Enter Dark Matter and Dark Energy. Can't see them. Can't measure them. But the most accepted models of the universe only make sense if they exist.
(Image: A University of Hawai'i team compared the strength of the Cosmic Microwave Background with sections of the sky where they located superclusters (red circles) and supervoids (blue circles). Microwaves tended to be stronger in the red and orange areas, and weaker in the blue areas. Credit: UH Institute for Astronomy.)
Now, for the first time, researchers at the University of Hawai'i's Institute for Astronomy may have actually measured the effects of one of them: Dark Energy.
A team led by Dr. István Szapudi believes it has been able to find direct evidence for the existence of Dark Energy, by measuring changes in microwaves that have moved through superclusters and supervoids.
(Okay. Some definitions:
(The universe has unimaginably vast areas that are dense with galaxies and also has areas that have comparatively few galaxies. The first are called superclusters and the second supervoids.
(Dark Matter: Based on theoretical calculations of the universe and how it works, there ought to be far more matter than we can actually find and measure. Astronomers assume it's there, but we just can't detect it. The missing stuff is called Dark Matter.
(Dark Energy: The universe is expanding, and something appears to be accelerating the expansion. What's causing the acceleration? The experts don't know, but some of them have a name for it. Astronomers call this mysterious—and until now theoretical—force Dark Energy.)
“We were able to image dark energy in action, as it stretches huge supervoids and superclusters of galaxies,” Szapudi said, in a press release from the Institute for Astronomy. His co-authors were Benjamin Granett and Mark Neyrinck. Their paper will be published within the next two months in the Astrophysical Journal Letters.
How it works is this, as Szapudi's team explains: If a microwave enters a supercluster, it gains energy. When it leaves the supercluster, it should lose that energy again. But if the supercluster is being affected by Dark Energy, being flattened in the 500 million years it takes for the microwave to cross it, then the microwave will actually retain some of the supercluster's energy.
“Dark energy sort of gives microwaves a memory of where they’ve been recently,” Neyrinck said.
The team looked at the 50 largest superclusters and at the 50 biggest supervoids in a region representing galaxies across about a quarter of the sky.
The team found that microwaves that had passed through superclusters appeared to have gained energy, while ones that had passed through supervoids lost energy. The distinctions were extremely small, but detectable.
See the Institute for Astronomy release on the paper here: http://www.ifa.hawaii.edu/info/press-releases/szapudi-7-08/.
© 2008 Jan W. TenBruggencate