Eli5: why are galaxies flat and not sphere?
In: Planetary Science
Some galaxies are spherical!
The reason why they are rare and most are flat is because stuff orbiting in different planes is bound to collide (well, the chance of directly colliding is quite small, but it’s enough if they get close enough to affect each other via gravity). Such arrangement is not stable, so stuff tends to end up orbiting along one plane.
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