Thread: Astronomers map dark matter 'beach ball'

NPR: From way out in space, our home galaxy would look pretty much like a flat disc of bright stars with spiral arms. But the Milky Way is actually surrounded by a vast halo of invisible dark matter that's shaped...

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This may sound strange, but how could they map it if they can neither see or detect it - hence the term "dark"?

They mapped it using our galaxy's gravitational effect on a small galaxy. Follow the link provided at the "more..." in the message for an explanation. Dark matter doesn't affect light, but does have gravity. That is questionable for me, I thought gravity bent light.

That's perhaps a discussion for it's own topic altogether, but gravity does NOT bend light. Mass curves space and light always travels in a straight line through space. So if you curve space with a mass, you get gravity, and light will still travel in a "straight" line through curved space. Curve space enough, and you won't even see it. Also, what they think to be the presence of dark matter because of not being able to see what is producing all of this gravity may, just may, be something else entirely. Remember that all they have is a guess; not even a theory. Law describes what is happening and theory describes why. In this case, it has not been proven. Yes, there seems to be something "missing" to link the formation of star clusters with the gravitational forces required to produce and maintain them. One would have to consider, in such a case as this, line of sight in relation to gravity, coupled with the curvature of space that is caused by gravity. Remember that ANYTHING that propagates from a point of origin, including gravity, finds its effects to occur on a more planar scale rather than curved as distance away from this point increases, whereby the curavture itself becomes planar over the distance squared. This means that once it reaches you, you will only be able to observe a very small percentage of it. Therefore, it is conceivable and more probable that the already existing mass in such a system is producing the REQUIRED amount of gravity to form star clusters - yet we simply cannot SEE it. Light from masses whose index of spacial curvature is greater than OUR distance to it squared will NOT be seen, and through the very same concept their entire gravitational influences cannot be measured - only a small portion if it so reaches us.