Subtitles section Play video Print subtitles Photons are oddballs. When they're not busy being waves, they're massless particles that can travel at light speed because, well, that's what they are, little packets of light. For decades it was also thought photons didn't interact with each other, but recently researchers have discovered how to bind photons together as though they were molecules. With flashlights, unlike ghostbusting equipment, you can cross the streams all you want. They don't bounce off each other or cause every molecule in your body to explode because photons don't much care for one another. Unless, that is, they're fired through a ultracold cloud of rubidium atoms. When scientists from Harvard and MIT fired a weak laser through a rubidium cloud, they observed photons coming out the other side in pairs and triples. Not only that, but they could tell from how much the photons were oscillating that they weren't just bunched up together coming out of the cloud -- they were bonded, like molecules. Photonic molecules! They could even tell how strong the bond was based on their oscillation frequencies! Before we get too ahead of ourselves, I should tell you that not all of this is new news. Back in 2013, scientists fired a blue laser at ultracold rubidium gas and observed the photons forming pairs when they came out the other side. What's new THIS time are that the photons formed the trios. Scientists weren't sure if it was even possible to form groups of three interacting photons. Turns out it's not only possible, but three photons interact even more strongly than pairs of photons. To explain how this happens, researchers believe that as the photons travel through the rubidium cloud, they're briefly captured by the atoms to form an atom-photon hybrid called a Rydberg polariton. The photon travels from atom to atom doing this, and if two polaritons come across one another, the photons can mingle thanks to their atomic partner. They become entangled, and when they reach the edge of the gas cloud the atoms stay behind while the photons stick together. It's like two shy people being introduced to each other by their more outgoing friends at a party. They'd never approach each other on their own, but once they meet they really hit it off. Apparently, they're even open to adding a third person to the mix. Ok, I'm going to abandon this metaphor before I get in trouble. These new photonic molecules have interesting properties, like taking on a tiny amount of mass, which is crazy when you remember photons by themselves are massless. They also travel about 100,000 times slower than normal, so you know, around a sluggish 10,000 kilometers per hour. What we can DO with these photon molecules remains to be seen. They could make it possible for computer logic gates to use light, instead of inefficiently converting light to electrical impulses and back again like some do now. Or they could be used in quantum computing to carry information, thanks to their entangled state. OR if adding more photons to the mix makes them interact more strongly, maybe it's possible to make entire crystals out of light! Time and more research will tell, so more research is needed. Be the light of our life, take a sec, and subscribe. Speaking of quantum craziness, did you hear scientists teleported stuff to SPACE? A handsome devil talks about it here. While photons in the visible spectrum usually won't interact, very high energy photons have a higher probability of bouncing off one another, a process called gamma-gamma scattering. Thanks for absorbing our photons into your eyeballs.