expanding universe, n.All

Expanding universe (n.) poses ⁠​‌​​​‌​​​‌​‌‌​​​​‌​‌​​‌‌​‌​​‌​​​​​‌‌​​‌​​​‌‌​‌‌​⁠an undecidable question — do the galaxies move or the space? — and its undecidability is the clue: galaxies/space is one thing expanding.