"How do you tell how old a goose egg is"
To a layperson, the answer to this question might seem obvious, namely, chop it down and count its rings. But an expert in these matters, such as I, knows that sometimes what works on a human might not work on a goose or its egg. In this case, this is what needs to be done.
Insert a tiny camera inside the egg in order to examine the wall of the egg from the inside. Make sure you don't crack it or damage the wallpaper. This is what it should look like:
You see those crossed out lines? That's the goose fetus counting the number of days it's been imprisoned inside the egg. Logic thus dictates, that's how old the goose egg is.