 So what did Newton think of his realisation? After Newton had theorised his law of universal gravitation he wrote the following that one body may act upon another at a distance through a vacuum or in other words a force between two objects due to gravity which we know acts on masses at a distance without requiring any medium such as air to transfer the force is to me so great an absurdity that no man could ever fall into it So Newton's quote is referring to gravity which Newton calls absurd If you consider the mechanical forces that you previously learnt about and that Newton would have encountered there is always a mechanical force at work that physically and directly pushes or pulls on another object For gravity this direct mechanical link is missing We tend to take understanding gravity for granted nowadays but if you think of it from Newton's perspective you can begin to see how great the leap this realisation was for his time