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    Despite a new measurement, the debate over the universe’s expansion rages on

    When it comes to the expansion rate of the universe, physicists have apparently agreed to disagree.
    Two types of measurements clash over how fast the cosmos is expanding (SN: 7/30/19). Now, a new estimate from the Atacama Cosmology Telescope, or ACT, further entrenches this disagreement.
    To tease out the properties of the universe, ACT observes light emitted shortly after the Big Bang, known as the cosmic microwave background. Those observations reveal that the universe is expanding a rate of about 67.9 kilometers per second for each megaparsec (about 3 million light-years), physicists report in two papers posted online and submitted to arXiv.org. The number aligns with that of an earlier cosmic microwave background experiment called Planck (SN: 7/24/18).
    “As an independent experiment, we see the same thing,” says cosmologist Simone Aiola of the Flatiron Institute in New York City. Located in the Atacama Desert in Chile, ACT observes the cosmic microwave background with a higher resolution than Planck did.
    To measure the expansion of the universe, the Atacama Cosmology Telescope mapped out the cosmic microwave background (one portion shown). Colors represent differences in the polarization, the orientation of the light’s electromagnetic waves.ACT Collaboration
    Both ACT and Planck disagree with most estimates from objects that emitted their light more recently, such as exploding stars called supernovas and bright hearts of galaxies known as quasars. Those studies tend to indicate a faster expansion rate of around 74 kilometers per second per megaparsec.
    If no simple explanation can be found for the discrepancy, it could dramatically alter physicists’ understanding of the contents of the universe and how the cosmos changes over time. For example, dark energy, the shadowy stuff that causes the universe to expand at an accelerating rate, might behave differently than scientists thought.
    Some researchers had speculated that an unidentified source of experimental error in the Planck data could have accounted for the mismatch. But with the independent measurement from ACT, that explanation has gone out the window. That frees physicists to focus on other explanations, like potential issues with the supernova or quasar measurements, or the possibility of unexplained new physics phenomena.
    Now, says cosmologist Adam Riess of Johns Hopkins University and the Space Telescope Science Institute in Baltimore, “we can proceed without the niggling worries.” More

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    Debate over the universe’s expansion rate may unravel physics. Is it a crisis?

    SANTA BARBARA, Calif. — The word “crisis” hung in the air from the very beginning of the meeting. In a room just steps from the ocean in Santa Barbara, astronomers and physicists shifted restlessly in their chairs. Sunshine and sea breezes beckoned, but the scientists had cloistered themselves to debate one of the biggest quandaries […] More

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    Scientists still can’t agree on the universe’s expansion rate

    SANTA BARBARA, Calif. — It’s one of the most talked-about issues in physics: Two measurements of the universe’s expansion rate disagree. Now, a technique that aimed to resolve the mismatch has produced a third estimate that falls between the previous two. So the controversy endures, scientists report in a study accepted in the Astrophysical Journal.  […] More

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    Hidden ancient neutrinos may shape the patterns of galaxies

    Subatomic particles born in the universe’s first second may imprint their effects on the sky RUN IN CIRCLES  Galaxies in the universe tend to cluster into rings (illustrated), and scientists have found signs that subatomic particles called neutrinos change the way matter is distributed in the circles. Zosia Rostomian/Lawrence Berkeley National Laboratory Share this: This […] More

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    A cosmic flare called the ‘Cow’ may reveal a new way that stars die

    The burst of light from far away may have been a new type of supernova GLOBAL OBSERVATIONS  An odd stellar flare called the “Cow” was observed by telescopes around the world, including the Australia Telescope Compact Array (shown) near Narrabri, Australia. Alex Cherney, CSIRO Share this: This article is only available to Science News subscribers. […] More

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    A second repeating fast radio burst has been tracked to a distant galaxy

    This series of brief radio signals comes from a galaxy 1.6 billion light-years away EARLY DAYS  The Canadian Hydrogen Intensity Mapping Experiment in western Canada spotted 13 new fast radio bursts last summer, one of which repeats. The telescope wasn’t even operating at full capacity at the time. CHIME Collaboration Share this: This article is […] More

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    Voyager 2 spacecraft enters interstellar space

    It’s the second probe ever to exit the heliosphere OVER AND OUT  The Voyager 2 spacecraft has crossed into interstellar space, six years after its twin probe, Voyager 1. The two spacecraft are providing an unprecedented look at the edge of the sun’s influence (lighter blue bubble in this illustration). JPL-Caltech/NASA Share this: This article […] More