The latest black hole image was created using a technique called interferometry, in which the radio waves emitted by the black hole and collected by eight telescopes located around the world are compared. If two sites collected waves that were “in-phase”, meaning the waves’ peaks lined up with one another, then the two waves would add together to create a bright spot on the image. If, on the other hand, the waves were out-of-phase, meaning one wave’s peak lined up with the other’s trough, the waves would cancel each other, producing a dark spot in the image. Working together, the telescopes are able to collect more detailed data than any one could alone.