image credit: Robert Rhode (Wikimedia Commons); image source; larger image

Greenhouse Effect - May 1, 2013

This is the famous "Keeling curve" of carbon dioxide concentration in the atmosphere versus time, from about 1958 to about 2007, measured in Hawaii. Notice that the rate of warming (indicated by the slope of the blue line) increases slowly but steadily over time.

Carbon dioxide is an important greenhouse gas. Greenhouse gases absorb the infrared radiation given off by Earth. This absorbed radiation is promptly re-emitted in all directions; much of it returns to Earth, raising the temperature of its surface by a substantial 33°C.

Carbon dioxide is produced by burning fossil fuels. As more countries industrialize, the use of fossil fuels increases, as does the amount of carbon dioxide in the atmosphere

The inset in the graph shows the annual cycle: For six months, plant photosynthesis absorbs carbon dioxide from the atmosphere, and the curve goes down; then, for the next six months, the decay of dead plants returns carbon dioxide to the atmosphere, and the curve goes up.

To learn more, visit Greenhouse Effect and also this UCAR page.

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

Solar Flares--Solar Prominences - Apr 1, 2013

This image of a solar prominence was captured in extreme ultraviolet light on December 31, 2012. The prominence is ionized gas--charged particles, with electrons stripped from atoms, which move due to forces from magnetic fields.

To learn more about solar prominences, visit Solar Flares--Solar Prominences.

To see a different solar prominence, with an image of Earth added to show the scale, click here.

image credit: Xiaodong Chen and Vigor Yang (School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA); image source; larger image.

APS Division of Fluid Dynamics 2012 Gallery of Fluid Motion - Feb 1, 2013

This image is a high-resolution computer simulation of the head-on collision of two tiny drops, one moving up and one moving down. The drops approach each other with a high velocity, so there is considerable energy in the collision. For more information, see this description.

The diameter of each drop is only about twice the thickness of human hair. Imagine how hard it would be to do this experiment and see what actually happens.

Also, compare the image at left, and also this additional Corrie White image, with the simulation above: Note how the edge of the disk and film break up into drops in a similar way.

image credit: NASA/Goddard Space Flight Center Visualization Studio; image source; larger image

NASA's IMAGE Satellite View of Aurora Australis from Space - Jan 1, 2013

You are looking at a composite: The image of the southern lights (Aurora Australis) is superimposed on a "Blue Marble" image of Earth; both images were captured by satellite. Click on NASA's IMAGE Satellite View of Aurora Australis from Space to see a video of this aurora.

Notice that the Aurora occurs at about the same latitude. That's because the Aurora's green light is produced by charged particles from the sun, which collide with oxygen atoms in the atmosphere. These charged particles follow the Earth's magnetic field lines. Where these lines come close together, near the two poles (like the field lines of a bar magnet), the Aurora can occur. For more on this process the Astronomy Notes.

image © Red Bull GmbH; image source; larger image

Mission to the Edge of Space - Dec 1, 2012

The figure at the bottom of the photo is Felix Baumgartner, shortly after he jumped from an altitude of 39 kilometers (24 miles). There, the thin atmosphere produces very little air resistance, so he was almost in free fall (in free fall, the only force acting on an object is gravity). He accelerated rapidly, broke the sound barrier, and went on to about Mach 1.2 (20% above the speed of sound).

For more detail on the jump, visit mission timeline. To learn more about the Stratos project, see Mission to the Edge of Space.

Image ©2011 American Physical Society; image source; larger image

Physics Images: Bent-Core Liquid Crystals - Nov 1, 2012

Here is an image of a "bent-core liquid crystal"-- to learn more about these substances, visit Physics Images: Bent-Core Liquid Crystals.

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.