Galaxies closer together than stars

I heard yesterday that relative to their size, galaxies are much closer together than stars. I’d never heard that, so I looked into it. Just using orders of magnitude, the sun is 10^9 meters wide and the nearest star is 10^16 meters away. The Milky Way is 10^21 meters wide, and the Andromeda galaxy is 10^22 meters away. So stars are millions of diameters apart, but galaxies are tens of diameters apart.

2 Responses to “Galaxies closer together than stars”

  1. S. Walker says:

    Is this just something you heard, or do you have a source? (Either Google or ask.com is usually my friend, but not this time.)

    I wonder if this poses any problem for the BBT. One would think galaxies would be radiating out from one another at a rapid pace, if the BBT were correct.

  2. John says:

    I heard the comparison of the relative distances between stars and galaxies in The Canon by Natalie Angier. I tested out the comparison by getting the raw numbers in my post from Wikipedia and doing a little arithmetic. As far as the big bang theory, it’s very well established empirically. Indeed the galaxies are rushing away from each other, on average. But some galaxies are getting closer, even passing through each other. Since galaxies are closer packed than stars, relative to their size, it’s more common for galaxies to collide than stars. And because stars are so loosely packed, galaxies can pass through each other without stars colliding.