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 from the American Physical Society's Physics Central. 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.

Image credit: Andrew Davidhazy, Rochester Institute of Technology

Wikipedia: Shadowgraph - Dec 1, 2010

This is a Schlieren image, which reveals differences in the density of air above the candles. To find out more about these images, visit Wikipedia: Shadowgraph, and to learn how to make one, visit Schlieren Photography Principles.

- Making one of these images is more complicated than making a shadowgraph, such as the image in From Physics Research.
- For more high-speed images by Andrew Davidhazy, visit this page.

image credit: Marco Nero (lasers by Wicked Lasers); image source; larger image

Physics 2000: Lasers - Nov 1, 2010

Lasers don't come only in red: you can buy handheld lasers that produce light in various wavelengths in the visible spectrum. Remember, lasers can be dangerous--so get adult supervision for any laser experiment you try.

- To learn how lasers work, check out the University of Colorado site Physics 2000: Lasers with several helpful applets.
- For some information on the differences between lasers that produce different colors, see this Laser Colors Q & A from the University of Illinois.
- And to learn about a laser that produces infrared light, see the feature at right on quantum cascade lasers.

image credit: Eurico Zimbres, Wikimedia Commons (taken at the San Diego Natural History Museum); image source; larger image

What Really Killed the Dinosaurs? - Oct 16, 2010

Dig into rocks around the globe at the right depth and you may find a thin layer like the one pictured above, a geological hint about our planet's past. This sedimentary layer contains much more iridium than the surrounding layers, and the element iridium is rarely found on Earth but plentiful in rocks in space. For this reason, some scientists believe that there was an enormous meteorite impact that covered the planet in its dust.

The iridium layer lends credence to the impact catastrophe theory that dinosaurs of the late Cretaceous were killed by a meteorite impact and its ensuing planet-wide effects. However, new evidence suggests the crater thought to be responsible due to its iridium content (pictured at right) happened before the mass extinction. See What Really Killed the Dinosaurs? for more on the debate.

image credit: William W Nazaroff (2005); image source; larger image

The Geothermal Power Plant - Oct 1, 2010

The above photo shows the Nesjavellir geothermal plant in Iceland, which produces power and hot water for the towns surrounding it. To learn more about how the plant works, see this site from the University of Rochester.

Iceland sits astride the mid-Atlantic ridge, where two tectonic plates are moving apart at about two and a half centimeters per year. Magma--molten rock--wells up in between the plates and heats the bedrock under Iceland. The bedrock heats the groundwater that the plant pipes to the surface to make a mixture of steam and brine (salt water).

For more on tectonic plates and Iceland, including a volcanic island nearby that was formed in 1963, see Physics to Go, Issue 55.