Some 60 million light-years from Earth — by the estimate of one team of researchers, anyway — a pair of strange galaxies is causing a cosmic stir. The bizarre galaxies, named NGC 1052-DF2 and NGC 1052-DF4 (or DF2 and DF4, for short), are the first known galaxies born without any significant amount of dark matter. If confirmed, their existence would throw a wrench into our understanding of how galaxies form and evolve. But, as Carl Sagan liked to say, extraordinary claims require extraordinary evidence. And, according to some researchers, the evidence for these dark-matter-deficient galaxies doesn’t hold up.