June 10, 2013
The season for noctilucent “night-shining” clouds is arriving in the northern hemisphere, when wispy, glowing tendrils of high-altitude ice crystals may be seen around the upper latitudes, shining long after the Sun has set. Found about 83 km (51 miles) up, noctilucent clouds (also called polar mesospheric clouds) are the highest cloud formations in the [...]
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June 10, 2013
Like gravitational parking spaces, Lagrange points provide locations where spacecraft can be positioned to conduct valuable scientific observations of the Universe and perhaps someday even offer foundations for more permanent human outposts. Named after Italian-French mathematician Joseph-Louis Lagrange, who first proposed their existence in a 1772 paper, there are 5 such points within the Earth-Sun (as well [...]
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