Recently the private rocket-ship company SpaceX managed to a) launch a rocket, b) have it not blow up, c) return a portion of the rocket for reuse later, d) on a floating barge in the middle of the ocean. I'll assume we all understand the significance of a) and b), but what's the big deal about c) and d)?

First, the reusing bit. Imagine that every single time you drove your car to work, as soon you arrived at your destination and got out, you incinerated it. Totally destroyed. Completely unusable. Want to go back home? Buy a new car. Take the kids to soccer? Shell out for a one-time-use van. Our current (and, really, entire past) rocket program is exactly that. The big tall boosters that do all the rocketing just get chucked into the ocean or burned up in the atmosphere. Only the teensy-tiny tip of the rocket actually makes it into space and sometimes gets returned.

That's kind of wasteful, so SpaceX developed a booster that heaves a payload up into the sky, then lands safely back to Earth. Polish it up, fill it up with rocket gas, and it's good to go again.

That brings us to d). Why the barge bit? Well, when a rocket goes off, it doesn't just go "up", it also goes "sideways". For example, by the time a rocket launched in California reaches space, it's somewhere over the eastern coast. To reuse the rocket, one option is to have it slow down and fly back to the landing zone. That's doable, but expensive, since you needs tons more fuel. Hence, the ocean barge. The rocket takes off, lofts its cargo into orbit, and lazily glides down to Earth.

All this makes access to space cheaper. Like, way incredibly stupendously cheaper. And that's good.

This week I had the honor of being invited to introduce a showing of the "Particle Fever" documentary as part of a Science on the Screen event here at COSI. I had to cancel because of a nasty stomach bug, which really bummed me out, but I have had the good fortune to know several people involved in the subject of the film. Particle Fever chronicles the development, testing, and running of one of the most ambitious scientific and engineering projects in human history: the Large Hadron Collider. Located near Geneva, Switzerland, the LHC is a beast of a machine: 17 miles of magnets, cooled nearly to absolute zero, propel bits of matter to the edge of the speed of light.

And then smashes them together.

For a brief moment, the collision point reaches temperatures and densities rarely seen since the earliest moments of the universe. The intense energies crack open protons, forcing their fragments to momentarily transform into a jet of more exotic particles.

It's not exactly easy - neither the building nor the analyzing. It took over 10,000 scientists and engineers almost a decade to even get the thing going. But the payoff is enormous: combing and sifting through the reams of data reveal clues about the fundamental working of our universe, and gives us a peek 14 billion years into the past.

As soon as I set up my desk at COSI, I put up a small whiteboard in front and labeled it "Ask me anything!” I'm happy to report that it wasn't long before someone took advantage of the opportunity. And what a question it was!

"Where do stars go when they die?"

It's a beautiful question because it evokes certain imagery. We're used to thinking of the stars as just...there. Even ancient astronomers noticed the occasional "new" star (which we now identify as nova, by the way). But nobody ever noticed a star going away. I mean, they last so dang long, especially compared to the puny handful of millennia we've been recording the heavens.

Indeed, most stars don't go away for a *very* long time. That's because most stars are smaller than the sun, and the smaller the star, the longer it lasts. Stars are powered by fusion: the intense gravity from the star's own weight pressing in on itself shoves atomic nuclei together, leaving a little bit of energy behind in the process. More massive stars press that much harder, increasing the rate of nuclear burning, using up their fuel faster. Smaller stars keep the weak fire going, burning dimly for trillions of years. In contrast, the biggest stars last only a few million years.

I know, either way it's a stupid-long time, but relatively speaking, there's a big age gap.

So small stars just kind of peter out. Medium stars like our sun leave behind white dwarves, which are balls of carbon and oxygen. The biggest stars blow up in spectacular fashion, leaving behind one of three dreary options: 1) nothing, 2) a neutron star, or 3) a black hole, depending on their exact mass and exactly how they go off.

Given enough time (and the universe has plenty of that), the galactic neighborhoods eventually fill up with these leftover remnants, which just kind of...float around.