You should read Eliezer's post That Alien Message.
Soon, confirmation comes in from high-orbiting telescopes (they have those) that the astronomical miracles do not seem as synchronized from outside Earth. Only Earth's telescopes see one star changing every second (1005 milliseconds, actually).
Almost the entire combined brainpower of Earth turns to analysis.
[...]
Three of their days, all told, since they began speaking to us. Half a billion years, for us.
Okay, I'll be addressing this pretty directly. I don't find it particularly convincing though.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.