The Physique behind the Musique

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User Note: We talked about frets on a guitar and how when you push the string into the fret board it raises the pitch on the note by changing the length of the standing wave on the string. Another interesting thing you can do is this: after plucking the open string, just lightly touch the string with your finger at the 12th fret. A sound like a bell or flute will result, as you create the second harmonic of the original standing wave. Here's what happens: by touching the string lightly while it's vibrating, you cause it to come to rest at that point you're touching. This results in another node, as shown above with the second harmonic. Touching the string at the 7th or 5th fret can make the third and fourth harmonics, with higher numbers of nodes. But if you touch the string someplace that does not result in equal segments between nodes, no harmonic is produced and the string stops. This is simply math. Guitar players can tell you all the spots where harmonics can be produced, even if they don't care too much about the math and physics behind it. (Some of them care though!)

Do You Know Why Do Cats Purr?

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One Quick Planet

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A Look Back on Planetary Discoveries

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Bees Sense the Electric Fields of Flowers

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A bumblebee visits a flower, drawn in by the bright colours, the patterns on the petals, and the aromatic promise of sweet nectar. But there's more to pollination than sight and smell. There is also electricity in the air.

Dominic Clarke and Heather Whitney from the University of Bristol have shown that bumblebees can sense the electric field that surrounds a flower. They can even learn to distinguish between fields produced by different floral shapes, or use them to work out whether a flower has been recently visited by other bees. Flowers aren't just visual spectacles and smelly beacons. They're also electric billboards.

"This is a big finding," says Daniel Robert, who led the study. "Nobody had postulated the idea that bees could be sensitive to the electric field of a flower."

Not the Most Hospitable Planet

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NASA's Hubble Space Telescope has captured an exoplanet's true color. HD 189733b has an azure color that's similar to Earth's, but there is no chance the planet holds life as it orbits extremely close to its host star.
See more at NASA

The Orbits of Potentially Harmful Asteroids

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Pictured above are the orbits of the over 1,000 known Potentially Hazardous Asteroids (PHAs). These documented tumbling boulders of rock and ice are over 140 meters across and will pass within 7.5 million kilometers of Earth -- about 20 times the distance to the Moon. Although none of them will strike the Earth in the next 100 years -- not all PHAs have been discovered, and past 100 years, many orbits become hard to predict.
See more at NASA