Английский язык. Ч.3 (Tests 10,11,12). Ильичева Н.А - 21 стр.

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while, but eventually the acceleration due to the planet’s gravity will make it
start to fall down again. If you threw the rock hard enough, though, you would
make it escape the planet’s gravity entirely. It would keep on rising forever. The
speed with which you need to throw the rock in order that it just barely escapes
the planet’s gravity is called escape velocity.
Now imagine an object with such an enormous concentration of mass in such
a small radius that its escape velocity was greater than the velocity of light.
Then, since nothing can go faster than light, nothing can escape the object’s
gravitational field. Even a beam of light would be pulled back by gravity and
would be unable to escape.
Massive objects distort space and time, so that the usual rules of geometry
don’t apply any more. Near a black hole, this distortion of space is extremely
severe and causes black holes to have some very strange properties. In
particular, a black hole has something called an event horizon. This is a
spherical surface that marks the boundary of the black hole, the horizon has a
very large velocity. In fact, it is moving outward at the speed of light! That
explains why it is easy to cross the horizon in the inward direction, but
impossible to get back out.
Text B
The Forces
The world around us is replete with means of exerting influence: balls can be
hit with bats, bungee enthusiasts can through themselves earthward from high
platforms, magnets can keep superfast trains suspend just above metallic tracks,
Geiger counters can tick in response to radioactive material, nuclear bombs can
explode. We can influence objects by vigorously pushing, pulling, or shaking
them; or by freezing, heating, or burning them. During the past hundred years
physicists have accumulated mounting evidence that all of these interactions
between various objects and materials can be reduced to combinations of four
21
while, but eventually the acceleration due to the planet’s gravity will make it
start to fall down again. If you threw the rock hard enough, though, you would
make it escape the planet’s gravity entirely. It would keep on rising forever. The
speed with which you need to throw the rock in order that it just barely escapes
the planet’s gravity is called escape velocity.
   Now imagine an object with such an enormous concentration of mass in such
a small radius that its escape velocity was greater than the velocity of light.
Then, since nothing can go faster than light, nothing can escape the object’s
gravitational field. Even a beam of light would be pulled back by gravity and
would be unable to escape.
   Massive objects distort space and time, so that the usual rules of geometry
don’t apply any more. Near a black hole, this distortion of space is extremely
severe and causes black holes to have some very strange properties. In
particular, a black hole has something called an event horizon. This is a
spherical surface that marks the boundary of the black hole, the horizon has a
very large velocity. In fact, it is moving outward at the speed of light! That
explains why it is easy to cross the horizon in the inward direction, but
impossible to get back out.

                                      Text B

                                    The Forces
   The world around us is replete with means of exerting influence: balls can be
hit with bats, bungee enthusiasts can through themselves earthward from high
platforms, magnets can keep superfast trains suspend just above metallic tracks,
Geiger counters can tick in response to radioactive material, nuclear bombs can
explode. We can influence objects by vigorously pushing, pulling, or shaking
them; or by freezing, heating, or burning them. During the past hundred years
physicists have accumulated mounting evidence that all of these interactions
between various objects and materials can be reduced to combinations of four
                                         21

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