麻豆传媒

Three cosmologists have for their discovery that the expansion of the universe is accelerating.

鈥淭he observation has changed our understanding of the universe,鈥� said physicist for the Nobel prize committee at a press conference in Stockholm, Sweden. 鈥淭his discovery is fundamental and a milestone for cosmology.鈥�

The accelerated expansion has been attributed to the energy of space-time itself, dubbed dark energy. Dark energy creates a repulsive force that counters gravity and is now tearing apart space-time. It鈥檚 鈥渄ark鈥� because physicists don鈥檛 know its exact nature.

Half of this year鈥檚 prize goes to of the Lawrence Berkeley National Laboratory in California, and the other half will be shared by of the Australian National University in Weston Creek, Australian Capital Territory, and of Johns Hopkins University in Baltimore, Maryland.

Too crazy to be right

In the late 1990s, Perlmutter鈥檚 team and another team led by Schmidt and Riess were independently studying distant exploding stars known as type-Ia supernovae. They were using these supernovae to measure how the universe鈥檚 expansion is changing with time. The expectation was that, billions of years after the big bang, it would be slowing down 鈥� but they found the opposite.

鈥淚t seemed too crazy to be right,鈥� said Schmidt, speaking to the Nobel committee press conference from his home in Canberra, Australia.

But it was right. The presence of dark energy has been independently backed up by measurements of the cosmic microwave background, the radiation left over from the big bang.

Dark choices

When asked about how it felt to receive a Nobel prize, Schmidt said, 鈥淚t sort of feels like [when] my children were born, weak at the knees, amazed.鈥�

Given that the Nobel committee have awarded a prize for an observation concerning something we still don鈥檛 quite understand, they were asked by the press why they didn鈥檛 consider awarding the prize for the equally mysterious dark matter, the substance needed to explain why spinning galaxies don鈥檛 fly apart.

In the early 1970s, made observations of the velocities of stars that imply dark matter exists.

鈥淲ith regards to Vera Rubin,鈥� said Botner, 鈥測es, she was one of the people who is said to have discovered dark matter. She鈥檚 not the only one. And there鈥檚 a history behind it which still has to be investigated. It鈥檚 not as clear-cut as today鈥檚 prize.鈥�

, a cosmologist at the University of Cambridge, commended the choice of dark energy for the Nobel. 鈥淭his award recognises an important and surprising discovery,鈥� he says. 鈥淓ven empty space contains energy and exerts a kind of 鈥榓ntigravity鈥� which causes cosmic expansion to accelerate. It will be a long time before theorists understand this force 鈥� it is part of the bedrock nature of space and time.鈥�

He did lament, however, that the prize can鈥檛 be shared between more than three individuals.