First Quarter Moon

In the Northern Hemisphere, the sunlit part of the moon moves from right to left.

Today is the first quarter Moon phase. It is a term that confused me as a child when I first started to pay attention to the night sky. The First Quarter Moon is also called, somewhat illogically, the Half Moon because the Sun’s rays illuminate exactly 50% of the Moon’s surface.

At the First Quarter in the Northern Hemisphere, the right half of the Moon is lit up, as shown below. In the Southern Hemishere, the left half is illuminated and near the Equator, the upper part is bright after moonrise, and the lower part is bright before moonset.

In the Southern Hemisphere, the sunlit part moves from the left to the right.

As Juliet told Romeo, “O, swear not by the moon, the inconstant moon, That monthly changes in her circled orb.”

via www.timeanddate.com

You know that ocean tides on Earth are mostly generated by the Moon’s gravitational pull. The largest tidal range is around Full Moon and New Moon when the Moon and the Sun’s gravitational forces combine to pull the ocean’s water in the same direction. These tides are known as spring tides or king tides. And with today’s First Quarter and again at the Third Quarter, the Moon and Sun pull in different directions, producing the smallest difference between high and low tide. These are known as neaps or neap tide.

No New Moon in February

First crescent New Moon

There was no New Moon in February. This happens (or is it that it doesn’t happen?) about once every 19 years. It only happens in February, as this is the only month that is shorter than a lunar month. When that happens, January and March have two New Moons, instead of just one. The New Moons on January 31 and March 31 are both considered Black Moons.

That term is used in several ways. It commonly is used to refer to a second New Moon in the same month. Those occur about once every 29 months. Time zones mess around with Moon phases. This year, Los Angeles has a Black Moon in March, while New York has a Black Moon in April.

The Black Moon is not the same as the Dark Moon. That is the last visible crescent of a waning Moon and in the Chinese calendar, it marks the beginning of the month.

When there is a third New Moon in a season of four New Moons, that is also called a Black Moon. Usually, each season has three months and three New Moons. When a season has four New Moons, the third New Moon is called a Black Moon and when there are four Full Moons it is called a Blue Moon.

The original meaning of the term New Moon is the first visible crescent of the Moon after conjunction with the Sun. (shown above) This is a thin waxing crescent and it is briefly and faintly visible as the Moon gets lower in the western sky after sunset.

The first crescent marks the beginning of the month in the Islamic calendar and some lunisolar calendars, such as the Hebrew calendar.

There is a longtime belief in many cultures that rituals performed at the time of the Full Moon and New Moon were more powerful. Neopagan and witchcraft systems such as Wicca follow this belief. Farmers once believed  (and might still believe) that planting during certain Moon phases will increase harvests.

 

A Waxing Crescent Moon to Start a Lunar Month

Full Moons get the most attention when it comes to lunar phases. But the New Moon (or Dark Moon) is also important in some cultures, and the waxing and waning phases and the two Crescent Moons also have beliefs attached to them.

In Cornwall, if a boy was born during a waning Moon, they said that the next birth would be a girl and both would be blessed.

In the lore of the Moon, it was said that to see the crescent Moon over the right shoulder was considered lucky, but seeing it over the left shoulder was unlucky. Since tonight’s Moon phase is a Waxing Crescent, be sure to look over your right shoulder tonight.

A Waxing Crescent is the first phase after the New Moon. This is actually an optimal time to see the features of the moon’s surface. During this phase, the Moon can be seen in the western sky after the Sun goes below the horizon. Right now, the Moon is close to the sun in the sky and mostly dark except for the right edge which becomes brighter as the days pass. The next phase is the First Quarter when it is  50% illuminated.

Muslims around the globe are observing the holy month of Ramadan, which begins for most on either around  April 12 or 13 in 2021 when it was a Waxing Crescent Moon phase. That is the phase that looks like a  )  while the Waning Crescent looks like a  (  .

Ramadan is the ninth month of the Islamic calendar and is observed by Muslims worldwide as a month of fasting to commemorate the first revelation of their holy book, the Quran, to Muhammad according to Islamic belief.

Since the Islamic calendar adheres to the lunar calendar of 12 months rather than the Gregorian calendar, a solar calendar used in the Western part of the globe, every month starts as the new crescent moon emerges. It continues for 29 or 30 days. Each year, this makes Ramadan start 10 to 12 days earlier. Their 12-month lunar year has a total of 354 or 355 days or is 11 days shorter than the seasonal year on which the Gregorian calendar is based.

What If There Was No Moon?

Twilight New Moon via Flickr

This past Tuesday was the New Moon which looks like no Moon to the unaided eye. This is the first lunar phase when the Moon and Sun have the same ecliptic longitude and the lunar disk is not visible. Actually, this phase is really a very thin first visible crescent of the Moon after conjunction with the Sun. That thin waxing crescent is briefly and faintly visible as the Moon gets lower in the westerly sky after sunset.

An article on Discover magazine’s website asks “What if the Moon disappeared tomorrow?” Before reading it, I would have guessed the effects on Earth would be dramatic, but that’s not exactly the case.

The effects would have been more dramatic three billion years ago when the moon was closer to Earth, but now the Moon is “far enough away that most of the things it does for us are very long term, like stabilizing our orbit over hundreds of thousands of years.”

Most of us wouldn’t notice the Moon was missing that first day. Tides would be reduced, but not completely absent because the Moon and the Sun both have an effect on tides.

At night, animals might be more affected by the absent Moon than people. We would miss seeing it and it would be darker all month – but no darker than it was last Tuesday.

Earth’s motion about its axis would be affected but since it increases the length of a day by about two milliseconds every century, I doubt that anyone will be upset.

Back those billions of years, the Earth had 4-hour rotations. But the Moon gradually slowed us down to 24-hour days. Thank you, Moon. I already feel like 24 hours isn’t enough.

Without the Moon, Earth’s tilt wouldn’t be as steady and so probably the most dramatic effect would be on our seasons and climate.

Don’t worry. The Moon isn’t going away.  Look up tonight at the waxing crescent.

December’s Full Moon rises on the night of Wednesday, December 11 and since for most of us in the north it brings in the winter season, it is often called the boringly obvious Full Cold Moon.

 

International Observe the Moon Night

Tonight – October 5 – is the 10th annual International Observe the Moon Night. One day each year, everyone on Earth is invited to observe and learn about the Moon together, and to celebrate the cultural and personal connections we all have with our nearest celestial neighbor.

This year is particularly special as it marks the 50th anniversary of the Apollo 11 Moon landing. NASA is also looking forward to their Artemis program, which will send the first woman and the next man to the Moon.

An important part of observing the Moon is to see how it changes over time. Readers of this blog know I pay a lot of attention to the Moon and its phases.  NASA even offers a Moon journal that you can watch the shape of the Moon changing over the course of a month, and keep track of where and what time it rises and sets.

If you choose to celebrate International Observe the Moon Night, you can register your participation and share your experiences on social media with #ObserveTheMoon or on NASA’s Facebook page.

Moon Moves

a waning “C” crescent and a waxing “D” crescent

I was out last night with a friend who commented that there was a clear “crescent Moon.” People commonly use that term when a sliver of Moon is showing, but there are two versions of the crescent sliver.

The Moon is always waxing (growing in the lit area we see) and waning, and moving closer and farther away from us. It is surprising how many people have never really noticed that the Moon looks like a looks like a “C” crescent, and later looks like a “D” in its waxing phase.

The phases of the Moon as viewed looking southward from the Northern Hemisphere. Each phase would be rotated 180° if seen looking northward from the Southern Hemisphere. The upper part of the diagram is not to scale, as the Moon is much farther from Earth than shown here.

In Hinduism, every part of the cosmos is seen as an action of a god and time is the endless repetition of the same long cycle. In Hindu mythology, Soma represents the god of the Moon.

Soma rides a sky chariot drawn by white horses. Soma was also the name of the elixir of immortality that only the gods can drink. The elixir is stored on the Moon. When the gods drink soma, they draw away from the Moon and it becomes smaller. (I wrote about soma earlier in another context.)

Most people know that the Moon changes its distance from Earth continually because the orbit of the moon is not a perfect circle. It is more like an ellipse, so it will have a point of perigee (closest point to Earth) and apogee (farthest point) each month. Today, May 6, it is at apogee and it is 251,318 miles or 404,457 km away from us.

Back on April 20 perigee, it was  229,108 miles or 368,714 km away. In cosmic terms, a difference of 22,210 miles or 35,743 km is not that much and only astronomers take note of the diference. But occasionally the media will decide to write a story about the “biggest Full Moon of the year” or something similar.

There is a nice animation at time.unitarium.com/moon/ that shows the movement of the Moon in your area and illustrates nicely why we see a Full Moon and how it appears when waxing and waning.  You can set it to any date, so I know that on my next October birthday the Moon will be waxing gibbous and approaching full. Unfortunately, it doesn’t allow you to go back before 2000 or I would take a look at what the Moon was up to when I was born.