So what happened last Saturday night?

I know - some sharp person is going to tell me there was an eclipse of the Moon, Saturday,March 3, 2007 - and they would be right. I know, because I watched it. But what exactly was happening?

I put that question to Professor Higgins, my shaggy-headed companion, and he just titled his head to the left a bit, and looked at me as if I was losing it. "Everyone knows the answer to that, Greg - the moon moved through the shadow of the Earth."

"Right," I answered. I know that. In fact, Manny Monte got a couple nice photos of it he was kind enough to share. But as you look at them, also think about exactly, was happening.

I mean, this is what it looked like as the moon began to emerge from the Earth's shadow.

And this is what it looked like a bit later if you happened to be one of a small group of ASSNE amateur astronomers (and visitors) who gathered at the eastern corner of East Beach in Westport. This second photo really captures the ambiance of being there - the moon, the water, clear skiesoverhead - clouds along the horizon with even some distant lightning flashes - and occasional car lights lighting the beach grasses, as they did in this time exposure. (Manny said he first cursed the car for coming by at that moment, but then decided he liked the results. I do too.)

But my question is about other motions - what exactly was going on?

Now, if you've heard me ask this kind of question before, you know I tend to obsess over getting the scientific reality of things firmly in my mind in a holistic - not fragmented - fashion. So, for example, I try not to say - or think - things, such as "the moon rose at 5:30 pm." That's conventional lingo, but it's just plain wrong. As any school child knows, the moon did NOT "rise." The Earth simply turned eastward enough so we could see the moon.

Am I quibbling over non-essential words? I don't think so. For me this is a critical point because a significant part of the reality we live in is the fact that we're on a spinning platform - a cosmic merry-go-round. Yet every day we use langauge that belies this truth and reinforces the pre-Copernican view of things. So at 5:30 it was "moon east," if you like, meaning the moon was on the eastern horizon. But it wasn't doing anything - we were.

Well, excuse me, it was doing something. But again, we tend to get what it was doing wrong. We tend to say it was "going around the Earth." Now I will agree, this is what it looks like - and an eclipse of the moon is a great way to get this action in your mind because it's another one of those counter-intuitive thngs. Because we start by thinking that the moon is rising, we tend to also assume that the moon will pass through the Earth's shadow on its way "up." Wrong!

The moon is actually going the opposite direction that it appears to go. Our spinning Earth - we're moving about 800 miles an hour here in Westport, MA - sure makes it seem as if the moon is rising and so, when watching an eclipse, we would expect the "leading" edge of the moon - the "top" one - to emerge from the Earth's shadow first. But it doesn't. It's the other edge that comes out first - the "bottom" edge.

The explanation is simple. The motion of the Earth makes the moon appear to rise, when in fact, it's own motion is making it appear to fall. Of course, it's apparent motion is much slower than the illusion of "rising" created by the spinning Earth, so unless we watch the moon from night to night and mark it's position against the background stars, we will hardly be aware of this opposite motion. And given that few folks in our society venture out at night without bringing along their own artificial sun, we tend to cut off any opportunity of getting in tune with this reality as well.

But even if we are aware of this motion of the moon against the background stars, we tend to say it is a result of the moon spinning around the earth each month. Yep - sort of. . . But this is, at best, an incomplete picture of reality.

We love to chop up reality into little, static pieces because they're easier to understand this way. So we get a picture in our head of the Earth standing still and the moon whirling around the earth each month like a ball on a string being twirled around our heads.

Not so. To get a better picture of the reality we witness during an eclipse we have to take an instant rocket trip - you can do this in your mind - to a point above the Earth - way, way above the Earth. From here we can watch it and the moon and the other inner planets revolve around the sun. If we have some way to mark their position, you'll find this old Earth is not only spinning very quickly, but it's also motoring right along at about 66,000 miles an hour in a roughly circular path around the sun.

Now check out the moon from this perspective. Watch it and the Earth for a couple of months. Does it look like the moon was going around the Earth? Remember, put everything in motion. I think what you will see is that the moon actually looks like it is going around the sun. The moon and the Earth look like a a pair of planets, very close together and one much smaller than the other. But they are both orbiting the sun. Only the moon's orbit looks different. Instead of being a smooth elipse around the sun it keeps weaving in and out of the Earth's orbit.

Oh what a beautifully crooked path it weaves!

At new moon it's between the Eartrh and the sun. At first quarter, as the Earth rushes forward, it falls toward the Earth and seems to be directly behind it. (An image jumps into my mind of the Earth sort of giggling at ths and shouting "you missed me again" to the moon. ) Then at full moon it has caught up with the Earth, but now it's outside the Earth's orbit with the sun shining directly on its face. Then at last quarter it actually has sped ahead of the Earth, but again is falling inward - towards the Earth and toward's the sun. In another week it will be a "new moon" again- invisible to us, but well inside our orbit towards and thus closer to the sun.

For me, that's a much different motion than I see when I simply think of the moon as spinning around the Earth each month. The sun is holding both the moon and the Earth in its grip. The Earth is holding the moon in its grip, but it's not all a one-sided thing. It's being influenceed by the moon so that they both are really relating to a common cenetr of gravity. And forget that image of a ball on a string. That's too simple as well. Think of all the forces at work here - think of how speeds and force are constantly changing as distance between the main players - sun, Earth, and moon - constatly varies. (Given thes incredible dynamics I'm amazed we were ever able to send a space craft to the moon - let alone to other planets. Hats off to the engineers!)

Then, of course, there's the matter of the Earth's shadow. That's a lot more complex than it seems as well. In fact, I tried to simulate an eclipse with a model Earth 8-inches in diameter and a model moon 2-inches in diamter. I set them the requried distance apart - whatever scale you use, the handy number to remember is 30. The moon is 30 earth diameters away. Problem is, it's just not that easy to get the "sun" in the right place - or the right size.

So, we need to understand that the Earth's shadow does reach to the moon and beyond - and it is big enough at the distance of the moon so that the moon can be buried in it not for an instant, but for a pretty long time - on March 3 it was for over an hour.

Why doesn't the moon plunge into the Earth's shadow every month? Good question, The reason is the plane of the moon's orbit is tilted about 5-degrees to the plane of the Earth's orbit. So most months the moon passes either beneath the Earth's shadow, or above it. Hey, what wide receiver wouldn't wnat such moves? Weave, bob, weave, nod, throw a shoulder inward, but go the other way . . . ;-)

Got all that? I do and I don't. I can know all that in my simple, linear, deconstructing mind where I chop things up into little mental bites that are easy to chew and swallow. I also know there's much more - that the whole system is in motion - the whole universe is in motion - that the only constant is change. The challenge - I should say the continuing challenge - is to sit on East Beach in Westport on a cold winter night while the clouds are racing over head and obscuring the horizon - and put it all together. You and your amateur astronomer friends debate exactly where the moon should be at the moment - behind which clouds - above which rock, or line of breaking waves.

Eventually, Danny, using binoculatrs, picks up a faint, ruddy glow trying to burn through som clouds. . The moon. The blood-red, eclipsed moon. And we all turn our binoculars or telescopes in that direction and visitors get out of cars to come see what the excitement is all about and I, for one, can't really explain it. Part of me knows quite a bit about it. But to stand there on East Beach and see this event - see the moon - watch it dodge in and out of the clouds and eventually get out of that one huge cloud, the shadow of the Earth , , , fiddle with telescope controls . . . talk to people . . . try to get out of the wind. . . exchange comments about Orion coming out . , . wonder if Bren, who is home puppy-sitting knows the skies have cleared . . .

And Just how big does the Earth have to be to cast a shadow that can reach more than a quarter of a million miles into space? Think of that - think of the earth-merry-go-round-the-sun and the moon-merry-g0-round-the-sun and the two platforms holding the "horseys" tilting five degrees relative to one another as they go round the sun . . . the weaving inside and outside and behind and ahead of the Earth and . . . well, all I can say is it's a magnificent dance and eventually I hope to pick up the rhythm and have the steps come naturally.

But for me, that's what was going on last Saturday night - and while the moon is out of the shadow for the moment, the dance continues, right now, as you read this . . . and that thought is justone more reason I remain rapt in awe.

Comments?

from james P. Burke:

As you describe in your post, the Earth and Moon can be seen to revolve around the Sun together, as a system, even though we picture the Moon revolving around the Earth.

The Earth-Moon system is (in its revolutions, but not rotation) like a large adult and a small child holding both hands and spinning around *each other* with the child doing most of the movement, but pulling the adult off-balance as it goes. Both bodies are involved, which is something that I think many people don't realize, since the center of mass of the system is within the Earth's surface.

from Greg Stone:

Now if you can only find a metaphor for the sun in your adult/child system it will be compelete. I really like it though. Thanks.

from Bruce Cartwright:

There's a lot of "Gravity" in James' comment. :)

from Robert Magnuson 3.6.07

hat's great Greg! It is hard for us here on our fixed and solid, unmoving earth (Not!!) to visualize all of that. It is hard enough to get out of our 'fixed earth' mentality (in our genes, even, courtesy of evolution) when seeing it in a science book.

A couple of other thoughts. When watching the movie 'The Lord of the Rings' I noted that an image of the moon looked obviously upside down to this astronomer. 'Ha!' said this astronomer to himself, proof that the movie was indeed filmed in New Zealand, that other 'land down under' where the heavens stand on their collective head. But then I shook my head and laughed at myself. Because the moon can easily look upside down even here in New England. How often have I viewed the full moon rising? A thousand times would be an exaggeration, since I am just a bit under 800 moons old, and even I have not watched every full moon rise during my time on earth. Full moons rising are extolled in verse and painting, and not badly at all by Manny with his camera. But how often have I observed the full moon setting? Only a few times, and only recently. Nobody writes about full moons setting, after all. It is a sign of my 'human centered thoughts' that I expect a full moon setting to look an awful lot like a full moon rising. But it isn't. Since the moon hasn't moved (except for its eastward crawl that is so hard to notice) and we have spun along below it's unconcerned gaze, and since we don't have eyes on the back of our heads, as we turn 180 degrees to see the setting moon, doggone if it isn't upside down!!! And backwards! Everyone knows that Mare Crisium is on the right side of the moon, and Tycho is on the bottom. So why is Mare Crisium on the left now, and Tycho at the top? Perspective.

And here's another perspective problem: how long does it take the moon to make one of its sinuous orbits around the earth? 27.32 days. I leave you to ponder why we always say that a lunar month is 29.5 days long.

from: Greg Stone 3.6.07

You do know the answer to that one, I assume ;-)

I loved your other comments - thanks - and you know, I watched the full moon set just a few days ago when I was checking the nova in Scorpio - but danged if I took any real notice - just a casual glance! Have to look again some day.

from Robert Magnuson 3.6.07

Well, I do, but it never would have occured to me without an astronomy text
to explain it. Again, it is the conceit that we are on a stable earth and
everything goes around us that keeps us from seeing the obvious. We measure
one orbit of the moon (in our minds) as one full moon to the next full
moon, but if the earth truly stood still, the moon would be full again in
only 27.32 days. Trouble is, the earth moves, so that when the moon has
made one full orbit, the earth is no longer between the moon and the sun,
so the moon does not appear full - the danged earth has moved about 30
degrees along its own annual orbit, and the moon then has to play catch-up
to get to where it APPEARS to be exactly where it was last month. 2.2 days
worth of catch-up to be exact. Now we see a full moon and we think the moon
has gone around the earth once, because that is what we SEE. In truth, the
moon goes around the earth 13 times, as seen from your imaginary point high
above the earth, in 12 lunar months as counted from a position sitting on
the earth. The extra orbit is broken into 2.2 day segments, but it accounts
for the the full turn that the earth makes around the sun while we have
been observing the moon from our 'stable' platform. In thirteen orbits, the
moon has only hit the moon-earth-sun alignment 12 times, so we think the
moon has orbited us 12 times, when in truth it goes around 13 times. Twelve
full moons 29.5 days apart equal 354 days; thirteen full orbits of 27.32
days equal 353.99 days. Close enough.

Bob

from Greg Stone 3.7.07

Yep - very nice explanation- but this is exactly why I prefer to see the moon as weaving in and out of our orbit - as falling behind us, then playing catch up and running ahead - for me it paints a better picture of reality than to think in terms of it circling us - the circling is what it looks like to us, but brings us back to our earth-centered system. And, of course, the Sun is the dominant force in this dance. And yes, I never would have understood this without the aid of an astronomy text - but my whole point is that we - and here I include the best of scientists in that "we" - we tend to understand these things in a linear fashion and we've come up with systems that help us make use of this knowledge, and we build wonderful models that allow us to make predictions - and yet we have not mad the picture of reality painted by these wonderful systems a part of our every day experience. Our intuition is still locked up in an Earth-centered system. Our gut tells us - and our language supports it - that the sun does the rising - the stars rise and set, etc.

Bob Magnuson wrote 3.7.07

I agree with every word you say. It stuns me to sit and try to think holistically about the mechanisms of just our galaxy, looking down to see the solar system as it wends its own way through its neighborhood. Some of the surprises that people have a problem grasping: why are Saturn's moons so scattered around the planet? Don't they have a 'plane of the ecliptic' of their own to follow. Yes, but when we can see the rings in all their glory, we are looking at the Saturn system from above or below, so we see the moons scattered across that same plane. When the rings close up, we see Saturn's moons looking like Jupiter's moons, all in a line. Then comes the question of how fast we are moving. Yes, the 66,000 mph that we rush around the sun, but also the nearly 600,000 mph that we whip around the galaxy, and the unknown speed of more than 1,000,000 mph that the whole danged galaxy is zipping toward M31. Or more properly, the closing speed at which both galaxies will eventually meet, not quite in the middle. And our entire local group is headed to the Virgo Cluster, I think, but does anyone know that speed? Talk about how difficult it is to decide - mph compared to what stationary object???

I just read, in a textbook only five years old, that our solar system is a
half light year in diameter. The latest studies seem to say that the Oort
cloud may extend out to nearly 1.5 ly from the sun, and form a halo around
it that has no relationship to the plane of the ecliptic. It is literally a
cloud. And that would make our solar system 3 ly in diameter. And it would
mean that our solar system extends out to roughly a third of the way to
Alpha Centauri. Those are some of my meditations when I stare into the
eyepiece trying to comprehend some of what I am seeing.

What an age in which to be an astronomer.

Now, the one thing I like about modern science is that we are starting to
move away from linear thinking. Especially in the realm of
multi-disciplinary science, we are starting to have biologists talking to
physicists, and both of them talking to archaeologists, and consulting with
linguists or geologists, or whoever, so that new theories are starting to
be proposed as having a context. And a lot of good science is happening
because of that. Earth scientists are talking to astronomers to find out
the implications of the Maunder minimum, and the length of the earth day at
different points in history, etc, etc, and the ideas that flow from those
consultations are so much more coherent than what was taught to us in
school.

Bob