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Continental drift: the final proof
1980s SHUTTLE ACCIDENT
A major malfunction astro-heroes. America needs these “all-American” symbols. Her armies are frustrated by faceless hijackers, her diplomats impotent to bring peace and disarmament, and the triumphs of her scientists are incomprehensible. But every time a shuttle rose from Cape Canaveral in Florida, a rapt public was reminded that there are still a few things Americans can do better, by damn, than anyone else. Mortal as they are, the astronauts are the targets onto which ordinary folks imprint their ideals. Christa McAuliffe, the schoolteacher in space, was the first “ordinary” citizen (besides two congressmen) to ride along. Her death is particularly painful because her voyage showed that plain folks can become heroes too. 6 FEBRUARY 1986
All seven crew members died when Challenger exploded on 28 January 1986
NASA/AP
SPACE travel is no longer routine. For a brief time, the space shuttle had us believing that perhaps it was. Now we can drape ourselves in the certitude of hindsight and chide NASA for running hell-bent, it now seems, to put the butcher, baker and candlestick maker into orbit. But will the public demand that NASA curtails its exploration of space? Will we put robots rather than flesh and blood into orbit? Of course not. Ten people have died aboard space capsules in over half a hundred flights since the US fell in love with spaceships. Ten times that number die in traffic accidents every day. NASA’s safety record has been admirable compared to the most daring earthly pursuits, and the only other game in town with which to compare it, the USSR, is neither as ambitious nor as open to scrutiny. In return for spending billions of dollars, America got a growing corps of
EARTH SCIENCE
CONTINENTAL DRIFT: THE FINAL PROOF NASA’s scientists have released the first direct measurements of continental drift. They show that the Atlantic is gradually widening, and that Australia is receding from South America and heading for Hawaii. The crustal dynamics project, run from NASA’s Goddard Space Flight Center, uses two techniques to measure the separation of places on the Earth to an accuracy of a few centimetres. Around the world, there are more than 20 stations equipped for one or both. Relative motions of the stations are expected, according to plate tectonics, the current theory of continental drift. This says that the Earth’s crust is made of several plates moving about the planet, and most of the major plates carry a continent on their backs. The exception is the large plate that floors the Pacific Ocean; fortunately for the crustal dynamics team, instruments can be sited on the island of Hawaii to monitor this plate. The first technique is very long baseline interferometry. Astronomers measure the distance between two radio telescopes, both looking at the same distant quasar, by measuring the difference in time between the signals being received at the two telescopes. They have been making measurements across the Atlantic for over 10 years, using 24 | Fifty years of New Scientist
061118_Arch_1980s.indd 24
three radio telescopes in the United States and three in Europe. They are now certain that Europe and North America are moving apart at a rate of 1.5 centimetres per year, with an error of less than half a centimetre a year. Other stations in the crustal dynamics project measure separations by bouncing laser signals off a satellite equipped with reflectors. A telescope next to the laser picks up the faint reflected flash of light, and the time taken for the round trip gives the distance to the satellite. Laser stations have shown a complex pattern of activity around the Pacific.
The Pacific plate is moving away from North America at 4 cm per year, while Australia (on the Indian plate) is encroaching on the Pacific plate at a remarkable 7 cm per year. These measurements are the most accurate, with errors less than 1 cm per year. Both the Pacific and Indian plates appear to be moving away from South America, at 5 to 6 cm per year, though these figures are less certain as they are based on only one laser station in South America. The motion of North America relative to South America and to Australia is negligible. 31 MAY 1984
EURASIAN PLATE
AMERICAN PLATE PACIFIC PLATE
!'$+
+4
-1 -7
INDIAN PLATE
-1
AFRICAN PLATE
+5
+6 Changes in distance (cm/year)
www.newscientist.com
3/11/06 2:06:50 pm
A major malfunction astro-heroes. America needs these “all-American” symbols. Her armies are frustrated by faceless hijackers, her diplomats impotent to bring peace and disarmament, and the triumphs of her scientists are incomprehensible. But every time a shuttle rose from Cape Canaveral in Florida, a rapt public was reminded that there are still a few things Americans can do better, by damn, than anyone else. Mortal as they are, the astronauts are the targets onto which ordinary folks imprint their ideals. Christa McAuliffe, the schoolteacher in space, was the first “ordinary” citizen (besides two congressmen) to ride along. Her death is particularly painful because her voyage showed that plain folks can become heroes too. 6 FEBRUARY 1986
All seven crew members died when Challenger exploded on 28 January 1986
NASA/AP
SPACE travel is no longer routine. For a brief time, the space shuttle had us believing that perhaps it was. Now we can drape ourselves in the certitude of hindsight and chide NASA for running hell-bent, it now seems, to put the butcher, baker and candlestick maker into orbit. But will the public demand that NASA curtails its exploration of space? Will we put robots rather than flesh and blood into orbit? Of course not. Ten people have died aboard space capsules in over half a hundred flights since the US fell in love with spaceships. Ten times that number die in traffic accidents every day. NASA’s safety record has been admirable compared to the most daring earthly pursuits, and the only other game in town with which to compare it, the USSR, is neither as ambitious nor as open to scrutiny. In return for spending billions of dollars, America got a growing corps of
EARTH SCIENCE
CONTINENTAL DRIFT: THE FINAL PROOF NASA’s scientists have released the first direct measurements of continental drift. They show that the Atlantic is gradually widening, and that Australia is receding from South America and heading for Hawaii. The crustal dynamics project, run from NASA’s Goddard Space Flight Center, uses two techniques to measure the separation of places on the Earth to an accuracy of a few centimetres. Around the world, there are more than 20 stations equipped for one or both. Relative motions of the stations are expected, according to plate tectonics, the current theory of continental drift. This says that the Earth’s crust is made of several plates moving about the planet, and most of the major plates carry a continent on their backs. The exception is the large plate that floors the Pacific Ocean; fortunately for the crustal dynamics team, instruments can be sited on the island of Hawaii to monitor this plate. The first technique is very long baseline interferometry. Astronomers measure the distance between two radio telescopes, both looking at the same distant quasar, by measuring the difference in time between the signals being received at the two telescopes. They have been making measurements across the Atlantic for over 10 years, using 24 | Fifty years of New Scientist
061118_Arch_1980s.indd 24
three radio telescopes in the United States and three in Europe. They are now certain that Europe and North America are moving apart at a rate of 1.5 centimetres per year, with an error of less than half a centimetre a year. Other stations in the crustal dynamics project measure separations by bouncing laser signals off a satellite equipped with reflectors. A telescope next to the laser picks up the faint reflected flash of light, and the time taken for the round trip gives the distance to the satellite. Laser stations have shown a complex pattern of activity around the Pacific.
The Pacific plate is moving away from North America at 4 cm per year, while Australia (on the Indian plate) is encroaching on the Pacific plate at a remarkable 7 cm per year. These measurements are the most accurate, with errors less than 1 cm per year. Both the Pacific and Indian plates appear to be moving away from South America, at 5 to 6 cm per year, though these figures are less certain as they are based on only one laser station in South America. The motion of North America relative to South America and to Australia is negligible. 31 MAY 1984
EURASIAN PLATE
AMERICAN PLATE PACIFIC PLATE
!'$+
+4
-1 -7
INDIAN PLATE
-1
AFRICAN PLATE
+5
+6 Changes in distance (cm/year)
www.newscientist.com
3/11/06 2:06:50 pm