Abstract Horror (Note-2)
A very special jolt of bliss for Friday (Horror) Night — a whole new monster (the ‘Phantom’):
Most models of dark energy hold that the amount of it remains constant. But about 10 years ago, cosmologists realised that if the total density of dark energy is increasing, we could be headed for a nightmare scenario – the “big rip”. As space-time expands faster and faster, matter will be torn apart, starting with galaxy clusters and ending with atomic nuclei. Cosmologists called it “phantom” energy.
To find out if this could be true, Dragan Huterer at the University of Michigan in Ann Arbor turned to type Ia supernovae. These stellar explosions are all of the same brightness, so they act as cosmic yardsticks for measuring distances. The first evidence that the universe’s expansion is accelerating came from studies of type Ia supernovae in the late 1990s.
If supernovae accelerated away from each other more slowly in the past than they do now, then dark energy’s density may be increasing and we could be in trouble. “If you even move a millimetre off the ledge, you fall into the abyss,” Huterer says.
Huterer and colleague Daniel Shafer have compiled data from recent supernova surveys and found that, depending on which surveys you use, there could be slight evidence that the dark energy density has been increasing over the past 2 billion years, but it’s not statistically significant yet (Physical Review D, doi.org/vf9).
Phantom energy is an underdog theory, but the consequences are so dramatic that it’s worth testing, Huterer says. The weakness of the evidence is balanced by the fact that the implications are huge, he says. “We will have to completely revise even our current thinking of dark energy if phantom is really at work.”
(If I’d been making this stuff up, about the entirety of cosmic space being a concealed monster poised to rip every particle in the universe apart, I’d have named the hero ‘Dragan Huterer‘ too.)