EXPLAIN THIS, EINSTEIN

Our laws of quantum physics explain quite a lot about our universe and its origins – but not this, not yet. This weird cold spot, located in the constellation of Eridanus in our Southern Hemisphere sky, is baffling. The insets show the environment of this anomalous patch, with its angular diameter marked by the white circles; it spans a mind-blowing 1.8 billion light-years. (For comparison, the Milky Way is only 100,000 light-years across.) One possibility is that the spot aligns with a supervoid: a vast, low-density region of space that would be one of the universe’s largest structures. But scientists have other guesses, too, including the controversial idea by Laura Mersini-houghton that it’s an imprint of another universe bumping into our own. If true, this would be the first evidence of a parallel universe – the tricky part is proving it.