This is minus one over r, so I get m MG over r with a minus sign, and that has to be evaluated between infinity and capital R.

这是r的负值，所以在mMG/r上加-号，它处于,无穷远和R之间。

youdao

Infinity is the force when we're thinking about it and our brains, negative infinity is when we actually plug it into the equation here, and the reason is the convention that the negative sign is just telling us the direction that the force is coming together instead of pushing apart.

说力有多大时，我们想到的,是无穷大，而方程解出来的,是负无穷，这是因为习惯上,我们用负号表示力的方向,是相互吸引而不是相互排斥的,所以我们可以用库仑定律。

麻省理工公开课 - 化学原理课程节选

Each car receives a special red license plate emblazoned with the infinity sign and the letters AU, for autonomous vehicle.

FORBES: Audi Follows Google's Lead, Gets Pass For Driverless Cars

Following approvals, Continental will receive its testing license and red license plate featuring an infinity sign to represent the car of the future.

ENGADGET: Continental gets automated vehicle approved for Nevada roads