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November 18, 2019

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Cosmologist鈥檚 lonely battle against 鈥楤ig Bang鈥 theory

James Peebles won this year鈥檚 Nobel prize in physics for helping transform the field of cosmology into a respected science, but if there鈥檚 one term he hates to hear, it鈥檚 鈥淏ig Bang Theory.鈥

The leading explanation for the universe in its earliest periods has held sway for decades, with Peebles鈥 early work investigating cosmic background radiation helping to cement many of the details. But 鈥渢he first thing to understand about my field is that its name, Big Bang Theory, is quite inappropriate,鈥 the 84-year-old told a rapt audience at an event honoring US-based Nobel Prize winners at a Swedish Embassy event in Washington recently.

鈥淚t connotes the notion of an event and a position, both of which are quite wrong,鈥 he said, adding there is in fact no concrete evidence for a giant explosion.

The Nobel committee last month honored Peebles for his work since the mid-1960s developing the now prevalent theoretical framework for the young universe. But he is careful to note that he does not know about the 鈥渂eginning.鈥

鈥淚t鈥檚 very unfortunate that one thinks of the beginning whereas in fact, we have no good theory of such a thing as the beginning,鈥 he said. 

By contrast, we do have a 鈥渨ell-tested theory of evolution from an early state鈥 to the present state, starting with 鈥渢he first few seconds of expansion鈥 鈥 literally the first seconds of time, which have left cosmological signatures referred to as 鈥渇ossils.鈥

Fossils in paleontology mean the preserved remains of living things from earlier geological ages. The oldest cosmological fossils are the creation of helium and other particles as a result of nucleosynthesis when the universe was very hot and very dense.

These theories are well-argued because of the preponderance of evidence and checks, unlike the theories for the mysterious phase before.

鈥淲e don鈥檛 have a strong test of what happened earlier in time,鈥 said Peebles, a professor emeritus at Princeton. 鈥淲e have theories, but not tested. Theories, ideas are wonderful, but to me, they become established when passing tests.

鈥淭heories of course, any bright physicist can make up theories. They could have nothing to do with reality. 

鈥淵ou discover which theories are close to reality by comparing to experiments. We just don鈥檛 have experimental evidence of what happened earlier.鈥

One of these theories is known as the 鈥渋nflation model,鈥 which holds that the early universe expanded exponentially fast for a tiny, tiny fraction of a second before the expansion phase.

鈥淚t鈥檚 a beautiful theory,鈥 said Peebles. 鈥淢any people think it鈥檚 so beautiful that it鈥檚 surely right. But the evidence of it is very sparse.鈥

Asked what term he鈥檇 prefer over 鈥淏ig Bang,鈥 Peebles replies: 鈥淚 have given up, I use Big Bang, I dislike it. 

鈥淏ut for years, some of us have tried to persuade the community to find a better term without success. So Big Bang it is. It鈥檚 unfortunate, but everyone knows that name. So I give up.鈥


 

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