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.

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….

Iron filings reveal the pattern of a magnet's invisible force field.

That gave me a lot to work with—Sun-Earth Day usually does, but the more opportunity to create hands-on experiences for our visitors, the better, and when it comes to curious natural phenomena, magnetism is a fertile subject for all sorts of seemingly magical fun.

So, I turned Chabot's Chemistry/Physics classroom into a public magnetism laboratory, giving visitors a chance to learn, or relearn, some of the basics of magnets, as well as to connect the tabletop experiments to phenomena that take place on enormous scales on the Sun and the Earth.

First was magnetic polarity: playing with a set of magnets, visitors got a feel for the behavior of magnetic poles—N and S—and how opposite poles attract and like poles repel. (It's always fun to feel the pull of attraction between two magnets, but there's something extraordinary about feeling the push of repulsion—your mind just expects to see little bumpers on the magnets, but there's seemingly nothing there!)

The Earth itself is a giant magnet, as most of us know—but what many of the adults found surprising and intriguing is the polarity of Earth's magnetic field. Using small magnetic compasses, we sought out the Earth's magnetic poles: north and south. By taking careful notice of which type of magnetic pole the compass needle ends pointed to, the fact that the magnetic pole of the Earth up near the geographic north pole is a south—or 'S'—magnetic pole was revealed! This is why in physics we are often careful to refer to magnetic poles as 'S' and 'N', not south and north, to avoid confusion.

At another station, visitors made their own compasses by magnetizing an iron nail stuck through a Styrofoam packing peanut and floating it in a bowl of water. Darned if that floating nail didn't stubbornly turn to point in the same direction, no matter what direction we tried to turn it!

Station 3 was about mapping the invisible magnetic force field surrounding various magnets. Human eyes cannot see magnetic fields—but they are there and have an influence. I had constructed magnetic field mapping devices for this purpose: used CD jewel cases, with paper labeling removed, filled with a sprinkling of iron filings. When shaken gently back and forth—as if panning for gold—the iron filings align and connect in gritty little strings and conform to the pattern of the magnetic field. The strong field converging at the two poles of a magnet were boldly evident, but also to be seen were the more tenuous curls of field lines arcing through the space around the magnet.

The patterns formed by the filings were very similar to the patterns seen in images of sunspots we compared them to. On the Sun, it is not iron filings that trace the invisible magnetic fields for us to see, but hot, electrically charged gas, or plasma (mostly hydrogen and helium, but also traces of calcium, iron, and other elements). Electric charges (electrons and ionized atomic nuclei) are strongly affected by magnetic fields when they move through them. Numerous ultraviolet images of the Sun were available on computer screens around the lab for visitors to compare the magnetic patterns and shapes to.

We had more: building an electromagnet from wire, an iron nail, and a battery. This demonstrates how magnetic fields are created by moving electric charge—in the electrically conductive wire of the electromagnet, in the circulation of electrical current inside the Earth's iron core, and in the motions of plasma on the Sun. It's all moving electricity, friend.

We also conducted "Magnetic Yacht Races": pushing, via the repulsion of like poles, a floating, magnetized 'yacht' across a pond of water. The challenge of steering and propelling the yachts led to some interesting yacht designs; certain configurations of packing peanuts and iron nails proved easier to maneuver and accelerate than others.

Happy Sun Earth Day 2010! I wonder what we'll be doing next year….

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The Vernal Equinox, where the Sun crosses the Celestial
Equator (red line) on the first day of Spring (March 20/21).
Credit: Space.com/Starry Night

"Can you tell me about the upcoming beginning of the Age of Aquarius?" said the voice on the phone. "I heard that it starts this Saturday…"

Now, I get a lot of phone calls and emails from people with astronomy and sky related questions. Very often it's something like, "What was that thing that tried to land in my front yard yesterday evening?!" or, "Is it true that Mars will be closer to the Earth this weekend than it has been in a gazillion years?" I've even had one or two asking if it's true that the world is ending in 2012.

Okay, I'm embellishing a bit. Those are all very good questions, and I do my best to provide a science-based answer — like, "Venus tried to land in your yard," or "The Mars extra-close encounter happened in 2003… and it had only been less than a century since the previous time," or, "We'll just have to wait for 2012 to roll around to find out…"

As for the Age of Aquarius question, that got me to wondering. I've always regarded this issue as astrology-related more than astronomy, but I also realized there are physical underpinnings to the definition. So I fired up Google and clarified some of the details for myself. The first thing I learned is that, among astrologers at least, there is little agreement on precisely when the Age of Aquarius is supposed to begin (or if it's already begun). Different astrologers at different times and from different parts of the world have tried to define this, resulting in multiple schools of thought on the subject.

But from a purely astronomical standpoint, the delineation of these Ages is based on a natural physical cycle, just as a year is defined by Earth's motion around the Sun and a day is defined by Earth's rotation on its axis.

An astrological Age (aka "Great Year") is determined by the position of the Vernal Equinox — at least by one of the schools of thought… The Vernal Equinox is that point in the sky occupied by the Sun when it crosses the Celestial Equator heading into the Northern Hemisphere. So, you can think of the Vernal Equinox as a distinct point on the sky (and it's easy to locate on the first day of Spring: Just look at the Sun — I take that back: DON'T look at the Sun!)

But the position of the Vernal Equinox shifts over time due to a cycle of change in the orientation of the Earth's rotation. The Earth spins like a top, but also like a top it undergoes a gyrating motion, called precession. One complete gyration takes about 26,000 years — so all of the points in the sky defined by Earth's spinning (the celestial poles and equator, and, yes, the Vernal Equinox) move around the sky over 26,000 years.

At this moment, the Vernal Equinox is in the constellation Pisces — at least, within the region of the sky defined by modern astronomers as encompassing all the stars of Pisces. So, if one were to acknowledge the constellation boundaries according to modern astronomers, then one would say that we are in the Age of Pisces still (and, by the same definition of constellation boundaries, the Vernal Equinox will remain in Pisces until about the year 2600, when it will cross the border into Aquarius.)

However, there is little agreement among different groups of astrologers on where one constellation ends and another begins–and to my knowledge none of them have adopted the modern astronomical boundaries.

So, when does the Age of Aquarius begin? Depends on who you talk to….

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A limb shot of Mercury's horizon taken by the
MESSENGER spacecraft on January 14, 2008.
Photo Credit "NASA/MESSENGER"

If you can take a name like "Mercury Surface, Space Environment, Geochemistry and Ranging" and craft it into a neat acronym like MESSENGER, then you may have a future working with NASA….

And no, this blog isn't about NASA acronymizations, but rather the heat-resistant robot behind one of them. MESSENGER is the space probe that NASA sent to Mercury to give the Solar System's innermost planet the first up-close look since 1975, when Mariner 10 flew by.

Though MESSENGER's main mission will begin in earnest when it returns to Mercury and finally settles into an orbit around the planet, on March 18th 2011, we were given a tantalizing peak last January 14th when the probe made its initial flyby.

What did this quick, on the fly snapshot tell us that we didn't know before? Well-a lot, considering Mercury has been one of the least understood planets in the Solar System, and was for a long time thought to be similar in character to our own Moon. Mercury is shaping up to be a lot less like Earth's Moon than its gray, cratered, airless appearance would mislead.

One key difference: density-how much material is packed into the planet; or how heavy a standard sized chunk of it would be. Our Moon is a lightweight on this score, with an average density of only 3.4 grams per cubic centimeter, while Mercury weighs in at a hefty 5.427 g/cc-almost as dense as Earth.

Another key difference: magnetic field. Planets like Earth and the Gas Giant worlds (Jupiter et al) generate respectable magnetic force fields, useful for everything from deflecting plasma flowing from the Sun (the "solar wind") to properly directing magnetic compass needles. Venus, Mars, and our Moon do not possess magnetic fields worth mentioning, as it turns out.

Mercury, on the other hand, does. Planetary magnetic fields are believed to be generated by currents in a planet's liquid outer core-like how the electric current in the wire coil of an electromagnet generates a magnetic field. Mercury's magnetic field suggests it still has some activity in its core-molten metals circulating in currents as the core slowly cools off. And speaking of Mercury's core, it appears to comprise 60% of the planet's mass-about twice what is "typical" for Terrestrial (solid) planets.

I've often imagined Mercury to be a cosmic goldmine, with its apparent richness in metals and its density. I wonder if an astronaut could just walk along and pick up chunks of gold from its surface….

Another interesting find by MESSENGER is that some of the flat plains on Mercury may have been formed by volcanoes, long ago. In particular, MESSENGER imaged a number of volcanoes along the edge of the Caloris Basin, a large impact basin-one of the largest in the Solar System, at 1550 kilometers across.

The news coming out of the innermost region of the Solar System makes me giddy. Too bad I have to wait until 2011 for my next look at Mercury. These things take time.

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Asteroid 35107, captured on Chabot Space
& Science Center’s telescope.

Photo By Conrad Jung and Gerald McKeegan

You must be very quiet; we are hunting…asteroids!

On July 14th, 2008, an almost Hollywood-like drama took place in space nearby: a "double," or binary, asteroid whizzed past Earth, grazing by at a distance of only 1.4 million miles. One of the rocks is over 200 meters across, the other a whopping 600 meters-about half the size of Half Dome in Yosemite!

1.4 million miles may sound like a large distance, but by the standard of big rocks flying by the Earth, that's breathtakingly close. Discovered only last January, this pair of asteroids went from being completely unknown to blasting by Earth's doorstep in only months. Had they actually hit the Earth, they would have caused major devastation at and near the impact site, with very little warning.

Fortunately, there are programs to search for and track these flying mountains-also called "Near Earth Objects" (NEOs)-and I'm very pleased to announce that Chabot Space & Science Center (specifically our 36-inch reflecting telescope, "Nellie") has very recently become an official contributor to the NEO search program of the International Astronomical Union's Minor Planet Center (MPC)! Nellie is designated by the MPC as Observatory G58.

In this MPC program, observatories around the world contribute by searching for and tracking NEOs: asteroids, and comets, whose orbits can carry them close to Earth and which are large enough to cause catastrophic damage should they hit us.

In order to take part in the NEO program, Chabot observers Conrad Jung (on the Chabot staff) and Gerald McKeegan (of the Eastbay Astronomical Society) conducted a four-month program to develop and hone the necessary skills and data processing techniques, as well as to configure telescope equipment, to meet MPC qualifications.

To that end, they observed a set of known asteroids-some NEO's and some "Main Belt" asteroids. (One of these Main Belt asteroids, "Carter 10683," was named for former Chabot board member and president of the Eastbay Astronomical Society, Carter Roberts, who, sadly, passed away earlier this year.)

Chabot's asteroid hunters will begin their tenure of official asteroid observation by verifying the orbits of recently discovered NEOs and reporting the additional observations to the MPC, where it will be used to refine our knowledge of the NEOs' orbits. The next step in the program will ultimately be to hunt for currently undiscovered asteroids.

The process for finding, tracking, and reporting NEO observations goes something like this. With a digital (CCD) camera attached to the telescope, a section of the sky is imaged three or four times in a half-hour period. The images are processed and compared, and any star-like dots that are found to move between one image and the next become suspect asteroids. (The word "asteroid," by the way, literally means "star-like"-so named because through most telescopes asteroids are too far away and too small to appear as anything more than points of light.)

The coordinates of any moving dots are calculated for all of the images they are in, and this information is sent to the MPC to be added to the data from other NEO hunting observatories. From the combined observations of all the observatories, a precision database of the orbits of near-Earth rocks is maintained, and with it NEOs that may pose a threat to the Earth may be identified.

Hunting NEOs may be like searching for needles in a really big haystack-but in jobs like this, the more eyes on the problem the better. Nellie is now one more eye on lookout duty…

Click here for a closer view of the asteroid shown above.

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