On this day at 02:56 UTC 44 years ago, Neil Armstrong became the first human being to leave one of these on the surface of another astronomical body. Three years and five months later, Eugene Cernan became the last man to do so, so far.
The last Space Shuttle touched down for the last time on this day two years ago.
Elon Musk of PayPal, Tesla and SpaceX fame has said that the impetus behind the development of SpaceX came when his son asked him, "is it really true that they used to fly to the moon when you were a boy?"
Now there are two-dozen or more private space ventures around the world. There is a plan to capture and retrieve an asteroid for commercial purposes. Other companies want to mine the moon. Still another plans to put an observatory there.
If we can just hold it together for a couple more decades, humanity might get off this rock, and we might do it in my lifetime.
But it's not looking too good.
(Updated and reposted from last year.)