The earth would be a frozen ball if it were not for the radiant heat of the sun.

要是没有太阳的辐射热，地球将会是一个冰冻的球体。

《柯林斯英汉双解大词典》

How do we know that the Earth is a smaller ball turning around one of those stars, the Sun?

我们怎么知道地球是一个更小的球，绕着其中一颗恒星——太阳转呢？

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All the gravity of all the mass in the cosmos should have been pulling the universe back inward, just as gravity pulls a ball back down to Earth after it's been thrown into the air.

宇宙中每一物体的每个引力都会对宇宙产生一个指向物体本身的拉力，就像在重力作用下，抛向空中的球会被拉回地面。

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The first pictures of Earth taken from space showed a solid ball covered by brown and green landmasses and blue-green oceans.

VOA: special.2011.01.04

Try this analogy (thanks to Veritasium.com): if the Earth were the size of a basketball, the moon would be a tennis ball about 24 feet away, and the Sun would be like a house nearly two miles away.

CNN: The sun, the moon and the Titanic

Unlike most shots, in which the golfer largely controls the flight of the ball through the air, a putt's terrestrial trajectory can be altered by a lot more variables the speed of the green, the contours of the earth, a spike mark, or any little object that might be in the ball's path.

WSJ: Tiger Woods Should Credit His Return to No. 1 on Improved Putt