Howmanythingscanyouseeinthenightsky?Alot!Onaclearnighty...
问题详情:
How many things can you see in the night sky? A lot! On a clear night you might see the Moon, some planets, and thousands of sparkling stars.
You can see even more with a telescope. And with bigger and bigger telescopes you can see more and more objects in the sky. And you can see those objects in more and more detail.
But scientists believe there are some things in the sky that we will never see. We won't see them with the biggest telescope in the world, on the clearest night of the year.
That's because they're invisible. They're the mysterious dead stars called black holes.
You might find it hard to imagine that stars die. After all, our Sun is a star. Year after year we see it up in the sky, burning brightly, giving us heat and light. The Sun certainly doesn't seem to be getting old or weak. But stars do burn out and die after billions of years.
As a star's gases burn, they give off light and heat. But when the gas runs out, the star stops burning and begins to die.
As the star cools, the outer layers of the star pull in toward the center. The star squashes into a smaller and smaller ball. If the star was very small, the star ends up as a cold, dark ball called a black dwarf (黑矮星). If the star was very big, it keeps squashing (塌缩) inward until it's packed together tighter than anything in the universe.
Imagine if the Earth were crushed until it was the size of a tiny marble. That's how tightly this dead star, a black hole, is packed. What pulls the star in toward its center with such power? It's the same force that pulls you down when you jump--the force called gravity. A black hole is so tightly packed that its gravity sucks in everything--even light. The light from a black hole can never come back to your eyes. That's why you see nothing but blackness.
So next time you stare up at the night sky, remember: there's more in the Sky than we can see! Scattered in the silent darkness are black holes--the great mystery of space.
32. According to the article, what causes a star to die?
A. As its gases run out, it cools down.
B. It has a collision(碰撞)with other stars.
C. It can only live for about a million years.
D. As it gets hotter and hotter, it explodes.
33. Which of the following statements is NOT true?
A. Black holes are dead stars.
B. Black holes have gravity.
C. Black holes are invisible.
D. There is nothing as mysterious as a black hole.
34. What happens AFTER a star dies?
A. It becomes invisible. B. It falls to Earth.
C. It gets cold with less gravity. D. It becomes brighter and easier to see.
35. Why can't you see light when you look at a black hole?
A. Because most black holes are so far away.
B. Because the gravity of a black hole is so strong that it sucks the light inward.
C. Because as the star's gases burn, it stops giving off heat and light.
D. Because as a star cools, its outer layers pull in toward its center.
【回答】
ADAB
知识点:阅读理解
题型:阅读理解
-
我们每天都生活在阳光不断变化的物质世界里。下列变化一定属于化学变化的是( )A.用干*做制冷剂进行人工降雨B...
问题详情:我们每天都生活在阳光不断变化的物质世界里。下列变化一定属于化学变化的是( )A.用干*做制冷剂进行人工降雨B.久置在空气中的澄清石灰水表面产生一层白膜C.伴随有发光、放热现象的变化D.*【回答】B知识点:各地中考题型:选择题...
-
以下各组国家中,人口增长模式不同的是A.阿曼和孟加拉国 B...
问题详情:以下各组国家中,人口增长模式不同的是A.阿曼和孟加拉国 B.巴西和匈牙利C.澳大利亚和美国 D.韩国和新加坡【回答】B知识点:人口与地理环境...
-
如图所示,一质量为m的物块恰好沿着倾角为的斜面匀速下滑。现对物块施加一个竖直向下的恒力F。则物块( ) ...
问题详情:如图所示,一质量为m的物块恰好沿着倾角为的斜面匀速下滑。现对物块施加一个竖直向下的恒力F。则物块( ) A.将减速下滑 B.将加速下滑 ...
-
对于一定量的理想气体,下列说法正确的是______。(选对一个给3分,选对两个给4分,选对3个给6分。每选错一...
问题详情:对于一定量的理想气体,下列说法正确的是______。(选对一个给3分,选对两个给4分,选对3个给6分。每选错一个扣3分,最低得分为0分) A.若气体的压强和体积都不变,其内能也一定不变 B.若气体的内能不变,其状态也一定不变 C.若气体的...
相关文章
- —WhatdoyouthinkofthespeechgivenbyChairmanXiJinpinginthe...
- Doyouknowtheboyinthepicture?HeisYiYangqianxi.HisEnglish...
- Don’tyouhateitwhensomeonesnubs(冷落)youbylookingattheirph...
- —Iknownothingaboutthehistoryofthetelephone.Couldyoutell...
- Isetouttochangethelivesofthosewhoneedhelpbyjoiningmysch...
- Generally,students'innermotivationwithhighexpectationsf...
- 【2019•襄阳市】—Ienjoywalkingonthecleanstreetsinthemorning. ...
- 完形填空Americanpeoplehavethehabitofsaying“Thankyou”whensom...
- I’msittinghereinthiscoffeeshop.YouknowtheonetherebyAlle...
- Whenyou'relyingonthewhitesandsoftheMexicanRiviera,thest...