Cosmic strings are theoretical fault lines in the universe, defective links between different regions of space created in the moments after the Big Bang. And they might be theoretical no longer – distant quasars show the fingerprints of these strings.

Compared to cosmic strings, black holes seem downright sensible. These strings – no relation to the subatomic strings of theoretical physics – are one-dimensional objects, meaning they have length, but no height or width. They are defects in the fabric of the universe, a byproduct of the universe cooling in the first instants after the Big Bang. The easiest way to think about these strings is to see them as the cosmic equivalent of the cracks that form in ice over a frozen lake.

Of course, that doesn’t capture the full measure of their one-dimensional weirdness. Since they have no width or height, they are incomprehensibly narrow, with a diameter that would make even a tiny photon look fat. They’re also dense, as a string that’s even a mile long would weigh considerably more than Earth. These strings expanded right along with the universe, ultimately stretching across the entire known universe in a more or less straight line, or forming massive rings many thousands of times bigger than our galaxy.