March 15, 2006 – The universe is expanding and it's flat. That's according to theoretical physicist Lawrence M. Krauss who spoke Wednesday to a group of about 70 students and community members during a lecture at the University of the Virgin Islands on St. Thomas.
Krauss, who is known for his ability to popularize the complicated subject of physics, was here attending a conference of some of the field's greatest minds, dubbed "Confronting Gravity: A Workshop to Explore Fundamental Questions in Physics and Cosmology" (See "World's Top Physicists to Meet in the Virgin Islands").
During his lecture Krauss said that if gravity were the only force in the universe, then planets would be colliding with each other instead of moving farther apart. And thus began what he called his "mystery story."
He said there's something preventing collisions from happening, but scientists who are working to find the answer don't know what it is yet. When asked if there had been any breakthroughs in the project – which has to be conducted underground to avoid interference from other known particles – Krauss said, "If we had, you'd be reading about it on the front page of the New York Times."
Krauss said it took 20 years to develop the equipment for the project, which is being conducted in the United States, Europe and elsewhere.
In a way that was almost comprehendible to the ordinary person, Krauss explained the difference between dark matter and empty space, along with why he thought the universe was flat instead of being curved.
While discussing these topics, he also gave a brief history of cosmological theory, tracing the field's path from Albert Einstein to Edwin Hubble, and ended by saying that the question of what makes up the energy in empty space is still unknown.
He explained that in 1915 Einstein's theory of relativity described a static universe in which gravity was the only force of energy. However, upon further research, Einstein discovered that if gravity were the only force, then planets and galaxies would be pulled toward one another, instead of maintaining a stable position or expanding away from each other.
To get around this problem, Krauss said, Einstein developed a cosmological constant which supported the theory of a static universe – a term which Einstein called the "greatest blunder" of his life after it was later disproved by the discoveries of Edwin Hubble.
Krauss said Hubble discovered that light emitted from galaxies – which appeared red if the galaxies were shifting away, and blue if they were moving closer – showed that most galaxies were moving farther away from Earth. He also said that Hubble noted that the farther away a galaxy was from any particular point in space, the faster it continued to move away from that point. "This further proved that Earth is not the center of the universe, and you can see that the galaxies are moving from any point in space," Krauss said.
He added that there are some galaxies such as the Andromeda Galaxy, which emit a blue light, and are consequently moving in a collision course toward Earth. However, Krauss said this would not happen for another five billion years.
This idea, called the Hubble Constant, is a measure of how much space is expanding in units of distance per second, Krauss continued. He said that nowadays scientists use the constant in conjunction with standard candles – sources of bright light in the universe that serve as reference points – to measure the distance galaxies are expanding over time. Supernovas, or exploding stars, often serve as standard candles and can frequently be seen through a powerful telescope such as the Hubble telescope, he added.
Krauss further explained various complicated mathematical formulas used by scientists to measure the Earth and then the universe to determine the rate at which the universe is expanding. Scientists, he said, were also able to discover that gravity is the weakest force in the universe, and that "every galaxy we see" is filled with "dark matter," a new kind of elementary particle, which keeps the galaxies from colliding.
He also said that about 70 percent of the mass making up the universe is empty space, and the energy that makes up empty space is tied to the expansion of the universe. "We don't know why that is," Krauss said. "And that's the biggest mystery in physics."
At the end of his lecture Krauss said if the mystery were solved scientists would be able to determine how the universe began and how it will end.
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