 This week I'm talking about neutrinos. They're everywhere. They're exciting. A lot of people like them. You might remember them a few while back, whenever, when people were talking about how they might be faster than light. People were freaking out. What if neutrinos are faster than light? Everything is going to crumble. The sky is going to fall. What about Einstein? Well, his feelings be hurt. But it turns out that they weren't faster than light, so everything's okay. But while neutrinos aren't faster than light they're still super awesome. They're one of the most abundant particles in the universe. There's tens of trillions of them going through you at any given second. So just think about that for a little bit. They're kind of like our little invisible friends that we have with us at all times, in a way, but they're always passing through us and not really saying hi. But where do neutrinos come from? Well, they come from all different places. They come from supernovas and they come from particle collisions and they come from your bananas and avocados. I'm not actually crazy. That's actually true. The potassium in bananas and avocados creates natural radio activity, which produces neutrinos. So you can munch on that for a little while. It's kind of healthy in a way. But I think the coolest thing that we do with neutrinos is how we sense them here on earth. Not the ones that come from your bananas and avocados, but the ones that come from supernovas. There's actually a really cool observatory in Antarctica called IceCube, and it's located at the South Pole, and it has around 5,000 optical sensors, which it suspends in a cubic kilometer of ice. It uses those optical sensors to sense for neutrinos. Why is this? Because when neutrinos interact with ice, they produce blue flashes of light, and we can actually measure those blue flashes of light and actually tell if we've seen a neutrino or not. The IceCube Observatory actually sees about six neutrinos a minute, but a lot of them come from collisions in the upper atmosphere. But occasionally when it's lucky, IceCube is able to actually see neutrinos from supernovas and actually see the blue flashes of light that those neutrinos produce in the ice. The flashes of light can sometimes actually expand to around six city blocks. So it's a huge flash of light that happens across a very large distance, and these optical sensors are actually able to sense these blue flashes of light and tell us if we've seen a neutrino. In a way, it's like this really cool pinart form of neutrinos, if you remember pinart because you grew up in the 80s. But why are neutrinos so cool if they're not faster than light? Well, they might not travel faster than light, but sometimes they can reach Earth before light does. They can actually pass through a lot of things faster than light can, and this is because they're weakly interacting particles. They interact with very little things, unlike photons, which have to interact with stuff and have to deal with a bunch of crap every day. Neutrinos don't have to deal with a bunch of crap every day. So if there's a bunch of space gas and space dust in the way, photons have to interact with it a little bit, but neutrinos don't have to interact with it at all. So they get sort of a superhighway. Also, sometimes supernovas produce neutrinos before they actually produce photons. And so neutrinos get a head start in that way as well. So while neutrinos don't travel faster than light, they can certainly reach Earth faster than photons can in a lot of cases. And this actually happened with supernova 1987A. Again, not the coolest name, but with supernova 1987A, which you can imagine we saw in 1987, the neutrinos actually reached Earth three hours before the photons did. So in this way, neutrinos are an early warning system for supernovas that we haven't even seen yet. So these neutrino observatories around the world actually detect neutrinos and can give astronomers an early warning signal for when there might be something beautiful in the sky that they should look at soon. So while neutrinos aren't faster than light, they can still sometimes reach Earth before photons do. And that's because they have to put up with less crap every day. They're weekly interacting particles. So neutrinos are kind of awesome and sex to be you, photons.