5 ms·
The directions are defined the same way as directions on the Earth or in the solar system using the right-hand rule to define north and east based on counter-cl
by ianburrell 7y ago
The directions are defined the same way as directions on the Earth or in the solar system using the right-hand rule to define north and east based on counter-clockwise rotation.
- saghm 7y agoAh, I forgot that the galaxy rotates as well. That definitely makes things a bit simpler.
- close04 7y agoIt's a quote from The Hitchhiker's Guide to the Galaxy. Only hit me at the very end of it... "digital watches are a pretty neat idea".
- spolster 7y agoWest can be defined in terms of spin direction, but western ( as in hemisphere) requires a meridian to define the boundary. I'd have assumed that we'd have put Earth on the galactic meridian, much like the Brits put London on the terrestrial one.
- BurningFrog 7y agoI expect it goes through Greenwich, as always!
- hanniabu 7y agoOkay, so once you have north, which way is east in a circle?
- ajuc 7y agoEast on Earth is the direction in which we rotate. Should be the same for a galaxy.
- dotancohen 7y agoYou are correct, it is determined by spin. However, for some reason that has never been explained to me, we define galaxies to spin in the opposite direction from planets.
- Keysh 7y agoWe don't define galaxies in general to spin in the opposite direction. Just the Milky Way. (The reason for this seems to be that Galactic "North" was defined long before we had the data to determine which way the Milky Way rotated -- or even that it rotated. By the time the rotation was definitively determined, it was too late to override convention. This may go back to William Herschel deciding that the "north pole" of the Galaxy should be in the same hemisphere of the sky that the Earth's north pole pointed toward. In retrospect, he had a 50% chance of being right...)
- RangerScience 7y agoI never thought about this. Will most solar systems form roughly on the same plane as the galactic disk, and will they generally have orbits in the same or the opposite direction as the galactic rotation of their star?
- Keysh 7y agoIt's basically random; the rotation of a solar system depends on the rotation of the gas clump that collapses to form the star and its system, and that depends on local details about the relative orientation of local gas clumps, the possible influence of winds from nearby massive stars and supernova shock waves, and general turbulent motions within molecular clouds.
- gmiller123456 7y agoIt's not very random. The galaxy also formed from a clump of rotating gas, and this heavily influences the direction all of the sub-bodies will rotate and orbit. Systems influenced by other forces would be the exception to the norm.