

It kind of depends how far away they go. There is this concept called a “light cone” and it’s basically the information that could possibly reach you as you go through space/time. If they land inside your light cone, they could possibly reach earth with a signal. It may take a long time and they are long gone, but it could be possible.
If they are outside the Earth’s light cone, there is no possible way for their signal to reach earth.
Because signals and other causal influences cannot travel faster than light (see special relativity), the light cone plays an essential role in defining the concept of causality: for a given event E, the set of events that lie on or inside the past light cone of E would also be the set of all events that could send a signal that would have time to reach E and influence it in some way.
“Because we are free men, we will be free to measure liquids in liters and milliliters… but not all liquids, only soda, wine, and alcohol because for milk and paint we will use gallons, pints, and quarts, god willing”
“How many liters are in a gallon, sir?” “Nobody knows.”
“Why not use meters and kilometers?” “We sill, soldier. But only in certain unpopular sports like track and swimming.”