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The Plan to Bring an Asteroid to Earth
A:Send a robot into space. Grab an asteroid. Bring it back to Earth orbit This may sound like a crazy plan, but it was discussed quite seriously last week by a group of scientists and
engineers at the alifomia Instiute of Technology. The four-day workshop was dedicated to investigating the feasibility and requirements of capturing a near-Earth asteroid, bringing it
closer to our planet and using it as a base for future manned spacetight missins.
This is not something the scientists are imagining could be done some day off in the future.
This is possible with the technology we have today and could be accomplished within a decade.
"Once you get over the initial reaction- "You want to do what?!'一it actully starts to seem like a reasonable idea," said engineer John Brophy from NASAS Jet Propulsion Laboratory,
who helped organize the workshop.
B: Though reamanging the heavens may seem an excessive undertaking, the mission has its merits. Parking an asteroid in a gravitatinally neutral spot between the Earth and the sun, known as a Lagrange point, would provide a stationary base fom which to launch missions further into space. There are several advantages to this. For one, launching materials from Earth requires a lot of power, fuel, and consequently money, to get out of our planet's deep gravity well. Resources mined from an asteroid with very litle gravitational pull could be easily shutled around the solar system.
And many asteroids have a lot to offer. Some are full of metals such as iron, which can be used to build space- based ha bitats while others are up to one-quarter water, which would be
either used for liesupport or broken down into hydrogen and oxygen to make fuel. As well, asteroid regolth placed around a spacep hull would shield it against radiation fom deep space, alowing safer travel to other planets.
An asteroid could be an altemative to setting up camp on the moon, or complement a moon base with more resouroes for heading further out in the solar system, said engineer Louis Friedman, cofounder of the Planetary Societly and another co-organizer of the Callech workshop.
C: There's also the potential for mining asterold materials to bring back to Earth. Even a small asteroid contains roughly 30 times the amount of metals mined over all of human history, with an estimated worth of $70 tllion. And astronomers would have the chance to get a close-up look at one of the solar system's earliest rlis, generating important sclentific
Though technically feasible, budging such a hefty target - - with a mass in excess of a millin tons一would not be easy.
"You're moving the largest mother lode imaginable,"E said former astronaut Rusty Schweickart, cofounder of the B612 Foundation, an organization dedicated to protecting Earth from asteroid strikesMost asteroids are iregular chunks of rock that spin chatically along rregular axes. Engineers would need to be absolutely certain they could control such a potentially dangerous object "It's the opposite of planetary defense; if you do something wrong you have a Tunguska event," said engineer Marco Tantardini from the Planetary Society, rering to the powerful 1908 explosion above a remole Russian region thought to have been caused by a meteoroid or comet Of course, any asteroid brought back under the proposed plan would be too small to cause a repeat of such an event.
D: Sil, these obstacles are like catnip to engineers, who love to go over every potential difiulty in order to solve it. Actually executing the asteroid retrieval plan would help demonstrate and greatly expand mankind's space-based engneering capabitties, said Friedman. For instance, the mission would teach engineers how to capture an uncooperaive target, which could be good practice for future planetary defense missions, he added. And if the challenges for a large asteroid seem too daunting, researchers could always start with a smaler asteroid, perhaps six to 30 feet across. Gradually larger objects could be part of a campaign where engineers learm to deal with progressively greater complcalions.
E: No matter the size of the asteroid, these plans would require hety investments. Even capturing a small asteroid would consume at least a blion dolars and anything larger would
be a mufibilindollar endeavor. Convincing taxpayers to foot such a bil could be tricky. Considering the resources available in any asteroid, private industry might be interested in
getting involved. One possible mission would be to simply execute the first part of the plan pushing the asteroid to nearEarth orbit 一and then convene a commercial competition
inting arnyone who wants to develop the capabilies to reach and mine the object.
Though the undertaking might be soentifally. exciting, this. wouldn't be the primary motivalion. An asteroid would provide great insight int the solar system's formation, it's not
enough to justify the expense of bringing one to Earth. Any interesting science can be done much cheaper with an unmanned robotic spacecraft, said chemist Joseph A Nuth from
NASA's Goddard Spaceflight Center."Ulimately, we would be developing this target in order to help move out into the solar system," Brophy said.
14-18为list of headings
A. An available goal, not a dream
B. What the asterold can offer
C. Need skill and care
D. Start from a smaller challenge
E. Seek for support
19. Louis Friedman B
20. Rusty Schweickart C
21. Joseph A Nuth E
22. Asteroid can offer
23. Less gravity
24. a landing place
25. Metal can be brought back to earth
26. Water can be used
The causes of linguistic changes
Mechanism of Linguistic Change
The changes that have aused the most disagreement are those in pronunciation. We have varlous sources of evidence for the pronundations of earlier times, such as the spelings.
the treatment of words borrowed from other languages or borrowed by them, the descriptions of contemporary, grammanians and spelling-reformers, and the modem pronuncialions in all the languages and dialeds concermed. From the middle of the siteenth century, there are in England writers who attempt to descrbe the postion of the speech-organs for the production of English phonemes, and who invent what are in effect systems of phonetic symbols. These various kind of evidence, combined with a knowledge of the mechanisms of speech-produdion, can often give us a very good idea of the pronunciation of an eartier age, though absolute certainty is never possible.
When we study the pronunciaton of a language over any period of a few generations or more, we find there are always large-scale regularities in the changes: for example, over a
certain period of time, just about all the long  vowels in a language may change into long[e:] vowels, or all the [bloconsonants in a certain position (for example at the end of a
word) may change into [p] consonants. Such regular changes are often caled sound laws. There are no universal sound laws (even though sound laws often reflect universal
tendencies), but simply particular sound laws for one given language (or dialect) at one given period.
It is also possible that fashion plays a part in the process of change. It certainly plays a part in the spread of change: one person imitates another, and people with the most prestige
are most lkely to be imitated, so that a change that takes place in one social group may be imitated (more or less acurately) by speakers in another group. When a social group goes
up or down in the world, s its pronuncation may gain or lose prestige. It is salid that, after the Russian Revolution of 1917, the upper-class pronundation of Russian, which had
formertly been considered desirable, became on the contrary an undesirable kind of accent to have, so that people tried to disguise it. Some of the changes in accepted
English pronunciation in the seventeenth and eighteenth centuries have been shown to consist in the replacement of one style of pronunciation by another style already existing. and it is Ikely that such subsitutions were a result of the great social changes of the period: the increased power and wealth of the middle classes, and their steady infitration upwards into the ranks of the' landed gentry, probably carried elements of middle-class pronunciation into upper-dass speech.
A less specifc variant of the argument is that the imitation of children s is imperfect: they copy their parents' speech, but never reproduceit exacty. This is true, but it is also true
that such deviations from adult speech are usually corrected in later childhood. Perhaps it is more significant that even。adults show a certain amount of random variation in their
pronunclation of a gven phone me, even if the phonetic context is kept unchanged. This, however, cannot explain changes in pronunciation unless it can be shown that there is some systematic trend in the failures of imitation: if they are merely random deviations they will cancel one another out and there will be no net changein the language.
One such force which is often invoked is the principle of ease, or minimization of ffort. The change from fussy to fuzzy would be an example of assimilation. which is a very common kind of change. Assimilation is the changing of a sound under the infuence of a neighbouring one. Fon example, the word scant was once skamt，but the /mhas been changed to m/ under the infuence of the folowing Itw. Greater efficiency has hereby been achieved, because In/ and IV are articulated in the same place(with the tip of the tongue against the teth-ridge), whereas /m/ is articulated esewhere (with the two lips). So the place of articulation of the nasal consonant has been changed to confom with that of the fllowing plosive. A more recent example of the same kind of thing is the common pronunciaion of fooball as foball.
Assimilation is not the only way in which we change our pronunciation in order to increase effciengy. It is very common for consonants to be lost af the. end of a word: in Middle
English, word-final [-η] was often lost in unstressed sylables, so that baken "to bake'changed from [bak?n] t.and. later to.. Consonant-clusters are oten simplfied. At onetime
there was a [t in words like castle and Christmas, and an intial [K] in words like knight and know. Sometimes a whole sllable is dropped out when two successive syllables begin with the same consonant (haplology): a recent example is temporary, which in Britain s oten pronounced as i建were temporary.
The pronunciation of living language undergo changes throughout thousands of years.
Large scale regular Changes are usually caled 27. sound laws. There are three reasons for these changes. Firsty, the infuence of one language on another; another aspect which
affect accent is 28.fashion.Secondly, 29.Children jimitate the words imperfect,and may also contibute to this change if there are insignificant deviations tough later they may be
corrected Finally, for those random variations in pronunciation, the deeper evidence lies in the 30. assimilation.
31. It is impossible for modem people to find pronunialion of words in an eartier age.False
32. The great change of language in Russian history is related to the nising status and fortune of middle classes. Not Given
33. AI the children learn speeches from aduts while they assume that certain language is difoult to imitate exactly. Not Given
34. Pronunciation with causal inaccuracy wll not exert big infuence on language changes.True
35. The link of 'mt can be infuenced being pronounced as. True
36. The [g] in gnat not being pronounced will not be spelt out in the future. Not Given
37. The sound of temporary' cannot wholly present its spelling. True
A Since the speakers can pronounce it with less effort
B Assimiation of a sound under the ifluence of a neighbouring one
C It is a trend for changes in pronunciation in a large scale in a given period