Category Archives: Physics

Flight by electrostatic repulsion

The Atlantic: Spiders Can Fly Hundreds of Miles Using Electricity. “Scientists are finally starting to understand the centuries-old mystery of “ballooning.””

“The upper reaches of the atmosphere have a positive charge, and the planet’s surface has a negative one. Even on sunny days with cloudless skies, the air carries a voltage of around 100 volts for every meter above the ground. In foggy or stormy conditions, that gradient might increase to tens of thousands of volts per meter.

Ballooning spiders operate within this planetary electric field. When their silk leaves their bodies, it typically picks up a negative charge. This repels the similar negative charges on the surfaces on which the spiders sit, creating enough force to lift them into the air.”

Link via MetaFilter.

“Are you sure there isn’t something else we could calculate?”

XKCD What if: Earth-Moon Fire Pole. “My son (5y) asked me today: If there were a kind of a fireman’s pole from the Moon down to the Earth, how long would it take to slide all the way from the Moon to the Earth? – Ramon Schönborn, Germany”

I loved this and am tempted to use it in one of my next physics lessons…

Link via MetaFilter.

A new look at the moon

NASA Goddard: Tour of the Moon in 4K. (YouTube, 4:56min)

“Take a virtual tour of the Moon in all-new 4K resolution, thanks to data provided by NASA’s Lunar Reconnaissance Orbiter spacecraft. As the visualization moves around the near side, far side, north and south poles, we highlight interesting features, sites, and information gathered on the lunar terrain.”

Link via MetaFilter.