Physics in Your World Features

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.

In Medieval Architecture, Signs of Advanced Math

Sun, 16 Aug 2009 00:00:00 EST

The Muslim design on the left dating from the 1300s may be more than a simple decoration. The tiles on the right show how basic shapes were used to create non-repeating patterns in a process not understood by Western mathematicians until the 1970s. Read these New York Times and Discover Magazine articles to learn more. See more pictures here. Also, if you click on "Peter J. Lu" above, and then scroll down, you can watch the Flash Video of his Harvard Physics Department colloquium on this work. [This feature was updated on August 17, 2009.]

Earth Observatory: Sarychev Peak Eruption, Kuril Islands

Sat, 01 Aug 2009 00:00:00 EST

This image was captured by astronauts on the International Space Station early in the June 12, 2009 eruption of Russia’s Sarychev Peak. See Earth Observatory: Sarychev Peak Eruption, Kuril Islands for a detailed explanation and quality animation of the event. Also, see this Bad Astronomy post for a video of the eruption at different speeds.

HyperPhysics: Coriolis Force

Thu, 16 Jul 2009 00:00:00 EST

You can create an image like this by dripping paint onto a rapidly spinning turntable. - The outward movement of the paint illustrates the centrifugal force. - The slight curvature of the outward-moving lines illustrates the Coriolis force (the turntable was spinning clockwise). - Learn about the Coriolis and centrifugal forces at HyperPhysics: Coriolis Force.

HyperPhysics: Blue Sky and Rayleigh Scattering

Wed, 01 Jul 2009 00:00:00 EST

The brilliant blue color of the sky is due to scattering by molecules in the atmosphere. - Visit HyperPhysics: Blue Sky and Rayleigh Scattering for detailed explanations about why the sky is blue and an overview of different kinds of scattering. - See this University of California article to learn why the sky appears blue, not violet.

1054 Supernova Petrograph

Tue, 16 Jun 2009 00:00:00 EST

This Anasazi painting at Chaco Canyon may be a depiction of the 1054 supernova, which we see today as a supernova remnant, the Crab Nebula. - Learn about the details of the painting and the 1054 supernova at 1054 Supernova Petrograph. - Find out more about the Crab Nebula from this Messier catalogue entry. - Check out this overview of how the 1054 supernova was recorded around the world. - See this Tata research page to learn how astronomers know the “guest star” from 1054 and the Crab Nebula are the same object, and for more information about worldwide reactions to the 1054 supernova.

Ship Tracks South of Alaska

Mon, 01 Jun 2009 00:00:00 EST

These tracks were made south of Alaska when water vapor condensed on particles in ships' exhausts. -- Click on the image for the same scene in false color, showing the relative size of the particles: yellow-orange indicates small particles; lavender-purple, large ones. -- To find out how the particle size affects the intensity of the scattered sunlight, visit Ship Tracks South of Alaska. -- To learn about the effects of aircraft contrails on Earth's climate, see this Physics in Your World.

A Tether in Space

Sat, 16 May 2009 00:00:00 EST

The white spherical object is a 1.6 m diameter satellite, part of the Tethered Satellite System-1, launched in 1992 from a boom extending out from the bay of the Space Shuttle. -- To learn more, visit APOD's A Tether in Space. -- To find out how the test turned out, see The Space Tether Experiment from The Exploration of Earth's Magnetosphere. -- Clearly a light, strong material is needed for the tether.

Impulse (When Push Comes to Shove)

Fri, 01 May 2009 00:00:00 EST

The idea of the airbag is to increase the time of deceleration of the head and upper body and correspondingly decrease the force required. To learn more, visit Impulse (When Push Comes to Shove). -- Notice the photo of the steering wheel, bent by the large force that it experienced; imagine the effect of the equal and opposite reaction force on the crash test dummy's head. -- Check out these crash test videos.

BBC News: Italy's Earthquake History

Thu, 16 Apr 2009 00:00:00 EST

This image shows the U.S. Geological Survey Shake Map of the April 6, 2009 Italy earthquake. According to the color code, at the epicenter, indicated by the star: -- the acceleration of the ground was from 14% to 26% of the acceleration of gravity -- the speed of the ground was from 12 cm/sec to 23 cm/sec. -- See the whole Shake Map . -- For a brief history of earthquakes in Italy, see BBC News: Italy's Earthquake History.

Chronoscapes

Wed, 01 Apr 2009 00:00:00 EST

In the hands of artist Pery Burge, spreading inks become art. To learn more about the process, visit Chronoscapes.

Ancient Observatories: Chaco Canyon

Mon, 16 Mar 2009 00:00:00 EST

This photograph shows the famous Sun Dagger at the Chaco Canyon National Monument in New Mexico, USA, a product of the Pueblo culture around the end of the first millennium A.D. -- The dagger passed through the center of the spiral at the summer solstice, the longest day of the year. -- Sadly, in 1989 one of the huge rock slabs that formed these shadows changed its position, possibly due to the effects of visitor activity at the site, so the Sun Dagger is a thing of the past. -- To find out more, visit Ancient Observatories: Chaco Canyon , The Solstice Project, and the National Park Service's Chaco Culture. [This feature was updated on 3/26/09.]

Newton's Third Law of Motion

Sun, 01 Mar 2009 00:00:00 EST

The woman's hand exerts a force that can break a board. But what about the force that hurts her hand? -- That's the reaction force, equal and opposite to the force she exerts. The faster she moves her hand, the more boards she can break, but also the more damage she can do to herself. -- To find out how she learned to break boards, visit Kung Fu Science. -- For examples of reaction forces, see Newton's Third Law of Motion from The Physics Classroom.

Astronomy Picture of the Day: Zodiacal Light

Mon, 16 Feb 2009 00:00:00 EST

This image, taken in New Mexico just before dawn, shows the Zodiacal light, which is scattered from particles of solar system dust concentrated in bands in the ecliptic plane. -- When this image was captured, the ecliptic was nearly vertical. -- These dust particles orbit the sun. -- To learn more about the image, see Astronomy Picture of the Day: Zodiacal Light.

Polarization and Interference Colors

Sun, 01 Feb 2009 00:00:00 EST

-- For this photo, the protractor was backlit, and the light passed through two crossed polarizers, one behind the protractor and one in front. -- Stress within the protractor affects the phase of the polarized light, producing cancellation of some wavelengths and reinforcement of others, and the result is the pattern of colors that you see. -- Materials like the clear plastic of the protractor are called birefringent. To learn more about them, see the Hyperphysics pages Polarization and Interference Colors and Birefringent Materials.

Multiple Reflections

Fri, 16 Jan 2009 00:00:00 EST

This is the famous "Mirrored Room" at the Knox-Albright Art Gallery. If you look closely, you can see: -- a table and chair, which are covered with mirrors, like the walls -- the hood around the camera that was used to take the picture. To learn more about multiple reflections, visit Multiple Reflections, and also see the simulation Multiple Reflections from Two Plane Mirrors.

Smithsonian Education - Minerals, Crystals, and Gems

Thu, 01 Jan 2009 00:00:00 EST

-- This is a crystal of fluorite (calcium fluoride), the official state mineral of Illinois. To find out more about it, visit its Wikipedia entry. -- For more on crystals, how they form, and how they are cut into gems, visit the Smithsonian's Minerals, Crystals, and Gems. While you're there, you can learn about the Hope Diamond.

Exploring the Moon: Apollo 8 Mission

Tue, 16 Dec 2008 00:00:00 EST

This month we celebrate the 40th anniversary of Apollo 8, the first manned-mission in orbit around the Moon. To learn more about the famous "Earthrise" photograph, visit Exploring the Moon: Apollo 8 Mission.

Hyperphysics: The Cloud Chamber

Mon, 01 Dec 2008 00:00:00 EST

The thick tracks in this Wilson cloud chamber were made by alpha particles--helium nuclei--emitted by thorium atoms in the metal rod at the bottom of the image. To see the effect of a stronger alpha source, visit Alpha Particle Tracks from Nuffield's Practical Physics.

Detecting Fluorescence: Green, Yellow, Orange, and Red in the Deep Sea

Sun, 16 Nov 2008 00:00:00 EST

To attract prey, this jellyfish fluoresces in the blue light of the ocean. In fluorescence, atoms or molecules absorb light at one wavelength and re-emit light at a longer wavelength, which corresponds to a lower energy. -- To find out how fluorescence is functional for ocean organisms, visit Fluorescence: the Secret Color of the Deep. -- To learn how fluorescence in the ocean is investigated, see Detecting Fluorescence: Green, Yellow, Orange, and Red in the Deep Sea .