ErnieM wrote:The large potion of our view of the whole universe along the plane of the Milky Way is obstructed by the huge bulge and the dust in the galactic arms.
Actually, this isn't the "large portion", but only a fairly small one. Just go outside when the Milky Way is high, and you'll see that it only "occludes" a relatively small percentage of the entire sky.
Hence our observation is only partial and limited towards the directions vertical to the galactic plane that are free of any obstructions. If there is no dark matter in these areas, does this mean dark matter only "lives" along the galactic plane?
No... quite the opposite. Because dark matter doesn't interact with electromagnetic radiation, it is not subject to the same momentum transfer mechanisms of ordinary baryonic matter, and therefore doesn't end up spinning in discs. Instead, it clusters in (approximately) spherical halos. So our galaxy is surrounded by dark matter in all directions, and we should see about the same density no matter what direction we look (which is borne out by observations of its gravitational effects on our galaxy and on other galaxies).
If present, then light must be passing through dark matter.
Yes, but it doesn't affect the passage of the light. That's why it is called
dark matter.
Is it not possible to see through the dust lanes using radio, x-ray and infrared telescopes? How about that part of the universe behind the bulge of the Milky Way? Is our Solar system permanently positioned in the same spot or does it periodically straddle in and out of the spur? If it does, is our perspective also changed in the same way when we switch between lanes on the freeway?
We can and do see through the dustier parts of our own galaxy using other wavelengths. Because we are orbiting inside the Milky Way, our viewpoint of the rest of the Universe changes... but only on a timescale of millions of years. Our position with respect to the galactic plane doesn't change enough with time to have much impact on our view, however.
[quote="ErnieM"]The large potion of our view of the whole universe along the plane of the Milky Way is obstructed by the huge bulge and the dust in the galactic arms.[/quote]
Actually, this isn't the "large portion", but only a fairly small one. Just go outside when the Milky Way is high, and you'll see that it only "occludes" a relatively small percentage of the entire sky.
[quote]Hence our observation is only partial and limited towards the directions vertical to the galactic plane that are free of any obstructions. If there is no dark matter in these areas, does this mean dark matter only "lives" along the galactic plane?[/quote]
No... quite the opposite. Because dark matter doesn't interact with electromagnetic radiation, it is not subject to the same momentum transfer mechanisms of ordinary baryonic matter, and therefore doesn't end up spinning in discs. Instead, it clusters in (approximately) spherical halos. So our galaxy is surrounded by dark matter in all directions, and we should see about the same density no matter what direction we look (which is borne out by observations of its gravitational effects on our galaxy and on other galaxies).
[quote]If present, then light must be passing through dark matter.[/quote]
Yes, but it doesn't affect the passage of the light. That's why it is called [i]dark[/i] matter.
[quote]Is it not possible to see through the dust lanes using radio, x-ray and infrared telescopes? How about that part of the universe behind the bulge of the Milky Way? Is our Solar system permanently positioned in the same spot or does it periodically straddle in and out of the spur? If it does, is our perspective also changed in the same way when we switch between lanes on the freeway?[/quote]
We can and do see through the dustier parts of our own galaxy using other wavelengths. Because we are orbiting inside the Milky Way, our viewpoint of the rest of the Universe changes... but only on a timescale of millions of years. Our position with respect to the galactic plane doesn't change enough with time to have much impact on our view, however.