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Is there intelligent(有智力的) life on other planets(行星)? For years, scientists said "No." or "We don't know."
But today this is changing. Seth Shostak and Alexandra Barnett are astronomers
(天文学家). They believe intelligent life exists somewhere
in the universe. They also think we will soon contact these beings(人;生物).
Why do Shostak and
Barnett think intelligent life exists on other planets? The first reason is
time. Scientists believe the universe is about 12 billion years old. "This
is long enough for other planets to have intelligent life," say Shostak
and Barnett. The second reason is size——the universe is huge. "Tools like
the Hubble Telescope (哈勃望远镜) have shown
that there are at least 100 billion galaxies (银河系)
," says Shostak. "And our galaxy, the Milky Way, has at least 100
billion stars. Some planets going around these stars might be similar to Earth.
"
In the past, it was hard
to look for signs of intelligent life in the universe. But now, powerful
telescopes (高倍望远镜) allow scientists to
discover smaller planets--the size of Mars or Earth--in other solar systems (太阳系).These planets might have intelligent life.
Have beings from space
already visited Earth? "Probably not," says Shostak. "It's a
long way away. However, intelligent beings may contact us in other way, such as
radio signals(信号). "In fact, they may
be trying to communicate with us now, but we don't have the right tools to receive
their messages. However, this is changing. By 2025, we could make contact with
other life forms in our universe and we might help each other.