Everything most people know about makes up a tiny fraction of the universe. Normal matter, the atoms and molecules we are used to, make up the tiniest fraction of the universe. In fact it makes up only around 5% of the universe. The rest of the universe is made up, hypothetically, of "dark matter" and "dark energy."

Awhile back I wrote about the best evidence we have ever had that the hypothetical "dark matter," originally conceived of to balance equations that otherwise couldn't explain the behavior of the universe, actually existed. But this discovery of evidence that "dark matter" is real still left about 70% of the universe merely hypothesized. Regular matter and dark matter only make up about 30% of the universe. The rest is a poorly understood thing called "dark energy" that was originally conceived of to explain the fact that the universe is expanding at an accelerating pace. Before, when people thought the expansion of the universe was either constant or slowing, normal matter and dark matter were all they needed to understand what was going on. But the discovery that the universe is flying apart at an ever faster rate meant SOMETHING else was out there causing the acceleration and dark energy was the hypothetical explanation.

Well, scientists may just have discovered evidence for dark energy. Scientists have discovered a giant, enormous, humongous nothingness in space. Now many people may think that space is full of nothingness, but it isn't. It is, among other things thinly spread out, filled with microwaves. Literally. Those microwaves are left over from the big bang. But now there is a huge hole discovered in the microwave background, or at least in our ability to detect it.

This report comes from the National Radio Astronomy Observatory:

Astronomers have found an enormous hole in the Universe, nearly a billion light-years across, empty of both normal matter such as stars, galaxies, and gas, and the mysterious, unseen "dark matter." While earlier studies have shown holes, or voids, in the large-scale structure of the Universe, this new discovery dwarfs them all...

The astronomers drew their conclusion by studying data from the NRAO VLA Sky Survey (NVSS), a project that imaged the entire sky visible to the Very Large Array (VLA) radio telescope, part of the National Science Foundation's National Radio Astronomy Observatory (NRAO). Their careful study of the NVSS data showed a remarkable drop in the number of galaxies in a region of sky in the constellation Eridanus.

"We already knew there was something different about this spot in the sky," Rudnick said. The region had been dubbed the "WMAP Cold Spot," because it stood out in a map of the Cosmic Microwave Background (CMB) radiation made by the Wilkinson Microwave Anisotopy Probe (WMAP) satellite, launched by NASA in 2001. The CMB, faint radio waves that are the remnant radiation from the Big Bang, is the earliest "baby picture" available of the Universe. Irregularities in the CMB show structures that existed only a few hundred thousand years after the Big Bang...

"Although our surprising results need independent confirmation, the slightly colder temperature of the CMB in this region appears to be caused by a huge hole devoid of nearly all matter roughly 6-10 billion light-years from Earth," Rudnick said.

How does a lack of matter cause a cooler temperature in the Big Bang's remnant radiation as seen from Earth?

Photons of the CMB gain a small amount of energy when they pass through a region of space populated by matter. This effect is caused by the enigmatic "dark energy" that is accelerating the expansion of the Universe. This gain in photon energy makes the CMB appear slightly warmer in that direction. When the photons pass through an empty void, they lose a small amount of energy from this effect, and so the CMB radiation passing through such a region appears cooler.

The acceleration of the Universe's expansion, and thus dark energy, were discovered less than a decade ago. The physical properties of dark energy are unknown, though it is by far the most abundant form of energy in the Universe today. Learning its nature is one of the most fundamental current problems in astrophysics...

So now evidence has been found even for dark energy. Though this by no means proves that the current theories of cosmology are 100% correct, it is a big step in our understanding of all the pieces that make up our universe.