An interesting alternative theory suggests a different explanation on gravitational forces around the outer edges of galaxies, which questions the existence of “dark matter” and all its mystery. Discovery reports:

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Aug. 3, 2007 — The mysterious dark matter that’s been called on to make sense of the ways galaxies twirl through space may not exist, if an alternative theory is right.
The surprising way galaxies rotate — as if they are much larger and heavier than they appear to be — has long implied to astronomers and astrophysicists that there is more matter out there holding things together than we see.
That unseen and unseeable matter has fallen under the catch-all term “dark matter.” These days, the most likely candidate for what makes up dark matter is some sort of weakly interacting particle that we’ve so far failed to detect.
But there is another radically different possibility: What if gravity itself doesn’t work quite the way we think? Maybe at the outer edges of galaxies where the gravitational acceleration — the g — of a galaxy is extremely small, gravity tugs just a tad bit more.

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