Solving for w

A “doomsday” that is billions of years away has little or no meaning for members of a species less than a million years old. (We’ll be lucky to survive the next hundred years!) So my initial reaction to a story on current cosmological hypotheses entitled “From Space, a New View of Doomsday,” is a snort of derision. Apart from the framing, however, this story (by Dennis Overbye in today’s New York Times) is full of interest, as the following excerpts demonstrate:

“That number, known as w, is the ratio between the pressure and density of dark energy. Knowing this number and how it changes with time – if it does – might help scientists pick through different explanations of dark energy and thus the future of the universe . . .

“One possible explanation for dark energy, perhaps the sentimental favorite among astronomers, is a force known as the cosmological constant, caused by the energy residing in empty space. It was first postulated back by Einstein in 1917. A universe under its influence would accelerate forever.

“While the density of energy in space would remain the same over the eons, as the universe grows there would be more space and thus more repulsion. Within a few billion years, most galaxies would be moving away from our own faster than the speed of light and so would disappear from the sky; the edge of the observable universe would shrink around our descendants like a black hole. . . .

“Another possibility comes from string theory, the putative theory of everything, which allows that space could be laced with other energy fields, associated with particles or forces as yet undiscovered. Those fields, collectively called quintessence, could have an antigravity effect. Quintessence could change with time – for example, getting weaker and eventually disappearing as the universe expanded and diluted the field – or could even change from a repulsive force to an attractive one, which could set off a big crunch. . . .

“But the strangest notion is what Dr. [Robert] Caldwell has called phantom energy, the dark energy that could lead to the Big Rip. . . .

“While the density of the energy in Einstein’s cosmological constant stays the same as the universe expands, the density of phantom energy would go up and up, eventually becoming infinite. Such would be the case if the parameter w turned out to be less than minus 1, say physicists, who admit they are stunned by the possibility and until recently simply refused to consider it.

“‘It crosses a boundary of good taste,’ Dr. Caldwell said, calling phantom energy ‘bad news stuff.’ Phantom energy violates physicists’ intuitions about how the universe should behave. A chunk of it could be used to prop open wormholes in space and time – and thus create time machines, for example.

“‘It could lead to such bizarre effects as negative kinetic energy,’ Dr. [Lawrence M.] Krauss said. As a result, objects like atoms would be able to lose energy by speeding up. . . .

“Dr. [Robert] Kirshner said phantom energy had been dismissed as ‘too strange’ when his group was doing calculations of dark energy back in 1998. In retrospect, he said, that was not the right thing to do.

“‘It sounds wacky,’ he said, referring to phantom energy, ‘but I think we’re in a situation where we’re going to need a really new idea. We’re in trouble; the way out is going to be new imaginative things. It might be our ideas are not wild enough, they don’t question fundamentals enough.'”

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Dave Bonta (bio) crowd-sources his problems by following his gut, which he shares with 100 trillion of his closest microbial friends — a close-knit, symbiotic community comprising several thousand species of bacteria, fungi, and protozoa. In a similarly collaborative fashion, all of Dave's writing is available for reuse and creative remix under a Creative Commons Attribution-ShareAlike 3.0 United States License. For attribution in printed material, his name (Dave Bonta) will suffice, but for web use, please link back to the original. Contact him for permission to waive the "share alike" provision (e.g. for use in a conventionally copyrighted work).

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