Tuesday, February 24, 2009

Texas officially appreciates astronomy

As I type this, the Texas House of Representatives and Senate are honoring the University of Texas and Texas A&M for our efforts in astronomical research past, present, and future. Here is the text of the concurrent resolution.

In spite of the issues that the state of Texas seems to have with science standards in public schools, the state legislature is very highly supportive of astronomy research. The state allocates a fair amount of money for the operation of McDonald Observatory and for the construction of new instruments and telescopes; few other states allocate funds specifically for astronomy research. And those funds make a huge difference for Texas astronomy.

Perhaps more important is the joint recognition of both the University of Texas and Texas A&M astronomy research groups. Modern astronomy research requires ever-more collaboration among institutions, and Texas astronomy is much more than just the group of us here in Austin.

Monday, February 23, 2009

Was Einstein Wrong?

Albert Einstein, who probably wasn't right about everything all the time.
Image Credit: Owen Jack Turner / Library of Congress
Thanks to Public Domain Clip Art for the tip!

The short answer: probably yes and no.

We astronomers get lots of email from all sorts of people about all sorts of topics. Most of those emails are quite legitimate questions or comments. But a small subset of the email we receive comes from people who think they have come up with a new theory; these ideas usually involve disproving Einstein's theories of relativity. And these ideas are invariably not grounded in scientific basis, but are based on taking a little bit of (often incorrect) knowledge and thinking way to hard about the consequences, all the while not worrying about major issues like experimental evidence or mathematical proofs. (See here for a satirical summary of typical mailings.) Most of us learn quickly not to even acknowledge any such correspondence, because many of the authors quickly become belligerent and threatening rather than taking the opportunity to learn a little bit about science.

As I said, Einstein is a frequent target of these misguided ideas, probably because if someone proves Einstein was wrong, then that person will be famous and potentially lauded as a genius the way Einstein is now.

So, it is always with some amount of worry when I see articles in the popular media questioning Einstein. And this has happened twice in the past couple of weeks. An article in Scientific American talks about the implications of "quantum entanglement" (one of the spookier aspects of quantum mechanics) on Einstein's special relativity, and a news release involving data from NASA's Fermi Gamma-ray Space Telescope talks about how there may be evidence from a gamma ray burst that calls parts of relativity into question.

First, let me say that Einstein has not been disproven. Both articles present new arguments and some new evidence that need to be considered. But the conclusions of both articles are that a lot of work needs to be done to verify the suppositions and results. The gamma-ray observation, in particular, has a lot of potential holes that need to be investigated before this claim can even be considered as evidence in a case against relativity. Still, the observations are tantalizing.

But we need to be cautious with our wording. I think most physicists and astronomers realize that Einstein's theories of relativity are incomplete. This doesn't mean that they are wrong. After all, general relativity has predicted some pretty bizarre effects before they were discovered (like black holes, the expansion of the Universe, and gravitational lensing). Our GPS systems are required to make use of general relativity in order to function, and they do indeed function quite well. Any theory that can do all of this is not completely wrong.

Where Einstein's theories run into problems are on the subatomic level. Quantum mechanics, the physics involved on atomic scales, is incompatible with relativity on the smallest scales. For example, quantum mechanics says there is a fundamental length known as the Planck length, below which little or nothing can be known (this length is tiny, about 1/100,000,000,000,000,000,000 the size of an atomic nucleus). Relativity has no such limit. While this sounds like no big deal, it is a fundamental difference between the theories that hasn't been overcome.

Or take the "quantum entanglement" that the Scientific American article talks about. Remember that relativity claims that no information can be sent faster than the speed of light. But it is possible to use quantum mechanics to put two subatomic particles in a state called "entanglement," sort of like a constant interaction. You can send one particle one direction and the other particle another direction. Say you have laboratories on two planets that are 2 light years apart, and you have a third laboratory exactly in between. That third lab makes an entangled particle and sends one to each lab. On one lab there is a machine that can force the particle to jiggle either up and down or left and right (for those who don't like the word "jiggle", I mean have a certain polarization). So, when the particle reaches the first lab, they force it to jiggle in one direction. Meanwhile, in the other lab 2 light years away, the second particle arrives at the same time as the first particle in the first lab. Because the two particles were entangled, this second particle is forced to jiggle in the same direction. The second lab can measure the direction of jiggling and know exactly what the scientists in a lab two light-years away are doing right at that instant; no two-year delay like Einstein would insist there had to be. And we've done this experiment here on Earth, and it works like I said.

To me, this is just saying that either Einstein's relativity or quantum mechanics (or, most likely, both) are not the last word in physics theories. There's something deeper going on. That doesn't mean that Einstein and/or quantum mechanics are wrong, in my opinion, just that they are partial, incomplete explanations of reality.

This is not unprecedented. Consider Isaac Newton, who in the 1600s was able to figure out laws of motion and gravitation. We still teach these laws today, and we even use them to send spaceships throughout our solar system. But Newton's laws are incomplete; they don't take relativity into account. Still, we don't consider Newton to be an idiot for not foreseeing a need for relativity, and in fact one of the requirements for relativity was that it reproduce Newton's Laws under "normal" situations.

Any ultimate theory uniting gravity with particle physics will have to reproduce quantum mechanics, special relativity, general relativity, and even Newton's Laws, at least in the conditions under which we've tested all of these theories. And, when we develop such a theory, I doubt that every physicists' plaster busts of Einstein will end up in the garbage.

Even if ultimately incomplete, Einstein's relativity made some amazingly correct predictions. Even when we study atomic-scale physics, we have to make corrections for special relativity in our models of atoms like iron. General relativity's concept of the equivalence of matter and energy (E=mc2) is at the root of our nuclear fission and fusion reactors (and bombs).

So, was Einstein wrong? Perhaps you could call it that. But given how relativity has pervaded and has shaped physics and technology over the last century, it has to be one of the best wrong answers a scientist could ever hope to make.

Thursday, February 19, 2009

Fiat Nox

LED street lights are certainly prettier than the orange sodium lights
Image Credit: Gemma Lighting

Believe it or not, the photo above shows what will soon be a major quandary for astronomers, both professional and amateur. Take a look at the streetlights in the foreground. They're a nice white color; you can see the colored paint on the pavement, and the lights seem reasonably bright. Then look in the background, and you'll see the orange glow of low-pressure sodium streetlights. If you've lived somewhere with the low-pressure sodium lights (like Tucson or San Jose), you know that it is impossible to see colors (other than light, dark and orange; even red cars look black under those lamps) and their glow is a little garish.

For many years, astronomers have been pushing for low-pressure sodium lamps. Because all of their light comes out in a single color, we can design filters that block that specific color of light. This allows astronomical observatories like Lick Observatory, just outside of San Jose, to keep operating within the blinding glow of lights from a large metropolitan area. Cities have been willing to use the low-pressure sodium lights not just because of astronomy, but because they are less expensive than most streetlights, and because they use less electricity than other types of streetlights. So, low-pressure sodium is economically friendly, too. Astronomers and astronomy-related groups like the International Dark-Sky Association have pushed hard on this economic end because, frankly, money talks.

But now we face a problem. The white lights in the picture above are LEDs, or light-emitting diodes. LED streetlamps are starting to become available. The LED lamps use less than half the electricity of low-pressure sodium lamps, they last five times longer than low-pressure sodium lights, and they are certainly prettier than low-pressure sodium lamps. But, because they emit light across the entire rainbow, they are not friendly for astronomers.

The economic arguments that proved so persuasive in getting low-pressure sodium lights installed are now going to be a primary argument against keeping those astronomy-friendly lights, and if we astronomers try and argue against money and energy-saving lights, we are going to lose both our dark skies and our credibility.

The city of San Jose, California, home to the aforementioned Lick Observatory, is going to install LED lights, and most people are quite happy that the ugly yellow lights are going away. Is this the end for astronomy at Lick?

Not necessarily. It is possible to make white-looking LEDs out of a collection of red, green and blue LEDs; this light can still be filtered out, though not as completely as the low-pressure sodium lamps (the last I heard, San Jose was considering these types of LEDs). Further, these lights can be more easily controlled, including having variable brightness. And, if people are happier with the colors of the lights, they might be more likely to follow other dark-sky related solutions, like shielding.

As I've written before, humans inherently distrust the dark. But excessive and poorly-designed lights not only hide the stars from astronomers; they are wasteful, environmentally unfriendly, and even a human health hazard! Dark Skies Awareness is therefore a cornerstone project of the International Year of Astronomy 2009.

But, in my opinion, professional astronomers and astronomy enthusiasts need to be careful in talking about dark skies. The old arguments of saving money and energy won't go as far as they used to; the LED lights show that human ingenuity can alleviate that problem without sacrificing light. And it is hard, though not impossible, to get most people to see that something as innately comforting as outdoor lighting can be harmful, especially for our own health.

I think that many types of lighting ordinances, especially in regard to light design and shielding, are still quite attainable goals. But I worry, perhaps too much, that LED outdoor lighting is going to remove that highly-successful economics argument from the dark skies sales pitch, and I worry that if we try and fight against LED lighting, we will come out on the losing end.

If you've never seen a truly dark sky from a site dozens of miles from the nearest town, it's hard to describe what you are missing. The sky is not black but glows ever so faintly. There are so many stars that familiar constellations like Orion and the Big Dipper are nearly impossible to find. The Milky Way is a bright glowing band stretching across the entire sky. And shooting stars are actually quite common. The experience is far less frightening than the murky shadows cast in the alleys of our cities. It's worth the trip to find those dark skies, and it's worth the political effort to try and bring those skies as close to people's homes as we can.

Tuesday, February 17, 2009

Help professional astronomers do research

Galaxy Zoo Logo
Image Credit: Galaxy Zoo

Lots of people have mentioned to me how they wish they could do astronomy, and look at pretty pictures all day. Readers of this blog know that pretty pictures occupy an unfortunately small amount of my professional time; I'm more likely to be filling out paperwork or deleting the 35th version of a university-wide email reminding me that some small street will be closed for a half hour three weeks from now when a new load of rattan is delivered to the Department of Underwater Basket Weaving.

In recent years, many scientists have started to realize how we can make use of the interest that the public shows in our work. In 1999, scientists at UC Berkeley launched SETI@home, a project that uses home computers when they are sitting idle to analyze radio data and look for extraterrestrial radio signals. The program was so popular that many other projects launched making use of distributed computing power, including a current effort that uses Playstation 3 units to study protein folding.

The concepts of "citizen science" include much more than just distributed computing. Ongoing projects include searches for extrasolar planets, hunts for tiny interstellar dust particles, and, of course, one of the oldest ongoing astronomy programs, the American Association of Variable Star Observers. Each of these projects would not be possible without innumerable volunteers who just want to do a little astronomy research.

In 2007, a project called the Galaxy Zoo started. The program was pretty simple: volunteers would be shown a picture of a random galaxy observed in the Sloan Digital Sky Survey, and they would classify it as a spiral galaxy or an elliptical galaxy. Over a million galaxies were included in the catalog, and it was hoped that the project would be completed in a couple of years. Galaxy Zoo was so popular, those galaxies were looked at 50 times over (i.e., 50 million classifications!) in just one year. (Read more about the history here.) Computers can't do the work well, and there are too many galaxies for just a few astronomers, but the community of volunteers made short work of the task!

In fact, Galaxy Zoo was so popular, it's back as a sequel: Galaxy Zoo 2. This time, instead of just deciding if a galaxy is a spiral or an elliptical, there are multiple questions for each galaxy; this allows the galaxy to be described more completely, which allows even more science to be done. It also means that, if you want to volunteer to help, you'll have the opportunity to study lots of pretty pictures of galaxies all day long, all while helping professional astronomers do some real scientific research.

If it sounds like fun, go to the Galaxy Zoo homepage, read about its history and how you can help, and then dig right in! Even if you only have a few minutes once in a while, that's okay! Every little contribution helps.

And, who knows, you might even discover something new and unexpected! It happened in the first Galaxy Zoo, so there's every reason to think it can happen again.

Professor Astronomy: Now on Twitter!

Only about 18 months after the bandwagon left the station, I've decided to show up on Twitter. Look for professor_astro. All the excitement of astronomy in 140 characters.

Monday, February 16, 2009

Stars Fell On Austin

Sunday morning was a time of some excitement here in Austin, when a fireball (an exceptionally bright meteor) zipped through the skies in broad daylight. Much of the city was out watching the Austin marathon as a meteor, most likely a chunk of rock about the size of a small automobile, burned up in Earth's atmosphere, complete with multiple sonic booms. So many people called 911 that my county's sheriff sent out a helicopter to look for debris.

But I missed the fun. I was indoors. I didn't see flashes, didn't hear booms, didn't suspect anything until my cousin emailed to ask if Martian Tripods were in the area. Thankfully, this wasn't an alien invasion (or at least they decided to go after Dallas first).

At first, there were some stories that the fireball was caused by debris from a satellite collision re-entering Earth's atmosphere; it didn't help that the FAA issued a notice that this may be the case. But the FAA doesn't deal with space debris, and, as Phil Plait laid out quite succinctly, all the facts point to an ordinary space rock.

Fireballs are rare, and those seen in the daylight are even rarer. But the Earth is a big place, and fireballs happen daily. Most go unnoticed, because 2/3 of the Earth is water, and much of the rest is sparsely populated. And people are not outside that much anymore -- we sleep at night, when meteors are most easily seen, and we tend not to look up much during the day. So, those lucky enough to see a fireball should consider themselves lucky. And those of us who were inside, well, we missed a good show.

Click here for a link to a video of the Austin fireball!

Thursday, February 12, 2009

Happy Birthday Abe Lincoln!

Through the fog of travel, I just realized that today is Abraham Lincoln's 200th birthday, too. I'd wax poetic on Lincoln's achievements, but (a) I've been awake for 24 hours now, and still have five hours until I'm home, and (b) a simple Google search will give you lots of other, more coherent essays and blog postings. Suffice to say, his 200th should be celebrated at least as much as that of Charles Darwin, if not moreso.

Happy Birthday Mr. Lincoln!

Happy Birthday Charles Darwin

Today is the 200th birthday of Charles Darwin, the biologist who proposed the modern theory of evolution and natural selection.

Darwin was a kind, well-rounded, and well-respected human being. He liked kids, was friendly with neighbors and strangers, and was a loving and caring husband. I suspect Darwin would have been righteously indignant of those who vilify him, and that he would have been mortified and angry by those who advanced war and racism in his name.

First and foremost, Darwin was an observer of the natural world. He studied biology via many different methods. He is most famous for his world "cruises" in which he studied the flora and fauna of many remote areas, including the Galapagos Islands. But Darwin also studied fossils and read the work of others. He took many years to digest all of this information and to develop his theory of evolution and natural selection. And he thought long and hard about the implications of his theories, and often struggled with seemingly contradictory information.

For example, Darwin worried quite a bit about the extravagant tails of peacocks. These tails hinder the birds, and should give predators an advantage over the birds; natural selection then says that the birds would lose the tails or be hunted to extinction. But yet, there the feathers are. And gradually Darwin came to realize that peahens were attracted by larger and more extravagant tails. So, the peacocks are in a balance between natural selection disfavoring big tails, and sexual selection favoring big tails. Based on the size of peacock tails, we can tell which is the driving force.

Darwin was truly the Albert Einstein of biology. Many of his ideas were decades ahead of the rest of biology. Some are just now coming into favor. And some of Darwin's ideas were, by modern standards, wacky. He proposed ideas on how animal species are distributed that are just plain wrong, especially once you know about plate tectonics (which Darwin didn't). Darwin didn't know about genes and DNA (how could he have?).

But Darwin's theories of evolution and natural selection are now the crucial underpinnings of all modern biology and medicine. Without evolution, we would not understand the emergence of new diseases, or the increasing antibiotic resistance of many bacteria, or the interrelatedness of species in various ecosystems. His theories have been and continue to be rigorously tested by experiment and the scientific method.

So, happy 200th birthday to a scientific genius, a man before his time, and, above all, a good human being.

Wednesday, February 11, 2009

Intermediate and Massive Stars Conference, Day 2

Yesterday was the second day of a conference here in Strasbourg, France, on intermediate-mass and massive stars. (As a reminder, here we mean stars that are about 5 or 6 times the mass of the sun and larger.)

Yesterday was one of those days that caused my brain to hurt a little, because the topics covered were fairly unfamiliar to me. The majority of talks were on the atmospheres of red giant and red supergiant stars. Stars, like some people, swell up and get rosy-faced as they get old. Exactly why this happens is a matter of quasi-philosophical debate, but when you make a computer model of a star that is using the last of its nuclear fuel, the model wants to swell up.

At any rate, when a star swells up, it cools off from temperatures like that of the sun (10,000 degrees Fahrenheit or hotter) to much cooler temperatures (only 5000 degrees Fahrenheit or cooler). At the same time, the outer layers of the star begin a slow roiling, like bubbling oatmeal, and the surface of the star gets fairly splotchy, with hotter patches, cooler patches, and perhaps even shells of dust and gas surrounding the main star.

When we look at a star, we just see a single point of light, so light from these bright and dark patches and shells of gas and dust all are blended into a single point, and it is the job of the red giant-studying astronomer to try and disentangle this mess.

To make it worse, red giant stars are cool enough that some atoms start to link up and form simple molecules, like carbon monoxide and titanium oxide. These molecules form and dissolve in the cooler and hotter parts of the star, and though they are fairly rare, they tend to absorb a lot of light. Think of it sort of like suntan lotion: a tiny bit of lotion can block almost all of the ultraviolet light from the sun. Now imagine that you are sloppy putting on the suntan lotion, so that you get patches of sunburn scattered among patches of healthy skin. The astronomer would then be like a dermatologist several miles away who is trying to determine how sunburned that distant speck of a person is.

Anyway, I don't work on this aspect of astronomy, so a lot of the techniques, nuances, difficulties, and big questions are unclear to me. And yet yesterday I found myself listening to hours of talks discussing computer models of red giant stars, observations of red giant stars, and other related astronomy. I did my best to learn what I could, and most of the speakers did a very good job of explaining the most important implications of what they were doing. So, even though I didn't follow the details all of the time, I understood why I should care about their work.

In addition to those talks, we also heard about stellar interferometry (which is a technique that allows us to actually measure the size and shapes of many red giant stars), and some new findings on variable red giant stars (stars that are changing their brightnesses). One of the neater findings there is that while we understand why many red giant stars vary their light in a regular manner (Mira-like variables, for those in the know), there are a number of red giant stars that change their light output regularly over much longer timescales than theory would predict. (It's always fun to see an astronomer toss his or her arms up in the air and say, "We don't know what's going on here!")

Today is the last day of the conference. Tomorrow I'll be traveling back to the US, a trip that will take 24 hours from the time I jump in a cab here in France until my plane lands in Austin, so I won't be blogging tomorrow, and I probably won't feel up to it on Friday. We'll see.

Tuesday, February 10, 2009

Massive Stars Conference: Day 1

First day of my conference is over, second day is starting. The jet lag is still nagging at me, as I woke up bright-eyed and bushy tailed at 5am, and now that breakfast is over, I'm tired again. Oh well,

Yesterday, the conference focused on the line between stars that end their lives as supernova explosions, and those that end their lives as a slowly fading ember called a white dwarf. I talked about my studies of white dwarfs, a couple of other people talked about their studies of supernovae, and a lot of people talked about detailed physics of the interiors of stars. I won't bore you with those details; I found it very interesting, but even 75% of astronomers' eyes would glaze over with the details.

Today will be more difficult for me, because we are going to a topic I don't understand very well: stellar atmospheres. This just means the structure and appearance of the outermost layers of a star. Most of the information we get about a star comes from these layers, and in the big red giant stars (stars nearing the end of their lives that have swelled up over 200 million miles across), the atmospheres are really complicated. It will be enough to make my eyes glaze over.

Thank goodness for coffee.

The Innocents Abroad

(The title of this post comes from a pretty funny Mark Twain book about a Mediterranean cruise with a bunch of American tourists)

The stereotypical American tourist is alive and well.

Overseas (at least in Europe), the stereotypical American tourist speaks loudly, expects everyone to speak English, and is unintentionally rude. (Watch National Lampoon's European Vacation for more sterotypes.) Now, it is true that most American travelers are not like that at all. But during my stay in France, I've noticed a lot of American tourists who make what I beleive is a boorish cultural faux pas: refusing to speak any French.

I don't speak French. I've never taken a French class. And my working vocabulary is quite limited: bonjour (hello), au revior (goodbye), s'il vour plait (please), merci (thank you), oui (yes), non (no), l'eau (water), cafe (coffee), Parlez-vous anglais? (Speak English?), and a few other random phrases, some of which will get me beat up (ferme la bouche, or "shut your pie hole"), and some of which are not all that useful in most situations: faux pas and sans coullottes (or however it's spelled). That's about it. I can read a lot more words than that, but I can't pronounce them or even recall them. Yesterday I tried to say my hotel room number (105, or cent cinq), but I screwed up and the hotel clerk thought I was asking something about the composer Saint-Saens. Whatever. I tried.

But I've noticed, at least at this hotel, that most of the other Americans aren't even trying to speak any French. Not bonjour, not s'il vous plait, not even cafe (come on, that one's an English word, too!). I think it's quite rude not to even try a couple of words, especially common ones.

I'm a strong believer in manners, and I think it is good form to learn a few words in a local language, even if it is just, "hello", "goodbye", "thank you", and "Do you speak English?" Sometimes it buys you an amazing amount of goodwill. Sometimes you get corrected on your pronunciation. But at least you don't come across as demanding (i.e., demanding that others speak your language). When foreigners visit America, don't too many of us claim that they should speak English or go home? Why shouldn't it be the same for Americans abroad?

Sunday, February 08, 2009

Bon jour!

That phrase is about 50% of the French I know. Yet today I find myself in Strasbourg, France, for a three-day workshop on intermediate-mass stars (for this conference, this means stars that are roughly six to twelve times the mass of our sun).

I'll blog more about it over the week, as time permits. Right now my brain is jello due to jet lag. Our plane landed this morning at what was midnight back home, so I was only somewhat tired on the plane. It didn't help that a toddler in the next row kept screaming the entire flight. Her parents tried very hard to keep her quiet, but I think she was over-tired and over-stimulated. Anyway, her scream was able to pierce through my normally trusty earplugs. But the flight was amazingly smooth. It's just a shame I was awake for the entire nine hours of it.

Thursday, February 05, 2009

A meteorite hits mars

A news story from Universe Today presents new images of Mars from the HiRISE camera on the Mars Reconnaissance Orbiter (a NASA spacecraft in orbit around Mars) that show a series of new impact craters on Mars, so new that they weren't there in 2003. The series of craters means that a meteor broke apart in Mars's atmosphere, and several pieces survived to crash into Mars's surface.

From the Earth, people see these fragmenting meteors (called "bolides") all the time, but only rarely do the pieces survive the fall through Earth's thick atmosphere. Since Mars has a much thinner atmosphere and much less weather to hide the signatures of an impact, the chances of finding these craters are much higher than on Earth. But it is still an amazing find. Neat!

UFO forecast

Moon and Venus setting in Spring 2007
The Moon and Venus setting into the sea on the evening of March 21, 2007. Click on the image to go to its original posting, where you can view a short movie of the setting pair. Image Credit: Ian Musgrave

I'm going to go out on a limb and predict that there will be a marked rise in the number of reported UFOs in the coming few months, at least in the northern hemisphere. It's not spring break for extraterrestrials, nor is it easier to see alien spaceships in that crisp March air. My prediction is based on the positions of two fully identified objects, the planet Venus and the star Sirius, which are the two objects most commonly mistaken for UFOs in the sky.

If you are out in the evening right now, the planet Venus is by far the brightest "star" in the sky. Venus is speeding around the sun, and in late March it will overtake the Earth, passing between the Earth and the sun. As Venus laps our planet in our perpetual races around the sun, it will appear to dive lower in the evening sky, finally disappearing and reappearing just days later in the morning sky.

When high in the sky, Venus shines very steadily, without twinkling like the other stars (here's why). But as Venus gets lower in the sky, its light has to pass through more and more of Earth's atmosphere. And, in the spring, the atmosphere tends to be more turbulent, as weather systems cross the continent and warm air and cold air collide. So, when low in the sky in the spring, even Venus can twinkle. And not only can it twinkle, but it can appear to rapidly change colors, because that same turbulent air bends affects different colors of light differently. So, instead of being a steady beacon in the night sky, Venus at times can appear to be a bright, color-changing point hanging low over the western horizon, slowly sinking toward the Earth. (If you click on the picture above, you can see a movie that shows the moon and Venus setting off the coast of Australia in 2007.)

Over the following couple of months, in April and early May, the star Sirius (the Dog Star, the brightest true star in the sky besides the sun, and also very high and bright in the sky right now) will perform a similar feat, as Earth's orbit appears to carry the sun between us and Sirius. Being a star, Sirius is even more apt to twinkle and flicker colors than Venus, and after Venus leaves the evening sky, Sirius will be the brightest object in the early evening sky.

One April, when I was working on my doctorate degree at UC Santa Cruz, I once received a telephone call from a local television station. They claimed to have video of a UFO disappearing into the Pacific Ocean, and they wanted me to watch the video and tell them what if was. I asked a few questions about precisely where and when the video was taken, what direction the camera was pointed, and how long it took the UFO to set. Thankfully, the reporters had all of that information. While we were talking on the phone, I pulled up some planetarium software, entered the relevant positions and times, and found that Sirius was setting in the western sky at precisely the same time and location. I didn't need to see the video (though I offered to watch it), because the identity of the UFO was painfully obvious. And the television crew was disappointed, but hopefully they learned a little something about astronomy.

There's one other reason that I think that UFO reports will go up over the spring. In addition to two bright objects both being low in the sky (and appearing to land as Earth's rotation causes the star and planet to set), and in addition to the fickle weather that can really beef up atmospheric turbulence (and so, on occasion, cause excessive twinkling and flickering colors), as the northern spring sets in, more people will be outside in the early evening, especially on the rare warm evenings (usually right before a storm front comes through, meaning that the atmosphere will be all the more turbulent). More people outside means more people likely to spy Venus and Sirius and not know what they are looking at.

In short, if you see a rapidly flashing and color-changing light low in the western sky this spring, you're not seeing an alien heading to spring break at Daytona Beach. You're probably seeing Venus or Sirius.

What should you do when you see something interesting in the sky and you don't know what it is? First, make a careful note of the current time, where you are, and what direction you are looking. You need to know these fairly precisely; "kinda toward the south" isn't good enough, but "south-south east" probably is. Second, go look at some planetarium software. There are many good free and commercial bits of software out there, and a lot of people I know use Stellarium, which is free. I don't know what the best software is; most of you wouldn't want to use my favorite software, because it is more complicated and would give you far more information than anyone but the most serious observer would want. Enter the specifics about where you were looking, the time and date, and then see if anything bright was around at that time. If you don't see anything obvious there, you may very well have seen a satellite. Go to heavens-above.com, which has a very large (but not complete!) listing of satellites and when they will be visible from your location. Again, with your location, precise time, and direction of observation, you may discover that you saw a satellite instead.

So, in short, if you hear a lot more about UFOs in the coming few months, remember that there's likely to be a rise in the number of false reports. Instead of packing up and heading for the hills, blame Venus and Sirius, and remember that I predicted it.

Wednesday, February 04, 2009

Signing day

Yesterday was signing day for college football, when high school football players can start signing national letters of intent, or what are essentially contracts promising to play (American) football at a college in exchange for a scholarship. This makes big news in the college football world, as everyone is wondering which great high school player will go to which college. Sometimes the recruits are indeed excellent players, sometimes they aren't. It's a bit of a guessing game played based on a recruit's performance by various statistics.

Although you don't hear about it, now is also astronomy's recruiting season. Most astronomy PhD programs have made offers of admission to promising undergraduates, and most programs will now try and woo their prospects, who have until April 15 to decide where they will go to school.

Like with football recruiting, there is a little bit of black magic in choosing who gets admissions offers. Unlike in football, astronomy students have to apply for entry to a program. Then a committee reviews the applications, including factors such as grades, performance on a physics exam, and letters of recommendation from advisors and teachers. Poor performance on tests can sometimes be made up for by good grades and good letters. Students who take part in research projects while earning a bachelor's degree can also help themselves, provided they show positive signs in their research work.

But good grades, good test scores, and good letters do not guarantee that a student will make a good astronomer, and poor performance doesn't mean a person would be a poor astronomer. There are many intangibles, and only time will tell if a given year's recruiting class is as good or not. Like the recruiting classes of college football, the outcome can be greatly different from the perceived potential.

Looking back on my own experience as a recruit, it was a lot of fun. I got to travel around the country on other people's dimes, and I was warmly treated at each stop along the way. My decision was tough: I was offered admission to several great astronomy programs, each of which would give me a good education and a good start to a career. In the end, my decision was based on criteria that some would scoff at. Where did I want to live for five or six years of my life? Where did I feel I would best get along with people? That narrowed it down to two places, and then I chose based on a bit of a whim. And I think I made the right decision.

So, good luck to all of the seniors out there, whether you are trying to decide where to study astronomy or where to play football! Enjoy the recruitment process, and be wary of high pressure. Make the choice that is best for you, not what is best for a coach or a professor.

Sunday, February 01, 2009

Happy Groundhog Day!

Every year, I write an article about how Groundhog Day is actually an astronomical holiday. Why do I do it? Am I stuck in some time warp where I am forced to write the same entry over and over until I get it right? Is it because I am lazy and don't want to write new material? Or is it because I have a point that I think is somewhat important that I want to get across?

The answers are: Not that I'm aware of, maybe, and yes, respectively. (And also that I think it is amusing that an arcane holiday involving men in silk hats dragging a mean-spirited rodent out of a hole in a log is actually related to astronomy. Thankfully these men don't harm the critter, though the critter routinely harms them.)

For those who don't want to read my previous posts on this austere holiday, let me summarize. Groundhog Day is (roughly) on a "cross-quarter" day, or the day exactly halfway between a solstice and an equinox. In this case, we are halfway between the winter solstice and the spring equinox, which means that winter is half over. Since there are 13 weeks in each season, there are six-and-a-half weeks left in winter (whether or not the varmint sees its shadow).

My purpose for re-telling this story every year is that, in this day and age, many of us are quite insulated from the motions of the Earth, whereas just a couple of centuries ago, these motions were crucial to life. At the winter solstice in late December, Earth's North Pole was pointed as far away from the sun as it gets. For those of us in the Northern Hemisphere, this means that the sun appeared low in the sky. Because the sun's rays were coming in at an angle, the energy and warmth from those rays were spread out more. Those spread-out rays were thus not able to warm the Earth as efficiently, and the hemisphere dipped into winter.

Since the winter solstice, the sun has been starting to climb higher in the sky, bit by bit. If we spent more time outdoors, this would be painfully obvious to us, and would have been a reason to celebrate: a higher sun means more direct energy which means warmer weather is coming! But since most of us live and work indoors, we don't notice this sign of the coming spring.

For those of us in the Southern Hemisphere, the sun has been almost imperceptibly sinking in the sky for the past several weeks, but now that sinking will start to become more noticeable, and autumn is only six weeks away.

Confused? You're not alone. It's hard to picture how this all works. It's not impossible, but it's hard. But you can easily observe the changing of the sun's position in the sky without needing sensitive measuring equipment. If you go out for some fresh air at roughly the same time every day, say over a lunch break, mentally measure the length of your shadow. (If you have a brick or block walkway where you can measure how many bricks "tall" your shadow is, this is all the easier!) Over the next few months, once a week or so re-measure your shadow at the same time of day. You'll notice a surprising difference!

Or, if you routinely are able to see the sunrise or sunset (maybe during a commute, or as you are waiting for the bus, or while you are eating dinner), make a mental note of where along the horizon the sun sets. Use a distant house, tree, hill, or other landmark as a reference. I've been able to see noticeable differences in just one or two days.

The Earth's motion around the sun is the root cause of these changes. We can't feel the orbit, but we can see the consequences. Our length of day. weather, and seasons all change because of this orbital motion. Next to the Earth's daily rotation, our orbit around the sun is the most fundamental impact of space on us and all life on Earth. I'd urge you to take a little time to try one of these experiments I mentioned. And, when you successfully detect the change in the sun's position, you'll be experiencing some of the most basic but most important astronomy anyone can study.