4 ms·

Rotating frames of reference are not inertial.

• akiselev 10y ago
  The center of the galaxy isn't rotating, it's just a point, no? Picking the criteria for such a point would be difficult and tracking it even more so, but what's the alternative?
  • bashinator 10y ago
    The center of the galaxy is almost certainly rotating, and is a supermassive black hole, not a point.
    • akiselev 10y ago
      That's just the massive object at the center of our galaxy.
      • bashinator 10y ago
        Since it's well agreed that virtually every galaxy (spiral or elliptical) has a central supermassive black hole, it's fair at this point to call it part of the galaxy.
    • kijin 10y ago
      A black hole is a point. Its size is zero, regardless of its mass. Its event horizon has a size, but we don't need to care about that. We do, however, need to care about the all the stuff that's revolving around that point, because even a slight imbalance will cause the galactic center of mass (barycenter) to move away from the black hole. Things get pretty wobbly out there.