You Are Here, Part II

The graphic below follows up on yesterday’s article Debunking the “2012″ Myth. The question is: how exactly is a supposed alignment of the sun with the core of the Milky Way supposed to cause catastropic destruction in 2012?

Graphic map of Milky Way. For better detail, click image to link to source page at atlasoftheuniverse.com.

Graphic map of Milky Way. For better detail, click image to link to source page at atlasoftheuniverse.com.

In this graphic, our Sun is depicted as lying behind the Milky Way’s barred core, in the Orion Arm. Ask yourself:  how can I figure out when the Sun would be “aligned” with this bright central region?


Below is a “top view” graphic from the same source.

Scale top view graphic of Milky Way. For detail view, click image to view source graphic at atlasoftheuniverse.com.

Scale top view graphic of Milky Way. For detail view, click image to view source graphic at atlasoftheuniverse.com.

In this view, the Milky Way’s core subtends an arc of around 20 degrees with respect to the sun. On a bright clear night, those of us  lucky enough to get a clear view of this portion of the Milky Way will see its bright “core” region as a bulge of roughly the same angular size.

In calculating the force and direction of gravitational bodies, one could, with a computer, conceivably perform that calculation for each point source involved and sum the vectors of the results. In the Milky Way’s case, this would require calculating attractive forces for each of the billions of stars between us and an imaginary “center” of the galaxy. Happily, it’s easier to determine the common center of mass of multiple celestial bodies (the point around which they actually rotate). Mathematically, it’s the same thing.

In calculating the “pull” of this imaginary point upon the Earth, one wouldn’t, therefore, get to ignore the effect of galactic arms and stellar bodies “behind” us. Nor would one get to ignore the enormously more powerful effects of our own Sun, Moon and local planetary neighbors – as we calculated in the spreadsheet attached to yesterday’s article.

The Milky Way has a diameter of about 120,000 light-years; we are about 26,000 light-years from the center. We’re about 93,000,000 miles from the Sun, or 1 Astronomical Unit (AU). Yahoo calculates there are about 63115.2 AU in a light year. So the center of the Milky Way is about 26,000 times 63,115 = 1,640,990,000 (1.6 billion) times our distance to the Sun.

Recalling Newton’s law from yesterday, gravitational attraction is inversely proportional to the square of the distance.

So enjoy the night skies, and forget about “cosmic conjunctions”!

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2 thoughts on “You Are Here, Part II

  1. ORION SPUR: Since we are inside the Milky Way, its spiraling arms, gas clouds and dust lanes obscure our view of our home galaxy at optical wavelengths. Until Hubble and others found that other galactic objects are truly not a part of the Milky Way, but separate and expanding galaxies in their billions, we had no clear idea of the shape of our own galaxy. The spiral Andromeda Galaxy proved to be a good visual model. It was thought we resided in the Sagittarius Arm of our galaxy. The advent of satellite and radio telescopy, and improvements in infrared and xray imaging, led to the current model showing us as residing in the Orion Arm, a “spur” of the parent Sagittarius Arm.

    Exploring the image links in my article, we see that constellation Orion is indeed our nearby neighbor, as are many of the brightest stars and nebulae known to us since antiquity.

  2. I agree with this article. I don’t think with one iota that the earth will come to a cosmic end, or at least, life on earth will become extinct.

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