The answer is in the center of mass.

答案就质心。

There's a simple way to figure out where the center of mass is.

有一个简单的方法找出质心。

In reality, both circle around their mutual center of mass, located between the two.

事实上，两者都着位于两者之间的相互质心旋转。

These are sets of two stars that orbit around a common center of mass.

即由两颗恒星组成的组合，它一个共同的质心运行。

Three times heavier and the center of mass will be three times closer. And so on.

重三倍，质心的位置就进三倍，此类推。

Within a given supercluster, all galaxy motions will be directed inward, toward the center of mass.

而在超星系团部，所有星系都部质心运动。

With a low center of mass, the wheel just swings back and forth like a pendulum, then stops.

当质心较低时，车轮就像钟摆一样来回摆动，然后停止。

And yet, collected together, they have a single total amount that they spin about their center of mass.

但聚集在一起时，它有一个单一的总的不变量，他总着它的质心旋转。

The stars all orbit the cluster's center of mass, even though there may not be anything at the very center.

所有的恒星都着星团的质心旋转，即使在最中心可能没有任何东西。

The moving parts that make one side of the wheel heavier also shift its center of mass downward below the axle.

使车轮一侧更重的运动部件也将其质心下移至车轴下方。

And so you have an inward force towards the planet's center of mass.

所你有一个朝地球质心的力。

The center of mass is a pointsomewhere along the plank that holds the two kids where their average weight falls.

质心跷跷板上支撑两个孩子平均重量的一个点。

And that is: center of mass.

质心。

In these situations, it’s more useful to describe what the center of mass is doing.

在这些情况下， 描述质心在做什么更有用。

When you throw the hammer, for example, it’ll rotate around its center of mass.

例如，当您扔锤子时， 它会其质心旋转。

In these situations, it's more useful to describe what the center of mass is doing.

在这些情况下，更多的描述有用的 质心的动作。

So, what is the center of mass?

那么，什么质心？

To make the seesaw work, theheavy kid must push that center of mass forward until it just touches the pivot.

要想让跷跷板摇动，重的孩子就得往中间挪直到质心移到中心。

We’ll also discuss what physicists mean when they talk about center of mass, and why that’s important.

我还将讨论物理学家在谈论质心时的含义， 及为什么这很重要。

When you throw the hammer, for example, it'll rotate around its center of mass.

例如，当你扔锤子时， 它将其质心旋转。