Nothing is more fatal to the progress of the human mind than to presume...that there are no mysteries in nature and there are no new worlds to conquer.
Davy was a noted chemist of the 19th century. When he made his observation about the human need to explore, a few blank spaces on the map of the world still remained, places that still offered raw mystery to anyone brave enough to undertake the expedition.
We're short on such places now--with two important exceptions: the sea floor and the sky. That's where an explorer can still lay eyes for the first time on places that no one else has ever seen.
We live in a golden age of planetary exploration. Day in and day out, telescopes and robotic spacecraft are discovering new countries on Mercury, Mars, and even our own moon. In just the last few years, Saturn's moon Titan has gone from a featureless orange ball to a world wrapped in dune seas and methane rivers. Asteroids have grown from points of light to spinning mountains of stone. Quiet spheres of ice have been revealed to harbor geysers and underground oceans.
There's more to come. In particular, the next couple of years will offer two encounters with pure exploration. As you read this, the Dawn spacecraft is firing its ion engines in order to reach the Solar System's largest asteroid, Ceres, for the first time. No mere space rock, Ceres is large and complex enough to hold plenty of surprises. Then there's Pluto. Call it a planet or not, we'll have our first close look at it when the New Horizons mission buzzes by the little world and its five (or more?) moons in 2015.
The frontier still awaits.