This means an observer can detect when their motion is accelerated by studying light signals.

Instead, an observer can only detect the information at the horizon itself, or inside, but never both simultaneously.

Gone were the days of complicated installations that all but the most inexperienced observer could detect with enough effort.

Across the street, a quick-eyed observer detected that slight linger.

A close observer might have detected that he was a man from Manhattan.

But even the keenest observer would not have detected the shape which appeared a moment later.

But he also thought it something that "some diligent observer, if help'd with better microscopes, may in time detect."

He said new steps were taken to insure that international observers would detect or prevent problems of intimidation in the elections.

Example: If the observer detected 12 meteors in 15 minutes, their hourly rate was 48.

Different observers could detect changes as little as 1/300 to 1/1500 of a fringe.