5 ms·
Based on which reference frame?
by stouset 10y ago
Based on which reference frame?
- akiselev 10y agoThe solar system's rotation is about the center of the galaxy so that would be the natural pick for an inertial reference frame, or the supermassive black hole believed to be in the center.
- kachnuv_ocasek 10y agoRotating frames of reference are not inertial.
- akiselev 10y agoThe 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 agoThe center of the galaxy is almost certainly rotating, and is a supermassive black hole, not a point.
- akiselev 10y agoThat's just the massive object at the center of our galaxy.
- bashinator 10y agoSince 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 agoA 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.
- ridgeguy 10y agoMinimum Doppler shift of the cosmic background radiation integrated around the entire sky?
- dmd 10y agohttps://en.wikipedia.org/wiki/Comoving_distance#Comoving_coordinates https://en.wikipedia.org/wiki/Comoving_distance#Comoving_coo...