Anti-crepuscular rays are beams of sunlight that appear to converge on a point opposite the sun. They are similar to crepuscular rays, but are seen opposite the sun in the sky. Anti-crepuscular rays are most frequently visible near sunrise or sunset. This photo of anti-crepuscular rays was taken at sunset in Boulder, Colorado. Crepuscular rays are usually much brighter than anti-crepuscular rays.<p><small><em> Image Courtesy of Carlye Calvin</em></small></p>Lunar eclipses are special events that only occur when certain conditions are met. First of all, the Moon must be in <a href="/the_universe/uts/moon3.html&edu=high">full phase</a>. Secondly, the <a href="/sun/sun.html&edu=high">Sun</a>, <a href="/earth/earth.html&edu=high">Earth</a> and <a href="/earth/moons_and_rings.html&edu=high">Moon</a> must be in a perfectly straight line. If both of these are met, then the Earth's shadow can block the Sun's light from hitting the Moon. The reddish glow of the Moon is caused by light from the Earth's limb scattering toward the Moon, which is reflected back to us from the Moon's surface.<p><small><em>Image credit - Doug Murray, Palm Beach Gardens, Florida</em></small></p>The massive 9.0 magnitude <a href="/earth/geology/quake_1.html&edu=high">earthquake</a> off of Honshu, Japan on <a href="/headline_universe/march112011earthquaketsunami.html&edu=high">11 March 2011</a> generated a <a href="/earth/tsunami1.html&edu=high">tsunami</a> that exceeded 10 meters on the coast near the epicenter. This image shows model projections for the tsunami wave height in cm which are in good agreement with the observed waves.<p><small><em><a href="http://blogs.agu.org/wildwildscience/files/2011/03/680_20110311-TsunamiWaveHeight.jpg">NOAA Tsunami Wave Height Projections image</a></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=high">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>According to a Greek legend, the sea god Poseidon placed the figure of <a href="/the_universe/Constellations/circumpolar/cassiopeia.html&edu=high">Cassiopeia</a> among the stars. It is said that Cassiopeia has a ridiculous upside-down position to punish her for having been pretentious.<p><small><em>Image courtesy of 1995 Visual Language (c). All rights reserved.</em></small></p>An artist's rendering of the moment of impact of a massive <a href="/our_solar_system/meteors/meteors.html&edu=high">meteorite</a> at the end of the Cretaceous (at the end of the <a href="/earth/geology/hist_mesozoic.html&edu=high">Mesozoic Era</a>). Many scientists have concluded for decades that a meteorite four to six kilometers in diameter impacted the Earth at this time, resulting in a <a href="/earth/past/KTextinction.html&edu=high">mass extinction of dinosaurs</a> and many other life forms.  Recent research suggests that perhaps <a href="/headline_universe/olpa/chicxulub.html&edu=high">massive volcanic eruptions</a> may be been responsible for the extinction.<p><small><em>Courtesy of Don Davis, NASA</em></small></p>

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Podcasts from the National Science Foundation

Geologists at Harvard University found evidence that sea ice extended to the equator up to 716.5 million years ago. Listen to this and other podcasts ...Read more
Brought to you by NSF

CMMAP - Studying Clouds and Climate

Clouds are an important part of Earth's weather and climate. Scientists use computer models to study our planet's climate ...Read more
Brought to you by CMMAP

Physics of Space Weather

The science of physics plays a key role in many space weather phenomena. Charged particles, magnetic fields, forces and motion, and the electromagnetic spectrum are all part of space weather ...Read more
Brought to you by CISM

Happenings During the Paleozoic Era

The Cambrian period, at the beginning of the Paleozoic, was the first time that multicellular life forms flourished on Earth. By the end of the Paleozoic, and beginning of the Mesozoic, all the continents ...Read more

Saturn

Saturn, the second largest planet in our Solar System, is famous for its magnificent rings. This gas giant has many moons and is the 6th planet from the Sun ...Read more

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Rock Eating Bacteria Found at the Bottom of the Sea

Seafloor bacteria on ocean-bottom rocks are more abundant and diverse than previously thought, appearing...Read more

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