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After a shaky start, the Martian flotilla that has arrived over the past few weeks is getting down to business. Two of the five craft in it seem to be working perfectly. Two are lost. And a fifth is sick, but undergoing treatment. The most spectacular pictures so far have been provided by Mars Express, the European Space Agency"s contribution to the fleet. On January 28th this reached its final working orbit (which takes it over both poles, and thus allows it to see the whole of Mars over the course of a few days as the planet revolves beneath it). It has, however, been sending back data since shortly after it arrived, and a few days ago its controllers released a series of beautiful photographs, including a stereo image of Valles Marineris, a huge canyon that may have been formed by flowing water. The most scientifically significant result, though, has come from Opportunity, America"s second Mars rover. One of Opportunity"s cameras has photographed evidence of stratification in nearby rocks. Such stratification indicates that the rocks concerned are sedimentary. The layers could be repeated wind-blown deposits, or consist of ash from successive volcanic eruptions. But the terrestrial rocks they most resemble are ones that have formed under water. The reason everyone is getting so excited is because there is a widespread assumption that any form of life which might dwell on Mars would need liquid water to live—or, even if it could now subsist by extracting moisture from ice, would have needed liquid water to evolve to that stage. Mars has seen more probes launched towards it than all of the other planets put together precisely because of this hope that it might harbour life. So there is a lot riding on the answer—not least the funding of future missions. Besides its scientific significance, the success of Opportunity has also helped to distract attention from the sudden refusal of Spirit, the first American rover to arrive on Mars, to talk to its controllers. This craft had tentatively, but successfully, nosed its way off its landing platform, and was about to drill its way into a nearby rock prior to doing a spot of chemical analysis, when it went silent. However, the engineers at NASA, America"s space agency, are nothing if not resourceful, and they have a good record of carrying out running repairs on spacecraft that are millions of kilometres away. In the case of Spirit, they think that one of the craft"s memory chips has got cluttered up with files created on the journey to Mars. That caused another chip, which manages the first, to throw a wobbly and to keep rebooting the computer. They are currently testing this idea by loading a diagnostic program on to the computer. In addition, as a precaution, they have deleted excess files from the equivalent memory chip on Opportunity. Spirit"s spirits may thus revive. As to the failures, the Japanese abandoned their fly-by craft Nozomi in December, and the British team in charge of Beagle 2, which is presumed to have landed on December 25th but from which no signal has been received, also seems to have called it quits. Still, a 40460% success rate (depending on whether Spirit is brought back into commission) is not bad by the historical standards of missions to Mars. Now, the real science begins. Mars Express is mentioned because______.
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After a shaky start, the Martian flotilla that has arrived over the past few weeks is getting down to business. Two of the five craft in it seem to be working perfectly. Two are lost. And a fifth is sick, but undergoing treatment. The most spectacular pictures so far have been provided by Mars Express, the European Space Agency"s contribution to the fleet. On January 28th this reached its final working orbit (which takes it over both poles, and thus allows it to see the whole of Mars over the course of a few days as the planet revolves beneath it). It has, however, been sending back data since shortly after it arrived, and a few days ago its controllers released a series of beautiful photographs, including a stereo image of Valles Marineris, a huge canyon that may have been formed by flowing water. The most scientifically significant result, though, has come from Opportunity, America"s second Mars rover. One of Opportunity"s cameras has photographed evidence of stratification in nearby rocks. Such stratification indicates that the rocks concerned are sedimentary. The layers could be repeated wind-blown deposits, or consist of ash from successive volcanic eruptions. But the terrestrial rocks they most resemble are ones that have formed under water. The reason everyone is getting so excited is because there is a widespread assumption that any form of life which might dwell on Mars would need liquid water to live—or, even if it could now subsist by extracting moisture from ice, would have needed liquid water to evolve to that stage. Mars has seen more probes launched towards it than all of the other planets put together precisely because of this hope that it might harbour life. So there is a lot riding on the answer—not least the funding of future missions. Besides its scientific significance, the success of Opportunity has also helped to distract attention from the sudden refusal of Spirit, the first American rover to arrive on Mars, to talk to its controllers. This craft had tentatively, but successfully, nosed its way off its landing platform, and was about to drill its way into a nearby rock prior to doing a spot of chemical analysis, when it went silent. However, the engineers at NASA, America"s space agency, are nothing if not resourceful, and they have a good record of carrying out running repairs on spacecraft that are millions of kilometres away. In the case of Spirit, they think that one of the craft"s memory chips has got cluttered up with files created on the journey to Mars. That caused another chip, which manages the first, to throw a wobbly and to keep rebooting the computer. They are currently testing this idea by loading a diagnostic program on to the computer. In addition, as a precaution, they have deleted excess files from the equivalent memory chip on Opportunity. Spirit"s spirits may thus revive. As to the failures, the Japanese abandoned their fly-by craft Nozomi in December, and the British team in charge of Beagle 2, which is presumed to have landed on December 25th but from which no signal has been received, also seems to have called it quits. Still, a 40460% success rate (depending on whether Spirit is brought back into commission) is not bad by the historical standards of missions to Mars. Now, the real science begins. What does the word "they"(Para. 3) refer to
Success, it is often said, has many fathers—and one of the many fathers of computing, that most successful of industries, was Charles Babbage, a 19th-century British mathematician. Exasperated by errors in the mathematical tables that were widely used as calculation aids at the time, Babbage dreamed of building a mechanical engine that could produce flawless tables automatically. But his attempts to make such a machine in the 1920s failed, and the significance of his work was only rediscovered this century. Next year, at last, the first set of printed tables should emerge from a calculating "difference engine" built to Babbage"s design. Babbage will have been vindicated. But the realization of his dream will also underscore the extent to which he was a man born ahead of his time. The effort to prove that Babbage"s designs were logically and practically sound began in 1985, when a team of researchers at the Science Museum in London set out to build a difference engine in time for the 200th anniversary of Babbage"s birth in 1992. The team, led by the museum"s curator of computing, Doron Swade, constructed a monstrous device of bronze, iron and steel. It was 11 feet long, seven feet tall, weighed three tons, cost around $500 000 and took a year to piece together. And it worked perfectly, cranking out successive values of seventh-order polynomial equations to 31 significant figures. But it was incomplete. To save money, an entire section of the machine, the printer, was omitted. To Babbage, the printer was a vital part of design. Even if the engine produced the correct answers, there was still the risk that a transcription or typesetting error would result in the finished mathematical tables being inaccurate. The only way to guarantee error-free tables was to automate the printing process as well. So his plans included specifications for a printer almost as complicated as the calculating engine itself, with adjustable margins, two separate fonts, and the ability to print in two, three or four columns. In January, after years of searching for a sponsor for the printer, the Science Museum announced that a backer had been found. Nathan Myhrvold, the chief technology officer at Microsoft, agreed to pay for its construction (which is expected to cost $373,000 with one proviso: that the Science Museum team would build him an identical calculating engine and printer to decorate his new home on Lake Washington, near Seattle). Construction of the printer will begin—in full view of the public—at the Science Museum later this month. The full machine will be completed next year. It is a nice irony that Babbage"s plans should be realized only thanks to an infusion of cash from a man who got rich in the computer revolution that Babbage helped to foment. More striking still, even using 20th-century manufacturing technology the engine will have cost over $830 000 to build. Allowing for inflation, this is roughly a third of what it might have cost to build in Babbage"s day-in contrast to the cost of electronic-computer technology, which halves in price every 18 months. That suggests that, even had Babbage succeeded, a Victorian computer revolution based on mechanical technology would not necessarily have followed. Researchers built the calculating difference engine according to Babbage"s design in order to show that______.
Plastic is the panacea of the ages. Nearly every man-made object (1)_____ (2)_____ of, or at least (3)_____ its very structure, to this wonder compound. Rain slickers, computer terminals, automobile engine parts, coffee cups (and the sugar stirrers too), breast implants, toy soldiers—they are all made up of plastic, or one of its many (4)_____ Since the (5)_____ of civilization, humankind bas been experimenting (6)_____ a multifunctional material—one that had to be equally strong and lightweight—to carry, contain and protect valuables. (7)_____ it could carry, contain and protect humans too, even better. Generations of tinkerers and scientists set off (8)_____ the challenge, striking gold some 170 years ago. By mixing natural rubber with sulphur they created the world"s most utilized material ever. In developing a (9)_____, malleable and durable substance, the most important inventions of the industrial age were to follow shortly thereafter. The automobile and airplane industries, to (10)_____ just two, owe their very existence to plastic. And, (11)_____ celluloid plastic strips, the Lumiere Brothers would never have brought moving pictures to the big screen. The development of plastic is a story of human (12)_____, ingenuity and luck. (13)_____ the legend now goes, in 1839, the American inventor Charles Goodyear (the famous tyre company would later use his name) was experimenting with the sulphur treatment of natural rubber when he dropped a piece of sulphur-treated rubber on a stove. The heat seemed to give rubber (14)_____ properties. It was stronger, more (15)_____ to abrasions more elastic, much less (16)_____ to temperature, (17)_____ to gases, and highly resistant to chemicals and electric (18)_____ Eyeing this as a cheaply and easily reproduced construction material, a whirlwind of work (19)_____ and the birth of (20)_____ plastic and plastic-derivatives were born from camphor to celluloid to rayon; cellophane, polyvinyl chloride (or PVC); styrofoam and nylon were soon to follow.
Success, it is often said, has many fathers—and one of the many fathers of computing, that most successful of industries, was Charles Babbage, a 19th-century British mathematician. Exasperated by errors in the mathematical tables that were widely used as calculation aids at the time, Babbage dreamed of building a mechanical engine that could produce flawless tables automatically. But his attempts to make such a machine in the 1920s failed, and the significance of his work was only rediscovered this century. Next year, at last, the first set of printed tables should emerge from a calculating "difference engine" built to Babbage"s design. Babbage will have been vindicated. But the realization of his dream will also underscore the extent to which he was a man born ahead of his time. The effort to prove that Babbage"s designs were logically and practically sound began in 1985, when a team of researchers at the Science Museum in London set out to build a difference engine in time for the 200th anniversary of Babbage"s birth in 1992. The team, led by the museum"s curator of computing, Doron Swade, constructed a monstrous device of bronze, iron and steel. It was 11 feet long, seven feet tall, weighed three tons, cost around $500 000 and took a year to piece together. And it worked perfectly, cranking out successive values of seventh-order polynomial equations to 31 significant figures. But it was incomplete. To save money, an entire section of the machine, the printer, was omitted. To Babbage, the printer was a vital part of design. Even if the engine produced the correct answers, there was still the risk that a transcription or typesetting error would result in the finished mathematical tables being inaccurate. The only way to guarantee error-free tables was to automate the printing process as well. So his plans included specifications for a printer almost as complicated as the calculating engine itself, with adjustable margins, two separate fonts, and the ability to print in two, three or four columns. In January, after years of searching for a sponsor for the printer, the Science Museum announced that a backer had been found. Nathan Myhrvold, the chief technology officer at Microsoft, agreed to pay for its construction (which is expected to cost $373,000 with one proviso: that the Science Museum team would build him an identical calculating engine and printer to decorate his new home on Lake Washington, near Seattle). Construction of the printer will begin—in full view of the public—at the Science Museum later this month. The full machine will be completed next year. It is a nice irony that Babbage"s plans should be realized only thanks to an infusion of cash from a man who got rich in the computer revolution that Babbage helped to foment. More striking still, even using 20th-century manufacturing technology the engine will have cost over $830 000 to build. Allowing for inflation, this is roughly a third of what it might have cost to build in Babbage"s day-in contrast to the cost of electronic-computer technology, which halves in price every 18 months. That suggests that, even had Babbage succeeded, a Victorian computer revolution based on mechanical technology would not necessarily have followed. Babbage wished to build a mechanical engine because______.
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