Active vs Passive

From: "Brian Quirt" <baqrt@mta.ca>

> Most of this post I can agree with, but I'm not sure about faster
> information. I would think that BY DEFINITION passive sensors HAVE to
> give more recent information

It's the difference between trying to aim a rifle at a target about 60
metres
away via a TV camera with a 4/10 second time delay, and aiming it via
listening
 to the noise the target makes while wearing a blindfold.
The data from the TV is twice as old as the sound (which takes 2/10 of a
second
to travel the distance), but considerably better for targetting
purposes.