Now is a great time to see Jupiter!

Even if you're not currently teaching astronomy topics, this is something you need to tell your students about. . . On October 29, Jupiter will be at opposition to the Sun, providing earthlings (including your students) a great opportunity to see the gas giant over the next few weeks. With good eyes, a decent pair of binoculars, and a wall to steady yourself against, you should be able to see some of its large moons. CLICK HERE to learn more. The site provides links to other sites that help students understand why Jupiter is in a favorable position for us to see it. CLICK HERE to see the recent "Astronomy Picture of the Day", which also highlights this event.

Colorful Real-Time Weather Maps

Here is on of my favorite sources for real-time weather maps. The site is provided by the University of Illinois (WW2010). When a storm is moving through, I like to start class by showing some of the colorful maps. CLICK HERE to see what the site has to offer. The site allows you to animate the images to watch how different aspects of the weather have changed. Play with it to see how it works.

Under Construction

What's the Recipe for a Cloud?

Here is my version of the "cloud in a bottle activity". To obtain a student handout and answer key for this activity, CLICK HERE.

Juice bottles are also suitable for this activity.

#104 - Montana Ice Caves are Natural Deep Freezes

Although there are ice caves scattered in the mountains of central and eastern Montana, the ice cave near Crystal Lake (above photo) and Big Ice Cave in the Pryors are two of Montana's most popular ice caves. Most (perhaps all) ice caves in the state are found in a rock formation called the Madison Limestone, which has been described as a 'geologic Swiss cheese" due to it's many caves and sinkholes. In fact, Montana's most famous cave, the Lewis and Clark Caverns, was formed in the same Madison Limestone as the two pictured above even though vast distances separate the three.

So what's an ice cave?. . .
Contrary to what you might think, the kind of ice cave featured here is not a cave formed in ice, but rather a cave that remains cold enough to contain ice all year long. As you saw in the video, smooth ice at least several inches thick covers the floor of Big Ice Cave. The air in caves is almost always cooler than air outside during summer, and warmer than outside air during winter because caves are well-insulated by the thickness of rock around them, however very few stay cold enough for ice to persist through the hot months of summer. So, what makes some caves so cold? There are two factors involved.

1. It's a density thing . . .
Whether you are studying geology, meteorology, oceanography, or astronomy, one of the most important underlying principles is "density". Density also plays a crucial role in the persistence of of ice in some of Montana's caves. Since molecules of cold air move slower than those of warmer air, colder air molecules tend to be closer together. This makes cold air denser (heavier for its volume) than warmer air. As a result, cold air tends to sink to the lowest location . . . In this case, the bottom of the cave.

2. Where do you keep your ice cream? . . .
When it comes to storing frozen foods, there are two basic types of freezer compartments. There is the kind located along the bottom, top, or next to the refrigerator compartment. To get frozen foods from these, you simply open a door. But as you do, the cold air inside flows out onto the floor and is replaced with warmer air from the room. After you shut the door, electricity is used to re-cool the air so your ice cream doesn't melt. These freezer compartments are like normal caves.

The second type of freezer compartment, which opens from the top, is much more efficient because when you open it the cold air does not easily escape. Sometimes called "chest freezers", "freezer chests", or "deep freezes", these are similar to ice caves. Ice caves are laid out in such a way that the entrance to the cave is located above the cave, so cold air doesn't flow out. Like the chest type of freezer, the opening to an ice cave is above the place where cold, dense air sits undisturbed.

Below: In the ice cave (left) there is no outlet for the cold, dense air from the previous winter. In the normal cave (right) cold air spills out and is replaced by warmer air throughout the spring and summer.

Terms: limestone, convection

Watch this video of my trip into the ice cave south of Lewistown in 2009.

What's up in the night sky!

CLICK HERE to find out what's in the sky right now, or at any time. To change the settings (times, dates), select "manual", make the changes, and then hit return on your keyboard. The site is provided by lightandmatter.com.

El Nino Explained on a "Pencast"

El Nino
brought to you by Livescribe

This is a way that students can listen to the teacher explain concepts online. Pencasts are especially helpful for students who have missed class, or just want another chance to have a concept explained. Pencasta are easily produced using a Livescribe "smart pen". To view a pencast, such as the El Nino Pencast (above), turn your volume on, select "full screen", then "hide preview" in the lower right, and then "play".