Diala Qasem

“Expansion of the universe!”

        The 2011 Nobel Prize in physics has been awarded to three American-born scientists for discovering that the expansion of the universe is surprisingly accelerating, and not slowing down, through the study of exploding stars known as supernovae.

One half of the prize will be given to Saul Perlmutter of the Lawrence Berkeley National Laboratory in Berkeley, Calif., and the other half jointly to Brian P. Schmidt of the Australian national university in Weston Creek, Australia and to Adam G. Riess of the Johns Hopkins University Space telescope Science Institute in Baltimore “for the discovery of the accelerating expansion of the Universe through observations of distant supernovae.”

“Imagine the amazement that the expansion [of the universe] was not slowing down but it was actually accelerating,” said Uppsala University professor Olga Botner during the Nobel Prize announcement in Stockholm Tuesday morning. “The unreal feeling could be likened to the feeling you get if you in your car step on the brake and suddenly you realize that your car is actually accelerating.”

In 1929 a discovery by Edwin Hubble that the Universe is in fact expanding at enormous speed was revolutionary. Hubble noted that galaxies outside our own Milky Way were all moving away from us, each at a speed proportional to its distance from us. He quickly realized what this meant that there must have been an instant in time (now known to be about 14 billion years ago) when the entire Universe was contained in a single point in space. The Universe must have been born in this single violent event which came to be known as the “Big Bang.”

Astronomers combine mathematical models with observations to develop workable theories of how the Universe came to be. The mathematical underpinnings of the Big Bang theory include Albert Einstein’s general theory of relativity along with standard theories of fundamental particles. Today NASA spacecraft such as the Hubble Space Telescope and the Spitzer Space Telescope continue Edwin Hubble’s work of measuring the expansion of the Universe. One of the goals has long been to decide whether the Universe will expand forever, or whether it will someday stop, turn around, and collapse in a “Big Crunch?”

This diagram illustrates two ways to measure how fast the universe is expanding. In the past, distant supernovae, or exploded stars, have been used as “standard candles” to measure distances in the universe, and to determine that its expansion is actually speeding up. The supernovae glow with the same intrinsic brightness, so by measuring how bright they appear on the sky, astronomers can tell how far away they are. This is similar to a standard candle appearing fainter at greater distances