Why did our galaxy morph into three distinct spinning phases?

The Milky Way's star-forming disk changed character twice over cosmic time: first as a chaotic, slowly-forming protogalaxy, then as a thick disk during a burst of star formation, finally settling into today's thin disk. Using cosmological simulations, researchers traced these transitions to shifts in how gas accumulates and spins—chaotic sloshing gives way to coherent rotation, which later requires slower accretion to maintain its structure. This explains why the local neighborhood looks so different from billions of years ago.