Miguel Morales has been spending a lot of time pondering what he calls “the end of the beginning of the universe”—the cosmic microwave background. Morales, professor of physics at the University of Washington, heads up the university’s Dark Universe Science Center, a group working to figure out gravity, dark matter, dark energy, galaxy formation and evolution, and other cosmological mysteries. Morales gave a talk earlier this month titled “The End of the Beginning.” It was the second of a four-part lecture series, The Big Bang and Beyond, sponsored by the UW alumni association in celebration of the 50th anniversary of the Department of Astronomy.
Morales gave a “Cliff’s Notes” history of the formation of the universe, noting that the end of the beginning came about 380,000 years after the Big Bang, when the hydrogen and helium plasma formed by that event cooled sufficiently to change phase and release light.
“It froze from an opaque helium hydrogen plasma to a clear, neutral gas,” Morales explained.
The “glowing wall of gas” left behind is the cosmic microwave background. Recent measurements have confirmed temperature fluctuations in the CMB.
“These are real, hot and cold spots that we see on the sky,” Morales said. “This is the writing of creation on the wall.”
Morales noted that this writing is extremely faint. He pointed out that the differences between the red an blue sections of the now-famous Planck map of the cosmic microwave background are just one part in 100,000.
“This is really a testament to precision measurement,” he said. He noted that, given this level of accuracy, we can learn a lot about what was going on in the early universe from the evidence left behind.
For example, scientists have teased out sound waves from the cosmic microwave background. The waves were created when the plasma oscillated in what was essentially a tug-o-war between gravity trying to collapse the mass and photons resisting that force. How those sound waves propagate could hold clues to what was going on in the early universe.
The early observations measured temperature, but Morales said the state of the art is to look at the polarization of the light, which could lead to a needle in the cosmic haystack.
“You might be able to see, in the polarization, the ghost of gravity waves from inflation,” he said. They actually thought they had something in observations from the BICEP2 telescope at the South Pole, but what they saw actually turned out to be spinning dust.
“The polarization that BICEP saw is contaminated by the galaxy,” Morales said. “We’re seeing stuff on the windshield here; it’s not all primordial.”
One of the greatest challenges in making these observations is fine-tuning the instruments to ignore the noise and not be faked out by the data.
“BICEP is a technical tour de force, the measurement is awesome. It’s just a little contaminated, and, to be honest, Planck is not sensitive enough to say how bad the contamination is,” Morales explained.
That, he said, is science.
“We’ll keep looking, scratching our heads, building yet more sensitive instruments as we learn to read the words about the universe written faintly on the sky.”