Re: Center of galaxies

From: Alexander Avtanski (avtanski_at_ispwest.com)
Date: 09/15/04 

Date: Wed, 15 Sep 2004 14:00:00 -0700

> So, if I understand you well, you could take away the Sun, for example,
> and still have all the planets in the solar system revolve around their
> center of mass?

Nope - they are going too-fast for this. But this is something
very different.

Now, look at this: Imagine a double star. Nothing else around.
The two components are with absolutely equal weight and size.
They are spinning around the common center of gravity - the
exact middle of the straight line from one to the other.
Around empty space.

Now, imagine you going to the center of the galaxy from the
previous message, getting the pebble that we left there, and
putting it smack in the middle between those two stars.

Do the stars revolve around it? Yes. Does it wobble? No.
Is it heavier than both the stars? No way! Is this pebble
holding the stars in place? No.

Now, just imagine the same thing, but with a bit more than
two stars - here is a galaxy that revolves around nothing.
(I'm not saying that there is nothing in the middle of each
galaxy, but that it's not necessary to have something heavy
there in order to keep the galaxy turning and turning and
turning...)

- Alex

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