Earth Odyssey

Date: 2015-10-07; view: 360.

The following article may help you to answer some of the question above. Read it in depth and answer the questions below.

Work in groups. Group A will answer the first question (They might have come by boat.), group B will speak about dinosaurs (There may have been a natural disaster.) Come up with as many answers as possible. Use modal verbs.

Pre-reading (2)

Working in pairs, discuss the following problems.

The puzzle of the birth and death of the Universe is one of the most exciting problems in science comparable in importance with the puzzle of the origin of life. Can you recollect the most popular ones? Which theories seem more plausible to you? What can threaten the Earth from outside? What has it overcome yet?

Reading (2)

For billions of years, Earth has been on a perilous journey through space. As our planet whirls around the sun, the whole solar system undertakes a far grander voyage, circling our island universe every 200 million years. Weaving our way through the disc of the Milky Way, we have drifted through brilliant spiral arms and witnessed the spectaculardeath of giant stars.

Many of these marvels may have been deadly, raining lethal radiation onto Earth's surface. Some may have wiped out swathes of life, smashed up continents or turned the planet to ice. Some may have been more benign, perhaps even sowing the seeds of life.

In a nearby spiral arm of the Milky Way, more than 1000 light years away from our solar system's present position, lies the Orion nebula, a birthplace of giant stars. Our solar system must at times have drifted much closer to such stellar nurseries. To do so is to flirt with disaster. What could be the consequences of such trips? A massive star burns its fuel rapidly, and in a few million years its core can collapse, unleashing the vast energy of a supernova. X-rays from a supernova just tens of light years away could destroy Earth's ozone layer, letting in harmful ultraviolet rays from the sun. High-energy protons or cosmic rays would continue to bombard Earth for decades, depleting ozone, damaging living tissue and possibly seeding clouds to spark climate change. Such convulsions might have triggered some of the mass extinctions that so cruelly punctuate the history of life on Earth.-perhaps even hastening the demise of the dinosaurs 65 mission years ago, according to a theory formulated in the 1990s.

We know Earth has suffered such episodes, including big chills some 650 and 700 million years ago. Their cause remains obscure. It could have been the weathering of mountains that pulled carbon dioxide from the air, or volcanic eruption, or changes to Earth's orbit around the sun- or a black cloud in space.

Then again, clouds may have had a happier influence on Earth. William Napier at the University of Buckingham in the UK has suggested that they could be staging posts for life, sheltering micro-organisms from cosmic rays and sprinkling them on to any receptive planet as it passes through.

Planetary scientist Ian Crawford of Birkbeck, University of London, proposes we can also look at the moon to find clear evidence of many astrocatastrophes. “The moon could tell us Earth's tale. It is a giant sponge soaking up everything thrown at it as we go around the galaxy. Up there, alien dust might have settled down to mix with the lunar soil. We might find fragments that would tell us what type of asteroids of comets were hitting the moon”, he says. Getting to it won't be easy. “We may need to sink a drill into an area known to have lots of lava flows”. Setting up a drilling rig on the moon is beyond our present capabilities.

To find out we would need to visit a variety of lunar surfaces, taking small rock samples to determine their ages, and then making a careful census of craters to see how the impact rate has fluctuated. We might find fragments that would tell us what type of asteroids or comets were hitting the moon. For the moment, we can only look at the craggy face of our old companion and wonder what stories it has to tell.

Stephen Battersby

New Scientist, December 2011

1. What is Earth's journey like?

2. Is it safe?

3. What changes could it have caused?

4. According to scientists where could we find more information?

Vocabulary (2)

1. Here are seven answers. Write the questions.

1. for billion years

2. the Orion nebula

3. Its core can collapse.

4. X-rays from a supernova

5. It could have been the weathering of mountains that pulled carbon dioxide from the air or volcanic eruption or changes to Earth's orbit.

6. clouds

7. to find clear evidence of astrocatastrophes