I would feel slightly guilty about such a young one turning to the dark side -- literally -- but if they're interested in science in this age, better this than something squishy.
Behold, the power of astronomy!
This was total link bait, of course, but fair is fair: I found this on RobiNZ Personal Blog, via a Google trackback.
Cutest. Kid. Ever.
Besides The Little Astronomer, of course.