Bad Astronomy's Phil Plait recently visited the SpaceX construction factory. His visit also included a chat with CEO Elon Musk. This should excite you. Plait is a consummate nerd, and Elon Musk is Elon Musk. Bring them together and you're bound to get good things (the quote up top, for instance).

Above: The SpaceX Falcon 9 rocket soared into space from Space Launch Complex-40 on Cape Canaveral Air Force Station in Florida, carrying the Dragon capsule to orbit at 3:44 a.m. EDT on Tuesday, May 22, 2012 | Photo and caption via Alan Ault/NASA

Earlier today, Plait recounted his conversation with Musk, and its profound influence on his perception of SpaceX's Martian ambitions, in a must-read blog post:

We talked about various topics for a while—the movie Interstellar, the history of SpaceX, terraforming Mars … and that was when I said something dumb.

“I know Mars is a long-term goal for SpaceX,” I started. Then, pretty much as an aside, I said, “because you want to retire on Mars … ”

Musk got a pained look on his face. “No, that’s wrong. That’s not why I want to get to Mars. That quote is from an article in the Guardian. They pushed me for a sound bite, asking if I wanted to retire on Mars. I eventually said yes. When I retire—hopefully before I go senile—and eventually die, then Mars is as good a place to die as any.”

That line made me laugh; it’s far better than anything printed in the Guardian article.

But still, I was taken aback. “OK then, the article wanted a sexy quote and got one. But if that’s not the reason, what is it?”

Musk didn’t hesitate. “Humans need to be a multiplanet species,” he replied.

And pretty much at that moment my thinking reorganized itself.

Read the rest at Slate.