But on Twitter, no such signal is necessary. Last night, spider researcher Catherine Scott saw the thread and looped in her friend Nate Morehouse, who studies spider vision at the University of Cincinnati. Morehouse was up late watching the Stanley Cup final and was distraught to see his team, the Pittsburgh Penguins, losing to the Nashville Predators. “I was all bummed out, and I decided to check Twitter before I went to bed,” he says. “I had like 150 notifications.”

“We can explain all of this!” he wrote to Levesque. Jumping spiders are visual hunters, which track their prey with the large pair of eyes at the front of their heads. The retinas of those eyes contain two types of light-detecting cells—one that’s sensitive to ultraviolet light and another that’s sensitive to green light. The latter cells aren’t only sensitive to green light; they react to red too, just less strongly. So jumping spiders can see red light, but it would just appear as a dimmer form of green to them.

No one has really studied the eyes of the zebra jumping spider, says Morehouse, but based on what we know from other species, it should react to laser pointers in exactly the way that Levesque and Lomax found. “It’s not a controlled experiment and the green laser might just be brighter or larger than the red one,” Morehouse tells me. “But if you had two equal laser pointers, one red and one green, we’d expect that the jumping spider should track the red one less enthusiastically.”

But there’s another reason why jumping spiders should fascinate astronomers, besides their occasional penchant for raining from the ceiling or chasing lasers. As Morehouse told Lomax and Levesque, their eyes “are built like… wait for it… Galilean telescopes.” These telescopes, which Galileo started using in 1609, are basically tubes with a lens at each end. Only three groups of animals have similar eyes: falcons, chameleons, and jumping spiders.

In the spider’s case, each of the two main eyes is topped with a large lens that’s fixed to the rest of the spider’s body. Beneath that is a long tube, filled with a clear gel. And at the bottom of the tube, the gel changes in a way that we still don’t understand, but that causes light to bend. It effectively acts like a second lens, even though there’s no distinct physical structure that you can dissect out.

The two lenses work in tandem: The top one collects and focuses light, while the bottom one spreads it out. This arrangement enlarges images before they hit the spider’s retina, which allow it to resolve a huge amount of detail for its size. A jumping spider can see objects as clearly as a pigeon or a small dog, even though its eye tube is less than a millimeter long, and its whole body gets no bigger than 5 millimeters.

Scientists know all of this because they can peer straight into a jumping spider’s eyes and study the retinas below. Those retinas have muscles and can swivel around like the back of a telescope, so the spider can change where it’s looking without moving its head. By watching them do this, and measuring their anatomy, people like Morehouse can work out how light travels through their eyes. And by extension, they can also calculate what sorts of things the spiders can see.