Turns out there are as many ways to photograph an eclipse as there are to watch it. With a bit of preparation and the generosity of strangers, I got to experience five of them during Sunday's annular eclipse.

My husband and I drove from the Bay Area up to Mt. Hirz near Lake Shasta which was smack in the middle of the optimal eclipse viewing path. About a mile from the top, we ran into an amateur astronomer named Ben who'd scoped the whole mountain the previous day and decided this was the best spot. He had a telescope, so we stayed with him.

A bit of cloud cover when the eclipse started had us all chewing our fingernails, but then it cleared up–and what a view!

Although I am an admirer of photography, I am not the most skilled practitioner. Flickr, however, is a treasure trove of beautiful images. All the pictures in this post are from photographers kind enough to share their work openly, for the enjoyment of the masses.

To make a hokey pinhole camera like I did, cut a square out of a piece of cardbord, tape aluminum foil over the empty square, and poke a hole in the foil with a pin. Stand with your back to the sun and hold the cardboard so the sun shines directly through the pinhole onto a piece of white paper. (This photographer made three holes, one of which was obviously best.)

photo by stevendamron

A better technique is to replace the pinhole with a pair of binoculars like my husband did. You keep your back to the sun and hold the binoculars in the same position as the pinhole camera and you get a larger, clearer view of the sun on the paper.

photo by jinxmcc

Astronomer Ben's wife had a pair of eclipse viewing glasses that were the best way to see color–the "ring of fire" when the moon is totally inside the sun. You can put these glasses–or a really thick filter, which is the same thing–in front of a camera as well as in front of your eyes. But the sun looks really small.

photo by °Florian

Best of all is an actual telescope. Then you can see sunspots!

photo by Mark Langridge

The fifth, final, and possibly my favorite way to see/photograph the eclipse requires no equipment at all–just some trees. When the sun is a crescent, it shines through the leaves to create hundreds of little crescents on the ground or wall.

photo by niiicedave

Photographing the sun is one thing. But the full mood of an eclipse, with its cool air and dusky light, is difficult to capture. Here's one picture (not from the path of full annularity) that really pulled it off:

photo by jimnista

Hypothetical exoplanet of a brown dwarf star--similar to a future Earth? Credit: Jeff Bryant

Every now and then, when seeing fresh examples of the world's problems, local or global, I take a deep breath, sigh, and think, "In a million years, what difference will it all make?" It may sound fatalistic, and of course current events do matter to our short-timer existences on Earth, but the thought gives me an odd sense of peace and gets me to thinking about the future—the far distant future—of the Earth. It's hard to imagine what the future will bring in ten, a hundred, or even a thousand million years. Where will evolution take life on Earth—including us? How far will human civilization stretch, and what turns will it take? What exciting twists and cliffhangers are in store for the climate? What will be on television?

Some things are a bit easier to predict: what the Sun will do and how the Earth and the Earth-Moon relationship will change.

I ran across a web version of the H.G. Wells novel "The Time Machine" a couple of weeks ago, and re-reading Chapter 11 I was reminded how insightful the story is with regard to visualizing future possibilities. In this chapter, the Time Traveler probes forward in time, going millions of years into the future and arriving in a tidally-locked Earth under a bloated, reddened Sun, with no Moon in the sky. The ocean was calm and cold, sporting only gentle, lazy swells, and the air was considerably less stocked with oxygen than today. Snow peppered the land and ice fringed the sea, and the only ubiquitous sign that life still existed was a green slime that coated the rocks of the shore.

"All the sounds of man, the bleating of sheep, the cries of birds, the hum of insects, the stir that makes the background of our lives – all that was over."

An alien, cold, and pessimistic view of the future? Well—it can hardly be classified as pessimistic; pessimism is an emotion based on the seeming unchangeability of things we can in fact change. But the Earth's future is commanded by forces scarcely within our power to affect.

For one, the Earth's rotation is slowing down. It used to spin much faster—maybe three times as much—but tidal effects of the Moon and Sun have been slowing it down for four and a half billion years. Imagine an eight-hour day, with the Sun crossing from horizon to horizon in about four. Wake up, it's only a couple of hours until lunchtime, and another two ‘til dinner. I got a whole three hours of sleep last night! Ahh!

Where is Earth's spin going? Shakespeare had the answer: "The Moon's an arrant thief…." The momentum of Earth's spin is being slowly siphoned off by the Moon through tidal interaction, which is simultaneously causing the Moon to move farther from the Earth. Once much closer to Earth, even today the Moon continues to inch away into space–quite literally, at less than two inches per year.

So in the very distant future, we can project that the Moon will have moved much farther from the Earth, and the Earth's rotation will have slowed down even more. At some point the Earth's rotation would match the Moon's orbital period and the Earth will become tidally locked with the Moon, always keeping the same face to it, just as the Moon is currently tidal-locked to the Earth.

In H.G. Wells' vision, the far distant future Earth is tidally locked to the Sun, and the Moon is apparently gone. Would this happen? Will there ever be an Earth with an unending day and unending moonless night (depending on your address)? That could happen, but the Moon would have to leave the picture first, perhaps wandering far enough out that a chance gravitational disturbance by another planet would knock it off the edge of its orbit.

The Sun is changing too—has changed, and will continue to change—as the dynamics of its nuclear fuel supply mix shifts. As atomic fusion converts hydrogen into helium, helium to carbon, and so forth, the availability of easily released energy will diminish, causing the core to shrink and heat up, in turn causing the outer layers to inflate, becoming more expansive but also cooler and redder. In the very long run, the outer layers will expand beyond Earth's present orbit.

So there is a future out there that we can be more certain of than the future shaped by human affairs. It's further out in time than the decades or centuries ahead—and frankly further out than H. G. Wells penned in at 30 million years (little will have changed with the length of a day and the mile markers to the Moon in that time, and I believe the Sun won't make much of a fuss for at least a billion, or more).

In the meantime, it's captivating to think what the scenery may be like around the place I stand today, a million or a billion years hence.

Phoebe and Saturn. Credit: NASA/Cassini

Who's Phoebe? That quirky blonde from Friends? The mysteriously magical nanny from that old sitcom? A bird? A plant? All that–but the one I'm talking about is the moon of Saturn, once thought to be a captured comet, and now believed by some scientists to be something much rarer: a captured planetesimal.

Phoebe: a bit more than 120 miles across—and more potato-shaped than spherical—with a surface gravity approximately 200 times weaker than Earth's (yes, I'd weigh about one pound standing on the surface), Phoebe is not of the stature of its larger, rounder fellow moons of greater fame: Luna, Ganymede, Titan, and the rest.

We've known of Phoebe's existence since 1899, when it was discovered by astronomer W. H. Pickering, and from the start Phoebe was observed to be different from Saturn's "mainline" moons—ones organized into a common orbital plane in close alignment with Saturn's equator, with nice, nearly circular orbits. Phoebe is too much a nonconformist for that; orbiting at a steep, rakish angle from Saturn's equatorial plane, backwards with respect to the conformist crowd, and with great elliptical eccentricity, Phoebe is a fringe radical! And at 30 times the distance from Saturn as our Moon is from Earth, it takes Phoebe longer to orbit Saturn (1.5 years) than Earth does to round the Sun!

All of these peculiarities added up to the hypothesis that Phoebe was not an "indigenous" satellite of Saturn—one that formed with Saturn early in the ages of the solar system—but a solar system object that was captured by Saturn at some point, and since has remained in orbit. And due to its low density (little more than one and a half times as dense as water ice), Phoebe was assumed to be a former comet. Comets passing close to gas giant planets like Saturn are sometimes flung in different directions, sometimes broken up, and sometimes even crash into the planet. But they can also be captured into orbit, as probably many of Jupiter's smaller satellites, and Mars' brood of two, were: former asteroids from the neighboring asteroid belt.

But a comet is a bit of material—ice and rock—left over from the formation of the solar system, about 4.5 billion years ago, pristine and barely altered from its original state. Recently, NASA's Cassini mission has suggested a different origination story for Phoebe, based on imagery and data obtained from our first up-close look at this object by the Cassini spacecraft, in 2004.

Phoebe may be a "planetesimal"—an object that formed in the young solar system, coalescing from dust and ice into a larger and larger body. Evidence suggests that Phoebe was warmed enough during its formation, and perhaps afterward by decay of radioactive materials, to have achieved a spherical shape, a differentiated rocky core and outer shell of lighter material and ices, and possibly even to have harbored liquid water—all very planet-like qualities. As well, it may have remained in this state for quite some time before cooling down and freezing.

Possibly originating in the Kuiper Belt, beyond Neptune's orbit, Phoebe would have migrated inward and eventually been captured when passing too close to Saturn — at the same time avoiding the typical fate of planetesimals, which is to merge with a forming planet. Planetesimals, once the bread and butter of the young solar system, are the building blocks of planets.

Phoebe, then, may be a very remarkable object–a quirky, mysteriously magical moon; a vision of the early solar system that once swarmed with such objects, even before the planets themselves appeared. It's a messenger from the past, possibly carrying within it evidence that could tell us where we came from.

See sea stars in the intertidal during one of the upcoming super-low tides.

QUEST blogger Andrew Alden’s recent post about Bay Area Tides got me thinking about pulling on my rubber boots and heading out to the intertidal during an upcoming low tide. In the next few weeks, we’ll get some really low tides during daylight hours—a great opportunity to see the organisms that live on the narrow edge between the land and the ocean.

Tides are caused by the gravitational pull of the moon and the sun. (See Science on the Spot: Watching the Tides for a nice, clear explanation.) The moon is a lot closer to the Earth than the sun is, so the moon’s influence on the tides is far greater than the sun’s. But sometimes, the sun and the moon can join gravitational forces and all that gravitational pull can create some really high (and really low) tides. Each year around January 2, Earth, in its elliptical orbit, is closest to the sun. Here, the sun’s gravitational pull on Earth (and Earth’s water) is strongest. The gravitational pull of the moon combines with the gravitational pull of the (relatively) nearby sun when the moon’s position is such that the Earth, sun, and moon are aligned in a straight line. This creates the highest high tides and the lowest low tides of the year. The exact dates vary each year, because it depends on where the moon is in its orbit. Usually we get these super high/super low sun-plus-moon tides, also called King Tides, in December and January. (When the earth is at the point in its orbit that is farthest from the sun, around July 2, and the moon is aligned just right, we also get super high and super low tides.) Super high tides can give us a preview of sea level rise and help us identify areas that are prone to submergence. And when the tide goes out, super low tides are a great opportunity to go tidepooling!

There are quite a few great tidepooling spots in the Bay Area, including Fitzgerald Marine Reserve, near Half Moon Bay. QUEST producer Joshua Cassidy made a fantastic short film about intertidal life in the Reserve. Natural Bridges State Beach in Santa Cruz is another great intertidal area. To see photos of some of its marine life, check out the QUEST Natural Bridges Tidepools Exploration (and see a fun audio slide show I made while I was an intern at QUEST).

My personal favorite place for tidepooling is Duxbury Reef, which is part of Point Reyes National Seashore and is close to Bolinas Lagoon. It has a really flat, rocky bench, and at low tide you can walk way out. Check out the turban snails (there seem to be zillions at this site), and the different species of seaweed (my favorite intertidal inhabitants). If you’re into identifying things and learning about intertidal ecology, there are a lot of great books out there: Seashore Life of the Northern Pacific Coast has nice color pictures, and Between Pacific Tides is a classic.

Wear rubber boots with a rugged sole (that seaweed is slippery) and maybe bring a magnifying glass or hand lens. Keep your wits about you, and look up and look around often so the tide doesn’t sneak in on you.

To choose a good day to go tidepooling, you need to look at a tide table, which lists the predicted times and tidal heights of all the high and low tides throughout the year. You can often get a tide table for your area at a local surf shop or bait shop. Or, check out NOAA’s Tide Predictions, which has tide tables for tidal stations throughout the country. (Tidal stations are places where the height of the water is measured regularly—often along with weather data. San Francisco’s tidal station is the oldest continuously operating tidal station in the western hemisphere, a fun fact I learned in the Watching the Tides video!) Find the tidal station closest to your tidepooling spot on NOAA’s map. My favorite, Duxbury Reef, is closest to the Bolinas Lagoon station. From the Bolinas Lagoon Station’s tide predictions page, download the station’s tide table—click on the Published Tide Tables Formats on the top right. Look for dates with a nice, low tide—something below 1.0 feet is generally pretty good, depending on the site. To time your visit, it is helpful to look at graph of the predicted height of the tide throughout the day. You can generate a graph for any day this year. In Northern California, wintertime low tides occur in the evening; find out what time the sun sets and plan to finish your intertidal excursion before it gets dark. We have some great low tides coming up on December 9, 23, 24, and 25—with heights at -0.9 feet—so ask for rubber boots for Christmas!

Moon today and during the Cretaceous

Although I am a lifelong fan of science, I've also been a lifelong fan of science fiction—so I sometimes experience conflict in the DMZ where the two meet.

Having been raised on Star Trek, where the science and technology routinely violate known scientific principles (faster than light warp drive, for example), I learned to have leniency on some of those violations—at least, the ones that exist in order to make the story work.

But the stories that get the science completely wrong, for no good reason, get my militia up in arms….

Such was my reaction when, a few weeks ago, I happened upon the last two minutes of the series premiere of a new television show—the one that involves time-traveling colonists going 85 million years into the past to live among the dinosaurs. (Don’t ask me any more about the plot; I’ve only ever caught the last two minutes of each show when I change the channel to wait for House. All I know is each episode seems to end with people creeping through a jungle at night carrying torches….)

So what irked me so badly? Scene: colonists in settlement in Cretaceous jungle, night time, looking up at the starry, Moon-adorned sky. A child muses, "Is that the Moon?" (never having seen it before). "It’s so big!" Indeed, the Moon aloft in these prehistoric skies was depicted as truly huge—I’d estimate ten or fifteen degrees across, about the width of your hand spread wide at arm’s length (20 to 30 times the size of the Moon we know).

Enter "brainy" teenage girl to explain: The Moon is moving away from the Earth a few centimeters each year, so here, 85 million years in the past, it’s much closer to Earth.

How much closer was the Moon to Earth 85 million years ago? Do the math, brain: The Moon is currently moving away from the Earth at about 3.8 centimeters per year, so 3.8 cm for 85 million years equals 323 million centimeters. Sounds like a lot, right? 323 million of just about anything seems like a lot. 323 million centimeters is 3,230,000 meters, or 3,230 kilometers. Or a little over 2,000 miles—which, coincidentally, is about the diameter of the Moon itself. Since the Moon is presently 240,000 miles from Earth, being 2000 miles closer to us in the past (about 0.8%) would not have made it perceptibly larger—let alone appearing as big as a cantaloupe!

The Moon has been moving away from the Earth since its formation, which took place about four and a half billion years ago. Through tidal interactions with the Earth, the Moon has "stolen" some of Earth’s rotational momentum (spin) to gradually boost itself farther and farther away, slowing the Earth’s spin as a result. Back in the day when the Earth and Moon were young and fresh—and much closer together—the Earth spun much faster: maybe once in 8 hours. (But that was WAY before life existed, so try not to imagine the dinosaurs experiencing much shorter days, please.)

Oh yeah, in that same two minutes of the show premiere, the "brainy" girl (it’s not her fault; it’s the show’s writers, of course) also had an answer for why all the stars in the Cretaceous sky bore no resemblance to the constellations we know today. The Universe is expanding, she said (correctly), and so in 85 million years that expansion has caused the stars to change position" (not so correctly). The Universe is expanding, yes, correct; the stars in Earth’s skies 85 million years ago would have looked completely different, yes. But the two have nothing to do with each other.

The Universe is expanding and carrying all of the galaxies and galaxy clusters farther and farther apart. But this has no effect on the stars gravitationally bound within each galaxy. At the scale of a single galaxy, like our own Milky Way, the gravity binding the stars together in that great spinning spiral overpowers the effect of space expanding.

The stars we see in our skies are all inside of our galaxy, to which they are gravitationally bound. It is merely the motion of those stars within the galaxy as they orbit the center that change their relative positions, and so the patterns of constellations that we perceive. Analogously, continental drift on Earth may move a pair of land masses away from each other, but that large-scale motion won’t cause the trees within either of those lands to move apart.

Nit picking? Yeah, maybe. But I even do it to Star Trek on occasion….

Total Lunar Eclipse 08-28-07. Credit: Conrad Jung

December 10, 2011 marks your last chance to see a total lunar eclipse—one of the most breathtaking celestial events that you can witness with your unaided eye–until 2014. For us on the West Coast, the drama of the Moon's occlusion will play out in the early morning hours of Saturday—weather permitting, as always.

A total lunar eclipse occurs when the Moon passes through the long shadow the Earth casts into space. We see a partial lunar eclipse when only part of the Moon grazes the Earth's shadow and a total eclipse when it is completely engulfed in darkness.

The overall eclipse begins at about 3:33 AM on the morning of December 10, when the Moon first touches Earth's penumbra, or "half shadow" (the region of space where only some of the Sun's light is blocked by the Earth). At the beginning, you might be challenged to notice anything different about the Full Moon, unless you're looking for something—in which case you might start to notice a slight darkening at one edge of the Moon's disk.

By 4:46 AM, the real show begins: the Moon will begin to enter the umbra, the Earth's full shadow, in which no direct sunlight shines. Now, a very noticeable "bite" will be taken out of the Full Moon—as if some great celestial creature is nibbling it at the edge. (To the Chinese, this animal was thought of as a dog or a dragon; to the Maya, often a jaguar; and if you mix your myths well, you might imagine those creatures eating green cheese….)

Finally, at 6:06 AM, with the Moon low near the western horizon, it will become completely engulfed in the umbra and will likely turn a dim, coppery, orange, or possibly even reddish color—like a shiny copper penny, or a molding orange. I hope that image doesn't spoil the experience for you….

This is totality, when the entire disk of the Moon is within the umbra. From Earth, the Full Moon goes very dark during totality. From the Moon, if you were so lucky to be there during totality, the Earth (in its "New" phase as seen from Luna) would be a black disk surrounded by a ring of red or orange light—from the Moon's perspective, a total solar eclipse.

Why is the Moon lit at all during totality if it's supposed to be in the umbra where no direct sunlight shines? And why orange and red tones?

The answer is in Earth's atmosphere, which simultaneously bends, or "scatters," the sunlight that grazes by the edges, and filters the colors of the sunlight to favor the redder wavelengths passing through. If you've seen sunlight shining around the edges of a cloud, making that "silver lining" and shedding light into the cloud's shadow, then you may have an idea how the sunlight is scattered around the edge of the Earth into the otherwise dark umbral shadow.

And, if you've seen the colors of a sunrise or a sunset—orange and red, more or less depending on atmospheric conditions—then you can understand why the light is reddish. Earth's atmosphere acts like a piece of red glass: white light, containing all the colors of the rainbow, enters the glass, but the bluer colors are absorbed, and only the orange and red tones pass through and shine onward. (What does Earth's atmosphere do with that stolen blue light? Take a look at a clear daytime sky and you'll see!)

So, for the 41 minutes of totality, you'll witness one of the most spectacular partnerships of the Earth and Moon, when the Earth "touches" the Moon with the tip of its shadow and the russet tones of all its sunrises and sunsets acting in concert.

Totality will end at 6:47 AM when the Moon's leading edge begins to depart the umbral shadow—and at 7:17 the show will be over for us when the Moon sets. Then, it's another three years until we can see such a sight again, so be sure to catch this one! Weather permitting, we'll have the Observatory Deck open at Chabot Space & Science Center from 4:00 to 7:00 AM, in case you'd like to watch the event in good company….

People have a propensity for attraction to extremes. We are fascinated by the biggest, the smallest, the farthest, the nearest, the most wildly colorful—you name it. We're Extreme Adjectives Junkies!

This point was brought to my awareness again leading up to last Saturday's "SuperMoon" event: when the Full Moon phase on March 19 coincided with the Moon being at perigee–the closest point to Earth in its elliptical orbit–and therefore at its largest apparent size, its brightest, and its most influential, tidally speaking. By the numbers, this periodic event hadn't happened for 18 years–though it should be noted that the Moon gets just as close to the Earth every month, but it's usually not a Full Moon when it does.

It seems every news media source—on air, on web, on print—was running the story, and there was a great deal of public interest…which was, of course, mostly fueled by the media coverage! I got calls from several news agents wanting the facts and my thoughts about the SuperMoon—and of course what they wanted to hear was that the Moon's closeness and size and brightness and gravitational attraction were all magnitudes greater than normal, that the moment had measureable effects on tides, earthquakes, and volcanic eruptions, and of course that there would be a bumper crop of werewolves and lunatics running around the night….

I felt bad when I had to deliver the sober, perhaps tepid, facts: according to the gossip, the Full Moon would be 14% larger in the sky and about 30% brighter than it is at the also-rare "Apogee Full Moon" when it is farthest from us. I suppose 30% brighter is nothing to sneeze at, though since our night vision sensitivity adjusts to lighting levels, we might not experience that great a difference. But 14% larger, while a detectable difference to our human perception, probably isn't enough to make us take notice if we were not otherwise alerted to the situation; I feel the mere suggestion that the Moon appears larger is a greater influence than the physical fact.

Put another way, if you were standing in the middle of a vast, flat, treeless plain, and you saw someone standing 700 feet away from you, with no visual cues for comparison, could you tell the difference if that person was 6 feet tall instead of 5-foot-1? That's analogous to the difference between seeing the Moon when it's nearest to us (perigee, 217,862 miles) and farthest away (apogee, 243,418 miles).

By the way, when I run the numbers, I calculate the Moon appearing less than 12% larger at perigee than at apogee…so either I've done my math wrong, or the "story" has grown larger with the telling somewhere along the line…. The quoted nearness of the perigee Full Moon may also have grown in stature from the fact; I was hearing numbers like 50,000 miles closer than at apogee, but doing the numbers I get a bit over 25,000. I'm tempted to call this the Paul Bunyan Full Moon instead….

But the perigee Full Moon is factually the closest, largest, and brightest of all Full Moons, and quite rare to boot, and that is more than enough to excite us Extreme Adjectives Junkies.

Your best bet for seeing a truly huge, awesome Full Moon is to catch it when it's rising, or setting, because our brains play a perceptual trick when the Moon is close to the horizon, making the Moon seem much larger than when it's high in the sky. You can dispel this "Moon Illusion" easily, either by holding up your pinky finger at arm's length, measuring the Moon against your finger's width, and comparing the result to any other time you measure it—or by looking at the bloated, near-horizon Moon with your head upside down (try it if you don't believe me!).

As for the physical effects on Earth by the SuperMoon (other than the lycanthropic overtones), the ocean tide levels were expected to be about an inch higher than usual…nothing to run for high ground over.

Bottom line: The Full Moon is splendid to watch from any distance. Just tell yourself it's really big and beautiful, and let your brain do the rest….

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Did you see the supermoon through this weekend’s cloudy skies? The supermoon is a full moon that appears to loom super large and super bright in the sky, because the earth and moon are as close together as they get. The moon’s orbit is shaped like an ellipse, and on March 19th, the moon was at the point in its orbit that is closest to the earth—this is called perigee. It is rare that perigee and a full moon happen at the same time. The last time this occurred was in 1993. Because of its rarity and celestial nature, the supermoon gets blamed for things that cannot possibly be its fault—a higher influx of patients to emergency rooms, weird animal behavior, and even last week’s earthquake and tsunami. None of these can be attributed to the supermoon. But the standard moon does have some important effects on earth’s biota.

Many species, particularly those living in the ocean, are tied to the phases of the moon. Corals spawn during the full moon, which may be advantageous because if all the corals release their gametes into the water at the same time, the chances of fertilization are higher. Similarly, seaweeds spawn synchronously, in step with the moon’s phases. Intertidal species may be particularly affected by the moon’s phases, because of the moon’s influence on the tides. The highest high tides and the lowest low tides occur during the new and full moon. (Tides are especially high during supermoons.) Many species of crabs release their larvae during the new and full moon. It is thought this timing may help the larvae, because it coincides with large tidal variation, which could bring larvae to the ocean quickly. Larvae would spend minimal time under inhospitable conditions.

Fishes also reproduce in time with the moon. There are several hypotheses about why this happens. Predation on fish eggs may be reduced during high tides. Or the adult fish may be responding to availability of food, which could be influenced by the moon. Or, the fishes’ reproductive hormones may be directly affected by the light patterns associated with the phases of the moon.

The amount of light shining from a full moon is 25 times greater than the light from a quarter moon, and 250 times greater than the light of stars shining in a moonless sky. The full moon’s bright light can keep animals up at night. Because of their increased activity, you often see a lot of road kill following a full moon.

Many people think the moon affects human physiology, but there is no evidence to support this claim. The idea is that the moon exerts a gravitational pull on the human body (we are 60% water), in the same way that the moon exerts a gravitational pull on the world’s ocean. However, the moon’s gravitational pull is quite weak, and small bodies of water (lakes, ponds, humans) are not affected. Studies of the effect of lunar cycles on human health and behavior have not shown any consistent pattern. Nonetheless, the myth that people go a little nuts during a full moon persists—in fact, the word “lunatic” has its root in the Latin word for moon, luna.

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Total Lunar Eclipse Dec 20/21 2010

One of the most striking and beautiful examples of the Earth-Moon relationship takes place during a total lunar eclipse, when the Moon passes through the Earth's shadow, transforming in a couple of hours from the stark brilliance of the Full Moon to the dark ruby-hued wonder of "umbral occlusion"—or totality.

Monday evening, December 20th, starting at about 9:30 PM, the Moon will begin to enter the Earth's partial, or "penumbral," shadow. Around 10:30, it begins to enter the umbra (full shadow), and by 11:40 will be completely engulfed: "totality." Totality will last until 12:53 AM Tuesday morning, when the Moon begins to leave the umbra.

While the extended weather forecast at the moment doesn't look favorable for the SF Bay Area, there are always freak changes in weather to hope for. Also, we'll be having a Lunar Eclipse celebration at Chabot Space & Science Center, rain or moonshine, which will be a lot of fun: Lunar Labs, planetarium shows, sci-fi movie reels, and every Moon-related song we could find—hope to see you there!

Though a total lunar eclipse is a rare event to see, this one is rarer still–not the least reason being that for the Western US it will be one of the highest lunar eclipses you can see, with the Moon reaching its apex for the night over 75 degrees from the horizon (practically overhead) close to mid-totality. For our latitudes in the Bay Area, the Moon can't get much higher than that. So, we get High Moon when the eclipse is at its best (weather permitting).

What makes this eclipse rare among the rare is the fact that the Moon is crossing several important features in the sky simultaneously. First, it's crossing the Ecliptic, the path of the Sun's apparent motion over the course of a year, cutting through the 12 constellations of the Zodiac. In essence, the Ecliptic is the projection of Earth's orbital plane onto the sky. Is it a coincidence that the Moon will be crossing the Ecliptic during this eclipse? Actually…not at all. By virtue of the geometry of a lunar eclipse, the Moon must be on the Ecliptic in order to pass through Earth's shadow, since the Earth's shadow, cast by the Sun's light, always runs along Earth's orbital plane, and so too the Ecliptic.

Another line is crossed during this eclipse because it happens on Winter Solstice. On this day, the Sun is located in Sagittarius, and so the Earth's shadow is cast toward the opposite point on the sky, in Taurus. Halfway around the circle of the Ecliptic from the Winter Solstice point you find the other solstice point, the spot on the Ecliptic where the Sun is located at Summer Solstice.

The Moon will also be crossing the Galactic Equator: the line representing the plane of the Milky Way Galaxy. This alignment is a bit more tangible than those with the Ecliptic and the Solstice point since the Milky Way is a visible sky feature—at least in areas not impacted by urban light pollution. If you live in a place where you can normally see the Milky Way on a dark night, you have an extra wonder to marvel at during this eclipse: when the bright Full Moon enters totality and goes dark, the subtle light of our galaxy will be revealed, with the Moon set like a darkling gem in a diamond bracelet….

Well, we can only hope for clear skies—but in either event, come up to Chabot and celebrate with us this midnight delight….

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Sittin' on the dock of the bay, watchin' the tides roll away.

This is important because the bay and ocean currents flooding in and out of the Golden Gate are notoriously treacherous.  The US Government realized early on the importance of San Francisco Bay and the need to better understand the movements of the water for navigation.  Soon after California became a State, American surveyors were sent to San Francisco to study the water conditions of the great port.  And the work has continued non-stop ever since.  For over 150 years the San Francisco Tide Station, now operated by NOAA, has produced a continuous recording of water levels and other vital maritime information.

Today the tide station uses state of the art equipment to measure the water movement of San Francisco Bay. The water gauges are connected to the NOAA Physical Oceanographic Real-Time System (PORTS), and measure nearly real-time water levels, surface and sub-surface currents and other information such as winds, weather and climate data.  This information is available to the public so sailors know the best times to cast off, make transits, load or unload cargo, or when to ride the tides in or out of the bay.  According to a report written by Captain Albert E. Theberge, NOAA (Ret.), “This information is critically important considering that there is an average of 261 deep-draft vessels entering San Francisco Bay each month and there are approximately 85,000 registered pleasure boats using approximately 100 yacht clubs in the Bay system.”

“The historical record from the tide station at San Francisco transcends the maritime history of the San Francisco Bay,” according to Captain Theberge.  “From the days when clipper ships relied upon tide predictions provided by the station to navigate the dynamic waters of the Golden Gate, to the modern day mariner that obtains real-time water levels so that the huge ship and crane barge operators can tell if they have enough depth in the channels and enough clearance under the bridges.”

In the process of collecting data to insure safe passage in and out of the bay, the San Francisco Tide Station has been instrumental in collecting a long and continuous stream of scientific data that has advanced our knowledge of the oceans and the earth. This data has benefited meteorologists, oceanographers and climatologists alike.  As we look to the future and attempt to better understand the changing climate and what that will mean to things such as sea level rise, the current and long-term data collected at this small station will become increasingly more important.  “San Francisco is an amazing city in terms of its heritage,” says Mary Jane Schramm, “ The human heritage as well as the magic and mystique of the great Golden Gate.  It’s a portal for exploration.  We are explorers and by virtue of having this facility here helps foster that process along.”

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