image credit: Zhong You and Kaori Kuribayashi; image source: image not available online; larger image

Fold Everything ` - Oct 1, 2012

This photo shows a stent, a small metal cylinder inserted into a diseased artery to open it up. To be inserted, the device must be collapsed, and origami folding provides a way to do that. The stent is shown in the photo above, both folded and unfolded.

Airbags are folded carefully to fit into small volumes inside an automobile. To find out how the mathematics of origami produces the folding design, visit Airbag Folding.

For a short National Geographic article on origami applications, see Fold Everything.

image credit: NASA/JPL-Caltech/MSSS; image source; larger image

Mars Science Laboratory Mission ` - Sep 1, 2012

The image above shows a view from Curiosity's landing site inside Gale Crater; the elevated area in the distance is the crater wall. For more information on this image, visit Wall of Gale Crater. To learn more about this crater, visit The Strange Attraction of Gale Crater.

A different Curiosity image shows distinct layering in Mount Sharp, located in the middle of Gale Crater. Curiosity will travel to Mount Sharp to investigate the geology there.

To learn more about Curiosity's mission on Mars, visit Mars Science Laboratory Mission.

image credit: NASA; image source; larger image

The Apollo Program: Apollo 15 ` - Aug 1, 2012

You're looking at the vicinity of NASA's Apollo 15 landing site, located almost in the center of the image, on the lava surface at the eastern edge of Mare Imbrium (click for a lunar map to find it). Naturally a smooth impact basin would be the best place for the lunar lander to put down. You can also see part of the Apennine mountain range in the image above.

The Apollo Program's mission was to explore and map the moon. To learn more about Apollo 15, see The Apollo Program: Apollo 15.

Do you see the squiggly line running up and down in the middle of the image? It's actually a trench called the Hadley Rille. Here is a video of Apollo 15 landing, with the Hadley Rille in the background. On a lava-filled basin, and with a mountain range and a rille so close, the astronauts could explore plenty of lunar geology.

image credit: U.S. Department of Energy; image source; larger image

Radioisotope Power Systems ` - Jul 1, 2012

The glowing pellet is an oxide of plutonium, the fuel for a radioisotope thermoelectric generator (RTG). It is photographed in the light it emits, because its radioactive decay produces considerable heat. The RTG converts this heat into electricity.

RTGs power the spacecraft that visited Mars, Jupiter, and Saturn--and the RTG keeps working over decades. To find out more, visit Radioisotope Power Systems.

image credit: NC State Department of Physics; image source; higher-res image/

The Invention of the Electric Guitar ` - Jun 1, 2012

The photo shows a modern electric guitar prototype developed in 1940 by a physicist at North Carolina State University. Check out this webpage to learn more.

Read about the development of the electric guitar in The Invention of the Electric Guitar.

(This feature was updated on September 24, 2013.)

image credit: U.S. Air Force; image source; larger image

Newton's 3rd Law ` - May 1, 2012

What is the purpose of the small rotor on the back of this helicopter? In fact, it's needed because of Newton's third law--for every action force there is an equal and opposite reaction. The helicopter puts a force on the main rotor shaft to make it turn, and the rotor shaft puts an equal and opposite force back on the helicopter. For an example of reaction forces, see this video.

This reaction force creates a torque that, by itself, would make the helicopter spin in the opposite direction as the rotor. To counter this torque, the small rotor on the tail creates an opposing torque, so the two are balanced.

(This feature was updated on September 22, 2013.)

image credit: CERN; image source; larger image

X-rays from free electrons ` - Apr 1, 2012

The spiral track above was made by an electron moving in a magnetic field. Since motion along a curved path requires a force perpendicular to the direction of motion, the electron is accelerated. Accelerated charges radiate electromagnetic waves, so the electron loses energy and spirals inward. To learn more about this process, see X-rays from free electrons.

image credit: A. Mugarza, C. Krull, S. Stepanow, G. Ceballos, and P. Gambardella, CIN2; image source; larger image

Electronic Handedness in Copper-Silver Combo ` - Mar 1, 2012

Notice how the two images above have opposite handedness? These images show electronic properties of a small layer of copper on top of silver, but neither silver nor copper have any handedness themselves. To learn more, visit this American Physical Society webpage.

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

image credit: D. Lafreniere, R. Jayawardhana, M. van Kerkwijk (University of Toronto); image source; larger image

APOD: Companion of a Young, Sun-like Star Confirmed ` - Feb 1, 2012

You are looking at the first telescopic image of a confirmed planet in orbit around a Sun-like star. The young planet is still quite warm, and therefore radiating considerable energy, which makes it relatively easy to detect. To learn more, see APOD: Companion of a Young, Sun-like Star Confirmed.

image credit: Odile Labbe, ONERA; image source; larger image

Wing Vortices ` - Jan 1, 2012

This image from ONERA, the French aerospace lab, shows a simulation of the wake of an aircraft, looking along the direction the aircraft is moving. The spirals of moving air are called wingtip vortices. To learn more, visit this animation from the Smithsonian Institution's How Things Fly.

Also, compare the image above with this photo (from PTG Issue 33, in the Archives) showing the pattern of smoke released behind the wingtip of a crop-duster. How well did the simulation model the crop-duster wake?

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