Fermilab Today

Looking out from our planet at the vast array of stars, humans have always asked questions central to our origin: How did all of this come to be? Has it always existed? If not, how and when did it begin?

How can we determine the history of something so complex when we were not around to witness its birth?

Scientists have used several methods: checking the age of the oldest objects in the universe, determining the expansion rate of the universe to trace backward in time, and using measurements of the cosmic microwave background to figure out the initial conditions of the universe and its evolution.

Hubble and an expanding universe
In the early 1900s, there was no such concept of the age of the universe, says Stanford University associate professor Chao-Lin Kuo of SLAC National Accelerator Laboratory. "Philosophers and physicists thought the universe had no beginning and no end."

Then in the 1920s, mathematician Alexander Friedmann predicted an expanding universe. Edwin Hubble confirmed this when he discovered that many galaxies were moving away from our own at high speeds. Hubble measured several of these galaxies and in 1929 published a paper stating the universe is getting bigger.

Scientists then realized that they could wind this expansion back in time to a point when it all began. "So it was not until Friedmann and Hubble that the concept of a birth of the universe started," Kuo says.

Tracing the expansion of the universe back in time is called finding its "dynamical age," says Nobel Laureate Adam Riess, professor of astronomy and physics at Johns Hopkins University.

"We know the universe is expanding, and we think we understand the expansion history," he says. "So like a movie, you can run it backwards until everything is on top of everything in the big bang."

The expansion rate of the universe is known as the Hubble constant.

—Amelia Williamson Smith

Photos of the Day

Floating bugs

A catydid hanging out on the glass-door entrance to Wilson Hall appears to float in mid-air. Photo: Steve Cozzens, FS

A black and yellow garden spider at the Receiving Department hides behind its stabilimentum. Photo: Justin Bower, FESS

In the News

Viewpoint: Deciphering gamma rays from a dwarf galaxy

From Physics, Aug. 18, 2015

The dwarf galaxies of the Milky Way are quiet backwaters in astrophysical terms, holding only a handful of stars. Yet the orbits of those stars reveal the presence of copious amounts of dark matter, the mystery substance that comprises over 80% of the matter in the Universe. Researchers thus see dwarf galaxies as promising dark matter hunting grounds, in which visible matter provides little disturbance. Now, two independent studies assess the hypothesis that faint gamma rays from a recently discovered dwarf galaxy could potentially be signatures of collisions between dark matter particles. At first glance, the analyses appear to deliver conflicting results. The first, by Alex Geringer-Sameth at Carnegie Mellon University, Pennsylvania, and co-workers, suggests that these gamma rays are a possible indication of dark matter, while the second, by Alex Drlica-Wagner at Fermi National Accelerator Laboratory, Illinois, and colleagues, indicates they could just be a fluctuation of the galactic gamma-ray background.

From the Center for Particle Astrophysics

Polar program priorities, from penguins to primordial polarization patterns

Craig Hogan

Craig Hogan, head of the Center for Particle Astrophysics, wrote this column.

Last week, a panel of experts convened by the National Academies of Science, Engineering and Medicine — specifically, the Polar Research Board's Division on Earth and Life Studies — released a new report about top national science priorities for the next decade of Antarctic and Southern Ocean research. Two strategic priorities address urgent issues of planetary as well as polar significance: changes in sea levels and sea ice and adaptation of polar biota to a changing environment. The third priority looks beyond the end of the planet, to the edge of space and time: The report recommends a "next-generation cosmic microwave background program" to address the question, "How did the universe begin, and what are the underlying physical laws that govern its evolution and ultimate fate?"

The report shows that our partners at the pole share our excitement about cosmology. The pattern of intensity and polarization in the cosmic microwave background — the light from the Big Bang that still fills the universe today — is one of the most powerful and precise probes of how physics behaves at its largest scales, emptiest spaces and earliest times. The South Pole is one of the best places on Earth for viewing and mapping it: very cold, very high and very dry.

The more sky we survey, the better the precision, and the higher the angular resolution, the more information about the universe we can extract from the maps. In the next-generation program, DOE labs will enable enormous upgrades in the scale of instrumentation, such as detectors and cameras. Right now, a new camera is coming together at Fermilab, on its way to the South Pole next year, with an order of magnitude more detectors than its predecessor. The next-generation program could increase survey speed even beyond that, by up to a factor of 30 or more.

The new instruments will lead to advances in many fundamental physical measurements, addressing deep mysteries such as the acceleration of the cosmic expansion. They will even reveal properties of our favorite Fermilab subject, neutrinos: Primordial neutrinos are a billion times more common than other matter particles in the universe as a whole, so even their tiny masses make a difference in shaping the largest-scale cosmic structures.

Our polar-minded colleagues do us a great service by counting cosmic background studies among their highest scientific priorities. Their holistic view of science reminds us of John Muir's adage that "when we try to pick out anything by itself, we find it hitched to everything else in the Universe." The South Pole is a good place to connect from the surface of the Earth to the beginning of time.

Safety Update

ESH&Q weekly report, Aug. 18

This week's safety report, compiled by the Fermilab ESH&Q Section, contains two incidents.

An electric chain hoist fell, striking an employee on the head and left forearm. He was taken to the emergency room by the Fermilab Fire Department. Six staples were used to close the head wound. A full review of the work planning process is under way. This is a DART case.

An employee reported to the Medical Office after feeling a bee sting on his lower back. He received first-aid treatment.

See the full report.

In the News

Ghostly particles detected beneath earth

From Live Science, Aug. 18, 2015

Using giant vats of organic liquid buried under a mountain in Italy, scientists have shed new light on the origins of ghostly particles known as neutrinos generated by the Earth.

This research could yield insights into what radioactive elements lie deep inside the Earth and how they influence the churning of the Earth's innards, researchers added.

Neutrinos are subatomic particles generated by nuclear reactions and the radioactive decay of unstable atoms. They are vanishingly tiny — 500,000 times lighter than the electron.

Neutrinos possess no electric charge and only rarely interact with other particles, so they can slip through matter easily — a light-year's worth of lead, equal to about 5.8 trillion miles (9.5 trillion kilometers) would only stop about half of the neutrinos flying through it. Still, neutrinos do occasionally strike atoms. When that happens, they give off telltale flashes of light, which scientists have previously spotted to confirm the particles' existence.