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Okay, we know what you're thinking, and we're sorry.  A couple of weeks ago, humanity reached a new milestone in space flight awesomeness, and we're just now bringing it up, but bear with us.  On December 21st, for the very first time, the private space flight company SpaceX managed to land one of its rockets after boosting 11 satellites into orbit.  It's the first time in history that a booster landed successfully after delivering its payload into orbit, and I'm pretty sure you could hear the entire Internet cheering.  

We were cheering, too!  And we really wanted to tell you all about it, but it was right around the holidays, so we decided to wait until this week, because on January 17th, SpaceX is going to try it again, this time landing one of its Falcon 9 rockets on a ship in the ocean.  

The basic idea behind making rockets reusable is pretty simple.  Rockets are expensive, so it'd be nice if we didn't have to keep building them from scratch.  The Space Shuttle program had its own solution to this problem: solid rocket boosters that parachuted safely into the ocean once they were done boosting.  They were later refurbished and reused, but for the Falcon 9, landing is a lot more complicated than attaching a couple of parachutes.  Instead, SpaceX uses the rocket's engines to slow it down, stabilize it, and gently land it vertically in a particular spot.  The kind of landing that could someday be used on the moon or Mars, too, and that might sound simple enough but it turns out to be incredibly difficult.  

The Falcon 9 is heavy for one thing, and it's hard to control something that massive when it's moving hundreds of meters per second, and you're fighting gravity at the same time, so the reusable rocket is designed to save some of its fuel to help it slow down and position itself for landing.  Plus, it has stabilizing legs to land on, and a whole lot of software to keep everything coordinated, but the landing on the 17th is going to be even trickier than last month's.

The mission for Falcon 9 is to launch Jason 3, a satellite that'll monitor Earth's oceans, and once that's on its way, SpaceX will try to land the Falcon on what it calls a drone ship, basically a platform floating on the middle of the ocean.  Trouble is, if you've ever been on a boat, you know that the ocean wobbles, so this flight will show us if the rocket can account for all that extra swaying.  If it can, then we're well on our way to having a reusable launch system, and if it can't, well, we can always try again next time.  There's a lot riding on this landing, so we're all rooting for you, SpaceX.

Now that's what's happening with spaceflight in our solar system, but what about space travelers in other star systems?  Even though we haven't found any aliens yet, according to a team of astronomers from Harvard and the Tata Institute of Fundamental Research in Mumbai, there's a new place we should be looking.  Their idea, which they presented last week at the meeting of the American Astronomical Society is that alien civilizations could be living inside globular clusters, clusters of very old stars at the outer edges of our galaxy.  Why hasn't anyone thought to look there before?  Because we've barely found any planets in those clusters.  There are more than 150 globular clusters in our galaxy, and we've only ever found one planet in any of them, known as Messier 4.  The astronomers propose that there could be plenty of planets out there in those clusters, but we just haven't spotted them because all the light from the other stars is making it hard to see them.  

When the team modeled how the planets might form within a cluster, they found that lots of them would probably end up in their stars' habitable zones, areas where life as we know it could survive.  Still, there are planets' in habitable zones all over the galaxy, so why should we look for signs of extraterrestrial life in globular clusters?  

Well, if planets formed within these old star clusters and if life happened to evolve on one of them, it would have billions of years to develop space travel and have plenty of nearby stars to visit.  Alien civilizations might even be sending messages between different systems, which is exactly what we'd be listening for.  So in our search for alien life, globular clusters are back on the map.  
Thanks for watching this episode of SciShow Space News, and thanks to everyone who commented Falcon 9, Falcon 9, don't forget about Falcon 9.  We didn't forget and we heard you.  We're so excited that you're as excited as we are.  If you wanna help us keep making episodes like this, just go to Patreon.com/SciShow, and don't forget to go to YouTube.com/SciShowSpace and subscribe.  

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