Snow Good

December 27, 2007 at 20:38 pm | Leave a Comment

Snow Good

One of the consequences of living on a planet that orbits a star is that we get seasons. Every planet in the solar system has reasons for seasons:

  • the tilt of the planet on its axis—which determines the angle of the incoming sunlight that strikes the surface (or upper atmosphere) of the planet;
  • the number of hours of daylight experienced on any given part of the planet (more hours of sunlight mean more warmth)

For those of us in northern hemisphere winter, right now we’re having shorter days and colder weather because our part of the planet is tilted away from the Sun and we have fewer hours of sunlight per day than the folks in the southern hemisphere, who are enjoying the height of summer weather.

This is all academic if you’re looking at some other planet, like Mars or Venus or Neptune, and trying to figure out what time of year it is on various places on those planets. It’s not so academic if you’re in the “middle of the experiment” so to speak.

Where I live it’s winter. There’s no question about it. We’ve had cold weather for some weeks now, and the Sun is much lower in the southern part of our sky than it is the rest of the year. Nighttime comes around 5 p.m. And, it has been snowing.

Today I looked out the window and saw these huge snowflakes falling. So, I did what anybody who’s been stuck in front of a computer all day indoors on a cold winter day would do: I grabbed my camera and started taking pictures to show to the folks I know in warmer climes. I even managed to capture a few short movies with my digital still camera (alas, I was shooting through screened windows, but hey— you grab your chances when and where you can).

So, here’s today’s real-life flash video demonstration of a seasonally caused weather pattern and what it looks like from indoors, in the form of a little music and visual-arts video. Click on the snowflake and enjoy!

To see this video here, you need to tell your browser not to block active content, or you need to get the Flash player. RSS readers who can’t access the video can download it here.

Creative Commons License

This work is licensed under a
Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Unported License.

See Mars for the Holidays

December 24, 2007 at 18:21 pm | Leave a Comment

See Mars for the Holidays (originally posted for Dec. 2007)

Star chart by C.C. Petersen/

The holidays (all kinds of them) are upon us. Whatever you celebrate at this time of year, take a few moments to step outside and look up at the night sky. Orion should be prominent, and not far away, one horn of the Hyades (in Taurus) seem to point at the planet Mars. If you have binoculars or a small telescope, check out the Orion Nebula not far from the three stars that make up Orion’s belt. And, don’t forget to include the Pleiades in your stellar and planetary travels!

(Note: this post and map refer to the sky and Mars as seen in December 2007.)

Happy Holidays from


December 22, 2007 at 15:46 pm | Leave a Comment

Smacking Mars

Ever hear of 2007 WD5? It’s all over the news right now, so I’m probably not telling you anything new about it, but just in case you’ve been out holiday shopping or traveling or hiding under a rock, here’s the scoop. 2007 WD5 is a 164-foot-wide asteroid that is moving in an orbit that will cross Mars’s orbital path in late January. It comes close enough to Mars that it will pass within 30,000 miles (48,000 kilometers) of the planet. It’s possible, although not likely, that this thing could actually smack into Mars’s surface. The chances are about 1 in 75. If it did, this rock (traveling at 30,000 miles per hour) would dig out a crater about the same size as the one that the Opportunity rover is exploring right now.

Victoria Crater on Mars

Over the next few weeks astronomers will get a better idea of the asteroid’s orbit and whether it will actually hit Mars or sail on by. You can follow the action by visiting NASA’s Near Earth Object Program web page for updates.

A Tribute to Carl Sagan

December 18, 2007 at 8:49 am | Leave a Comment

Celebrating the Life of a Phenomenal Man

Image of Carl Sagan

Carl Sagan, from the Planetary Society web site.

It has been 11 years since astronomer Carl Sagan died following a battle with myelodysplasia. To commemorate his loss, and more important, to celebrate his life, many of us are blogging about Dr. Sagan or putting comments about him on the Celebrating Sagan blog.

To say that Dr. Sagan was a hero to a great many of us would be an understatement. For all of us who came to science popularization as a result of the phenomenal Cosmos series (created with Ann Druyan), who read his science popularization books, and who followed in his footsteps as writers and researchers, Carl Sagan was the foremost practitioner of science outreach and popularization. Simply put, he embraced and shared a passion for science and truth.

Cosmos may have brought him to public attention in a very broad way, but it was hardly the first thing he did. Do a search on Amazon and you’ll find an amazing number of products—books, music, DVDs, CDs, and so on—that he had a hand in creating (or that he inspired). All are still popular more than a decade after his passing.

One of his greatest hits isn’t something that you can pick up at Amazon or download from iTunes. It’s called the Voyager Record—a sort of audio-visual time capsule that recorded a brief moment of humanity’s time in the universe. There are copies of this album on the Voyager 1 and Voyager 2 spacecraft, each of which is speeding out from the Sun, never to return. Whenever I think of Carl Sagan, I think of those albums. He headed up the committee that created them; he fought for them to be put on the spacecraft, and in some sense, they carry his vision of humanity (with all our brilliance and foibles) along with them.

The Voyager Record

I often wonder what Carl Sagan would say today, if we were still alive and watching the current rush by some short-sighted politicians in the world to dehumanize science and scientists. These “leaders” seem to care for little more than the next election, the next corporate donation, the next fundamentalist endorsement. Would he have to rewrite the book Demon-Haunted World, where he describes the fallacies of too much reliance on short-sighted religious prophets and the uneducated embrace of pseudo-sciences by people who fear science? Would he need to add on new chapters with examples of people who disregard their critical thinking skills just so they won’t be bothered by uncomfortable truths about their leaders, their country, their planet?

I’ve had many “godly” people tell me that Carl Sagan hated religion, which of course is nonsense. Most times they haven’t taken the time to read his works and understand his points. A careful reading of his works has showed me that Sagan wasn’t about hate. He disliked, intensely, the way that many people willingly let others do their thinking for them. He disapproved of the silliness of pseudo-sciences and those who use science to promote nonscientific theories as a cover for religious indoctrination in the schools. But, hate people or religion? There’s no proof of it. And science is all about the honest search for truth and the proof of it.

Carl Sagan’s greatest legacy is and will continue to be the embrace of science and what it can tell us about the universe. How the cosmos works, where it’s come from, where it’s going, our place in it; those are things that science can tell us about. We have to be willing to do our part, too, by stepping up to the challenge and using science as the exploration tool that it is. And that, along with a record of images and sounds from our planet, is all a large part of what Carl Sagan left for us as a gift and a encouragement to explore our cosmos and all the ideas (whether uncomfortable or not) that exploration brings.

Our Interstellar Reach

December 14, 2007 at 9:15 am | Leave a Comment

Voyager 2 at the Brink of Deep Space

One of my favorite missions made the news this past week. The Voyager 2 spacecraft, which is on its way out of the solar system on a trajectory to deep space, is nearing the limits of the Sun’s influence on space. In August of this year it crossed the solar wind termination shock, a point in space where the solar wind smashes into the thin gas that exists between the stars. The solar wind basically blows a big bubble of gas (from the Sun) into surrounding space; the “edge” of that bubble is called the heliopause. Crossing the “membrane” of that bubble registers as a blip in the data the spacecraft sends back, alerting astronomers that a momentous event has occurred. Voyager passed this goalpost in space did so a bit earlier than astronomers expected, which implies that the heliopause is not as symmetrical as they thought. Because the solar wind varies a bit in its extent, Voyager may well bounce and out of the heliopause.

I first heard about the Voyager mission back in the late 70s, just after it was launched. It sent back some amazing images of Jupiter, and by the time Voyager 2 got to Saturn in 1981, I was working at a newspaper in Denver, Colorado. I asked the managing editor if I could go out to Jet Propulsion Labs in Pasadena, California for the Voyager 2 Encounter of Saturn, and before I knew it, I was on my way, duly accredited as a reporter.

It was an interesting experience, and only whetted my appetite for more planetary science. A few years later, I went back to school to study more astronomy and planetary science, and so I always look back on the Voyager 2 flyby of Saturn with fond memories. Sometime in the next few years, Voyager 2 will get completely free of the heliopause and truly be in deep space. I remember back in 1981 thinking about Voyager 2 and its future mission; here we are, three decades later, and it’s just NOW getting to the heliopause. This tells us in a very visceral way that space is big!

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