Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

If galaxies are moving farther apart, why are there still galactic collisions?

JOSHUA COLBERT, SILVER SPRING, MARYLAND
The expanding universe is just the playing field where galaxies interact with each other. The most important way they interact is by gravity, whose range is, theoretically, unlimited. Every galaxy attracts every other galaxy, and their mutual pull slows the rate of moving apart from each other. The closer two galaxies are to each other, the stronger their gravitational attraction is (and the slower the pace at which expansion would tear them apart).

Already a subscriber? Register now!

Registration is FREE and takes only a few seconds to complete. If you are already registered on Astronomy.com, please log in below.
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

ADVERTISEMENT
ADVERTISEMENT
BoxProductcovernov

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook

Loading...