One of the key reasons gridlock happens is our inability to maintain a constant speed.

交通堵塞的主要原因之一是我们无法保持恒定的速度。

What we want to achive is a round link turn, which keeps my speed constant and in control.

我们想要的是一个连接处平滑的转弯，这样可以 保持滑行速度恒定，并使速度在自己的掌控中。

To be an inertial observer, one has to maintain a constant speed and direction relative to the rest of the universe.

作为惯性观测者，必须相对于宇宙的其余部分保持恒定的速度和方向。

But in other galaxies and places in the universe where things are different, that the speed of light constant is different.

但在宇宙中的其他星系和地方情况却不同，光速常数是不同的。

Well, as a planet orbits the Sun it may not keep a constant speed but it does maintain its angular momentum.

当行星绕太阳运行时，它可能不会保持恒定的速度，但它的角动量会保持不变。

Outside forces can change an object's direction or speed,   but constant forces create a constant speed.

外力可以改变物体的方向或速度，但恒定的力会产生恒定的速度。

In a 2008 experiment, drivers were instructed to drive along a circular road, following the car in front of them while trying to maintain a constant speed.

在2008年的一项实验中，司机们被要求沿着环形道路行驶。他们要在在保持恒定速度的同时跟随着前面的车辆。