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70% of Our Universe is A Mystery

15 April 2013
Published in Space
Written by  Explore Utah Science
70% of Our Universe is A Mystery NASA-Cassiopeia A Supernova remnant

Astronomy week starts today and the surprise is how little we know about our universe.

When you look up into the sky at night, most of what you see is black space that appears to be nothing. Astronomers and physicists, however, know this "nothing" is actually something—composed of energy they cannot see, but know is there. It is one of the great mysteries in the universe.

Everything we can see on earth and in space including, planets, asteroids, comets, supernovae, and nebulae are all made of matter—atoms composed of protons, neutrons, and electrons, but that is only about 4% of the universe.

Between 20-25% is dark matter, which is thought to be made of invisible particles with some properties similar to matter, but don't appear to emit light or other electromagnetic radiation that can be detected with telescopes. Scientists are still trying to identify and characterize dark matter particles, and recent experiments on the International Space Station may have found the first signatures of dark matter in the universe.

Remarkably, even less is known about the remaining 70% of the universe, which is made up of something called dark energy. "That is something that we don't understand very well at all," remarks Kyle Dawson, Assistant Professor of Physics and Astronomy at the University of Utah. However, adds Dawson "We know it [dark energy] drives everything right now in terms of how the universe is changing over time."

Dawson says that for centuries "everybody mistakenly believed that the universe is static. They thought the universe was, is, always will be, in exactly the form that we see today."

That was the prevailing thought until Albert Einstein came up with his Theory of General Relativity (or Theory of Gravity) in the early 1900s. "His theory predicted that was impossible. The universe has to be moving with time, it has to be expanding or contracting with time. There is no such thing as a stable universe in his theory," says Dawson.

In 1998, two groups of scientists measured properties of distant Supernovae – exploding (or dying) stars – to determine how the universe is changing over time. Dawson says they found that not only is the universe expanding, but that the expansion is accelerating. These findings were the first real evidence for the existence of dark energy. "They both independently proved that the universe is expanding and accelerating exactly as would have to be if there was a lot of dark energy out there." he says.

Now researchers are trying to better define what dark energy is. "It's not possible to observe it directly," says Dawson. "What we have to do instead is to keep making more and more precise measurements of how it affects the global system that we call our universe."

Along with two hundred other scientists, Dawson participates in the Sloan Digital Sky Survey, which in eight years has created three-dimensional maps of over 930,000 galaxies. "What we do with our project right now, is try to measure dark energy with other techniques by making a map of the universe in as much detail as possible," explains Dawson. "What we try to record is the velocity and position of basically every galaxy we can measure."

Dawson and his collaborators are using this information to look at the effects of dark energy on other celestial objects, in addition to the Supernovae that originally confirmed it's existence.

"Imagine that you're looking at it through Supernova, you're looking at it through a very small window at one angle," says Dawson. He adds, to get a more comprehensive understanding of dark energy requires seeing it from different perspectives. "If I'm looking at it from the door of my room I want to go run across to the other side of the room to ... see what it looks like on the backside. I want to look at it from the side, and from up above. But, each perspective requires a different type of measurement."

Dawson says that for the most part new techniques and instruments to look at dark energy have already been invented. Now they just have to be utilized. He expects that the next decade will yield many interesting discoveries.

Kyle Dawson will present a public lecture explaining dark energy and how it is measured on Wednesday April 17 at 4:30pm at the Marriot Library, RM 1130 on the University of Utah campus.

April 15-20 is Astronomy Week. Check our Events page for listings.

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