Friday, August 19, 2005

A Good Smooch

Anyone who looks low in the west early on a clear evening for the next couple weeks will witness an unusual sight. Venus and Jupiter, the two brightest planets, will draw closer and closer together from day to day, will then have an eye-catching conjunction (close pairing) on the evenings of August 31 to September 2, 2005, and then will begin to move apart.

The direction to look is low in the west-southwest, and the best time is about 40 to 60 minutes after your local sunset. The brightest of the two "stars" shining there will be Venus. Jupiter closes in on it from the upper left during August and passes closest to it on September 1st, when the two will appear separated by hardly the width of your finger held at arm's length (about 1.2 degrees).

Also in the vicinity is the much dimmer star Spica. If Spica isn't bright enough to show through the twilight, binoculars should reveal it easily. In addition, the waxing crescent Moon joins the party on September 6th and 7th.

Accompanying this release is a series of daily sky scenes that illustrate what to look for in the fading twilight on any date from August 21st through September 7th. They can also be played in sequence as a QuickTime movie to show the dance of the planets, Spica, and the Moon throughout this period.

Although these objects appear the same distance away as you watch them in the deepening dusk, this is very much an illusion. Venus is roughly 106 million miles from Earth (its distance changes during the period illustrated), while Jupiter is 575 million miles away, more than five times farther. The Moon is about 220,000 miles distant; Spica lies 1.5 quadrillion miles in the background.

Such big distances are better expressed by how long it takes light to cross them. Venus is about 10 light-minutes from Earth. Jupiter is 52 light-minutes from us, the Moon is only 1.2 light-seconds away, and Spica is some 260 light-years away. The light reaching your eyes from these sights has been in flight for very different amounts of time -- something to think about when gazing at this unearthly view.

posted by Matthew @ 7:16 AM 0 comments

Tuesday, August 16, 2005

Another Letter to Poland (which could also be read as an open letter to Bill Cosby)

posted by Matthew @ 8:47 AM 1 comments