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.

image credit: ReignMan, Creative Commons; image source; larger image

Hyperphysics: Electric Guitars ` - Jun 1, 2012

This photo shows the electric guitar pickups from a Fender Stratocaster. Notice that there are three different pickup locations, and each location has a pickup (the circular dots) for every string. Each individual pickup contains a magnet, a coil, and thousands of turns of insulated wire wrapped around the magnet.

To find out how an electric guitar produces sound from a vibrating string, see Hyperphysics: Electric Guitars. To learn about the physics of vibrating strings, see this additional Hyperphysics page.

Image credit: Jupiter405; image source; larger image

Hyperphysics: Torque ` - May 1, 2012

Think about the forces on this sailboat: The force of the wind on the sail (perpendicular to the fabric of the sail), tends to rotate the boat. A force that can rotate an object is called a torque. In this case, if the torque of the wind isn't balanced, it will tip the boat over. The weight of the sailor, and also the weight of the hull that's out of the water, both create torques in the opposite sense, to balance the torque of the wind.

For more on torques, see Hyperphysics: Torque, and also this other Hyperphysics page.

image credit: CERN; image source; larger image

Hyperphysics: Electromagnetic Waves ` - Apr 1, 2012

In the photo above of a handheld citizens band radio, the metal coil is the antenna. When the radio is transmitting, the radio produces an electric current that surges back and forth in the antenna, which emits radio waves. And when the radio is receiving, radio waves induce a tiny alternating current in the antenna. The current in the antenna carries the radio signal.

For a drawing of an electromagnetic wave (radio waves are one example) see Hyperphysics: Electromagnetic Waves. To learn more about the CB antenna shown in the photo, go to this Wikipedia article and scroll down.

image credit: NASA; image source; larger image

Structure and Optical Isomerism ` - Mar 1, 2012

Have you noticed that the left hand is the mirror image of the right hand, but they cannot be superimposed? That's also true for some molecules containing carbon atoms. In the image above, the molecule on the left cannot be superimposed on the one on the right.

To learn more about such molecules, check out Structure and Optical Isomerism.

Such left-handed and right-handed molecules rotate the plane of polarization of light in opposite directions. To find out more about polarized light and this important effect, click here. Also, you can learn how Louis Pasteur explained it.

image credit: NASA, Troy Cryder; image source; larger image

Kepler Mission ` - Feb 1, 2012

The NASA Kepler observatory searches for extrasolar planets by monitoring about 100,000 stars in a small patch of sky. The observatory looks for stars that periodically dim as a planet passes in front of the star. Kepler was launched in 2009, and by January, 2012, it had already found 33 confirmed extrasolar planets and about 2300 candidates. To learn more, visit Kepler Mission, then click on "Mission Overview."

(This feature was updated on September 21, 2013.)

image credit: Carla Thomas, NASA; image source; larger image

How Things Work: Winglets ` - Jan 1, 2012

The photo shows two NASA F/A18s. The smoke streaming from the wingtip of the one on the right reveals the wingtip vortex, which increases the wing's drag. This vortex occurs because the pressure underneath the wing is greater than the pressure above the wing; this excess pressure generates a flow of air around the wingtip, creating the vortex. These vortices can trail behind the aircraft for miles, creating a hazard for following aircraft, particularly small ones.

To reduce the drag caused by these vortices, "winglets" have been added to the wingtips of some airliners, as you can see in this Wikimedia photo. To learn more, visit How Things Work: Winglets.