In the Dark
A mysterious force is tearing the universe apart!
- By Ed Regis
- Air & Space magazine, March 2005
(Page 2 of 6)
“Only really weird things have repulsive gravity,” says Turner.
To address the problem, astrophysicists have rushed in with a succession of “really weird things” that dark energy could be made of. They’ve proposed exotic new particles such as axions, accelerons, and, jokingly, “bigons.” They’ve proposed strange new force fields and mysterious forms of energy such as quintessence, k-essence, phantom energy, and negative kinetic energy—whatever that is. And they’ve proposed various scenarios for the end of the universe at large: a Big Crunch (a grand cosmic collapse) if dark energy weakens, or a Big Rip (where the cosmos is out of here) if it strengthens.
Still, some theorists find all this dark energy conjecturing a bit too much. Georgi Dvali, a physicist at New York University, does not think that dark energy actually exists. In “Out of the Darkness,” an article in the February 2004 issue of Scientific American, he wrote: “Researchers commonly attribute the acceleration to some mysterious entity called dark energy, but there is little physics to back up those fine words.”
Not that Dvali’s own solution is any less quirky. The reason that the universe is flinging itself apart, he thinks, is that gravity is leaking out of the cosmos, radiating away, slipping off furtively to somewhere else. Like where? Why, into other dimensions. “The extra dimensions not only sap the strength of gravity,” he wrote, “but also force cosmic expansion to accelerate without any need to stipulate the existence of dark energy.”
Other dimensions? Well, why not? After all, they’ve already successfully explained the disappearance of so many things. The other dimension, as we know, is where Jimmy Hoffa ended up, along with Judge Crater, D.B. Cooper (who parachuted out of a Northwest Orient 727 with $200,000), the missing Florida ballots, all that lost airline luggage, and Elvis.
Truly, these are heady days for astrophysicists.
The first clue that the expansion rate of the cosmos was increasing appeared in 1998, when two separate groups of observational astronomers, one working with the Supernova Cosmology Project and the other with the High-z Supernova Search Team, were canvassing the universe for Type 1a supernovas to measure the rate by which cosmic expansion was, as they assumed, slowing down. Type 1a supernovas are stellar explosions of a known magnitude, so they are regarded as “standard candles,” celestial bodies whose distance can be gauged by their brightness—the farther the object, the fainter it appears.
The expected slowdown was thought to be a simple function of the pull of gravity. The universe, after all, is full of matter—and not only luminous matter, such as stars. A large part of the universe’s mass is thought to be dark matter, a substance whose existence was first postulated in the 1930s by astronomer Fritz Zwicky of Pasadena’s California Institute of Technology to explain his observations of galaxies huddling together in large clusters. From what he could tell, the clusters didn’t seem to have enough visible matter in them to produce the gravity needed to hold them together. Therefore some unseen mass must be exerting the required gravitational effect.