On Thu, Sep 27, 2018 at 4:27 PM Brent Meeker <[email protected]> wrote:
> *The dark matter of a galaxy responsible for the flat rotation curve is > presumably in a cloud of spherical orbits around the galaxy. It doesn't > collapse to a disk, as the visible matter does, because being dark it > doesn't radiate away energy via EM in collisions. * > Dark Matter wouldn't radiate anything electromagnetic but there has been speculation that if Dark Matter is accelerated it might radiate something comparable to it, you could call it Dark Light; although there is as of now zero empirical evidence that it actually exists. > > *But it must still radiate gravitational waves in collisions. Are > there estimates of how long this would take to collapse dark matter to a > disk? * > I think it would take far far longer than the current age of the universe. Because the Earth accelerates as it circles the sun it must give off gravitational waves, however its been calculated that the Earth only radiate away about 200 watts of power in the form of gravitational waves, your toaster uses about 6 times as much. The energy radiated away only becomes significant when the object is very dense, and the smaller the orbit its in the more energy in the resulting gravitational waves; and its proportional to the fifth power of the orbital radius so the very last orbit before collision is the one that produces nearly all of the gravitational wave energy and takes less than a second. The orbits of Dark Matter particles in galaxies must have a radius of many thousands of light years, not less than a mile as in 2 neutron stars last orbit. John K Clark > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
