Making Friends with the Night Sky: Women and the Moon

Our earliest calendar - linking the lunar cycle with the menstruation cycle

Maui astronomer Harriet Witt describes the connection between women and the Moon.

Listen here [2:41m]:

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What’s the facts:

The earliest astronomers may have been women, who discovered that the cycle of the Moon was synchronized with their menstrual cycle.  Having an external cue for this internal cycle would have allowed women to time the birth of their children and perhaps help regulate the population of their tribe or clan in an environment with limited resources.

Our earliest evidence of the connection between the Moon cycle and menstruation cycle – indeed, our earliest evidence of the practice of astronomy – is found on a reindeer bone over 20,000 years old, called the Ishango Bone.  This bone is also believed to be early evidence of the beginning of mathematical thought.  The Ishango bone is one of our first calendars (other ancient calendars also traced the cycles of the Moon).

Original air date 4 August 2009.

Making Friends with the Night Sky: The Full Moon

Lunar eclipses can occur during the full moon period

Maui astronomer Harriet Witt describes our full moon, and how the alignment of the Sun, Earth and Moon – syzygy – can affect the planet.

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What’s the facts:

Halfway through our lunar cycle, the Moon and the Sun are now on opposite sides of the Earth, so we see a fully sun-lit full Moon.  At this time, the Moon rises as the Sun sets, and the Sun rises as the Moon sets.  This alignment of Sun, Earth and Moon is called syzygy (pronounced “SI-zi-gee“) and occurs during both new and full moon.  This alignment magnifies the ocean tides on Earth (both the Sun and the Moon cause tides through gravitational force), and the full moon is a time when lunar eclipses can occur, about once or twice a year.   Imagine standing on the Moon at this moment; you would see a “new Earth”, or the dark side of the Earth, up in the sky.  Similarly, you would see a “full Earth” during the period of new moon.   In many ways, full moon is a period of opposition.  It is also a period of celebration, with many holidays occurring during full moon in tradiational cultures, such as the Chinese Lantern Festival, the Hebrew Passover, and the Muslim Shab-e-Bara’at.  The bright night also inspires full moon parties.   Have fun celebrating our closest celestial neighbor!

This Astrofact is dedicated to Mahina, our four-legged full moon.

Original air date 1 August 2009.

Making Friends with the Night Sky: The New Moon

A glimpse of the moon through the trees, as it phases from new moon to cresent.

Maui astronomer Harriet Witt describes the new moon, the start of the lunar cycle.

Listen here [3:26m]:

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What’s the facts:

“A month is a Moonth, a Moonth is a moon.”  For many traditional calendars – Hawaiian, Chinese, Hebrew, Islamic – this is still true, although our western calendar has been tweaked to fit the months into one year.  The new moon is the start of the lunar month, and the time when the moon lies between the Sun and the Earth (this is called syzygy, a great Scrabble word).  Imagine yourself floating out in space well above the Sun, Moon and Earth, and you will see these three bodies in a row, with the Sun-lit side of the Moon facing away from the Earth.  So where is the new Moon in the sky?  Directly in front the Sun!

Why doesn’t the Moon block, or eclipse, the Sun every time the new moon phase happens?  It’s because the plane of the Moon’s orbit is actually inclined by about 5° relative to the plane of the Earth’s orbit (the ecliptic plane).  So most of the time, the Sun, Moon and Earth are out of alignment during new moon.  However, the Moon’s orbit actually rotates, or precesses, every 27.2 days.  So perfect alignment at new moon occurs about once every 18 years, a period the Babylonians called a Saros cycle (a complete explanation can be found here).  In fact, there are several Saros eclipse cycles because the Sun-Moon-Earth alignment doesn’t have to be perfect, so we get about two eclipses at new moon every year.

New moon is a great time for star-gazing as the Sun and the Moon will have both set in the evening.  So be sure to enjoy the dark skies that accompany the new Moon!

Original air date 22 July 2009.

Making Friends with the Night Sky: The Waxing Crescent Moon

The waxing crescent - the start of the lunar cycle

Maui astronomer Harriet Witt describes the waxing crescent moon -  the first phase in the lunar cycle – and Earthshine.

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What’s the facts:

The waxing crescent is the first phase in the new Moon to new Moon lunar cycle.  You can catch it by looking toward the western sky early in the evening; there you will see a bowl-shaped sliver pointing toward the setting Sun, following it down to the horizon.  The opposite side is darker but not completely dark – it is faintly lit up by sunlight reflected from the Earth’s surface, called Earthshine.  The origin of Earthshine was first figured out by Leonardo Da Vinci in the 1500s; scientists now use Earthshine to track global cloud coverage and variations in the Earth’s climate. The waxing and waning crescent phases are the best time to observe Earthshine, so enjoy our spotlight on the Moon!

Original air date 22 July 2009.

Making Friends with the Night Sky: The Waning Crescent

The waning crescent appears on the left in the Northern hemisphere, and the on right in the Southern hemisphere

Maui astronomer Harriet Witt describes the “old” waning crescent Moon.

Listen here [3:30m]:

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What’s the facts:

The waning crescent, or “old moon”, can be seen shortly before dawn, a thin sliver that rises ahead of the Sun.  You have a short period to catch it; after the Sun rises, the thin crescent is hard to see in the bright glare of day.  The waning crescent occurs toward the end of the new Moon to new Moon cycle, a siderial period of  27 1/2 days if you measure the Moon’s position relative to the stars, or a synodic period of 29 1/2 days if you measure relative to Sun.  The difference is due to the Earth’s motion around the Sun.  During a “moonth” the Earth has traveled about 1/13th of its yearly orbit (at a rate of 1.3 million miles per day).  So from our point of view, the Sun has moved to a different part of the sky relative to the stars – by about 28 degrees – over the lunar cycle.  Every month brings a new perspective!

Original air date 13 August 2009.

Making Friends with the Night Sky: The Gibbous Moon

The moon entering its gibbous or hua phase

Maui astronomer Harriet Witt describes the waxing gibbous Moon.

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What’s the facts:

Progressing from the first quarter, the Moon enters its waxing gibbous phase, on the way to full bright moon.  The Moon is showing more of its sunny side to us on Earth, and is taking on an egg-like shape.  That’s why Hawaiians call the gibbous phase (gibbous is derived from the latin word “gibbus”, or “hump”) the “hua” or “egg” phase.

Original air date 1 August 2009.

Making Friends with the Night Sky: Seeing stars that aren’t really there!

The red supergiant Antares in the constellation Scorpius.

Maui astronomer Harriet Witt describes one of the brightest stars in the constellation Scorpius, a distant red supergiant that may no longer exist.

Listen here [4:22m]:

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What’s the facts:

In the center of the constellation Scorpius lies the bright red star Antares, the 16th brightest star in the night sky.  Antares is what is known as a red supergiant – its surface is cool and hugely extended, 800 times larger than the Sun. Indeed, if Antares were in the Solar System, it would engulf Mercury, Venus, Earth and Mars.  Stars become red supergiants at the end of their lifetimes, when they have exhausted most of their hydrogen fuel, and they on their way to a spectacular stellar death in the form of a supernova.  The red supergiant stage of a star’s lifetime is relatively short – a few hundred thousand to a million years.  In contrast, the light we see from this star was emitted 600 years ago, since it takes light 600 years to travel the 600 light-years of distance between us and Antares.  So it is possible that Antares is no longer there.  Ponder that while you’re enjoying your view of Scorpius tonight!

Original air date 30 June 2009.

Making Friends with the Night Sky: The First Quarter Moon

The First Quarter Moon

Maui astronomer Harriet Witt describes the First Quarter Moon and brings you out into space, so you can see how lunar phases work. So take sometime out of your busy day, take a deep breath, and let Harriet bring you on a journey through the night sky.

Listen here [4:24m]:

What’s the facts:

It is called the First Quarter Moon, because that is what the moon looks like to us here on Earth (1/4 of a big round ball). To us, it seems as though the stars, the planets, and the moon, change throughout time, but really, we are turning, taking a different view of the night sky as we do. Our lunar phases are relative to the Sun (our source of light), and changes as the moon follows its orbit around the Earth, and the Earth spins and follows its orbit around the Sun. It’s pretty complicated once you think about it!

Original air date 22 July 2009.

Making Friends with the Night Sky: What is Night?

The Earth...at night!

Maui astronomer Harriet Witt asks a simple question: what is night?  The answer requires us to view our planet from a completely different perspective. The answer just might surprise you.

Listen here [4:24m]:

What’s the facts:

Night or nighttime is the period of time when the sun is below the horizon. Nights are shorter than days on average, but vary in length as it is based on factors such as season, latitude, longitude and timezone. Night lets our bodies know when to sleep and when animals can go out to hunt, but it’s also important to science. Without the absence of the Sun, we may never have seen the stars in the sky, and astronomy would not be what it is today. So next time you’re taking out the trash and you get spooked when something stirs in the dark, take a minute to look at the sky and appreciate it, and remember that light is right around the corner.

Original air date 30 June 2009.

Making Friends with the Night Sky: Maui’s Fishhook

The constellation Scorpius, known in Hawaiian culture as Maui's Fishhook

Maui astronomer Harriet Witt describes how different cultures have different names for the constellations in the night sky, and how the legend of Maui’s Fishhook (also called Scorpius, or the Scorpion) was probably important to the Polynesians who first settled Hawaii.

Listen here [4:24m]:

What’s the facts:

Ancient Hawaiian legends state that Maui, one of the many demigods of Hawaii, once threw a magical fishhook, (Manai-a-Kalani or “fishhook from the Heavens”) into the Pacific Ocean to pull out the other Hawaiian islands. Maui had received this sacred fishhook from his father Akalana and was sent off in a canoe with his brothers to catch the giant ulua fish named Pimoe.  This was a hard task, because if one were to look at Pimoe, the fish would die instantly and turn into solid land. Maui dropped his fishhook into the ocean and Pimoe grabbed a hold of it. Struggling to keep a hold of the line, Maui’s brothers turned around and the line snapped. Pimoe died and turned into hard land.  Maui pulled the great hook out from the land and threw it up into the sky, where it became the constellation known as Maui’s fishhook. It still hangs there today, known to many as Scorpius.

Hawaiians were natural astronomers, studying their skies very carefully. They used their knowledge of the sky to navigate to the islands, to know when to fish, and to manifest their spirituality. They even had a name for each night of the moon’s phases. That’s 29 names! To learn more about Ancient Hawaiian astronomy from Harriet Witt herself, click here.

Original air date 14 July 2009.