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“Bye Bye Moon” is not meant to be a sequel to Goodnight MoonDid you know that the moon’s distance from Earth varies each month? I didn’t know that until this week, even though I know a lot about our Moon and I write about it at least once a month here.

Our Moon has a rather eccentric orbit and it is moving away from us at about one and a half inches per year. Scientists attribute this to tidal friction with the Earth’s oceans which also slows down how fast the Earth rotates, This lengthens our day by about 1 second every 40000 years.

Okay, it is not something we really will notice or need to worry about, but because scientists can do simulations, they can figure out that four and a half billion years ago when the moon was being formed,  it was only about 15,000 miles from Earth. Now, it is about 238, 831 miles from Earth.

Back then, an Earth day might have been only 5 or 6 hours long and there would be 1400 days in one year. More recently, at least relatively, around 900 million years ago there would be 480 days of about 18 hours each in one Earth year. That would certainly give us a very different lifestyle.

And projecting into the future, we would expect longer days but fewer of them in a year.

Even though we can’t observe these changes within a lifetime, it awesome and full of wonder to me that these changes are happening.

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The French scientist Jean-Bernard-Léon Foucault made his most famous pendulum when he suspended a 28-kg brass-coated lead bob with a 67-m-long wire from the dome of the Panthéon in Paris.

He set it in motion and to mark its progress he attached a stylus to the ball and placed a ring of damp sand on the floor below.

The audience was amazed to see the pendulum inexplicably appeared to rotate. It left a slightly different, but precise, trace in the sand with each swing.

Amazingly, they were witnessing that the seemingly motionless floor of the Panthéon was slowly moving. It was Foucault’s way of showing that the earth revolves on its axis.

At the latitude of Paris, the pendulum’s swing rotated clockwise 11° per hour, making a full circle in 32.7 hours. In the Southern Hemisphere it would rotate counterclockwise. If it was set up on the Equator, it wouldn’t revolve at all. In much more recent experiments with a pendulum at the South Pole, the period of rotation is 24 hours.

It is such a simple and elegant demonstration of a complex idea – precession as a form of parallel transport – that it fascinates children and adults.

Foucault pendulums are installed around the world, at universities, science museums and planetariums. The United Nations headquarters in New York City has one. The largest Foucault pendulum in the world, Principia, is housed at the Oregon Convention Center.

zodiac revised

NASA is science and astrology is not. But that doesn’t mean that very logical, well-informed people don’t look at their horoscope once and awhile. And everyone knows what their zodiac (“circle of animals”) sign is supposed to be.

A few months ago, NASA put out some zodiac information that the popular press picked up on and took further than NASA intended.

On the science side of things, NASA made the point that the sky and positions of the stars and constellation is significantly different from the sky that the ancients used when they came up with the zodiac signs that we all have known.

The zodiac signs were created based on the calendar year of the Babylonians who  lived over 3,000 years ago. They divided the zodiac into 12 equal parts pie slices, even though they seem to have known that there were actually 13 constellations in the zodiac.  Twelve just worked neater.

The Earth orbits the Sun, so the Sun appears to pass through each of those 12 zodiac signs. That worked out nicely with their 12-month lunar calendar.

Orion stars

You can see Orion’s familiar 3-star belt. Can you see in this group of stars what the ancient Greeks thought looked like a giant hunter with a sword attached to his belt.?

What is the zodiac anyway? NASA explains it like this:

Imagine a straight line drawn from Earth though the sun and out into space way beyond our solar system where the stars are. Then, picture Earth following its orbit around the sun. This imaginary line would rotate, pointing to different stars throughout one complete trip around the sun – or, one year. All the stars that lie close to the imaginary flat disk swept out by this imaginary line are said to be in the zodiac.

One thing that NASA announced was that the thirteenth sign – which had been there all along – was Ophiuchus. NASA didn’t come with that Latin name either (meaning “serpent bearer”) it had been written about by Greek astronomer Ptolemy in the second century.

I first heard about this “news” because I follow NASA’s Tumblr account. where they said “We didn’t change any zodiac signs, we just did the math.”

In those 3000 years, the Earth, which wobbles a bit as it orbits, has shifted our view of the sky. The Earth’s axis (North pole) isn’t pointing in the same direction it was to the Babylonian viewer.

But the news that there was a thirteenth zodiac sign (Ophiuchus) and the shifting sky meant that more than 80% of us were born under a different sign. That would be true if someone redrew the sky charts and used those revised charts to do your horoscope based on when you were born. The sign you always thought was your sign actually was your sign – three millennia ago.

I had a friend in college who was really into astrology. She did a chart for me and made the point that those horoscopes that you see in magazines and online are so general for a sign that they mean almost nothing. You need a chart done for you based on the day and time you were born. I learned that astrologers use “artificial” constellations that are fixed in the Sun’s path as seen from Earth and use that to track planetary movements. Therefore, the zodiac sign dates remain the same for astrologers no matter what NASA says..

Of course, NASA doesn’t really care about your horoscope. I think their interest in all this is pretty close to my own interest in astrology. It makes you pay more attention to celestial observations.

But, if you have looked at your horoscope and found it not to be so accurate, maybe you want to consider the more modern view of the sky that was up there when you were born.  I moved from being a Libra to being a Virgo. If you were born today you are born under Ophiuchus. Some Capricorns are now finding out they are a Sagittarius. It’s like a commercial for DNA ancestry testing that I see on television – you thought you were a Cancer and now you’re a Gemini. Poor Scorpio went from being about a month to just six days long.

I checked my Libra horoscope while I was writing this. Bummer: “You probably aren’t going to feel very friendly. You’re most likely to want to sequester yourself at home and not see or speak to anyone.”  I checked in on Virgo – not much better: “Today you might get the feeling that someone in your family is hiding something. The atmosphere might be strained and somewhat tense.” Why can’t I have this one? “Venus, your personal planet, enters a dynamic and positive sector of your chart, making this the perfect time to make over your life, attitude and relationships.”

Here are NASA’s revised 13 signs and dates:

Capricorn: Jan. 20 – Feb. 16
Aquarius: Feb. 16 – March 11
Pisces: March 11 – April 18
Aries: April 18 – May 13
Taurus: May 13 – June 21
Gemini: June 21 – July 20
Cancer: July 20 – Aug. 10
Leo: Aug. 10 – Sept. 16
Virgo: Sept. 16 – Oct. 30
Libra: Oct. 30 – Nov. 23
Scorpio: Nov. 23 – Nov. 29
Ophiuchus: Nov. 29 – Dec. 17
Sagittarius: Dec. 17 – Jan. 20

zodiac-beit_alpha

Mosaic pavement from a 6th century synagogue at Beth Alpha, Israel showing the zodiac surround the central chariot of the Sun (a Greek idea) and the corners depict the 4 “turning points”  of the year, solstices and equinoxes.

Our Moon is always up there and one half is always illuminated by sunlight and the nighttime half is in its own shadow, even though we don’t always see that.

I post a lot about the Moon and I’m hardly alone in being fascinated by it. You may have an astronomical interest in it, or maybe a more Romantic interest. Either way, you probably only think of the view of the Moon from Earth and not the other way.

Right now we are in the last quarter phase when we see half the moon’s day side, and half its night side. I recently discovered that the shadow line dividing day from night is called the lunar terminator.

Here’s another way to view the moon, if only theoretically. If you were on the moon now while it is in its last quarter phase, as it is today, and you were looking back at Earth, you’d see the Earth at its first quarter phase.

Perhaps some day, a lunar-living blogger will post regularly about the phases of the Earth.

 

firts-quarter-earth

As seen from the moon, the terminator on the first quarter Earth depicts sunrise, as the first quarter Earth waxes toward its full phase.

 

The term supermoon denotes a new or full moon that occurs at roughly the same time the moon is nearest Earth in its monthly orbit. Astronomers use the term perigee to describe the moon’s closest point to Earth, from the Greek words peri meaning “near” and gee meaning “Earth.”

Our first supermoon of 2014 occurs on the very first day of the year. There will be a second supermoon on January 30.  We won’t have a single calendar month with two supermoons again until January 2018.

“Supermoon” is not a term from astronomy, but from astrology. The belief is that a supermoon has some kind of effect on people on Earth.  It certainly has the effect of high tides.

“Supermoon” is a term that was coined by Richard Nolle over 30 years ago, but it has become more popular in our Internet age.

2014 will have a total of five supermoons: the two new moons of January, and the full moons of July, August and September.

The International Space Station is visible to observers on Earth on a regular basis. The space station flies about 220 miles overhead, circling the globe once every 90 minutes. Usually, the station is invisible us on Earth during some of those orbits because the sun isn’t shining on it and lighting it. When the station’s path aligns with Earth’s day-night terminator, the spacecraft is in nearly constant sunlight and it shines.

I signed up last year for Spot the Station and I get alerts for when the station passes over Paradelle. I’m not sure most readers will understand why I enjoy looking up and seeing it passing overhead. With clear skies, it looks like a moving star and it can be as bright as Venus.

Part of the attraction is knowing that this “star” has people in it. As a kid during the “space race,” I wanted to be an astronaut.  I knew the odds were low, but I also wanted to be shortstop for the NY Yankees. I set my dreams high, and when they had to be brought back to Earth, I settled for watching the skies and watching the games.

Yesterday the space station was visible here at 5:37 PM and visible for 3 minutes (at 77 degrees, appearing from WSW and disappearing in the Northeast. For those few minutes, I was flying over Paradelle and looking down on the clouds and the big blue marble below.

Between looking at the space station and watching the “falling stars” from the Geminid meteor shower this week, I do feel a bit more connected to space. That’s a good thing, right?

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Hands off Hello Not all labyrinths are traps Happy to be inside but already missing summer outdoors.  The plant feels the same way. There’s something in the first cold nights when autumn teases winter that seem to require a fire. Still drinking morning tea in the afternoon.  #teaetiquette

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