![\"h_butoday_706834main_20121113-solareclipse_full\"](\"\/federal\/files\/2017\/08\/h_butoday_706834main_20121113-solareclipse_full.jpeg\")
During the solar eclipse on August 21, the moon will completely block the sun\u2019s energy from reaching Earth within a 60-mile shadow that will sweep across the US, presenting scientists with a unique research opportunity. Photo courtesy of NASA.<\/em><\/p>\nOn August 21, 2017, the US will play host to a rare natural phenomenon: a complete solar eclipse<\/a> that will cut a swath from Oregon to South Carolina. And as people across the country clamor outside, eclipse glasses in hand, to see the remarkable sight of the moon blocking the sun, Joshua Semeter<\/a> and his research team will be busy using GPS sensors to gather data on the Earth\u2019s upper atmosphere.<\/p>\n Semeter, a Boston University College of Engineering professor of electrical and computer engineering<\/a>, and his team will scatter inexpensive GPS sensors in the path of the eclipse to take measurements as it moves overhead. If all goes as planned, the project will not only deepen our understanding of Earth\u2019s upper atmosphere\u2014which has the potential to disrupt technology like GPS navigation systems\u2014but will also demonstrate how cheap GPS sensors like the ones in smartphones could be used for broader \u201ccitizen science\u201d initiatives.<\/p>\n During the total solar eclipse, the Moon will turn off the ionosphere\u2019s source of extreme ultraviolet radiation: The ionosphere will go from daytime conditions to nighttime conditions. Image courtesy of NASA\u2019s Goddard Space Flight Center\/Katy Mersmann.<\/em><\/p>\n<\/div>\n During a total solar eclipse, the moon is perfectly aligned between the Earth and the sun, blocking the sun\u2019s energy from reaching the Earth within a large shadow that moves across the Earth\u2019s surface. On August 21, this eclipse shadow, which Semeter calls a \u201csupersonic sun shade,\u201d will be 70 miles across and sweep across the US at between 1,500 and 3,000 miles per hour, taking about 90 minutes to travel from coast to coast. People directly under the eclipse path will have the eerie experience of watching the sun seemingly disappear during broad daylight, while those further from the path will see the sun partially covered.<\/p>\n But this total solar eclipse is more than a rare natural phenomenon: for scientists, it is a unique research opportunity. \u201cIt\u2019s like a controlled experiment,\u201d Semeter explains. \u201cMother Nature is providing us a nice experimental environment.\u201d<\/p>\n![\"ionosphere](\"http:\/\/www.bu.edu\/today\/files\/2017\/08\/tsis_eclipse-1.gif\")
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