Apr 20 2004
From The Space Library
NASA launched its Gravity Probe B (GP-B) on a Boeing Delta 2 rocket from Vandenberg Air Force Base in California at 12:57 p.m. (EDT). NASA had designed the satellite to test two fundamental aspects of Albert Einstein's theory of relativity. According to Einstein's theory, time and space create a veritable fabric in space. When massive objects, such as Earth and other planets, distort the fabric of space, causing relatively smaller objects to move towards them, they create gravity. Einstein's theory of relativity also states that large objects twist the fabric of space around them as those objects spin on their axes. Gravity Probe A, which NASA had launched in 1975, had tested the former part of the theory, and GP-B would test both aspects. GP-B contained some of the most accurate scientific instruments ever constructed, including the most precise gyroscopes ever built. (Thomas H. Maugh II, “Einstein's Theory Rockets into Orbit,” Los Angeles Times, 21 April 2004; NASA, “The Gravity Probe B: The Relativity Mission,” http://www.nasa.gov/mission_pages/gpb/index.html (accessed 23 March 2009).
Scientist Menglin Jin of NASA's GSFC published research based on the first use of satellites to create a multiyear record of Earth's land-surface temperatures. Jin had used remote-sensing data, which satellites had collected from 1981 to 1998, to develop an 18-year record of global land-surface temperatures more comprehensive and detailed than data derived from ground-station measurements. According to the satellite data, average global land-surface temperatures had increased by 0.43°C (0.77°F) per decade, whereas ground-station data had indicated an increase of 0.34°C (0.61°F). The different findings produced different measurements because satellites measure actual land-surface temperatures ~ also known as skin temperatures ~ and ground stations measure air temperatures 6.6 feet (2 meters) above land surfaces. However, Jin also noted regional variations in temperature changes, with the central regions of North America and Asia experiencing some declines in temperatures. (NASA, “Satellites Act as Thermometers in Space,” news release 04-121, 20 April 2004; Menglin Jin, “Analysis of Land Skin Temperature Using AVHRR Observations,” Bulletin of the American Meteorological Society 85, no. 4 (April 2004): 587-600.
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