photo credit: Fjellanger Widerøe A.S.; image source

Oceanography: Waves

This photo (hi-res image) shows water wave diffraction near the northern coast of Norway. For more on coastal waves, see Oceanography: Waves, especially the sections "Waves entering shallow water" and "Wave reflection."

(This feature was updated on July 7, 2013.)

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PhET Simulations: Lunar Lander

Security note:
Once you have clicked on the "simulation" link below, be sure to read the Java Security Advisory before running the simulation: To do that, click the "Read now" button on the yellow band near the top of the PhET page.

Try your hand at touching down on the moon with PhET Simulations:  Lunar Lander. As you play this game, you'll build an intuitive understanding of Newton's Laws.

To learn more about Apollo 11, the first moon landing, visit Apollo 11 at 35.

(This feature was updated on May 5, 2013.)

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image credit: NASA, H. Bond and E. Nelan (STScI), M. Barstow and M. Burleigh (Univ. of Leicester), and J. Holberg (Univ. of Arizona); image source

White Dwarf Stars

This Hubble image (hi-res version) shows the star Sirius and its companion, a collapsed star called a white dwarf. In x-rays, the relative intensities of Sirius and the companion are reversed--see Sirius A and B. For more on white dwarfs, see White Dwarfs & Planetary Nebulas from the Chandra X-ray Observatory and SolStation's Sirius 2.

Astronomy Picture of the Day

Check out these image collections in astronomy and astrophysics:

• The NASA/Smithsonian High Energy Astrophysics Picture of the Week
• NASA's Astronomy Picture of the Day (APOD)
Worth a Look Archive