We're finding we're hitting a ceiling with most children's programming for DS2. One idea DH and I are weighing is watching segments of Myth Busters as a family. While it won't satisfy burning big questions, I see it as an intellectual snack for my little man with a mechanical bent. Somewhat tangential to your OP, but hopefully helpful still.
It's so challenging finding appropriate media. Some backdated IMAX films are proving to be the most gentle, accessible videos for our DS. The cinematography is stunning, too.
It's not video, but this series by Stephen Hawking for children fits the bill content-wise. Will definitely be buying as a read-aloud for my DS if his interest is there later.
http://www.amazon.ca/gp/aw/d/1416985840
