You've got a magnetic field, maybe even magnetic susceptibility, the electric field. We're not going to worry about these magnetic fields or electric fields in this class So, pretty much we're going to focus on this set of variables here.

你也会引入磁场，或许甚至磁化率，以及电场，我们这堂课不需要关心,这些磁场或,电场之类的东西,基本上我们只关注,这里的一组变量。

麻省理工公开课 - 热力学与动力学课程节选

In fact, there's a property of gravitational fields anywhere, even in outer space, but there is some residual field between all the planets and all the stars in the universe, that the force on a body is proportional to the mass of the body.

实际上,这是任何地方的引力场都具备的属性,甚至是在外太空,在所有的行星和恒星之间,存在着某种剩余场,在这个场里作用在物体上的力,和物体的质量之间存在比例关系

耶鲁公开课 - 基础物理课程节选