What is the greatest threat to life on our planet? Is it climate change? Shortages of food or water? Or might an altogether bigger danger come from somewhere further away: space?
We’re not talking about an invasion by little green men here. Instead, how about the prospect of being hit by a gigantic meteorite, zapped by lethal cosmic rays or fried by the deadly energy of an erupting star?
It wouldn’t be the first time. Good old planet Earth has had a rough ride over the last 3.7 billion years, with some spectacularly devastating events. The most famous mass extinction was 66 million years ago, when it’s widely believed a meteorite killed off the dinosaurs. A 110-mile-wide crater in Mexico with the same geological age supports this theory.
Believe it or not, this wasn’t the most brutal episode in our planet’s history. That was when a staggering 96% of life was wiped out at the end of the Permian period, 252 million years ago. Scientists don’t know for sure why this happened, but any potential explanations carry with them the grim possiblity that similar events could happen again.
For example, some experts believe that our Sun has a very dense, dim twin star which is too far away to observe directly. This sleeping giant, dubbed the “Death Star”, could distort the paths of orbiting chunks of icy rock and hurl them towards the rest of the Solar System.
Is this what happened 252 million years ago? Or is there instead, perhaps, a distant, ninth planet in our Solar System which pulls in passing comets and sends them hurtling our way?
If that isn’t enough to put you off your breakfast, then consider what’s happening to our friend, the Sun. The star that has given us the warmth to sustain life is gradually turning into a deadly foe. Like all stars, it is slowing dying, burning through its energy supplies. As it does so, it expands, and in about 2 billion years it will have grown so much that the heat will make life on planet Earth unbearable.
While all this sounds a little macabre, take comfort from the fact that the chance of being hit by a giant interstellar projectile is incredibly slim, and that 2 billion years is a very long time.
And there’s another thing: if the dinosaurs had not snuffed it when they did, it’s extremely unlikely that human beings would have had the chance to evolve at all.
2. What evidence is there that a meteorite wiped out the dinosaurs?
3. Why was 96% of life destroyed at the end of the Permian period?
4. Which verb means: ‘to throw’?
5. True or false: All stars eventually run out of energy.
2. 请你在不参考课文的情况下完成下列练习。选择一个意思合适的单词填入句子的空格处。
1. Last year was __________. I’m glad to see the end of it.
rough riding a rough rider a rough ride rough ride
2. Washing clothes in boiling water __________ bacteria.
makes extinct kills off snuffs wipes off
3. Can we change the topic? Talking about it _________ my food.
put me off puts off puts off me puts me off
4. One day I’d love to travel to _________! I’d even buy a one-way ticket to Mars.
space the space the Space spaces
5. Earth orbits _________.
the Sun the Moon the planets the solar system答案
1. 阅读课文并回答问题。
1. When did dinosaurs become extinct?
Many scientists believe that dinosaurs became extinct 66 million years ago.
2. What evidence is there that a meteorite wiped out the dinosaurs?
A huge crater was discovered which struck Earth at the same time as when the dinosaurs became extinct.
3. Why was 96% of life destroyed at the end of the Permian period?
Scientists aren’t sure why this happened. It may have been caused by an object hitting the Earth, for example a comet or icy rock sent our way by a dim star or ninth planet.
4. Which verb means: ‘to throw’?
To hurl.
5. True or false: All stars eventually run out of energy.
True. All stars eventually burn through their energy supplies.
2. 请你在不参考课文的情况下完成下列练习。选择一个意思合适的单词填入句子的空格处。
1. Last year was a rough ride. I’m glad to see the end of it.
2. Washing clothes in boiling water kills off bacteria.
3. Can we change the topic? Talking about it puts me off my food.
4. One day I’d love to travel to space! I’d even buy a one-way ticket to Mars.