足球比赛上半场时间 年9月高口阅读上半场第三篇

年9月高口阅读上半场第三篇  

Question 11-15
LIKE the space telescope he championed
astronomer Lyman Spitzer faced some perilous moments in his career. Most notably
on a July day in 1945
he happened to be in the Empire State building when a B-25 Mitchell bomber lost its way in fog and crashed into the skyscraper 14 floors above him. Seeing debris falling past the window
his curiosity got the better of him
as Robert Zimmerman recounts in his Hubble history
The Universe in a Mirror. Spitzer tried to poke his head out the window to see what was going on
but others quickly convinced him it was too dangerous.
Spitzer was not the first astronomer to dream of sending a telescope above the distorting effects of the atmosphere
but it was his tireless advocacy
in part
that led NASA to launch the Hubble Space Telescope in 1990. Initially jubilant
astronomers were soon horrified to discover that Hubble's 2.4-metre main mirror had been ground to the wrong shape. Although it was only off by 2.2 micrometres
this badly blurred the telescope's vision and made the scientists who had promised the world new images and science in exchange for $1.5 billion of public money the butt of jokes. The fiasco
inevitably dubbed "Hubble Trouble" by the press
wasn't helped when even the limited science the crippled Hubble could do was threatened as its gyroscopes
needed to control the orientation of the telescope
started to fail one by one.
By 1993
as NASA prepared to launch a rescue mission
the situation looked bleak. The telescope "probably wouldn't have gone on for more than a year or o" without repairs
says John Grunsfeld
an astronaut who flew on the most recent Hubble servicing mission. Happily
the rescue mission was a success. Shuttle astronauts installed new instruments that corrected for the flawed mirror
and replaced the gyroscopes. Two years later
Hubble gave us the deepest ever view of the universe
peering back to an era just 1 billion years after the big bang to see the primordial building blocks that aggregated to form galaxies like our own.
The success of the 1993 servicing mission encouraged NASA to mount three more (in 1997
1999 and 2002). Far from merely keeping the observatory alive
astronauts installed updated instruments on these missions that dramatically improved Hubble's power. It was "as if you took in your Chevy Nova [for repairs] and they gave you back a Lear jet
" says Steven Beckwith
who from 1998 to 2005 headed the Space Telescope Science Institute (STScI) in Baltimore
Maryland
where Hubble's observations are planned. Along the way
in 1998
Hubble's measurements of supernovas in distant galaxies unexpectedly revealed that the universe is expanding at an ever-increasing pace
propelled by a mysterious entity now known as dark energy. In 2001 the space observatory also managed to make the first measurement of a chemical in the atmosphere of a pla in an alien solar system.
Despite its successes
Hubble's life looked like it would be cut short when in 2004
NASA's then administrator Sean O'Keefe announced the agency would send no more servicing missions to Hubble
citing unacceptable risks to astronauts in the wake of the Columbia shuttle disaster of 2003
in which the craft exploded on re-entry
killing its crew. By this time
three of Hubble's gyroscopes were already broken or ailing and no one was sure how long the other three would last. Citizen petitions and an outcry among astronomers put pressure on NASA
and after a high-level panel of experts declared that another mission to Hubble would not be exceptionally risky
the agency reversed course
leading to the most recent servicing mission
in May 2009.
No more are planned. The remainder of the shuttle fleet that astronauts used to reach Hubble is scheduled to retire by the year's end. And in 2014
NASA plans to launch Hubble's successor
an infrared observatory called the James Webb Space Telescope
which will probe galaxies even further away and make more measurements of exopla atmospheres.
According to Grunsfeld
now STScI's deputy director
plans are afoot for a robotic mission to grab Hubble when it reaches the end of its useful life
nudging it into Earth's atmosphere where most of it would be incinerated. Only the mirror is sturdy enough to survive the fall into an empty patch of ocean.
But let's not get ahead of ourselves - Hubble is far from finished. The instruments installed in May 2009
including the Wide Field Camera 3
which took this image of the Butterfly nebula
3800 light years away
have boosted its powers yet again. It might have as much as a decade of life left even without more servicing. "It really is only reaching its full stride now
after 20 years
" says Grunsfeld.
A key priority for Hubble will be to explore the origin of dark energy by probing for it at earlier times in the universe's history. Hubble scientist Malcolm Niedner of NASA's Goddard Space Flight Center in Greenbelt
Maryland
is not willing to bet on what its most important discovery will be. "More than half of the most amazing textbook-changing science to emerge from this telescope occurred in areas we couldn't even have dreamed of
" he says. "Expect the unexpected."