A joint Fermilab/SLAC publication
The discovery of the first direct evidence for cosmic inflation was made possible by the contributions of hundreds of scientists—including many from Department of Energy national laboratories.

On Monday morning, scientists around the world felt a wave of ecstasy as they learned of a breathtaking discovery: A particular pattern of light coming from the early universe, imprinted on the cosmic expansion during its first moments, had been seen by the BICEP2 collaboration. This polarization of cosmic background light displays a faint but distinctive pattern of swirls that can be created only by an extraordinarily exotic process—a stretching of space-time called gravitational waves—caused by subatomic, quantum fluctuations in the early universe. Its unique signature reaches us intact across all the vast stretches of space since the beginning of time. (See Physicists find evidence of cosmic inflation.)

The discovery, which looks back at the infant universe when it was only a trillionth of a trillionth of a trillionth of a second old, was made possible by researchers from 11 institutions in the United States, Canada and the United Kingdom.

The collaboration was managed by four co-leaders including Chao-Lin Kuo, an assistant professor at SLAC National Accelerator Laboratory and Stanford University, who led the development of the BICEP2 detector.

The detector is one of the most advanced in the world and the success of the experiment—which managed to detect a far stronger signal than most scientists had expected—is thanks in great part to its transformational technology.

That technology includes a new generation of sensors, called modified “transition-edge sensor bolometers,” or TESs, that were developed at institutions including Argonne National Laboratory, Lawrence Berkeley National Laboratory, NASA’s Jet Propulsion Laboratory, the National Institute of Standards and Technology, and Stanford University over the course of a decade.

“It’s exciting that the same technology I developed to search for tiny particles of dark matter is also being used to do research on the scale of the universe,” says Kent Irwin, a researcher at SLAC and Stanford who invented the first version of the TES while a graduate student.

Still, the discovery came sooner than anyone expected and the implications for cosmology are profound. For example, the BICEP2 data directly measure just how fast the early universe expanded. The results are also allowing scientists to delve much more concretely into the new physics that governs cosmic origins, and how it connects to the unification of the Standard Model particles and forces studied at Fermilab’s Tevatron and CERN’s Large Hadron Collider. Cosmic polarization experiments may even provide real data addressing the quantum system underlying the “Theory of Everything,” the long-sought framework that would unify the Standard Model with gravity.

The newly discovered effect is strong enough that other experiments may soon be able to confirm the result, perhaps even using data already obtained. The next step will be to improve the quality of the measurements.

Future experiments seek to do just that. They include BICEP3, a more sensitive telescope that will look at a larger patch of the sky and collect data 10 times faster than its predecessor, and an upgrade to the South Pole Telescope, which is now in development.

Plans are also underway for an even more ambitious fourth-generation experiment by a large consortium of national labs and universities. Such an experiment would deploy hundreds of thousands of detector sensors and stare at a much broader swath of the cosmos, offering a unique opportunity to study many aspects of new physics, including neutrino masses and dark energy. The resulting discoveries would have implications for theories ranging from string theory to multiverse theories of cosmic origins.

The BICEP2 discovery extends and enriches the science reach of this enterprise to a new and deeper level—one many had hardly dared to dream about until this week.


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