At that time, the Newtonian theory of gravity and the concept of escape velocity were well known.
At that time, the Newtonian theory of gravity and the concept of escape velocity were well known.
那时，牛顿引力理论和逃逸速度的观念是广为人知的。
At that time, the Newtonian theory of gravity and the concept of escape velocity were well known.
那时，牛顿引力理论和逃逸速度的观念是广为人知的。