Monday, August 26, 2013

Astronomy Versus Astrology

If I had a dollar for every time someone in casual conversation had called me an astrologer or astrologist (instead of an astronomer), my retirement funding would be a lot more secure. Often, it's an honest mistake, where the speaker really does understand that astronomy is a science and simply isn't sure of the science's proper name. What's much worse is when I run into a "true believer" in astrology, who thinks that our personality, our character, and our destiny is shaped by the arrangement of stars and the position of celestial objects at the moment of our birth.

Some years ago, I wrote an article for Sky & Telescope magazine setting out an astronomer's reaction to astrology. A much revised and updated version is now on-line, thanks to the Astronomical Society of the Pacific. If you have wondered about astrology and what to say to those who believe in it, this short article may assist you. At the very least, you might find it amusing. In it, I also describe a new field for predicting things called "jetology" (where your future is determined by the position of all the jumbo jets at the moment of your birth.) The article is in PDF file format at:

Tuesday, August 20, 2013

As the World Turns

It's a dizzying thought, but the solid ground beneath our feet is moving at great speeds through space. For example, our planet turns once a day. Every 24 hours, the place where you live on the surface of the Earth goes in a big circle around the center of our planet. In the San Francisco Bay Area, this motion happens at a speed of about 818 mph. (Children, you can do this without adult supervision, because gravity holds all of us firmly to the Earth's surface.)

Our planet turns around an imaginary stick that goes from the Earth's north pole through its south pole. We call the line of that imaginary stick the Earth's "axis." As our planet turns around its axis, the Sun appears to rise in the East and set in the West and we have day and night. At night, as we turn, we see everything in space slowly turning around us. But we know the Sun during the day and the stars at night are not really turning. They sit in space and mind their own business. The motions we see in the sky hour by hour just reflect the turning of planet Earth. Do you want to see this motion displayed?

On the magnificent photo I have attached to this little posting, you can actually see the turning of the stars (around the still point of the north pole of the sky). Master photographer Phil McGrew captured the turning of the sky above the Golden Gate Bridge. I was so enchanted with this photo, I asked him to give me permission to share it with all of you. You can see more of his photos at his web site:

The photo is actually made up of more than 180 20-second exposures, skillfully added together. Instead of being a point, each star becomes a curved line as the Earth turns with the camera and photographer attached to it. Astronomers call the curved lines "star trails."

Can you think of other ways that you are moving even while sitting still in your favorite armchair? We'll discuss these other motions in future posts.

Friday, August 16, 2013

Astronomy Talks Have a YouTube Channel

The Silicon Valley Astronomy Lectures, which I have the pleasure of moderating, feature noted scientists giving nontechnical illustrated talks on recent developments in astronomy. I am happy to announce that they are now available on their own YouTube Channel, at:

The talks include:

* Frank Drake (the father of the search for radio signals from civilizations in space) discussing his modern view of the Drake Equation,

* Michael Brown explaining how his discovery of the dwarf planet Eris led to Pluto being kicked out of the planet club,

* Alex Filippenko (selected as the U.S. Professor of the Year, a few years ago) talking about the latest ideas and observations of black holes,

* Natalie Batalha (mission scientist for the Kepler Project) sharing the latest planet discoveries from outside the solar system, and

* Chris McKay updating the Cassini discoveries about Saturn's moon Titan (the only moon known to have an atmosphere thicker than Earths).

The lectures are taped at Foothill College near San Francisco (where I teach), and co-sponsored by NASA's Ames Research Center, the SETI Institute, and the Astronomical Society of the Pacific.

Note that the top page of the YouTube channel shows the lectures in the order they happened to be uploaded to YouTube. If you want to see them in chronological order, select the Playlist option.

Both new and older talks in the series will be added to the channel as time goes by. Many well-known astronomers have given talks in this series since its founding in 1999; recent lectures are being recorded so that people around the world can "tune in."

(About the picture: This is a false color image of the Helix Nebula, the last gasp of a dying star located about 650 lightyears away.  A relatively low-mass star is collapsing and losing its outer layer in a final internal adjustment before it dies as a white dwarf.  The material the star loses is excited by the energy of the shrinking star and set to glow.  In this image, infrared radiation (as measured from the Spitzer telescope in space) is shown in green and red, ultraviolet radiation (as measured by the GALEX telescope in space) is shown in blue.)

Wednesday, August 7, 2013

Good Meteor Shower Starts This Weekend

Whenever small chunks of cosmic dust or dirt hit the Earth's atmosphere at high speed and heat up, they make a flash of light that's visible from the ground. We call these meteors or "shooting stars." When the Earth encounters an organized swarm of cosmic material, we call it a meteor shower.

The Perseids (one of our most reliable meteor showers) is best this year the night and morning of Sunday Aug. 11 to Monday Aug. 12, and the night and morning of Monday Aug. 12 to Tuesday Aug. 13th.

Watching for meteors is easiest for most people’s schedules in the evenings (before midnight). However, the meteor display is generally better after midnight (making night owls and early risers happy.)

The Perseids are better after midnight for two reasons this year:

a. The Earth turns after midnight to face the shower (so that the meteors are coming more directly at us)
b. The crescent Moon will set by then, so its light will not bother meteor shower fans. (On Aug. 11, the Moon sets at 10:32 pm, while on Aug. 12th the Moon sets at 11:10 pm.)

Whenever during those two nights you decide you want to watch, here are Fraknoi’s Friendly Meteor Shower Tips for best viewing:

1. It’s more important to decide WHERE to watch them, than WHEN to watch them. The crucial issue is that meteors are faint, so you need a location where the sky is DARK. That means getting away from city and car lights as much as possible. The darker your site, the more you will see.

2. Of course, if it’s foggy or cloudy, you won’t see a thing. So make sure you get to a place where the sky is not only dark but CLEAR.

3. Don’t use a telescope or binoculars. (Meteor showers are one of the most democratic of sky shows; those of us in the 99% can enjoy them as much as those in the 1%!).) Your eyes are the best tool, because the flash can be anywhere in the sky. So restricting your view to a small part of the sky makes it more likely you will miss many of the meteor flashes.

4. Dress warm for night-time temperatures and be patient. Meteor showers are far more subtle than fireworks. You will need to relax and wait for time to pass. First, it takes a while for your eyes to get adapted to the dark (I recommend at least 15 minutes) and, second, a minute or several minutes might pass without a single flash. Eventually, though, you should see significantly more shooting stars than on a regular night.

5. So (perhaps most important) try to take someone with you with whom you like to spend time in the dark.

The Perseid meteors are cosmic “garbage” (dust and dirt clumps) left over from a regularly returning comet, called Swift-Tuttle (after the two astronomers who first discovered it). When comets get near the Sun, their ice evaporates, leaving behind some of the dirt that was frozen inside them. Since comets are "left-overs" from the early days of our solar system, you can tell yourself that each flash you see is the “last gasp” of cosmic material that formed about 5 billion years ago.

(Our photo, by ESO Photo Ambassador St├ęphane Guisard, shows a bright Perseid meteor in 2010 over the grouping called the Very Large Telescope at the European Southern Observatory in Chile.)