Home » News & Blogs » Ask Ethan: How Do We Know Space Is Expanding?
Bookmark and Share
Starts With a Bang!

Ask Ethan: How Do We Know Space Is Expanding?

17 Feb 2018, 15:01 UTC
Ask Ethan: How Do We Know Space Is Expanding? NASA / GSFC

If you take a look out at the Universe, and in every direction you look, you see objects rushing away from you, what would you conclude? Would it be that you’re a repellant, somehow? That the fabric of space itself is expanding? That you’re at the center of an earlier explosion, and everything else is just speeding away from the explosion point? These, as well as other options, might all seem reasonable, but somehow, scientists always say “the Universe is expanding” as though no other alternative would do. Why is that? Our reader Buck wants to know, asking:

How do we know space is expanding? In relation to what? Red shifting galaxies growing farther apart could be doing so in infinite space as opposed to expanding space.

Believe it or not, the answer is written on the face of the Universe itself.

Latest Vodcast

Latest Podcast

Advertise PTTU

NASA Picture of the Day

Astronomy Picture of the Day

astronomy_pod