image credit: NASA/Goddard Scientific Visualization Studio; image source; larger image

NASA Finds Thickest Parts of Arctic Ice Cap Melting Faster - May 1, 2013

The bright white region near the center of the image shows the year-round Arctic ice in 2012. To see the startling decrease since 1980, visit NASA Finds Thickest Parts of Arctic Ice Cap Melting Faster and slide the white line in the middle of the image to the right.

image credit: Solar Dynamics Observatory/NASA; image source; larger image

Sun - Apr 1, 2013

You are looking at the sun, imaged in extreme ultraviolet light (invisible to us) and shown in false color. To learn more about the sun, visit this this National Geographic article, and also this Hyperphysics page.

Notice how irregular the edge of the sun looks. Hot matter streams from the surface and returns, or occasionally some breaks off and heads out into the solar system. See From Physics Research for more information on this matter and how it moves.

This image was captured by NASA's Solar Dynamics Observatory on March 26, 2013.

(This feature was updated on April 9, 2013.)

credit: Corrie White & Igor Kliakhandler; image source; larger image

Liquid Drop Art - Feb 1, 2013

This image was created by photographer Corrie White in her basement workshop. She uses a device a device that releases several drops from the same location in rapid succession, at predetermined time intervals. For more of work, see Liquid Drop Art.

To learn about the image, see this commentary by a physicist.

To see how Corrie does it, check out her illustrated Drop Photography Guide on Flickr.

image credit: NASA; image source; larger image

Atmospheric Optics: Aurora, Northern Lights - Jan 1, 2013

This image shows a view of the Aurora Borealis captured from the International Space Station as it flew over Nebraska. For more information, see NASA Image of the Day Gallery. For a video of an aurora over the Indian Ocean, visit Aurora from ISS orbit.

To find out more about auroras, visit this Atmospheric Optics page and also the Exploratorium's Auroras: Paintings in the Sky.

image credit: STS-41B, NASA; image source; larger image

Astronomy Picture of the Day: To Fly Free in Space - Dec 1, 2012

This is astronaut Bruce McCandless, orbiting along with the Space Shuttle in 1984 as he tests his rocket pack. When he stepped outside to begin his spacewalk, why didn't he fall back to Earth? He stayed in orbit because before and after he stepped outside, McCandless and the Shuttle had the same velocity. The force of Earth's gravity bent his path into the same orbit as the shuttle; that's because the acceleration of gravity does not depend on the mass of the object being accelerated. To learn more about McCandless' spacewalk, see Astronomy Picture of the Day: To Fly Free in Space and Footloose.

Now look at the image at the top right of Felix Baumgartner beginning his supersonic skydive. When he stepped out, his balloon had been lifting him slowly in the thin stratospheric air, so his initial velocity was quite small. Gravity then pulled him back to Earth.

To learn more about gravitational orbits, visit Satellite Motion.

image credit: Ravedave; image source; larger image

How does an LCD display work? - Nov 1, 2012

Take a look at this video to see how a liquid crystal display (LCD) TV screen works. For more information, see this Case Western Reserve page.

The molecules of a liquid crystal have a tendency to line up, rather than point in random directions. For more, see these pages from Kent State University and from Simon Fraser University.

image credit: Robert J. Lang; image source; larger image

Robert J. Lang Origami - Oct 1, 2012

Traditional origami is made by folding one square piece of paper, with no cuts allowed. This piece of origami art, Scorpion varileg, Opus 379, was created by physicist Robert Lang, who left his day job to do origami full-time. You can learn about his work on Robert J. Lang Origami; in the "Science" section, you'll see how origami can be applied to problems in engineering and industrial design. For much more on Lang himself, see this New Yorker article.

image credit: NASA/JPL-Caltech/Univ. of Arizona; image source; larger image

Mars Science Laboratory--Curiosity Rover - Sep 1, 2012

As Curiosity executed its complex landing on Mars last August, another NASA probe, the Mars Reconnaissance Orbiter, captured this remarkable image. It shows Curiosity, along with its parachute, descending toward the surface. The magnified view on the right has been processed to show the details of the parachute--that's why the surface of Mars looks so dark. To learn more about this image, click here.

Since the Martian atmosphere is thin, the parachute could not slow Curiosity down enough to land safely. Retrorockets fired, and while they were still firing, the Rover was lowered to the surface by cables. Once Curiosity was on the ground, the cables were cut.

For a NASA simulation of Curiosity's landing, see Seven Minutes of Terror. And to watch the Jet Propulsion Laboratory mission controllers during the landing, don't miss control room reactions.

To see the parts of the Curiosity spread out on the Martian surface, click on this JPL image. For more images, videos, and much more, visit Mars Science Laboratory--Curiosity Rover.

image credit: NASA, JPL, USGS; image source; larger image

Impact Cratering - Aug 1, 2012

The Galileo spacecraft captured this image as it passed by the moon on its way to Jupiter. See the smooth dark areas? They were created three to four billion years ago when large volcanoes erupted and lava filled in the low-lying regions. Most of the smooth dark areas are round--these started off as enormous craters. Later, volcanoes erupted and filled them in, producing "impact basins." To find out more about how impact basins were formed, visit Impact Cratering.

In the right half of the image above, look at the region close to the edge of the shadow, where the craters stand out most clearly (that's because the angle of the sun is low). Note how the whitish regions of the moon are almost completely filled with craters, whereas the smooth, dark areas have very few. For a possible explanation, called the "late heavy bombardment," visit NASA's The Solar System's Big Bang.

image credit: F. Gauthier-Lafaye; image source; larger image

The Oklo Fossil Fission Reactors - Jul 1, 2012

This photo shows part of a natural nuclear reactor-- an underground uranium deposit where a chain reaction occurred spontaneously. In fact, such a natural reactor was predicted, beginning in 1956, and then discovered in 1972.

To find the reactor, physicists search for a deposit of uranium with a slightly lower concentration of U-235 than is found elsewhere on Earth. This U-235 deficit would be caused by the chain reaction of a small fraction of the U-235 nuclei. To learn more, visit The Oklo Fossil Fission Reactors and also this Astronomy Picture of the Day page.