Physics in Your World Features

Why Leaves Aren't Trees

Wed, 01 Sep 2010 00:00:00 EST

This is a lemon leaf that was wounded to interfere with its circulation. Note how the network of veins enabled nutrients to flow beyond the wound. - Click on the image to see a similar experiment with a ginkgo leaf. - To learn about the controversy over how these different vein structures developed, see Why Leaves Aren't Trees.

High speed photography

Mon, 16 Aug 2010 00:00:00 EST

Look at the cavity behind the falling object that made this splash--you can learn how this cavity collapses if you check out From Physics Research. - For more splash photos, see this page by Andrew Davidhazy, especially the splash sequence at the bottom. - To learn about taking pictures that stop motion, see High speed photography.

Ocean Waves

Sun, 01 Aug 2010 00:00:00 EST

The side-view photo above shows how the back of a breaking wave spills over the front. - This happens because as the wave enters more shallow water, its speed slows down, and the back of the wave overruns the front. - If the reduction in depth happens quickly, the breaking wave creates a cylindrical cavity, as in the wave above. - For more on ocean waves, see Ocean Waves and Ocean in Motion.

Tensile Structure

Fri, 16 Jul 2010 00:00:00 EST

The roof of the Denver International Airport is a tensioned fabric structure designed by Horst Berger, a civil engineer famous for his large-scale fabric projects. The photo of the Denver airport above shows double-curved "minimal surfaces" that are characteristic of soap films (see From Physics Research). - Visit Tensile Structure to learn more about this kind of construction. - See this article from Structure magazine for information about Berger's career and numerous photos of his work.

The Mystery of the Racing Rocks

Thu, 01 Jul 2010 00:00:00 EST

What could cause rocks like this--of various sizes--to slide across the desert of Death Valley and leave these long tracks? The force of the wind... the force of moving ice sheets? To find out about these possibilities, visit The Mystery of the Racing Rocks and The Mystery of the Rocks. Also check out The Sliding Tracks of Racetrack Playa for other explanations and more images.

Scientific American: What happens when an aircraft breaks the sound barrier?

Wed, 16 Jun 2010 00:00:00 EST

This is an Air Force F-22 Raptor producing a cloud as it breaks the sound barrier above an aircraft carrier. - To learn more about how the cloud forms, and see a similar photo, check out Scientific American: What happens when an aircraft breaks the sound barrier? - For more U.S. Navy pictures of these clouds see the Navy's Featured Galleries and search on “sound barrier.” To learn more, see Hyperphysics’ Sound barrier.

Star Life Cycle

Tue, 01 Jun 2010 00:00:00 EST

Our Sun is typical low-mass star in the galaxy, in the prime of its life, steadily fusing hydrogen as it will do for another five billion years. For an overview of our Sun’s and other stars' lives, check out Star Life Cycle. For more details, see Main Sequence Stars and Sol. You have probably heard that the Sun will one day expand and consume the Earth. In fact, the Sun might even expand to the orbit of Mars. Read what happens when stars leave the main sequence here.

Physics in Action: Plasma Power

Sun, 16 May 2010 00:00:00 EST

You’ve probably seen a plasma globe in class or at a novelty shop before. The glass is filled with a low-pressure, inert gas, which becomes ionized by the electric current from the central electrode to form tendrils of plasma. Understanding plasma may be the answer to our energy crisis. The tendrils of a plasma globe are the cool cousins of the fires within a star, which fusion researchers hope to reproduce on Earth. Read Physics in Action: Plasma Power to learn more about plasmas and fusion reactors.

Earth Observatory: Ash Plume across the North Atlantic

Sat, 01 May 2010 00:00:00 EST

You are looking at the Icelandic volcano plume from above as it continued to spew ash days after the initial eruption. The red region in this infrared image reveals the intense thermal emission of at least 60 megawatts. For more on the eruption, see Earth Observatory: Ash Plume across the North Atlantic. Throughout mid-April, the Icelandic volcano’s plume of ash traveled east into Europe’s airspace, grounding flights for over a week (click on the image above to see the plume’s path). You can see images of the volcano at different times in April at this NASA page. For more on volcanic activity in Iceland, check out the Physics to Go issue Dynamic Earth.

Astronomy Picture of the Day: Saguaro Moon

Fri, 16 Apr 2010 00:00:00 EST

This Astronomy Picture of the Day shows a full moon, illuminated by reflected sunlight--for more on this image, see Astronomy Picture of the Day: Saguaro Moon. But we can also see the moon by reflected Earthshine, as shown in this APOD of a new moon. Compare the pattern of the maria (the smooth dark surfaces on the moon) in these images. The moon rotates with the same part facing Earth--is that consistent with what you see? To learn more about this, and about tides in the solid Earth and moon, see this Bad Astronomy post.

Fusion Basics

Thu, 01 Apr 2010 00:00:00 EST

The sun's energy source is the fusion of protons into helium. To learn about this process, visit UCAR's Fusion Inside the Stars and Nick Strobel's The Sun's Power Source. For more on fusion, see Fusion Basics.

Feeling that Cold Wind? Here's Why

Tue, 16 Mar 2010 00:00:00 EST

This February 13 snow cover analysis confirms what much of the United States experienced this winter: even states that don’t often see snow have seen snow. Before you conclude that the Earth is cooling, check out Feeling that Cold Wind? Here's Why.

NRAO Image Gallery

Mon, 01 Mar 2010 00:00:00 EST

The radio telescope pointed toward the heavens is a powerful symbol of astronomers' quest to understand the universe. For photos of other radio telescopes at the National Radio Astronomy Observatory, see NRAO Image Gallery. Also, see the NRAO's How Radio Telescopes Work.

South Pole Foucault Pendulum

Tue, 16 Feb 2010 00:00:00 EST

These three physicists set up a Foucault pendulum at the South Pole to look for the daily rotation of the plane of swing due to the Coriolis force. With the pendulum suspended so it could freely turn in all directions, Earth rotates beneath it once per day, so in the Earth's frame of reference the pendulum is observed to swing through 360° in 24 hours. For more on this kind of pendulum, see the University of New South Wales' Foucault pendulum (This feature was updated on June 21, 2010)

Topography Along the Enriquillo-Plaintain Garden Fault, Haiti

Mon, 01 Feb 2010 00:00:00 EST

On January 12, 2010, a 7.0 magnitude earthquake devastated the nation of Haiti, especially its capital, Port-au-Prince. For an account of events as they happened, see this page from BBC News. See Topography Along the Enriquillo-Plaintain Garden Fault, Haiti for a brief explanation of what caused the earthquake. The United States Geological Survey has also produced a poster with detailed maps of the region’s tectonic activity.

The Real Levitation

Sat, 16 Jan 2010 00:00:00 EST

This frog defies gravity with diamagnetic levitation—many materials that we ordinarily think of as non-magnetic are actually diamagnetic and can be manipulated using magnetism. Learn about several kinds of magnetic levitation at The Real Levitation, and see why frogs were used here. It's easy to show that grapes are diamagnetic--just see this Exploratorium snack. For an explanation of diamagnetism, see the text at the end of the snack. You may have seen the Levitron, the spinning and levitating top, in a physics classroom before. Read about how it works here.

Lasers light up blood-flow dynamics

Fri, 01 Jan 2010 00:00:00 EST

If you shine a laser beam at a small angle to a piece of white paper, so the beam spot spreads out, you'll see what is called a speckle pattern (do this experiment with adult supervision). If you shine the beam on your skin, you'll see a different kind of pattern. The image shows how laser speckle imaging can show the difference between normal blood flow, in the finger on the left, and increased blood flow due to the warming of the skin (the figure on the right was immersed in hot water). To find out more, see Lasers light up blood-flow dynamics and also this article from the National Research Council Canada.

Andromeda Galaxy

Wed, 16 Dec 2009 00:00:00 EST

You don’t need to be a professional astronomer to take images like this one. Our closest spiral galaxy neighbor, the Andromeda Galaxy, is easily viewed through binoculars or a small telescope. You can learn more about the amateur astronomy community and techniques here. Amateur astronomers contribute to astronomy in important ways. When a mysterious object hit Jupiter in July of this year, an amateur astronomer was the first to see the impact. Read the story and see images of the event at What Hit Jupiter? You can even contribute without a telescope. Volunteers studying images of galaxies discovered a new class of galaxy called Green Peas. See the Physics at Home feature below for more information about the Galaxy Zoo website.

Maple Seeds and Animals Exploit the Same Trick to Fly

Tue, 01 Dec 2009 00:00:00 EST

How do maple seeds spiral downward so gracefully? The spinning seed creates a vortex above the leading edge that provides lift. Read a detailed explanation in this Caltech press release, where you can also listen to a podcast from Caltech researcher Michael Dickinson.

Strings, standing waves and harmonics

Mon, 16 Nov 2009 00:00:00 EST

What makes a violin sound like a violin and a flute sound like a flute? These waveforms give us a clue. They were generated using recordings of a violin (upper waveform) and tin whistle (lower waveform) playing the same note, yet the shapes of the waveforms are very different. Learn more about the qualities of musical sound here. Violins and flutes produce sound in very different ways. See how stringed instruments work at Strings, standing waves and harmonics , and compare strings with woodwinds after reading How Do Woodwind Instruments Work?.

Why The French Like Nuclear Energy

Sun, 01 Nov 2009 00:00:00 EST

This photo shows the Centrale Nucléaire de Saint-Laurent. You can find a satellite image here. Nuclear power plants generate 75% of the electricity consumed in France. Read this Frontline article to learn about France’s conversion from fossil fuels to nuclear power. For more detailed information about nuclear power in France, see this US News article. One reason other countries hesitate to adopt nuclear power is the possibility of a serious accident. Learn about the devastating accident at Chernobyl here.

X-ray Photography: Inner Beauty

Fri, 16 Oct 2009 00:00:00 EST

This graceful picture is actually the x-ray image of a nautilus shell. Read more about x-ray photography at X-ray Photography: Inner Beauty, and learn the basics behind x-ray light at this NASA site. Be sure to check out more x-ray photographs from the featured artist above here.

What Wavelength Goes With a Color?

Thu, 01 Oct 2009 00:00:00 EST

White light is actually full of color, and we can see these colors by shining white light through a prism. For a more detailed explanation, with diagrams, see this HyperPhysics page. For the correspondence of color and wavelength, see What Wavelength Goes With a Color?. Check out this page from the Sloan Digital Sky Survey for an interactive animation showing how color changes with wavelength. Look at the photo above and see whether the prism bends red light or purple light more.

Spontaneous Separation of Charged Grains

Wed, 16 Sep 2009 00:00:00 EST

These red and blue sand grains are mixed together—for now. Click the image to see what happens next. These differently colored sand grains aren’t being sorted with any outside help, they’re sorting themselves by charge. Find out why at Spontaneous Separation of Charged Grains. Check out this Physics Central article to explore granular materials further. Don’t miss the video on the research page of the standing wave made by shaken particles.

NSSL Lightning Information: Q&A about Lightning

Tue, 01 Sep 2009 00:00:00 EST

What is lightning? What causes thunder? This site from the NOAA answers these basic questions and more. For more details on rare varieties of lightning, read these press releases about ball lightning and upward lightning.