A beam of light is supposed to shine off into infinity, but when Darth Vader and Luke Skywalker whip out their lightsabers for some spark-flying action, the light blades extrude like stick deodorant and then just stop.
It's like they're sticks of light-matter.
Hollywood may have made that stuff up, but now, scientists at MIT and Harvard have actually made that stuff – not enough for a lightsaber, only a subatomic smidgeon. But even that much is a big deal.
Light-matter existed previously only in theory, but now, for the first time, it has been observed in reality, researchers from the Center for Ultracold Atoms say.
To oversimplify things, we'll say that photons are subatomic particles that make up light. They have no detectable mass the way most matter does, and usually, they don't stick together. You can shoot two lasers at each other, and the photons will pass right through one another.
But physicists Mikhail Lukin and Vladan Vuletic recently got them to stick together to form molecules.
They published the results of their work in the science journal Nature this week.
The newly created photon molecules don't behave like traditional light, but more like a lightsaber, Lukin said. "The physics of what's happening in these molecules is similar to what we see in the movies."
But don't picture yourself swashbuckling with a lightsaber just yet. As in the creation of pretty much all unusual matter, scientists have to produce extreme conditions in laboratories that can't exist naturally anywhere on Earth.
They pumped atoms of rubidium, a kind of metal, into a vacuum chamber – air would otherwise rapidly alter them. This created a metal cloud that they cooled down with lasers to about -450 degrees Fahrenheit, near what is called absolute zero. That makes atoms almost stand still.
Then they the fired photons into the atom cloud.
The photons, elements of light, did not shoot through at the speed of light but acted a little like regular matter instead. They bumped into the atoms in a way similar to the way regular matter would.
In the process, the photons slowed down enough to bump into each other and bond into molecules.
It was a first.
Though that's fascinating, it doesn't make for a handy lightsaber.
But it could help in the future development of super computers known as quantum computers, Lukin said. And with some work, scientists could make whole crystals out of light.
So, if Darth Vader shows up with a lightsaber, your great-grandchildren may be able to throw photon rocks at him.
But don't count on it.