In space, no one can hear you scream, but with the right equipment, it is possible to detect a roar. The instrument that detected the mysterious roaring signal was the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE), which NASA built to extend the study of the cosmic microwave background spectrum to lower frequencies.

The scientific objectives of the mission, while ARCADE floated high above the Earth’s atmosphere, 23 miles highFree of interference from our planet, they were to find heat from the first generation of stars, search for relics of particle physics from the Big Bang, and observe the formation of the first stars and galaxies.


The first evidence of this spatial roar was discovered by Alan Kogut and his NASA team, 1 the announcement was made in American Astronomical Society issue 213 on January 7, 2009.

ARCADE was able to perform ‘absolutely calibrated zero level’ measurements, meaning it was measuring the actual brightness of something in actual physical terms rather than relative terms. This was different from typical radio telescopes, which observe and contrast two points in the sky. By looking at all the ‘light’ and comparing it to a blackbody source, ARCADE was able to see the combination of many dim sources. It was then that the intensity of a particular signal became apparent..



Since then, scientists have sought to see where the radiation is coming from as they seek to describe the properties of the signal. The latter became apparent rather quickly. According Al Kogut, who led the ARCADE team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland

It is a diffuse signal that comes from all directions, so it is not caused by a single object. The signal also has a frequency spectrum, or ‘color’, which is similar to the radio emission from our own galaxy, the Milky Way.

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Scientists call the signal ‘synchrotron radio background‘, the background is an emission from many individual sources and blends into a diffuse glow. But because the ‘space roar’ is caused by synchrotron radiation, a type of emission of high-energy charged particles in magnetic fields, and because each source has the same characteristic spectrum, it is difficult to identify the source of this strong signal.

The mysterious thing is that the signal is six times stronger than expected: It has been known since the late 1960s that the combined radio emission from distant galaxies should form a background of diffuse radio from all directions. The space roar is similar to this expected signal, but there don’t appear to be six times as many galaxies in the distant universe to make up for the difference, which could point to something new as the source.

It is now being debated whether this source is inside or outside the Milky Way. Still, one reason it probably doesn’t come from our galaxy is because the roar doesn’t seem to follow the spatial distribution of the Milky Way’s radio emission. Once you know with certainty where it comes from, you have to determine what it is.

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The American Physicist David brownFor example, he has pointed out that the space roar could be ‘the first great empirical success of M-theory’, a broad mathematical framework encompassing string theory. “There could be a Fredkin-Wolfram automaton scattered throughout a multitude of alternate universes, producing recurring physical time with endless repetitions of all possible physical events.” What this implies is that the early universe had much more real matter than today, which explains the powerful radio signal..

Other possible, less theoretical sources could be large-scale diffuse mechanisms such as clusters of galaxies that merge turbulently, or an entirely new class of individual sources of radio emission in the universe unknown until now, incredibly numerous. Anything along that line is highly speculative at this point, and some suggestions that have been raised include the annihilation of dark matter, supernovae from the first generations of stars, and many others.

Some scientists have suggested that gases in large galaxy clusters could be the source, although it is unlikely that ARCADE instruments could have detected radiation from any of them. Similarly, there is a possibility that the signal may have been detected in the earliest stars or originated in many otherwise faint radio galaxies, the cumulative effect of which is what is being recorded with ARCADE. But if this were the case, then they would have to fluff incredibly tight, to the point that there is no gap between them, which seems unlikely.