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Visiting Assistant Professor of Physics | Vassar College

Latest Jobs - 23 February 2017
US - NY - Poughkeepsie, The Department of Physics and Astronomy at Vassar College invites applications for a three-year full-time position at the rank of Visiting Assistant Professor beginning in fall semester of 2017. Vass

Looking Deeper Into Our Cosmic Past

Inside Science - 23 February 2017
Looking Deeper Into Our Cosmic Past

Scientists reveal plans for future experiments to study the faint remnants left behind by the Big Bang.


Southern polar lights over the Amundsen-Scott South Pole Station, with BICEP2 telescope visible in the foreground.

Image credits:

Dr. Keith Vanderlinde, NSF


Thursday, February 23, 2017 - 13:45

Yuen Yiu, Staff Writer

(Inside Science) -- What exactly happened in the beginning of the universe?

Scientists are trying to answer this ultimate question by deploying more telescopes to help in their quest. The global collaborative project known as Cosmic Microwave Background-Stage 4 aims to construct new ground- and space-based telescopes, as well as expand the capabilities of existing ones. It will be the continuation of the ongoing CMB-Stage 3 project to study the remnants of our distant cosmic past.

Adding new telescopes will allow scientists to obtain higher resolution data of the cosmic microwave background, which is the oldest observable light in the universe and contains tiny hints of what happened at the very beginning.

Peeking behind the curtain

The cosmic microwave background was first measured in 1964 by Arno Penzias and Robert Wilson by accident. The detection of this background radiation confirmed the Big Bang theory as the correct explanation of our universe's origin, beating its main rival, the Steady State theory, which posited that matter is created continuously throughout the universe over an infinite time scale. In contrast, the Big Bang theory describes an initial creation event, the remnants of which can be detected today. Penzias and Wilson were awarded a share of the Nobel Prize in physics in 1978 for their discovery.

The cosmic microwave background, as measured by telescopes that see in the microwave spectrum, provides a backdrop to our visible universe. Everywhere you look in the sky, if you can see microwaves, you would see the background radiation from 13.8 billion years ago.

However, those microwaves do not mark the beginning of the universe, but only the beginning of free photons, which can travel long distances and someday reach a telescope. Before the curtain of the early universe lifted, the universe was opaque and photons couldn't travel freely. In fact, according to our current understanding, this first light occurred about 380,000 years after the Big Bang. This was long before any stars or galaxies formed, but also long after the initial inflation of our universe.

But if we cannot see past the cosmic curtain of the early universe, how can we ever figure out what happened during the first 380,000 years?

"The idea is that the universe leaves imprints on [the background] in different ways, and we can look for those imprints, and infer what the universe was doing," said Mark Devlin, an astrophysicist from University of Pennsylvania in Philadelphia. He is also a member of the Conceptual Design Team of the CMB-S4 project.

One of the main motivations for the CMB-S4 project is to better understand the initial rapid expansion of the universe, which occurred within the first instant of the birth of our universe. This period of lightning-fast growth, known as the inflationary epoch, was responsible for creating a huge portion of our universe, and is estimated to have lasted less than one quadrillionth of a quadrillionth of a second. It is truly the "big" and "bang" part of the Big Bang.

"The physics of inflation is still unknown," said Cora Dvorkin, an astrophysicist from Harvard University in Cambridge, Massachusetts. She spoke about the CMB-S4 project at a meeting of the American Physical Society, held in Washington, D.C. this January. "We can shed light on the physics of inflation by using CMB observations."


Timeline of the universe, from the Big Bang to present time. (NASA/Public Domain)

More eyes on the sky

The cosmic microwave background emits microwaves with energy that correspond to a temperature of around 2.7 degrees Kelvin. In comparison, the "imprints" mentioned by Devlin correspond to fluctuations around 0.0001 K, approximately a difference of one part in 100,000. Looking for these signals is like looking for fingerprints on the roof of a football stadium.


The detailed, all-sky picture of the cosmic microwave background. The color map covers a range of 0.0002 Kelvin.  (NASA and WMAP Science Team/ Public Domain)

"To get to the sensitivity levels that are required to find either inflationary signal, or just say that's not findable, requires about a factor of ten increase in the current capabilities of all of [the current telescopes] combined," Devlin said.

In other words -- the effort requires more data. The data can come from either building more telescopes or making the current ones bigger, or both.

"The detectors are sensitive as they ever could be. The only way to get more sensitivity is to have more detectors on the sky," Devlin said.

Those additional capabilities will take time and money to build. According to the project's website, the CMB-S4 will be a U.S.-led effort with participation from international partners. Per the request of potential U.S. funding agencies, the scientific community is preparing a report on the technical and financial requirements of the project, which will be reviewed by a federal advisory committee this August, before being formally transmitted to the agencies for their approval.

Cosmic inflation is not the only thing CMB-S4 is set to study. A 221-page "Science Book" detailing the main objectives of the project is now available online. "We expect to learn more about dark matter, dark energy, neutrinos, [in addition to] inflation," Dvorkin said.

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Picture of Yuen Yiu

Yuen Yiu

Yuen Yiu covers the Physics beat for Inside Science. He's a Ph.D. physicist and fluent in Cantonese and Mandarin. Follow Yuen on Twitter: @fromyiutoyou.

Astronomical Optics Scientist | Space Telescope Science Institute

Latest Jobs - 23 February 2017
US - MD - Baltimore, The James Webb Space Telescope (JWST) is a world-class, space-based astronomical observatory scheduled for launch in October 2018. It will revolutionize many branches of astrophysics by achievin

Humans May Have Altered Arctic Ice Much Earlier than Thought

Inside Science - 23 February 2017
Humans May Have Altered Arctic Ice Much Earlier than Thought

Aerosol pollution may have suppressed global warming and increased Arctic sea ice from 1950-1975.


Image credits:

NASA/Kathryn Hansen via Flickr


Thursday, February 23, 2017 - 10:00

Nala Rogers, Staff Writer

(Inside Science) -- For 40 years, heat trapped by human-caused greenhouse gas pollution has been eating away at Arctic sea ice. But for a brief span in the 20th century, Arctic sea ice was actually increasing -- and that may be our fault too, according to a new study.

The researchers used historical measurements to learn how the ice had changed, then modeled climate variables to untangle the causes. They found that between 1950 and 1975, certain types of air pollution counteracted the effects of greenhouse gases that hold heat in the Earth's atmosphere. The balance of these gases at that time cooled the Earth and helped sea ice to grow. The findings emphasize the fragility of the Arctic sea ice system, with humanity's changing pollution habits buffeting the region first one way, then the other.

"I think what it's telling us is that humans had an impact on the Arctic much earlier than had been thought," said John Fyfe, a senior scientist at Environment and Climate Change Canada in Victoria, British Columbia and one of the authors of the study, which appeared today in Geophysical Research Letters.

When people burn fossil fuels, they produce a range of different pollutants that can "force" the climate to react in different ways. Greenhouse gases -- like carbon dioxide -- trap heat and warm the planet, while fine particles suspended in droplets, known collectively as aerosols, usually cool the planet by reflecting the sun's energy away.

"It's a tug-o-war between these two forcings as to what the climate is actually going to do," said Fyfe.

In the mid-20th century, coal-burning power plants and other sources released huge amounts of sulfur dioxide, which then formed toxic sulfate aerosols in the atmosphere. Past research has suggested that the cooling influence of these sulfate aerosols helped counteract warming from greenhouse gases, said Fyfe. But around 1970, the U.S. Clean Air Act and other air quality regulations started curbing sulfate aerosol production. Sulfate aerosols degrade relatively quickly, so people soon enjoyed air that was healthier to breathe. Meanwhile, production of greenhouse gases -- which linger in the atmosphere much longer than sulfate aerosols -- has continued, causing average global temperatures to rise. 

The new study examined what this meant for Arctic sea ice. Unlike land ice, floating sea ice doesn't affect sea levels when it melts and freezes. But it does play an important role in the global climate and ocean currents, acting somewhat like the radiator and water pump in a car, said Andrew Mahoney, a sea ice geophysicist at the University of Alaska in Fairbanks who was not involved in the study. Sea ice is also crucial to Arctic ecosystems, supporting nutritious algae that other organisms feed on, he said. The ice releases algae as it melts, so changes to the yearly freezing and thawing cycles could throw the food web out of whack.   

"The growth and melt of sea ice is like a pulse in the Arctic that's timed to all of the other species that live there," said Mahoney.

Researchers have documented rapid declines in Arctic sea ice since the late 1970s, when the satellite record begins. Earlier data are scarce, but past research has suggested that Arctic sea ice increased between about 1950 and 1975. Fyfe and his colleagues confirmed these findings using data from several historical sources, including maps that once helped Russian ships navigate icy northern waters. The data show that Arctic ice went through an expansion as dramatic as its subsequent decline, said Fyfe. 

Next, the researchers used a mathematical model of Earth's climate to simulate different scenarios, playing out what would have happened without particular pollutants or natural phenomena. The simulations indicated that about a third of the sea ice increase was due to natural processes, while two-thirds was due to aerosol pollution from human, or anthropogenic, sources.

"Arctic sea ice was increasing -- that's clear and unequivocal now during this time period," said Fyfe. "And through these model experiments, we've been able to determine that the increase was due to anthropogenic aerosols."

Not everyone is convinced about the role of aerosols, however. Vladimir Semenov, a climate scientist at the Institute of Atmospheric Physics and the Institute of Geography in Moscow, who was not involved in the study, attributes the period of ice growth mostly to natural variability, although he said aerosols probably also play some role.

"It's an interesting result in the sense that the model showed that such a response [of aerosols on sea ice] is possible," said Semenov. "But to make sure whether it's just an outlier, or really some reliable physical result, you have to check other models."

Mahoney agrees that the new study needs to be replicated with other climate models. But, he said, the results are plausible, and they demonstrate the profound effects of our species' actions.

"I think it suggests that the climate may be more sensitive than we realize to human activities," he said. "When we try to do an environmental accounting of the impacts of our activities, we need to be very broad in our thinking about what to include."

Filed under Republish

Authorized news sources may reproduce our content. Find out more about how that works. © 2016 American Institute of Physics

Author Bio & Story Archive

Nala Rogers

Nala Rogers is a staff writer and editor at Inside Science, where she covers the Earth and Creature beats. She has a bachelor’s degree in biology from the University of Utah and a graduate certificate in science communication from U.C. Santa Cruz. Before joining Inside Science, she wrote for diverse outlets including Science, Nature, the San Jose Mercury News, and Scientific American. In her spare time she likes to explore wilderness.

Online MCAT Physics Instructor – The Princeton Review | Tutor.com

Latest Jobs - 22 February 2017
US - Nationwide, Online MCAT Physics Instructor – The Princeton Review   The Princeton Review is looking to hire part-time Online Physics MCAT Instructors and we want to see if you are interested in an o

Postdoc Positions in the area of Biological Physics | Max Planck Institute for the Physics of Complex Systems

Latest Jobs - 22 February 2017
DEU - Dresden, The Max Planck Institute for the Physics of Complex Systems in Dresden announces the opening of several postdoctoral positions in the area of Biological Physics, to work with Jan Brugués, Mich

Soft Matter Research for Undergraduates (REU) Program at Cleveland State University | Cleveland State University

SPS Jobs - 21 February 2017
US - OH - Cleveland, A Research Experience for Undergraduates (REU) program, “Synthesis, Assembly, and Characterization of Soft Matter,” will be run by the Department of Physics and Department of Chemical &am

Full-Time Lecturer - Physics | California Polytechnic State University

Latest Jobs - 21 February 2017
US - CA - San Luis Obispo, PHYSICS DEPARTMENT, FULL-TIME LECTURER. The Physics Department in the College of Science and Mathematics at Cal Poly, San Luis Obispo, CA is seeking to hire one or more Full-Time Lecturers for academ

Postdoctoral fellow | Medical College of Wisconsin

Latest Jobs - 20 February 2017
US - WI - Milwaukee, Two postdoctoral positions in the Medical Physics Division of the Department of Radiation Oncology, Medical College of Wisconsin are available immediately for individuals who have recently received a


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