The Northern Lights are the result of collisions between gaseous particles in the Earth's atmosphere with charged particles released from the sun's atmosphere. Variations in colour are due to the type of gas particles that are colliding. The most common auroral color, a pale yellowish-green, is produced by oxygen molecules located about 60 miles above the earth. Rare, all-red auroras are produced by high-altitude oxygen, at heights of up to 200 miles. Nitrogen produces blue or purplish-red aurora.
Posted 7 years ago by Chrissie10 in category: beautiful   Comments (0)




Bill describes the Alignment Optical Telescope used in the Lunar Module on the Apollo missions to the moon. This telescope took star sightings which were used to align the Module's guidance system. Bill shows how the telescope used an Archimedes spiral inscribed on its eyepiece to replace the heavy motors, worm gears, and rigid tracks used in a traditional sextant -- this shaved weight from the Lunar Module and allowed it to carry more fuel.
Posted 7 years ago by Grandpa in category: space   Comments (0)



Abbott & Costello
Posted 7 years ago by batu44 in category: classic   Comments (0)


Airplane black boxes, explained nicely.
Posted 7 years ago by vanbussed in category: interesting   Comments (0)