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  3. Gravity is one of those things we take completely for granted. And there are

Gravity is one of those things we take completely for granted. And there are

游客2023-08-04  27
问题     Gravity is one of those things we take completely for granted. And there are two things about it that we take for granted: the fact that it is always there, and the fact that it never changes. If the Earth’s gravity were ever to change significantly, it would have a huge effect on nearly everything because so many things are designed around the current state of gravity.
    Gravity is an attractive force between any two atoms. Let’s say you take two golf balls and place them on a table. There will be an incredibly slight gravitational attraction between the atoms in those two golf balls. If you use two massive pieces of lead and some amazingly precise instruments, you can actually measure an infinitesimal attraction between them. It is only when you get a gigantic number of atoms together, that the force of gravitational attraction is significant.
    The reason why gravity on Earth never changes is because the mass of the Earth never changes. A change in mass great enough to result in a change in gravity isn’t going to happen anytime soon.
    But let’s ignore the physics and imagine that, suddenly there was no force of gravity on planet Earth. This would turn out to be a pretty bad day. We depend on gravity to hold so many things down—cars, people, furniture, pencils and papers on your desk, and so on. Everything would start to float. What’s more, two of the more important things held on the ground by gravity are the atmosphere and the water in the oceans, lakes and rivers. Without gravity, the air in the atmosphere would immediately leap into space. This is the problem the moon has—the moon doesn’t have enough gravity to keep an atmosphere around it, so it’s in a near vacuum. Without an atmosphere, any living thing would die immediately and anything liquid would boil away into space.
    In other words, no one would last long if the planet didn’t have gravity.
    If gravity were to suddenly double, it would be almost as bad, because everything would be twice as heavy. There would be big problems with anything structural. Houses, bridges, skyscrapers, table legs and so on are all sized for normal gravity. Most structures would collapse fairly quickly if you doubled the load on them.
    What this answer shows you is just how integral gravity is to our world. We can’t live without it. It is one of the true constants in our lives. [br] What do we tend to think of gravity?
选项 A、It will never change significantly.
B、It will change some time in the future.
C、It has nothing to do with our daily life.
D、It is always there on Earth.
答案 D
解析 细节题。根据题干中的we tend to think of gravity定位到原文第一段。该段第二句中提到，关于重力，我们认为下面两种情况是理所当然的：一是它自始至终就在那里，二是它从未改变。由此可知，只有D项表述符合原文，故选D。
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