Dark energy is a theory among astrophysicists that there is a force pulling galaxies apart - a force that that is accelerating, and will eventually lead to the destruction of every molecule in the universe. The theory first came about roughly a decade ago to explain why distant galaxies are moving away from our own more rapidly than ones that are close by. According to Live Science's Jeanna Bryner:

New measurements of this accelerating expansion . . . provide details about the nature of the unseen and unknown dark energy that is at work.

The results, announced today at a news conference organized by NASA, reveal a decrease in the mass of galaxy clusters in more recent times, which would be a consequence of this hastening and ripping force that some think could eventually tear apart even star systems, planets and eventually the very molecules we're made of.

"If there were any doubts 10 years after the initial discovery that the universe was speeding up, this should really dispel them," said Michael Turner of the University of Chicago's Department of Astronomy and Astrophysics, who was not involved in the current study.

What does this mean? In a few billion years, we won't be able to see any galaxies in the space around us. And, perhaps, it means the death of the universe will be a lonely business indeed.

More images and a complete report at LiveScience.

In the 16th century, Copernicus hypothesized that the Earth is not the center of the solar system, but rather the sun is. Later, cosmologists expanded this idea into the Copernican Principle: Earth is not in a special place in the universe, therefore our observations of local space can be used to infer data about the rest of the universe. When astronomers observed that the universe appears to be expanding at an accelerating rate, they needed to add something to their equations to make it all make sense. That something is dark energy, which would have to exist in massive quantities (as yet, pretty much undetectable) to explain this expansion.

Here's the thing - the universe is really, really, really huge. Just the part we can see is almost incomprehensibly big, and there's a whole lot of universe we can't see. No one knows how big the whole universe is, but it's entirely possible that our part of the universe is just a tiny fraction of the whole. Physicists from Oxford University are considering the idea that the universe we can observe is actually anomalous, a giant void with a low density of matter. The rest of the universe may look substantially different. Doing some number crunching revealed that their model of the universe works without dark energy, but isn't quite as accurate as the current dark energy model. However, they need more observations of certain types of supernovae to refine their numbers - in a few months, their equations may look better with more data.

What's particularly cool is that this maverick theory that tosses a very accepted tenet of astronomy right out the window is being published in Physical Review Letters, one of the most respected physics journals. It sure beats excommunication. Image by: NASA.

Overturning Copernicus, eliminating dark energy. [Nobel Intent]

Tsunami invisibility cloak, dark energy v. the void, sorting nanotubes with light, and more. [EurekAlert!]

Last week, we told you about two galactic clusters colliding, providing visual (and x-ray) evidence of the existence of dark matter. Dark energy is even more elusive, but astronomers who were looking at an entirely different cosmic object may have stumbled across a major clue.

The large blue glow in the image (taken with the Large Binocular Telescope at the Mt. Graham International Observatory to confirm XMM-Newton's discovery) is a galactic cluster with the catchy name 2XMM J083026+524133. It's heavier than any other cluster, and it's farther from Earth than any other as well. In fact, it's twice as far as the next farthest. Here's the mystery — really distant clusters should be very young, because it takes their light so long to reach us. Young clusters shouldn't be big, because it takes time for all those galaxies to pull together. A huge, distant cluster is seemingly impossible. That's where dark energy comes in.

Dark energy, to put it into very simple terms, is a sort of anti-gravity force that actually pushes space apart and speeds the expansion of the universe. If it exists, that is. It is one possible explanation for 2XMM J083026+524133's distance. It might be an old cluster that appears more distant than it should be due to dark energy fueled expansion of space. What is the source of all the dark energy in the universe? Tony Iommi. Image by: ESA.

Cosmic Heavyweight. [Science News]

Earlier this week I pondered whether dark energy is just a new version of an outdated theory, but a team of astronomers in Antarctica is doing the hard work of trying to find out. The South Pole Telescope (SPT) uses 1,000 advanced optical sensors to peer at distant galaxy clusters looking for subtle variations in the cosmic background radiation. Those variations will give scientists a better idea of the structure of the universe, and whether or not dark energy is part of it.

The SPT is the largest Antarctic telescope. Despite the frigid cold of the region, the optics are further shielded from background heat by being chilled to a temperature not far from absolute zero. Photo by: The University of Chicago.

Cosmologists Probe Mystery Of Dark Energy With South Pole Telescope. [Science Daily]

Aether (also called ether) was a theoretical substance that supposedly permeated the entire universe, including solid matter, more or less evenly. While aether theories evolved over time, it was generally believed to be made of particles so tiny we couldn't detect them. The inherent properties of the aether determined many of the physical properties of the universe, such as the speed of light and the strength of gravity. These forces propagated as waves through the aether. Aether theory survived into the 20th century - Einstein even adapted it to fit his theory of special relativity, although it was so drastically changed that it was hardly aether theory at all. In his 1920 address "Ether and the Theory of Relativity," Einstein said:

The ether of the general theory of relativity is a medium which is itself devoid of all mechanical and kinematical qualities.

To be certain, neither theory is "bad science" in any way. They are the types of theories that physicists come up with when they are working out beyond the current observational abilities of humans. Eventually, physicists identified the dual wave/particle properties of electromagnetic energy. This, along with experiments that confirmed general relativity, negated the need for aether theory. Likewise, new experiments conducted with the Large Hadron Collider later this year could detect new particles like the Higgs boson that will give us additional clues to the physical makeup of the universe. Will they invalidate dark energy? Photo by: NASA.

The whole picture occupies a space of 100 million light years and this computer simulation "paints" the densest areas red. The yellow lines show the intensity of the galaxies' velocities as they fall into the highest-density area. The speed of the galaxies' rush towards the center of the structure depends on the the balance between dark matter, dark energy and the overall expansion of the universe. Astronomers are learning how to measure this "infall pattern" by using a large survey of galaxies at different epochs. [European Southern Observatory]