A New Probe of Dark Energy

by Paul Gilster on April 29, 2006

What we know about dark energy can be pretty much summed up in these words: “We know that it dominates the universe. In fact, it comprises an estimated 73 percent of the universe, while so-called dark matter accounts for 23 percent, and matter of the familiar kind — the stars, galaxies, all known life — comprises only four percent.”

The speaker is David Lambert, a University of Texas at Austin astronomer and the director of UT’s McDonald Observatory. And it has always seemed to Centauri Dreams that these numbers — what we know and see of the universe is no more than four percent of the total — should inspire a certain humility. Yes, we know more than those before us, but just how far we are from comprehending the nature of ‘reality’ seems obvious. There are real reasons to wonder whether the human mind is capable of ever understanding ultimate reality.

Perhaps a quote from Martin Rees about the beginning of the universe is appropriate:

“There are lots of ideas of what might have happened at the very beginning, but we can’t say whether there are other big bangs apart from ours. If there are, we can’t say whether they are before or after or alongside ours, because to make such a statement implies that you can have a single coordinate system covering them all and a single clock that can be coordinated and synchronized between the different universes. So we can’t trace things right back to the beginning, we can’t say whether our universe is the only one, and we can’t even say whether there are only three dimensions of space.”

But now we’re on the edges of string theory, so perhaps it’s time to focus on something less abstract. How about cold cash? Money talks in cosmology, or at least the study of it, and the news that businessman Harold C. Simmons has ponied up a $5 million challenge grant — he’ll match the next $5 million in private support received — to the University of Texas is heartening. Simmons is trying to support people like the aforementioned Dr. Lambert in their quest to run HETDEX — the Hobby-Eberly Telescope Dark Energy Experiment, at McDonald Observatory.

And Lambert, who calls the nature of dark energy ‘…the number-one question in all of science,” believes that the combination of large telescope, plentiful observing time and an instrument that will produce a three-dimensional map of up to one million galaxies may help us solve the riddle. Or, at least, make the kind of incremental progress that is at the heart of tackling the universe on its own terms, doggedly pushing back the frontiers of the knowable without being blinded by prior assumptions. As for Simmons, what an example of the role philanthropy can play in opening up the cosmos!

Eric James April 30, 2006 at 0:13

Has anyone considered the possibility that dark energy is a consequence of relativity? Could the extremes of distance and relative motion essentially create a perceived (from our vantage point) gravitational acceleration of the universe into the distance?

If we could see that far, wouldn’t the extreme distance look something like a blackhole… only turned inside out?

Could the CMBR be a form of Hawking radiation emminating from this distance field?

Just curious…

Administrator May 1, 2006 at 6:11

Wow, would that make a good story — the microwave background as Hawking radiation! What an ingenious notion, and no, I haven’t run into it anywhere else. But as to your larger question on dark energy as a consequence of relativity, I hope other readers may be able to weigh in, as I’m not conversant enough with the broad range of dark energy studies to know if this has been suggested or with what parameters. Fascinating idea, though.

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