Cosmic Look-Back Time
The time in the past at which the light we now receive from a distant object was emitted is called the look-back time. When astronomers discuss events in distant objects, they take for granted that the actual event occurred earlier because of light travel time.
It is similar to finding a series of photographs of a child in a 300 year-old time capsule. We could see how the child was developing 300 years ago, even though he/she would no longer be alive.
Cast The First Stone 