As discussed above, aberration occurs because the observer moves relative to parallel beams of light coming from the star.

Imagine that an observer moves along the curve in time, using the attached frame at each point as her coordinate system.

No matter what speed the observer was moving at, he would always measure the speed of light at 186,000 miles a second.

How can observers moving at different speeds all measure light at the same speed?

As an additional safeguard against trouble, Norwegian observers moved into Hebron last week.

Suppose that an observer is moving along a geodesic for the connection.

The observers then moved on their own, getting closer to the mine held during daylight than any other unit had done under cover of darkness.

First, because the source and observer are moving away from each other the doppler effect causes an increase in wavelength.

Out on the barrens, the camouflaged observers were probably picking up their gear and moving closer to the motel.

Paths: A path is defined as channels along which the observer can customarily, occasionally, or potentially move through.