In the early 20th century, physicists discovered cosmic rays- energetic particles zooming through deep space.
Many of these come from the sun, and can cause the northern lights. However, a few, very mysteriously, come from somewhere else with enormous energy.
“The real puzzle is no one has any idea what in the universe is capable of doing that," said Corbin Covault, professor of physics at Case Western Reserve University. "There's some ideas, like massive black holes sucking material down in the middle of galaxies, but when they do the calculations it's really, really not obvious.”
To investigate the origins of these mysterious particles, scientists like Covault from all over the world teamed up to build the Pierre Auger observatory, in Argentina.
“It's literally the size of Rhode Island - 3,000 square kilometers - spread out over the ground. Our sixteen hundred particle detectors, they're primarily they're just pure water,” Covault said. “But when the particles hit the water tank they make a flash of light and so we can detect it. And by recording the signal from these water tank detectors we can infer the existence of this highest energy particle."
In the Chilean desert, Auger is helping us figure out where in the universe these mystery particles are coming from.