Page 63 - Reading Success B9

In our solar system today, there are over 30,000 asteroids flying in space, colliding
with other asteroids and planets. Our very own planet is caught right in the middle of
all of this action and is constantly at risk of being hit. Such a collision with an asteroid
has a powerful enough impact to destroy all life forms on Earth, thereby erasing
thousands of years of human history in a single strike.

Asteroids are large or small chunks of rock and metal flying around in space at
speeds upwards of 80,000 km/h. Asteroids are believed to have formed millions of
years ago during the birth of the universe, a time more popularly known as the "Big
Bang". These chunks of rock, instead of forming into planets, turned into floating
space missiles flying around in space powered by the gravity of the asteroid belt.
Most of these space missiles can be found in the asteroid belt, the home of our solar
system’s asteroids. It is about 150 million miles from our planet, containing thousands
and thousands of asteroids, some even miles in diameter.
Should an asteroid be knocked loose from the belt’s gravitational pull and head
towards Earth, our planet becomes at risk of being hit. For a loose asteroid to be
classified as hazardous, the asteroid must be larger than a kilometer in width and be
found within 8 million kilometers from Earth. According to scientists, it is very probable
that a large asteroid will hit the Earth in the future because asteroids have hit our
planet before in the past. For example, the last major asteroid to strike the Earth is
believed to have caused the extinction of the dinosaurs. In addition, scientists
estimate that an asteroid more than 800 meters in diameter hits the Earth every one
million years and a smaller asteroid hits our planet every century. An asteroid bigger
than a single kilometer has the potential energy to end 30% of the Earth’s total human
population. The power of an asteroid of this size would be equivalent to the explosion
of about two million Hiroshima bombs! An explosion like this could wipe out a
population of living creatures within a hundred mile radius of its point of impact.

Thus, an asteroid is the most dangerous force that can be found in our solar
system. A single asteroid’s strike against our planet would not only bring the
human race back to the dark ages but also cause the death of billions of people.
Unfortunately for us at the moment, the locations of only a fraction of all the asteroids
in space are known. Others we don’t know even know about at all.

Main Idea

What is the main idea of this story?

a. how asteroids are formed

b. how to predict asteroid collisions
c. the extinction of the dinosaurs

d. the dangers posed by asteroids

66_Reading Success B 9