The twisted history of cosmic microwaves

    What was that “baby picture” of the universe that was all over the news today? The image is a false-color map of cosmic microwaves. Yes, the same type of radiation that cooks food fast also permeates the universe and reflects something about its structure during the first fraction of a second after the big bang.



    The microwaves were discovered in 1965. They’ve been traveling through the cosmos for more than 13 billion years, where some were intercepted and analyzed by a satellite called Planck. They released their results yesterday – the most detailed analysis yet of these photons from the past, often called the cosmic microwave background.

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    I’ve written dozens of stories about these cosmic microwaves, but the most memorable for me was an obituary – because the best stories usually involve people. The obituary was for one of the most respected cosmologists of all time – Robert Dicke – who worked at Princeton University and died in 1997 at the age of 80.

    He had the insight to realize these microwaves would exist and he devised the right kind of antenna to find them:

    In the early 1960s, scientists knew that the galaxies were receding from one another in what appeared to be an expanding universe, but the big bang idea hadn’t taken hold.

    Projecting back in time, Dr. Dicke speculated that the expanding universe must have sprung from a dense primordial soup of hydrogen and helium atoms.

    Such a state of matter must have been very hot, and would have radiated intense energy, Dr. Dicke realized. Some trace of this energy still should permeate the universe in the form of a faint background hum of microwaves.He thought these microwaves might be detected with a sensitive antenna.

    But Dicke was scooped by another team who found the same thing with a similar antenna and a lot of serendipity. How? Read on here.

    The cosmic microwaves in question were emitted about 300,000 years after the big bang, when the universe had cooled enough for the first atoms to form out of a soup of charged particles. That transition changed the universe from opaque to transparent and allowed light to propagate outward. Over the next 13 some-odd billion years, the wavelength of that light was stretched out from the visible range to longer-wavelength microwaves.

    Scientists continue to monitor and study these microwaves because detailed maps show hot and cold spots that they say reflect the distribution of matter during the first fraction of a second after the big bang. Various theories about the birth of the universe make predictions about the pattern in these spots – which are seen as splotches of false colors in the image. According to the news releases and this New York Times story, as well as some of my friends from the Kavli Institute for Theoretical Physics, this latest image backs a favored theory, known as inflation.

    Inflation posits that the universe underwent a burst of superfast expansion during its first second. The theory explains the relative uniformity of the universe – though according to the New York Times, it’s lopsided:

    Astronomers released the latest and most exquisite baby picture yet of the universe on Thursday, one that showed it to be 80 million to 100 million years older and a little fatter than previously thought, with more matter in it and perhaps ever so slightly lopsided.

    So this latest map may require some explaining. It’s a good thing there are still some surprises to be found out there.

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