31 A2+ the science of light

CHAPTER 1 See the Light? WHAT IS LIGHT? Lucy stayed up late one night. She slept through her alarm the next morning. Her father came into her bedroom. He turned on the light and shouted, "Get up now, Lucy. It's late!" Lucy answered, "Dad, the light's shining in my eyes. It hurts! Please turn it off." Her father didn't listen to her, "You're going to be late for school! Why are you still in bed?" "Dad," she explained, "I had to work after school. Then I stayed up late studying because I have a test today." Lucy's explanation brought the problem to light. Now her father understood why she was so tired. He felt bad. His daughter was the light of his life, and he didn't like to fight with her. "Oh," he said, "I'm sorry I was so angry. Let's get you to school."

第一章看见光了吗？什么是光？ 一天晚上露西熬夜了。 第二天早上闹钟响了，她一直睡到天亮。 她父亲走进她的卧室。 他打开灯，喊道：“快起来，露茜。 这是迟了!”露西回答说：“爸爸，灯光照在我的眼睛里。 这很伤我的心!请把它关掉。” 她父亲不听她的话，“你上学要迟到了！你怎么还躺在床上？”“爸爸，”她解释说，“放学后我还要工作。 然后我熬夜学习，因为我今天有一个考试。” 露西的解释使问题一目了然。 现在她父亲明白她为什么这么累了。 他感到很难过。他的女儿是他的生命之光，他不喜欢和她吵架。 “哦，”他说，“对不起，我刚才太生气了。 我们送你去学校吧。”

"I know. I can't miss my test!" Lucy said. She looked worried. Her father said, "I know you're working hard. But don't worry, there's a light at the end of the tunnel." Lucy asked, "What do you mean?" "You know, things seem bad right now, but you'll soon be on vacation," her father answered. Lucy said, "Yeah, but right now that feels like light years away!" "It will be here before you know it," her father said, "Now, I give you the green light to sleep as late as you want on Saturday!" Lucy laughed. "Thanks, Dad." The word "light" is used in many expressions. Most of them are about things getting better or looking brighter. This may be because light helps us see, and we couldn't live without it. But what is light exactly?

“我知道。我不能错过考试！”露西说。 她看上去很担心。她的父亲说：“我知道你很努力。 但别担心，隧道尽头会有光明的。” 露茜问：“你这是什么意思？”“你知道，现在情况看起来很糟糕，但你很快就会去度假的，”她父亲回答说。 露西说：“是啊，但现在感觉就像光年那么远！”“它很快就来了，”她父亲说，“现在，我允许你星期六想睡多晚睡多晚！”露西笑了。 “谢谢,爸爸。”“光”这个词被用在很多表达中。 大多数都是关于事情变得更好或看起来更光明。 这可能是因为光帮助我们看东西，没有它我们就无法生存。 但光到底是什么？

CHAPTER 2 Night Light IS THERE LIGHT IN SPACE? Have you ever looked at the stars and thought about light? Cosmologists try to answer questions about stars, planets, and other things in space. They think the universe started about 14 billion years ago. They believe that all the matter in the universe was in a small ball. This ball got very hot and expanded really quickly. They call this the Big Bang Theory. Cosmologists believe that a lot of energy came out of the Big Bang. It spread matter out across the universe. This matter became cooler, and after millions of years, stars and planets were created. As the universe expanded and cooled, matter lost energy and some became light. Cosmologists are still learning more about this oldest light in the universe.

第二章夜光太空中有光吗？ 你曾经看着星星，想到过光吗？ 宇宙学家试图回答关于恒星、行星和太空中其他事物的问题。 他们认为宇宙起源于大约140亿年前。 他们相信宇宙中所有的物质都在一个小球里。 这个球变得非常热，膨胀得非常快。 他们称之为大爆炸理论。 宇宙学家认为，大爆炸产生了大量能量。 它将物质扩散到整个宇宙。 这些物质变得更冷，数百万年后，恒星和行星诞生了。 随着宇宙的膨胀和冷却，物质失去了能量，一些变成了光。 宇宙学家仍在进一步了解宇宙中最古老的光。

Cosmologists know that light comes from stars. The light on the Earth comes from one star, the sun. The Earth turns as it travels around the sun. This movement gives us day and night. When a place on the Earth is facing the sun, it is daytime there. When it is turned away from the sun, it is nighttime. The sun's light also gives us seasons. The Earth takes one year to go round the sun. But the Earth is tilted. So when it travels around the sun, it is summer in the part that is tilted towards the sun and it is winter in the part that is tilted away. Often the moon looks really bright, but it doesn't make its own light. It reflects light from the sun. The sun's light shines on different parts of the moon as the moon travels around the Earth. That is why the moon looks different at different times of the month.

宇宙学家知道光来自恒星。 地球上的光来自一颗恒星——太阳。 地球绕太阳公转时自转。 这个运动给了我们白天和黑夜。 当地球上的一个地方正对着太阳时，那里就是白天。 当它背向太阳时，就是黑夜。 太阳的光也给了我们季节。 地球绕太阳一周需要一年的时间。 但是地球是倾斜的。所以当它围绕太阳运行时，向太阳倾斜的部分是夏天，向太阳倾斜的部分是冬天。 月亮通常看起来很亮，但它自己并不发光。 它反射太阳光。 当月球绕地球运行时，太阳光照射在月球的不同部分。 这就是为什么月亮在一个月的不同时间看起来不同。

The sun isn't the only star in the sky, but it's the only one we see during the day. We can see about 2,500 stars in the night sky, but there are many more stars in space. Long ago, people looked at groups of stars and saw pictures. They created stories, called myths, about these pictures. For example, people saw two bears in the stars, so they created myths about how the bears got there. Today, we know that stars are made of gases that give off light and heat. Cosmologists can't see all the stars in the universe, but they can see many of them with large telescopes. Now we know there are billions and billions of stars in the universe!

太阳不是天空中唯一的星星，但它是我们白天看到的唯一一颗星星。 我们可以在夜空中看到大约2500颗星星，但在太空中有更多的星星。 很久以前，人们看星星，看图画。 他们创造了关于这些照片的故事，称为神话。 例如，人们在星星上看到两只熊，所以他们创造了关于熊是如何到达那里的神话。 今天，我们知道恒星是由释放光和热的气体组成的。 宇宙学家无法看到宇宙中的所有恒星，但他们可以用大型望远镜看到其中的许多恒星。 现在我们知道宇宙中有数以亿计的恒星！

Stars are all different sizes. The sun looks small from the Earth, but it is actually huge it is bigger than one million Earths! Stars are also different colors, too. Hot stars look white or blue. Cooler stars look red or orange. Our sun may feel hot to us, but compared to other stars, it is nice and cool. Cosmologists use telescopes to learn about the stars. The Hubble telescope is special because it is in space. It can see farther than telescopes on Earth. By using the Hubble telescope, cosmologists learned about a star cluster called NGC 6397. The stars in this cluster are so close together that two of them sometimes hit each other. When two stars hit each other, they become one star that is very bright.

星星的大小不一。 从地球上看太阳很小，但实际上它很大，比一百万个地球还大！星星也有不同的颜色。 热星看起来是白色或蓝色的。 温度较低的恒星看起来是红色或橙色。 我们的太阳对我们来说可能很热，但与其他恒星相比，它是凉爽宜人的。 宇宙学家使用望远镜来了解恒星。 哈勃望远镜的特殊之处在于它位于太空中。 它比地球上的望远镜看得更远。 通过使用哈勃望远镜，宇宙学家了解了一个名为NGC 6397的星团。 这个星团中的恒星靠得很近，有时会有两颗互相撞击。 当两颗恒星相互碰撞时，它们会变成一颗非常明亮的恒星。