Saturday, December 8, 2007

The Earliest Sunset!

Well, we've made it. Tonight was the earliest sunset of the year!
Every decent earth science student knows that today was NOT the shortest day (that's on the Winter Solstice around December 21), but not a lot of people can explain tonight's early sunset. It turns out that the rate at which the Sun travels across the sky is not constant - the tilt of Earth's axis and its elliptical orbit conspire to push the Sun ahead of our clocks, and then slow it down again, twice every year. Astronomers call the difference between time told by the Sun (apparent solar time) and clock time (mean solar time) the "equation of time".
The chart on the left above, called the analemma, combines the equation of time with the position of the Sun relative to the equator. Click it for a larger view, and notice that through most of the fall the Sun has been running ahead of the clock, but in December it began to slow dramatically.
It's the Sun slowing down relative to the clock that's moving the daylight period later into the day even as the days get shorter!
This photo composite was made by Tom Matheson over the course of a year, snapping a picture of the Sun at exactly 8 AM (by the clock) each day. Here is a labeled image of Tom's photo.

Saturday, November 24, 2007

Clear Skies....Get Yer Coat On and Get Out There!

We're in for a few days of clear skies, and even though the nearly full Moon will dominate the entire night sky for the next few days, you should bundle up and get out for a little bit of winter sky orientation. The Moon's light will make observation of Comet Holmes difficult if not impossible.
Moonlight will wash out all but the brightest stars, but you can use that fact to help you locate the bright stars of the "Winter Hexagon".
Refer to this PowerPoint file (The Winter Hexagon) to learn to know the 6 bright stars that mark the winter skies. (if you need a PowerPoint viewer, get it here) Tonight the Moon is between Aldebaran and Capella, and over the next few evenings it will work its way toward a close encounter with Mars - between Capella and Pollux - on the night of 11/26.
For good viewing you should have a clear view of the sky to the EastSouthEast of you, and be as far from artificial lighting as you can get. Give your eyes about 15 minutes to adjust to the dark once you're outside (that's why you want yer coat on!)
And I've turned on the comments option, so let everyone else know if you get out there, and what you're able to see.

Sunday, November 11, 2007

Comet Holmes

If you haven't seen it yet, get out to see Comet Holmes tonight. The image above will help you find it if you know Cassiopeia, or you can check out this larger sky chart here to orient yourself with the horizon and more stars.
A comet's tail trails off away from the sun, blown by the solar wind - it has nothing to do with the direction the comet is moving - (see this animation to understand better). Our present comet/Earth/Sun alignment gives us a rare "head-on" view (a fuzzy circle), rather than the more familiar side view (the tail is behind the fuzzy spot we're seeing).

The excerpt below comes from this Sky and Telescope article...

he comet remains as bright as ever to the naked eye, though its average surface brightness continues to drop as it enlarges. As of last night it was 14 arcminutes wide, or nearly ¼° — half the apparent diameter of the Moon. During this dark-of-the-Moon period (which will end around November 15th), seize whatever chance the weather allows to show family, friends, and strangers something memorable. This is how new amateur astronomers are born.

Saturday, November 10, 2007

Recent Atmospheric Optics: Glories and Sundogs!

On our approach to the Denver airport 2 weeks ago, Mr. Patrick and I were treated to an interesting optical effect called a "glory", and we've posted a video of it on Youtube.
You can read about how the glory forms here

While enjoying a few days on the road during this past week, I got these shots of some nice sundogs over the Long Island Sound: and a wider view here:

Sundogs are about 22 degrees (two fists or one outspread hand) on either side of the sun.

You can read about how sundogs form at Les Cowley's atmospheric optics page:

Monday, October 22, 2007

Santa Ana Winds and Wildfires in California

You've probably read or heard about the wildfires in California (if not, read this). The fires are being fanned by the hot, dry, "Santa Ana Winds" that come down off of the mountains east of the coast. As the already dry air descends, it is compressed and its temperature rises. Read about the Santa Ana Winds here and here is a great site that tells a little about the winds and has some great animations of how the winds grow and strengthen. A little complicated, maybe, but really interesting. Here are some links to maps that show the pressure system responsible: (this one surprised me....look at the gradients in Montana and northern Mexico. It's got a map of the wind field, too, but it's a little hard to read.)

Saturday, October 13, 2007

Earth Science Picture of the Day?

The amazing clouds that filled the Hudson Valley on Tuesday, 10/9/2007 are a potential "Earth Science Picture of the Day" submission, and this MetAR helps explain what was going on. If any of you are interested in authoring a description/explanation of the phenomenon, see me and I'll help you polish and submit it. Email me now, or see me Monday if you want to go for it. -Kloog

Thursday, October 11, 2007

A Few Pics from the Catskill Geology Trip

We had quite a wet trip this past week, but everyone survived and actually learned a little geology too. See some more pics from the trip here.

Friday, October 5, 2007

Lake Boils as Volcano Awakes

From the article:
"Hundreds of Indonesians have begun evacuating the slopes of a rumbling volcano in East Java following increased levels of toxic fumes and tremors, a local rescue official said on Thursday."

Kelut Volcano information and location in Google Earth

video of lake bubbling with CO2

Thursday, October 4, 2007

California Landslide!

From this news article:

"The city began noticing cracks on Soledad Mountain Road in July and water and gas main breaks in August. A water line in the neighborhood was replaced with an above-ground pipeline in September to avert damage from the moving earth"

Read the rest of the article by clicking the link above, see some video here, and get it in Google Earth here

Wednesday, September 12, 2007


A magnitude 8.4 'quake hit Sumatra earlier today very near where the devastating quake of December 2004 hit. Read about it here

Saturday, September 8, 2007

La Nina Strengthens Hurricane Forecasts

It's interesting that sea surface temperatures and currents in the tropical Pacific Ocean can affect the Atlantic Tropical weather, and even our climate in the northeastern US.
Read about La Nina and El Nino here, and read the recent article on the new La Nina here.

Friday, September 7, 2007

Distant Space Collision Meant Doom for Dinosaurs

"WASHINGTON (Reuters) - A collision 160 million years ago of two asteroids orbiting between Mars and Jupiter sent many big rock chunks hurtling toward Earth, including the one that zapped the dinosaurs, scientists said on Wednesday."

Read the story here.