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When the end of the world comes, we’ll know what to blame. Scientists have found compelling evidence that the Sun has a baby brother, a dark star whose eccentric orbit is responsible for periodically showering the Earth with comets and meteorites.
The dark star -- named Nemesis by astronomers -- is thought to be a brown dwarf that spins round the Sun in an orbit so large it is measured in light years, the distance light travels in a year, equivalent to about 6,000 billion miles.
The research suggests that, every 26m years, the star’s eccentric orbit brings it within one light year of the solar system. There it causes havoc in the Oort Cloud, a huge region surrounding the solar system that contains billions of bits of cosmic rabble left over from the formation of planets.
Of the millions of rocks it throws out of orbit at each visit, some hurtle Earthwards, and have several times nearly wiped out life on Earth.
Astronomers have long wondered if the Sun has a smaller partner. Recently, two independent groups of researchers have found evidence of one.
One group, led by John Matese, professor of physics at the University of Louisiana at Lafayette, confirms the notion that it is most likely to be a brown dwarf, a star that never accumulated enough mass to ignite and which has simply sat in space smoldering for billions of years.
Matese studied 82 comets from the Oort Cloud and found common elements in the shape of their orbits that could only be explained if they had been influenced by the gravitational pull of an object several times the size of Jupiter and existing about 25,000 times farther from the Sun than the Earth.
Matese said: "A companion to the Sun orbiting at these distances would have little effect on the planets. But it would play a big role in the way comets ’made their way’ from their birth places in the planetary disc out to the Oort Cloud and in how they can return to the inner solar system."
Further research was published by Richard Muller, professor of physics at the University of California, Berkeley, following yses of moon rock samples brought back to Earth by Apollo 14.
The absence of a protective atmosphere means the moon has been subjected to intense bombardment in its 4.5 billion-year existence.
Muller’s breakthrough was to find a way to date how long ago any particle was melted -- meaning he could build up a picture of whether the moon gets a constant barrage or suffers spells of intense bombardment.
He said, "The evidence clearly shows that the moon has gone through spells of relatively frequent impacts and others of reduced intensity. I believe it is likely that this is because the Oort Cloud is being disturbed by a massive body that is throwing comets out of stable orbits, a small fraction of which could reach the Earth."
Muller and others believe that the dark star probably takes about 26m years to complete an orbit around the sun.
Other scientists have already noted that mass extinctions of life on Earth seem to occur in a pattern with gaps equivalent to multiples of 26m, suggesting some regular is causing the comets to come Earth’s way.
The best-known such was the one that wiped out the dinosaurs 65m years ago, but that was not the worst; the planet has suffered several such large mass extinctions.
Astronomers have found the first Earth-sized planet orbiting another star. The discovery raises the chances of finding planets that could support life as we know it.
The Nemesis influences the comets by ______.

A.
exerting effects on their birthplace
B.
gravitational pull of planets
C.
affecting the Oort Cloud
D.
influencing their way to the Oort Cloud and the inner solar system
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【单选题】Stratford-on-Avon, as we all know, has only one industry -- William Shakespeare -- but there are two distinctly separate and increasingly hostile branches. There is the Royal Shakespeare Company (RSC)...

A.
The sightseers never go to see the plays.
B.
Sightseers and playgoers often come from different places.
C.
Playgoers often visit the Warwick Castle.
D.
Playgoers spend more money than sightseers.

【单选题】Pay-as-you-drive schemes will reduce the amount of traffic on motorways.() A.Right B.Wrong C.Doesn’t say

A.
Too many cars
B.
Everyone agrees that there are simply too many cars on the road but who will be the first to stop using theirs Although everyone hates being stuck in traffic, no one sees their cars as part of the growing problem. However, with traffic growth up to 84 per cent expected by 2025 and the ever-increasing cost of accidents and delays already at $160 bn in Europe, there is a growing need to change our ’culture’ and develop alternative forms of transport as quickly as possible.
C.
One answer is to make cars more expensive by increasing taxes on petrol. However, tax increases will affect the people who live in the country more than city drivers and do little to reduce inner city traffic. The Government is also looking at pay-as-you-drive schemes on motorways but this will push cars on to smaller ’free’ roads, which will make the problem worse,
D.
A successful transport policy is not just a question of making the car too expensive but of offering car drivers a real alternative. Many motorists dislike driving to work but say public transport services are too slow, offer poor quality and are tar too expensive. If new transport policies are to succeed, public transport needs to be quick, reliable and affordable.
E.
Transport planners are also developing ways of managing the existing road network more efficiently. New technology such as smart cards and electronic monitoring of roads will lead to a more efficient use of transport systems. However, technology will not reduce the number of cars on the road or solve the real problem of how to persuade car drivers to leave their beloved cars at home more often.