The amount of angular momentum, say, a spinning skater has depends on both the speed of rotation, and the weight and distribution of mass around the center.
角动量的大小，取决于旋转中的滑冰选手的旋转速度、体重和绕旋转中心的质量分布。
Then as the star moves around the center of mass, you see that all these lines drift in unison.
随着恒星绕在，质量中心转动，你能看到所有这些线，一致得移动。
As another example the center of mass of the earth and moon moves in an approximately circular orbit around the sun.
作为另一个例子，地球和月亮的质心就是在一个绕太阳的近似的圆轨道上运行。
Why? The reason of the accelerated expansion contains two factors: a galaxy takes place the mass loss; and a galaxy revolved around the center-mass of the universe.
宇宙不仅膨胀，而且正在加速膨胀，其原因有两个：一是星系质量损失；二是星系环绕宇宙中心旋转。
This, and the presence of the Arctic Ocean in the center of the great land mass, give the area a markedly different conformation and climate from that around the opposite pole.
再加上北冰洋又处在大块陆地的中央。这一切使得这块区域相对于地球另一端来说，在构架和气候方面存在显著的不同。
This, and the presence of the Arctic Ocean in the center of the great land mass, give the area a markedly different conformation and climate from that around the opposite pole.
再加上北冰洋又处在大块陆地的中央。这一切使得这块区域相对于地球另一端来说，在构架和气候方面存在显著的不同。
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