image credit: © Felice Frankel, from "Envisioning Science, the Design and Craft of the Science Image;" larger image

Ferrofluids ` - Dec 1, 2011

Physics becomes art in Felice Frankel's photo of a ferrofluid with permanent magnets underneath. In a ferrofluid, a region of approximately constant magnetic field produces a pattern of spikes.

A ferrofluid is a concentrated suspension of nanometer-sized magnetic particles. To learn more, see the Physics Central feature Ferrofluid Fun.

image credit: Shaddack, Wikimedia Commons; image source; larger image

Relativity Powers Your Car Battery ` - Nov 1, 2011

If you own a car with a lead-acid battery, you might be interested to know that 80% of the voltage comes from Einstein's theory of special relativity. Lead works so well in storage batteries because its atom has a large nucleus, and the innermost electrons rotate at a significant fraction of the speed of light, bringing relativity into play. To learn more, visit this American Physical Society site.

(This feature was updated on March 3, 2014.)

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

What is a contrail and how does it form? ` - Oct 1, 2011

The contrails in the photo above were generated by an Air Force C-141 Starlifter. Jet fuel is a mixture of hydrocarbons, which burns to produce carbon dioxide and water vapor. The water vapor condenses upon cooling to form small water droplets--the contrail--which is essentially a cloud. To  learn more, check out What is a contrail and how does it form? from the National Weather Service. Like clouds, contrails can affect global warming--to  find out how, see From Physics Research and Worth a Look.

Image credit: HawaiianMama, Wikimedia Commons; image source; larger image

HyperPhysics: Global Positioning Satellites ` - Sep 1, 2011

The image shows a Global Positioning System (GPS) receiver that pinpoints a cyclist's location to an accuracy of about 10 m. The receiver analyzes radio signals from several GPS satellites, each containing an atomic clock accurate to about one second every 30,000 years. For more on GPS, see HyperPhysics: Global Positioning Satellites and also this NASA site.

Image credit: Axel Rouvin, Wikimedia; image source; larger image

Nonlinear Geoscience: Fractals ` - Aug 2, 2011

Look up at the clouds and look at the patterns you see. It turns out that if you zoom in or out, you still see the same patterns, a property mathematicians call self-similarity.

In Nonlinear Geoscience: Fractals, notice how the streambed in the photograph has divided again and again, showing the same structure at different scales. The streambed and the sky are only two examples of the many fractals found in nature.

Image credit: NASA; image source; larger image

What is Microgravity? ` - Jul 1, 2011

The photo shows astronauts training in a NASA plane that flies in a parabolic arc--the same path a projectile follows--so they can experience free fall, just as they will in space. To find out what these flights are like, check out the Reduced Gravity: Vomit Comet Blog. To learn about gravity in space, see the first page of Fluids in Space, also from Physics Central, and What is Microgravity? (but don't be fooled by the title--there is plenty of gravity in space around the Earth, and it keeps satellites in their orbits).

image credit: Amy Snyder, © Exploratorium; image source; larger image

Chaotic Pendulum ` - Jun 8, 2011

The photo above shows a three-way double pendulum at the Exploratorium, and you can see a video about this exhibit at Chaotic Pendulum. (A double pendulum is essentially one pendulum hung underneath of another--see this diagram.) In general, the motion of this pendulum is chaotic.

image credit: © 2011 Theodore Gray periodictable.com (used with permission); image; larger image

Fiestaware ` - May 12, 2011

The distinctive color of orange-red Fiestaware, which was popular in the 1930s and 1940s, is produced by uranium oxide in the glaze. For more information, see Fiestaware, and for a list of similar items, see Radioactive Consumer Products (the two websites referenced here are from Oak Ridge Associated Universities).

image credit: Jim Krider, Physics Instructional Resource Team, Arizona State University; larger image

Flame Tube ` - Apr 12, 2011

In the classic Ruben's tube demonstration, the tube containing the Bunsen burner gas has a speaker at each end that emits a pure tone. The tones have the same frequency and are in phase. The frequency of the tones is selected to set up a large standing wave inside the tube, and the resulting pressure distribution produces the pattern of flames. Read more on standing waves here.

image credit: Wikimedia Commons; image source; larger image

3C273 - Quasar in Virgo ` - Feb 1, 2011

In a telescope, object 3C273 will look like an ordinary star to you--it looked like an ordinary star to astronomers until the 1950s, too. In fact it is a quasar, or quasi-stellar radio source. These objects might look like stars, but they emit radio noise and are very distant--in the case of 3C273 above, nearly 2.5 billion light years away.

3C273 is bright enough to be seen with a very good backyard telescope. If you can find it, you can look back billions of years in time. Read 3C273 - Quasar in Virgo to learn how to find it in the night sky.