After watching Star Trek, I thought it would be a good connection to read about some real explorers. So far we've read about Matthew Henson's journey to the North Pole (crazy! why risk your life for that?), and William Beebe's journey into the deep ocean. It's a great geography tie-in as well, and we got onto Google Earth and looked at maps and satellite pictures.
I do so love how homeschooling can follow a twisty-turny path. We really are explorers ourselves, boldly going where no one has gone before. In fact, everyone is an explorer, pushing out into the unknown. And the journey along the way is the whole point.