11 Gravity

Gravity written by Dawn McMillan

《地心引力》作者道恩·麦克米兰

forces Gravity is an invisible force of nature. A force is a push or a pull. Gravity is a pull. If you throw a stone in the air, it will fall down because it is pulled by the Earth's gravity. When you fall off your bike or spill your drink, gravity is at work! Gravity is what makes things fall down to Earth.

重力是一种看不见的自然力。 力是推或拉。 重力是一种拉力。如果你把一块石头扔向空中，它会掉下来，因为它受到地球引力的牵引。 当你从自行车上摔下来或打翻饮料时，都是重力在起作用!重力是使物体落向地球的原因。

science It was a famous scientist, called Isaac Newton, who first thought about gravity. One day, when he was sitting under an apple tree, an apple fell on his head. He wondered why the apple fell down. Why didn't it go up, or sideways? This made him think that something pulled the apple down.

第一个想到万有引力的是一位名叫艾萨克·牛顿的著名科学家。 一天，当他坐在一棵苹果树下时，一个苹果掉在了他的头上。 他想知道苹果为什么掉下来。 为什么它没有上升，或者横着走? 这使他认为有什么东西把苹果拉下来了。

Earth Gravity is important to all living things because it keeps us in place on Earth. If gravity didn't pull us down, we would float off the planet. All our water would float off, too, and even the air that we need to breathe would float away!

地球引力对所有生物都很重要，因为它使我们保持在地球上的位置。 如果地心引力不把我们往下拉，我们就会飘离地球。 我们所有的水也会飘走，甚至我们需要呼吸的空气也会飘走!

weight Gravity pulls things closer to each other. If an apple falls off a tree, both Earth and the apple are pulling each other. But we don't notice the tiny pull of the apple because Earth is huge, and it has a very strong pull. When gravity pulls on your body, it is called weight. The further away from the centre of Earth you are, the less you weigh. If you were on a mountain top, you would weigh a little less.

重力使物体彼此靠得更近。 如果苹果从树上掉下来，地球和苹果就会相互拉拽。 但我们没有注意到苹果的微小拉力，因为地球很大，而它的拉力非常强。 当重力作用在你的身体上时，它被称为重量。 你离地球中心越远，你的体重就越轻。 如果你在山顶上，你的体重会轻一点。

particles Things like wood, stone, and water are made from very tiny particles. Even air is made up from little particles. We are also made from particles, but they are too small for us to see. The more particles something has, the more gravity pulls on it. That is what makes things feel heavy.

像木头、石头和水这样的东西都是由非常微小的颗粒构成的。 甚至空气也是由小颗粒组成的。 我们也是由粒子构成的，但它们太小了，我们看不见。 粒子越多，对它的引力就越大。 这就是让事情感觉沉重的原因。