Do astronomers have instruments that can look back in time?
Sure. Even your eye can look back in time as you look at stars in the sky. But no instrument can look farther back in time for a GIVEN OBJECT than its light travel time. For example, we may be able to look at the quasar 3C 273 when it was 1.5 billion years younger than today, but we cannot look at the nearby star Alpha Centauri at a time younger than 4.3 years; its light travel distance to Earth. Nor can we see what 3C 273 looked like 4.3 years ago.
