Yet Another Dark Matter Alternative

Physicists are still trying to detect dark matter, which some theories posit may make up more than 80 percent of the mass of the universe. I've always had a problem with it; it just seems counter-intuitive that we wouldn't be able to detect something that has such a major effect on our world. 

There are alternative theories. Now one of them seems to have passed a critical test (although it still has to pass muster, i.e., peer review).  

or decades, a band of rebel theorists has waged war with one of cosmology’s core concepts — the idea that an invisible, intangible form of matter forms the universe’s primary structure. This dark matter, which seems to outweigh the stuff we’re made of 5-to-1, accounts for a host of observations: the tight cohesion of galaxies and packs of galaxies, the way light from faraway galaxies will bend on its way to terrestrial telescopes, and the mottled structure of the early universe, to name a few.

The would-be revolutionaries seek an alternative cosmic recipe. In place of dark matter, they substitute a subtly modified force of gravity. But attempts to translate their rough idea into precise mathematical language have always run afoul of at least one key observation. Some formulations get galaxies right, some get the contortion of light rays right, but none have pierced dark matter’s most bulletproof piece of evidence: precise maps of ancient light, known as the cosmic microwave background (CMB). “A theory must do really well to agree with this data,” said Ruth Durrer, a cosmologist at the University of Geneva. “This is the bottleneck.”

Now, two theorists say they’ve finally squeezed an alternative theory of gravity past that obstacle. Their work, which was posted online in late June and has not yet passed peer review, uses a tweaked version of Einstein’s theory of gravity to reproduce an iconic map of the early universe, a feat that even some rebels feared to be impossible. “For 15 years we’ve just been dead in the water,” said Stacy McGaugh, an astronomer at Case Western Reserve University and a longtime advocate for modified-gravity theories who was not involved in the research. “It’s a huge leap forward.”