In the real world, no one's going to measure it instantaneously, but we can make the difference as small as we like.

在现实生活中,没人能一瞬间测出来,但我们可以使差值越来越小

耶鲁公开课 - 基础物理课程节选

That means we can also measure velocity slightly later and make the slightly later come as close to right now as we want.

那我们也可以测出稍微迟一点的速度,让那个速度接近我们前面测得的速度

耶鲁公开课 - 基础物理课程节选