that they cheated on exams or used cheat sheets. And who knows if both!

We are going to review, in an understandable way for children and adults, what is that of the lunar phases and we will also see a trick so that everyone can know if the Moon is in the last quarter or in the crescent without having to memorize anything.

## What are the phases of the moon

Thanks to Copernicus and Galileo, we all know, including churchmen, that the Moon revolves around the Earth and that the Earth revolves around the Sun.

We should also know that the Moon takes, more or less, 29 and a half days to go around the Earth, which is what is called lunar month.

In order for us to see the Moon, it needs to be illuminated by the Sun. So, depending on the orbital position of the Moon, we will see it completely, we will see it partially, or we will not see it at all.< /p>

Let's clarify this: when, in its orbital path, the Moon interposes itself between the Sun and the Earth, the first illuminates the lunar part that is not visible from our planet, leaving the visible part in absolute shadow. It is the so-called new moon.

On the contrary, when the Moon is on the opposite side of that orbital path, there is no such interposition and the Sun illuminates the visible side, so we can observe it, especially if it is at night. This is called a full moon.

## How many and which are the phases of the moon

Four lunar phases are distinguished:

### Full moon

The Moon is completely illuminated by the Sun. Its nocturnal appearance is that of a luminous and radiant disk. Its spherical shape can be clearly distinguished.

### Last Quarter

As the days go by, the illuminated part decreases and the dark part increases. After about seven days, when only is visible the left half of the luminous disk, we are in the phase of fourth waning.

But the Moon continues to wane for a little over a week, resembling a thinning lemon slice, with the tips pointing to the right.

### New Moon

Then it disappears completely from our view. It is the new moon and the phenomenon occurs seven days and nine hours after last quarter and fourteen days and eighteen hours after full moon.

### First Quarter

After the new moon, the illuminated part begins to increase again for a little more than seven days.

It again resembles a slice of lemon that increases in size daily and whose tips are oriented to the left, until, finally, we can see illuminated the right half.

This is what we call first quarter and the Moon will continue to grow for another seven days and nine additional hours, until it is fully illuminated again, that is say, going back to the phase of full moon.

How long is a lunar cycle? The average of a complete lunar cycle is 29 and a half days . Which obviously coincides with the lunar month.

And how long does each phase of the Moon last? Well, it is not necessary to have an Honors Degree in Mathematics to calculate it. Dividing 29 days and twelve hours into four phases, the result is 7 days and 9 hours per lunar phase.

## We always see the same side of the moon illuminated

This is another curiosity about the Moon and its phases: the side we never see is called the hidden side of the Moon Why does this happen?

Very simple: in addition to the translation movement around the Earth, the Moon also rotates on itself, with the peculiarity that its rotation movement also lasts 29 and a half days, exactly the same as its orbital movement around our planet.

The only way we could see the different lunar surfaces would be for the Moon to rotate faster or slower than it does around the Earth.

This is very easy to understand by simulating its rotation and translation movements on the Earth using two spheres.

## Did you already know that the moon is very deceitful?

We never have a problem telling the full moon from the new moon. But things change when the Moon is in the last quarter or in the crescent.

It is then that the doubt assails us: if the peaks of the lemon slice that looks like the Moon are to the left, is it a crescent? And when they are to the right is it the last quarter? Or was it the other way around? What a mess!

When in doubt, remember this mnemonic, as simple as it is true: the Moon is such a liar.

And why is the Moon such a liar? Because when it is in the first or last quarter it tries to deceive us.

And it is that the left edge of the Moon in last quarter draws a capital letter C . Precisely the C with which the word begins rising.

And when the Moon is at first quarter, its silhouette resembles a capital letter D. Just the letter with which the word begins decreasing.

Always remember: the Moon lies and tries to confuse us, making us believe that it is waning when it is growing and vice versa.

So, starting today, you'll never again have trouble distinguishing which moon phases our satellite is in. And we can also assure you that all those to whom you tell this little secret will be so surprised that they will never be confused with the phases of the Moon again.

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