69 Gravity in the Solar System-Mid

Gravity in the Solar System FOCUS Question How does gravity affect objects in the solar system?

太阳系中的引力焦点问题引力如何影响太阳系中的物体?

Gravity and Weight Imagine walking on the Moon. You have to wear a heavy spacesuit to protect you because there is no oxygen. Imagine how hard it would be to move around with all that heavy gear. Actually, it would be much easier than you think! On Earth, your weight is caused by gravity pulling your mass toward the center of the planet. The Moon has much less mass, or total amount of matter, than Earth, so its gravitational pull is much weaker. On the Moon, your mass does not change, but you would weigh one-sixth of what you weigh on Earth. The gear you are wearing would also be much lighter. Your muscles however, are just as strong on the Moon as on Earth. It is much easier to lift your body and your spacesuit off the surface. Astronauts on the Moon had to move very carefully to avoid stepping or jumping too far. It's all about mass and gravity, but what is gravity?

重力和重量想象一下在月球上行走。 因为没有氧气，你必须穿很重的太空服来保护自己。 想象一下，带着那么重的装备四处走动有多难。 事实上，这比你想象的要容易得多!在地球上，你的重量是由重力将你的质量拉向行星中心造成的。 月球的质量或物质总量比地球小得多，所以它的引力要弱得多。 在月球上，你的质量没有变化，但你的体重是你在地球上体重的六分之一。 你所穿的装备也会轻很多。 然而，你在月球上的肌肉和在地球上一样强壮。 把你的身体和太空服从地面抬起来要容易得多。 在月球上的宇航员必须非常小心地移动，以避免走得太远或跳得太远。 这都是关于质量和重力，但重力是什么?

Gravity and Distance Gravity is a force that attracts all objects to each other. How strongly they are attracted depends on two key factors: the masses of the objects and the distance between them. Two large, rocky asteroids in space attract one another because of gravity. If they are far apart, the force is very weak. If they begin to move toward one another, the force increases They may pull together and form one larger asteroid. Do You Know? A meteor is a piece of rock that gets close to Earth. Earth's gravity pulls it down. You might see a streak of light in the sky as the meteor burns up in our atmosphere.

重力和距离重力是一种吸引所有物体的力。 它们被吸引的强度取决于两个关键因素:物体的质量和它们之间的距离。 太空中两颗巨大的岩石小行星因重力而相互吸引。 如果它们相距很远，力就很弱。 如果它们开始向对方移动，力就会增加。它们可能会拉在一起，形成一颗更大的小行星。 你知道吗?流星是一块接近地球的岩石。 地球引力把它往下拉。 当流星在我们的大气层中燃烧时，你可能会在天空中看到一道闪光。

Gravity and Mass Are you and the classmate sitting next to you pulled together by each other's gravitational force? Yes, you are! Gravity attracts you to your pencil and to the bird outside your window and to any other objects that have mass, but it is hard to notice small pulls of gravity. Even large buildings are not massive enough to cause noticeable attraction. Earth's pull on these objects is much greater than the pull of these objects on each other, because Earth is so much more massive than they are. The more massive, the stronger the attraction. Objects like moons, planets, and stars have a noticeable gravitational pull. Math Moment From weakest to strongest, order the strength of the gravitational attraction between Earth and each object in this picture: the student, the building, and the ice cream cone.

重力和质量你和坐在你旁边的同学是被彼此的引力拉到一起的吗? 不，你是!重力把你吸引到你的铅笔、窗外的鸟和任何其他有质量的物体上，但你很难注意到重力的小拉力。 即使是大型建筑也不足以引起明显的吸引力。 地球对这些物体的引力要比它们彼此之间的引力大得多，因为地球的质量比它们大得多。 质量越大，引力就越强。 像卫星、行星和恒星这样的物体都有明显的引力。 从弱到强，按地球和图中每个物体之间的引力强度排序:学生、建筑和冰淇淋蛋筒。

Gravity and the Moon Earth's gravity keeps the Moon orbiting Earth once every 27.3 days. The Moon pulls on Earth, too. causing ocean tides. Water on the side of Earth facing the Moon. is pulled toward the Moon This causes a high tide As the Moon pulls on Earth, the water on the opposite side gets left behind. This causes a high tide on that side, too. Low tides occur between the high tides. As Earth rotates, each coastal location passes through high and low tides twice a day.

地球的引力使月球每27.3天绕地球一周。 月球也拉着地球。 引起海洋潮汐。水在地球面向月球的那一面。 随着月球对地球的引力，地球另一侧的水被甩在了后面。 这也引起了那边的涨潮。 低潮发生在高潮之间。 随着地球自转，每个沿海地区每天都会经历两次高潮和低潮。

The Sun and the Planets You probably know that Earth orbits the Sun. It is the Sun's gravity that keeps Earth and the other planets in the solar system orbiting around it. Can you guess what determines the strength of the gravitational pull between each planet and the Sun? It is the mass of each planet and its distance from the Sun.

太阳和行星你可能知道地球绕太阳运行。 太阳的引力使地球和太阳系中的其他行星围绕太阳运行。 你能猜出是什么决定了每个行星和太阳之间引力的强度吗? 它是每个行星的质量和它到太阳的距离。