In its 4．5 billion years，Earth has evolved from its hot，violent birth to the celebrated watery blue planet that stands out in pictures from space．But in a new book，two noted University of Washington astrobiologists say the planet already has begun the long process of devolving into a burned-out cinder， eventually to be swallowed by the sun．①
By their reckonin9，Earth’sday in the sun has reached 4：30 a．m．，corresponding to its 4．5 billion—year age．By 5 a．m．，the l billion-year reign of animals and plants will come to an end．At 8 a．m． the oceans will vaporize．At noon--after l 2 billion years--the ever---expanding sun，transformed into a red giant,will engulf the planet，melting away any evidence it ever existed and sending molecules and atoms that once were Earth floating off into space．o
“The disappearance of our planet is still 7．5 billion years away．but people really should consider the fate of our world and have a realistic understanding of where we are goin9，”said UW astrophysicist Donald Brownlee．“We live in a fabulous place at a fabulous time．It’s a healthy thing for people to realize what a treasure this is in space and time，and fully appreciate and protect their environment as much as possible．”
The prospects of humans surviving by moving to some other habitable planet or moon aren’t good， Brownlee and Ward contend，because even if such a place were found，getting there would be a huge obstacle．Various probes sent into space could survive Earth’s demise，and just a few grams of material could arguably carry a DNA sample from every human，they say，but it’s not likely the human species itself will survive．。Long before the planet’s final end，life will become quite challengin9，and finally impossible，for humans．
As the sun gets hotter and grows in size，it will envelop Mercury and Venus．It is possible it will stop j ust short of Earth，the authors say，but the conditions still would make this a most—inhospitable planet．More likely，though，the sun will consume Earth as well。severing all the chemical bonds between molecules and sending its individual atoms out into space，perhaps eventually to form new planets．That would leave Mars as the nearest planet to the sun．a(chǎn)nd on Mars the fading sun’s glow would be like that of Earth’S moon．
That end is still some 7．5 billion years distant，but by then Earth will have faced a variety of“ends” along the way，the authors say．The last dinosaur perished long a90．Still tO come are the last elephant， the last tree，the last flower，the last glacier，the last snowflake，the last ocean，the last life．
“It’S a healthy thing to think of the place of Earth among the other planets，and its place in the sun．The sun gave life and ultimately it will bring death．kaoshida[484 words]
1．According tO the new book，the life expectancy of the Earth is______．
A．1 billion years
B．4．5 billion years
C．7．5 billion years
D．12 billion years
2．It can be inferred from this passage that______．
A．1ife is nothing
B．the world is precious
C．man can never conquer nature
D．the future of human species is gloomy
3．The authors of the new book believe that the human species will______．
A．disappear long before the disappearance of the Earth
B．survive in the universe even if the Earth disappears
C．find a place tO live after the disappearance of the Earth
D．be sent into space by various spacecrafts
4．All of the following things would come tO an end before the final end of the Earth，EXCEPT______
A．Mars
B．a(chǎn)nimals
C．plants
D．oceans
5．The authors of the new book intend tO tell readers primarily that______．
A．the Earth is nothing but one planet in the solar system
B．nothing can survive for ever
C．we should cherish our life and environment on Earth
D．the sun gave lire and ultimately it will bring death
By their reckonin9，Earth’sday in the sun has reached 4：30 a．m．，corresponding to its 4．5 billion—year age．By 5 a．m．，the l billion-year reign of animals and plants will come to an end．At 8 a．m． the oceans will vaporize．At noon--after l 2 billion years--the ever---expanding sun，transformed into a red giant,will engulf the planet，melting away any evidence it ever existed and sending molecules and atoms that once were Earth floating off into space．o
“The disappearance of our planet is still 7．5 billion years away．but people really should consider the fate of our world and have a realistic understanding of where we are goin9，”said UW astrophysicist Donald Brownlee．“We live in a fabulous place at a fabulous time．It’s a healthy thing for people to realize what a treasure this is in space and time，and fully appreciate and protect their environment as much as possible．”
The prospects of humans surviving by moving to some other habitable planet or moon aren’t good， Brownlee and Ward contend，because even if such a place were found，getting there would be a huge obstacle．Various probes sent into space could survive Earth’s demise，and just a few grams of material could arguably carry a DNA sample from every human，they say，but it’s not likely the human species itself will survive．。Long before the planet’s final end，life will become quite challengin9，and finally impossible，for humans．
As the sun gets hotter and grows in size，it will envelop Mercury and Venus．It is possible it will stop j ust short of Earth，the authors say，but the conditions still would make this a most—inhospitable planet．More likely，though，the sun will consume Earth as well。severing all the chemical bonds between molecules and sending its individual atoms out into space，perhaps eventually to form new planets．That would leave Mars as the nearest planet to the sun．a(chǎn)nd on Mars the fading sun’s glow would be like that of Earth’S moon．
That end is still some 7．5 billion years distant，but by then Earth will have faced a variety of“ends” along the way，the authors say．The last dinosaur perished long a90．Still tO come are the last elephant， the last tree，the last flower，the last glacier，the last snowflake，the last ocean，the last life．
“It’S a healthy thing to think of the place of Earth among the other planets，and its place in the sun．The sun gave life and ultimately it will bring death．kaoshida[484 words]
1．According tO the new book，the life expectancy of the Earth is______．
A．1 billion years
B．4．5 billion years
C．7．5 billion years
D．12 billion years
2．It can be inferred from this passage that______．
A．1ife is nothing
B．the world is precious
C．man can never conquer nature
D．the future of human species is gloomy
3．The authors of the new book believe that the human species will______．
A．disappear long before the disappearance of the Earth
B．survive in the universe even if the Earth disappears
C．find a place tO live after the disappearance of the Earth
D．be sent into space by various spacecrafts
4．All of the following things would come tO an end before the final end of the Earth，EXCEPT______
A．Mars
B．a(chǎn)nimals
C．plants
D．oceans
5．The authors of the new book intend tO tell readers primarily that______．
A．the Earth is nothing but one planet in the solar system
B．nothing can survive for ever
C．we should cherish our life and environment on Earth
D．the sun gave lire and ultimately it will bring death