As someone who grew up with the US space program -- when that only meant NASA -- I was blown away by the accomplishment of Elon Musk's SpaceX crew on Friday.
They sent a Falcon 9 rocket to rendezvous with the International Space Station, but even more impressively, they managed to get the first stage of the rocket (the part that provides enough lift to get it off the launch pad and into space) to separate, return to Earth, and land upright on a barge in the ocean. The video above looks like you're watching a takeoff in reverse, but that's the image from the live feed as the first stage gently returns to a stable vertical position on the platform.
This means that, for the first time ever, there's such a thing as a reusable rocket -- a much less expensive option than having to build a new one from scratch because the previous one landed in the water and was lost forever. After more than five decades, SpaceX just changed the rocket business. Impressive.
In his Slate column, Phil Plait explains the science behind this achievement.