Chapter 8:

Our Earth

Foucault's Pendulum and Other Inventions

Foucault made daguerreotypes of the sun and the solar spectrum in 1844-45, within 5 years of Daguerre's invention of his type of photography. From an exhibition at L'Observatoire de Paris, we see his pendulum pictured in popular magazines and see one of his mechanisms for keeping the pendulum moving. We also see some of his daguerreotypes.

Auroras Seen Simultaneously at North and South Poles for the First Time

NASA Press Release, October 29

Scientists using NASA's Polar spacecraft have captured the first-ever movie of auroras dancing simultaneously around both of Earth's polar regions. During a space weather storm on October 22, Polar's Visible Imaging System observed the aurora borealis and aurora australis (northern and southern lights) expanding and brightening in parallel at opposite ends of the world. The images confirm the three-century old theory that auroras in the northern and southern hemispheres are nearly mirror images -- conjugates - of each other.

"This is the first time that we have seen both auroral ovals simultaneously with such clarity," says Dr. Nicola Fox, the science operations manager for the Polar spacecraft, based at NASA's Goddard Space Flight Center, Greenbelt, Md. "With these images, we have the ability to see the dynamics of conjugate auroras."

Auroras occur when fast-moving particles trapped in Earth's magnetic field come crashing down into the gases of Earth's upper atmosphere. Those particles (electrons and protons) can only move along the invisible magnetic field lines, which are connected to Earth near the North and South poles. When a space weather event pours energy into the space around Earth and energizes the magnetic field, those particles travel to both ends of the field lines, creating auroral displays in approximately 2500 mile diameter rings encircling each pole.

"For the first time, the northern and southern auroral ovals were observed simultaneously with enough resolution to confirm that the northern and southern aurora are mirror images of each other on a global scale," says Dr. John Sigwarth, a space physicist at the University of Iowa who helped design and operate the VIS cameras. "Further analysis of these images should help us determine if the all of the auroral features are exactly mirrored down to the finest detail." Preliminary research suggests that while the auroras mimic each other on broad scales, there are also some fine features that do not match.

The first recorded sighting of conjugate auroras occurred in September 1770, during the expeditions of Captain James Cook. While exploring Australia and the South Pacific on the HMS Endeavour, Cook's crew noted "a phenomenon appeared in the heavens in many things resembling the Aurora Borealis." Later studies of the Qing-shigao, a draft history of the Chinese Qing Dynasty, revealed that an aurora was observed on the same night - September 16, 1770 - in the northern hemisphere.

In the years since then, scientists have conducted ground- and aircraft-based studies of simultaneous auroras in both hemispheres. In the 1980s, NASA's Dynamics Explorer spacecraft snapped three images of auroral crowns around both poles, but those images were taken on different days and times and did not allow researchers to study the variations of the ovals.

Polar was launched by NASA in 1996 to study the aurora, the radiation belts, and other phenomena in the space around Earth.

Images and movies are available at:
http://www.gsfc.nasa.gov/topstory/20011025aurora.html

You can learn more about the mission by visiting:
http://istp.gsfc.nasa.gov/istp/polar

How Volcanoes Work

A Web course from Vic Camp of San Diego State University is at http://www.geology.sdsu.edu/how_volcanoes_work

See the International Space Station Overhead

spaceflight.nasa.gov has information about the International Space Station and other NASA projects.

For information on how to see the ISS in the night sky, visit:
http://spaceflight.nasa.gov/realdata/tracking/
http://spaceflight.nasa.gov/realdata/sightings/index.html

Satellite Photos on Demand

You can view satellite photos for most places in the U.S. and many places elsewhere. For urban areas, you can even specify a street address.

Home page: http://www.globexplorer.com/

Microsoft has a similar site ( http://terraserver.microsoft.com), but Globexplorer.com is easier to use.

National Geophysical Data Center

The Web site of the NGDC of the National Oceanic and Atmospheric Administration

Volcano Homepages

Monserrat volcano:
http://www.geo.mtu.edu/volcanoes/west.indes/soufriere/goft/

General information on volcanoes:
http://volcano.und.edu/
Includes a list of recent eruptions and all the eruptions that have killed more than 500 people!

Historical volcanoes:
http://www.aist.go/jp/GSJ/~jdehn/v-home.htm

NASA Observatorium on the Web

NASA's Observatorium is a public access site for Earth and space data.

NEAR Shoemaker spacecraft results on the Web

View of the Earth from the NEAR Shoemaker spacecraft as it passed the Earth in January 1998 along with earlier views of the asteroid Mathilde are available.