As Time Goes By This dynamic long-exposure photograph shows
ESO’s Very Large Telescope in action, as well as revealing the
rotation of the Earth in space. Just as the Sun rises in the
east and sets in the west, so do the stars appear to slowly
march across the sky. Their leisurely pace is imperceptible to a
casual observer, but you can test the effect for yourself: on
the next clear night note the position of a bright star, and
then check again a few hours later. The change is not caused by
the motion of the stars themselves, but rather the rotation of
the Earth. Long-exposure photography is the ideal way to capture
this motion. A camera is set up on a tripod, and the shutter
opened to the sky. Normal snapshots gather light for a fraction
of a second, but these special images need starlight to pour
onto them for much longer, like a bucket collecting rainwater.
To obtain this image, ESO Photo Ambassador Gianluca Lombardi
collected light for a total of 25 minutes. This may not seem
like a long time, but the str