The discovery of dark matter would mean a major breakthrough in efforts to advance our understanding of the universe. This is why any hint of such a discovery is greeted with mounting excitement. It's also why such hints should be met with scepticism, writes Richard Panek.

An announcement of the possible discovery of dark matter—for instance, the one this past June 15 from the XENON1T collaboration that generated headlines around the world—merits either of two responses.

One is “Big deal.”

The other is “Big deal.”

The actual discovery of dark matter would in fact be a really big deal, one of the biggest in the history of physics. It would solve a mystery that has been plaguing cosmologists for nearly half a century, but more importantly, it would help validate a reinterpretation of the universe that renders everything we’d previously thought to be the cosmos in its entirety (galaxies, stars, planets, people, pixels) only four or five percent of what’s actually out there.

SUGGESTED READING Cutting edge science at HowTheLightGetsIn Global By Throughout the 1970s, astronomers using new instruments found that spiral galaxies like our own Milky Way were rotating in a way that didn't make sense, at least according to the laws of gravitation. The outermost wisps of gas and dust and stars were rotating at the same rate as the innermost clots of gas and dust and stars. On the scale of our solar system, the analog would be if the outermost and innermost planets were keeping pace with each other in a race around the Sun, even though Neptune is 73 times more distant from the Sun than Mercury.