Magic Meteor Astronomy - IELTS Listening Answers & Explanations

Woman: This is "Magic Time" from the BBC. I am Faith. In today's programme we invite a professor of astronomy. Welcome Lewis.

Man: Thanks a lot, Faith.

Woman: What magic information will you introduce to us?

Man: We all know the Leonids in August are coming, so today let's talk about meteors.

Woman: Good topic. At one time or another, almost everyone has glimpsed a swift little streak of light dashing across the night sky. Nearly everyone makes wishes when they see them and blame both good and bad luck on their presence.

Man: Yes. These sudden celestial visitors are meteors. We often call it "shooting star". The glowing trials are caused by the incineration of a piece of celestial debris entering our atmosphere.

Woman: Many meteors are quick flashes, but some last long enough for us to track their brief course across the sky.

Man: Right. Now and then, a meteor truly will light up the night, blazing brighter than Venus – although rarely, even brighter than the Moon – leaving in its wake a dimly glowing trail that may persist for minutes.

Woman: Lewis, can we see some meteors every night in one year?

Man: Yes. Under a dark sky, any observer can expect to see between two and seven meteors each hour any night of the year. These are sporadic meteors.

Woman: Sporadic meteors?

Man: Yes. Their source bodies – meteoroids – are part of the dusty background of the inner solar system. Several times during the year, Earth encounters swarms of small particles that greatly increase the number of meteors. The result is a meteor shower, during which observers may see dozens of meteors every hour. Concentrations of material within the swarms may produce better-than-average displays in some years, with rates of hundreds per hour. And we're treated to a truly amazing display in which thousands of visible meteors can be seen for a brief period. The phenomenon is called meteor storms which are more magnificent than meteor showers.

Woman: Ah ha! That's wonderful!

Man: Definitely. The meteors that appear during a meteor shower seem to come from one point in the sky. This illusion is an effect of perspective, just as a roadway seems to converge in the distance. Usually, meteor showers get the name of the constellation from which the meteors appear to radiate. Such as during the Perseid shower in August, meteors seem to streak from a point in the constellation Perseus.

Woman: When is the biggest meteor storm?

Man: According to records, in 1833, a storm of 60,000 meteors an hour shocked the world.

Woman: 60,000? That's unbelievable!

Man: By the 1860s, scientists had known that many meteor showers were annual – including the normally placid Leonids, which produced the big storm – and that they were somehow related to comets.

Woman: Really?

Man: Yes. But most of the meteors people have seen during one of the annual showers arise from fluffy particles not much larger than sand grains. As a particle enters Earth's atmosphere, it collides with gas atoms and molecules. The particle becomes wrapped in a glowing sheath of hearted air and vaporized material boiled off its own surface.

Woman: Whether meteor is very near to us when it appears?

Man: No. In fact, it is an illusion. However even well-trained professionals can be fooled. Such as airline pilots have swerved to avoid meteors that were actually 160km away. A meteor that appears brighter than any of the stars and planets is a fireball.

Woman: Fireball? That's so interesting

Man: Yeah. Most meteors are seen 80 to 120 kilometres above the ground. Sometimes, someone will claim to see a fireball land on a hilltop, but in fact a real fireball first appears at a height of about 125 kilometres and loses its brightness while still at least 20 kilometres above the ground.

Woman: Yes. What colours do meteors have?

Man: Usually, most meteors look white, but some also appear blue, green, yellow, orange, or even red.

Woman: What will happen if a meteoroid gets to the surface of the Earth without being completely vaporised?

Man: It will be meteorite.

Woman: I heard meteorites were long ago thought to be cast down as gifts from angels.

Man: Yes. And others thought the gods were displaying their anger.

Woman: Really?

Man: As late as the 17th Century, many believed they fell from thunderstorms (they were nicknamed "thunderstones"). Many scientists didn't believe the accounts of people who claimed to have seen meteors and some experts were sceptical that stones could fall from the clouds or the heaven.

Woman: Yes.

Man: One of the most significant meteorite events in recent history destroyed hundreds of square miles of forest in Siberia on June 30th, 1908. According to local witnesses a ball of fire streaked through the sky and seemed to enter the atmosphere at an oblique angle. It exploded, sending out hot winds and loud noises and shaking the ground enough to break windows in nearby villages. Small particles blown into the atmosphere lit the night sky for several days.

Woman: So, nowadays, the prevailing theory holds that a meteor exploded just above the surface?

Man: Yes. Most impact craters and basins larger than the Meteor Crater are heavily worn away or have been buried by rocks and dirt as the earth's surface changed. At present, Chicxulub Basin centered in Mexico's Yucatan Peninsula is the largest one. The diameter of basin is around 300 kilometres. Rock samples obtained by drilling into the basin show that an asteroid struck the earth there about 65 million years ago.

Woman: Does that the same period with the dinosaurs disappeared?

Man: That's right. Many scientists believe this debris caused climate changes which made the dinosaurs not survive.

Woman: We do really hope that will never happen again.

Man: Right.

Woman: OK. Thanks for watching today's programme. See you next week.