Interferometry

Interferometry

(alt-text)

It's important to note that while the effective size of the dog can be arbitrarily large, it's not any more of a good dog than the two original dogs.

What If? is now on YouTube!
Check out the first video for the answer to
“What if we aimed the Hubble Telescope at Earth?”
and follow xkcd’s What If? The Video Series channel to be notified about each new video.