📖 Unit 12: Life on other planets - Reading lớp 8

Venus is more like Earth in some ways (1) ______ any other planet. It is almost the same size as Earth. It is a similar distance (2) ______ the Sun compared to the other planets. It is made mostly of rock and has an atmosphere (gases that (3) ______ a planet).

Venus has flat plains and high places, just (4) ______ Earth. It has huge extinct (dead) volcanoes and big craters. Meteorites crashing into the planet made the big (5) ______. But Venus has no moon.

In other ways, Venus is not (6) ______ all like Earth. It is not a place you would like to visit. The atmosphere is poisonous. It is made (7) ______ mainly of a gas called carbon dioxide. The clouds are filled with (8) ______ of acid “rain” that (9) ______ eat through your clothes and through you. The atmosphere is so thick that its weight would (10) ______ you.

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Most scientists believe that for another planet to have life on it, it must be similar to Earth in several ways. It is likely to need an atmosphere (air) and water. It also must orbit a star, like the Sun, at a good distance. This star would provide the right amount of light and heat for life to exist.

Scientists have studied planets and moons in our solar system to see if they can support life. Space probes have searched for traces of bacteria or other tiny living things on Mars. Some scientists are also looking for the possibility of life outside our solar system. Using radio telescopes, they hope to capture signals from intelligent aliens.

So far, no evidence of extraterrestrial life has been found. However, scientists have discovered hundreds of planets that orbit distant stars. Some of these planets are an ideal distance from their stars, and some are roughly the size of Earth. It may be possible that life has developed on one or more of them.

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An unidentified flying object (UFO) is any light or object seen in the sky that can't be explained. Hundreds of UFO sightings are reported every year. More than nine-tenths of them are later identified as ordinary objects. They turn out to be planes, satellites, or planets. Others are later identified as balloons, kites, clouds, or birds. But some are deliberate fakes.

UFOs have been reported since ancient times. Modern reports of UFO sightings began in 1947. Some observers reported seeing saucer-like shapes in the sky. Since then, UFOs of any shape are often called flying saucers.

The United States Air Force took these reports seriously. Air Force officials did not necessarily believe in visitors from outer space. They wanted to be sure that UFOs were not a threat to America. A UFO might, for example, be an enemy airplane.

Project Blue Book was the Air Force's program for investigating UFOs. It ran from 1947 through 1969. The Air Force investigated 12,618 UFO sightings. All but 701 were identified.

The Air Force concluded that UFOs were no threat. All sightings could be explained by science. There was no evidence that UFOs came from other planets.