how big is our universehome-download pdf-print-friendly pdf-credits
image seven wmap image

how far

- the sun
and planets


- across the
milky way



the distant

- how far
can we see
- how big is
the universe

milky way image
making a mental model: how big is
the universe that we can see?

Imagine that our entire Milky Way galaxy were the size of a CD. On this scale, the nearest spiral galaxy, Andromeda, would be another CD about eight feet away.

The furthest galaxies we have ever seen, pictured in the Hubble Deep Field above, would be CDs about nine miles away. The edge of the observable Universe, the furthest we can possibly see, is only another mile beyond that.


how far can we see

Time, not space, limits our view of the universe. Beyond a certain distance, light hasn’t had time to reach us yet since the beginning of the universe.

The image above is the oldest and youngest picture of the universe ever taken. Oldest, because it has taken the light nearly 14 billion years to reach us. Youngest, because it is a snapshot of our newborn universe, long before the first stars and galaxies formed. The bright patterns show clumps of simple matter that will eventually form stars and galaxies.

Although this light fills the entire night sky, it is so faint and has so little
energy that it is detectable only with special instruments. This colorized image was taken by NASA’s Wilkinson Microwave Anisotropy Probe.

2003. NASA’s WMAP satellite takes images of the most distant part of the Universe observable from Earth. The image shows the furthest we can see using any form of light.

ABOVE: The furthest we can see (image colorized and enhanced). The patterns show clumps of matter that will eventually form galaxies of stars.