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Old March 13 2013, 02:46 PM   #110
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Location: North America
Re: Earth ship Valiant

Warped9 wrote: View Post
I do have some question about the magnetic storm. The galaxy edge is 20,000 light years away (the rim) or about 3000 l.y. (the upper or lower surface) and that's an awful long way to be tossed.
The Wikipedia article for the Milky Way galaxy is at, but I'll directly cite its sources which appear authoritative.

The thickness of the galaxy's disk is only 1000 light years [NASA source at].

The wiki claims that the Sun is between 16 and 98 light years from the central plane of the Galactic disk [academic article whose abstract, which contains the relevant information, is at]. I referred to that upthread, but I didn't dig deeper like I should have. Looking at that abstract, I see a much narrower range of values of less than 20 light years, from 23-29 parsecs, or about 75 to 94.5 light years.
article's abstract wrote:
The distance of the Sun from the Galactic plane inferred from classical Cepheid variables is Z_solar = 26 +/- 3pc
It's possible that whomever wrote the wiki article made a mistake there.

In any case, points out that:

Scientific American wrote:
Finding one's location in a cloud of a hundred billion stars--when one can't travel beyond one's own planet--is like trying to map out the shape of a forest while tied to one of the trees. One gets a rough idea of the shape of the Milky Way galaxy by just looking around--a ragged, hazy band of light circles the sky. It is about 15 degrees wide, and stars are concentrated fairly evenly along the strip. That observation indicates that our Milky Way Galaxy is a flattened disk of stars, with us located somewhere near the plane of the disk. Were it not a flattened disk, it would look different.
So, the sun might be a little off-center out of the plane of the disk, but it can't be much, relatively speaking. Therefore, from this information, it's only 400-500 light years to the galaxy's edge.

So, my question back to you is, where is your 3000 light year figure coming from?
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