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Have you ever gone out at on a cloudless night, when there is no bright Moon in the sky or city lights to obscure your view, and been blown away by the astonishing number of stars in the sky? Probably for as long as people have been around, to look up into the sky, we have wondered what the many spots of light in the sky mean. Thousands of years ago, the earliest civilizations observed the heavens. Early man observed the heavens because the Sun, Moon and stars gave indication of coming seasons to farmers and hunters. The sky aided in navigation especially for nomads and sailors. And many ancient civilizations thought the sky gave signs of life, war, earthquakes, the fate of kingdoms...and more. Since the invention of the telescope, we have been able to "see" further away and study stars and galaxies, as well as many of the more mysterious objects in our Universe.
A near-Earth <a href="/our_solar_system/asteroids.html&edu=elem">asteroid</a> - named 2012 DA14 by astronomers – passed within 17,200 miles from Earth on February 15, 2013. On closest approach at about 1:25 p.m. CST on February 15, although it was within the orbit of the <a href="/earth/moons_and_rings.html&edu=elem">Moon</a> and even geosynchronous <a href="/space_missions/satellites.html&edu=elem">satellites</a>, it didn't strike Earth!  Find out more from <a href="">NASA</a>! Fragments of a meteorite hit Chelyabinsk, Russia on 2/15/2013 <a href="">injuring over 500</a>. Learn about <a href="">meteors and meteorites</a>.<p><small><em>NASA/JPL-CalTech</em></small></p><a href="/the_universe/Cosmology.html&edu=elem">Cosmology</a> is the study of the overall structure of the universe.  The observable universe is the universe that reveals itself through <a href="/physical_science/magnetism/em_radiation.html&edu=elem">electromagnetic radiation</a> that can be detected on Earth.  Astronomers observe some rather interesting and perplexing structure in the <a href="/the_universe/Current.html&edu=elem">current universe</a>.  This image shows the results of a computer simulation depicting a large chunk of our universe.<p><small><em>Image courtesy of G. L. Bryan, M. L. Norman, UIUC, NCSA, GC3</em></small></p>Many cultures have seen distinctive patterns, called constellations, formed by the stars in the heavens. Constellations are usually comprised of bright stars which appear close to each other on the sky, but are <a href="/the_universe/Constellations/constellations3.html&edu=elem">not necessarily close</a> to each other in space. Many societies associated patterns among the stars  with <a href="/mythology/stars.html&edu=elem">gods and goddesses</a> or stories from their culture.<p><small><em>Image: (c)1995 Visual Language, All Rights Reserved</em></small></p>As a star like our sun is running out of fuel in its core it begins to <a href="/sun/fate.html&edu=elem">bloat into a red giant</a>. This will happen to our sun in 5 billion years. Then after a few million years the outer layers of the red giant will begin to puff off, leaving behind only the dead core of the star  - a <a href="/the_universe/WD.html&edu=elem">white dwarf</a>. A typical white dwarf is very dense and hot, and is about the <a href="/the_universe/40Eridanus.html&edu=elem">size of the Earth</a>.A spoonful of white dwarf material on Earth would weigh as much as a car. Strange, isn't it?<p><small><em>Image courtesy of NASA, STScI.</em></small></p>Stars don't last forever. Occasionally, a star bigger than our Sun will end its life in a huge explosion, called a <a href="/the_universe/supernova.html&edu=elem">supernova</a>. The center of the star collapses in less than a second, blowing away the outer layers of the star.  There are many beautiful images of supernova remnants, the expanding shell of gas made up of the outer layers of the original star. This image is the Vela Supernova Remnant.<p><small><em>Image courtesy of the Anglo-Australian Observatory/Royal Observatory Edinburgh</em></small></p>There are over 900 <a href="/the_universe/uts/megalith.html&edu=elem">rings of stone</a> located in the British Isles. The most famous of these stone rings is of course, <a href="/the_universe/uts/stonehenge.html&edu=elem">Stonehenge</a>.    The stones of Stonehenge were put in place between 3,000 B.C and 2,000 B.C. by neolithic people.Some speculate that the site was built as a temple of worship of the ancient Earth deities. Some say it was used as an <a href="/the_universe/uts/stonehenge_astro.html&edu=elem">astronomical observatory</a> of sorts. Still others say it was a burial ground.<p><small><em>  Image courtesy of Corel Photography.</em></small></p>

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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