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Hands On Mineral Identification helps you to identify over 14,500 minerals! By M. Darby Dyar, Ph.D. See our DVD collection.
Art and science combine to show an ancient view of the Sun and Earth. Look closely to see the Sun in the center. Four images of Earth surround the Sun. Each Earth represents the different seasons, spring, summer, autumn and winter. Original art by Andreas Cellarius (1596-1665).
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(c)1995 Visual Language, All Rights Reserved

As the World Turns

In our time, scientists (and most people!) know that the constellations seem to move across the sky because the earth rotates on its axis. What, you may ask, does the turning of the earth have to do with the constellations' motion across the sky? The answer is that the earth moves in a way that makes it look as if the constellations are moving. It is a case of apparent motion. In the case of the earth and the constellations the earth rotates, with us on it, from west to east. The constellations appear to move from east to west, moving "backwards" from the real rotation of the earth. Actually, instead of saying the constellations rise we should say that the earth has rotated so that we can see different constellations. Then, as the earth continues to rotate the constellations apparently move across the sky. We now know that it is us, on earth, that have moved. As the night progresses constellations that are near or below the ecliptic "set" in the west, we know that the part of the earth we are standing on has turned so that the Earth is blocking our view of the stars that have "set".

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The Summer 2010 issue of The Earth Scientist, available in our online store, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.

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Traveling Nitrogen Classroom Activity Kit

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Gamma Ray Bursts - The Most Powerful Objects in the Universe?

In the 1960's, the United States launched some satellites to look for very high energy light, called Gamma Rays. Gamma Rays are produced whenever a nuclear bomb explodes. The satellites found many bursts...more

Galaxies

During the early 1900's, which is not very long ago, astronomers were unaware that there were other galaxies outside our own Milky Way Galaxy. When they saw a small fuzzy patch in the sky through their...more

Neutron Stars

Neutron Stars are the end point of a massive star's life. When a really massive star runs out of nuclear fuel in its core the core begins to collapse under gravity. When the core collapses the entire star...more

Spiral Galaxies

Spiral galaxies may remind you of a pinwheel. They are rotating disks of mostly hydrogen gas, dust and stars. Through a telescope or binoculars, the bright nucleus of the galaxy may be visible but the...more

White Dwarfs

When stars like our own sun die they will become white dwarfs. As a star like our sun is running out of fuel in its core it begins to bloat into a red giant. This will happen to our sun in 5 Billion years....more

Algol

What's in a Name: Arabic for "head of the demon" Claim to Fame: Represents Medusa's eye in Perseus. A special variable star that "winks" every 3 days. Type of Star: Blue-white Main Sequence Star, and...more

Sirius B - Bizarre White Dwarf Companion of Sirius A

What's in a Name: Nicknamed the "Pup" because it is the companion to Sirius, "the Dog Star" Claim to Fame: Highly compressed white dwarf remnant. Density about 50,000 times that of water. It has approximately...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA