by Ralph Carr, U.K. correspondent 

Dark Matter: A primer

Starboard truss of the ISS, with Alpha Magnetic Spectrometer-2 (AMS) visible at center left.

Starboard truss of the ISS, with Alpha Magnetic Spectrometer-2 (AMS) visible at center left.

During their observations on the Universe at large, scientists have constructed a visualisation, a mathematical model, which attempts to describe the way things work. Using all of the available marketing skills, the model has been called The Standard Model.

Very generally speaking, The Standard Model describes how all the matter in the universe came into being from condensing energy, shortly after the Big Bang, or “Event 1.”

After the first expansion, the universe has been steadily spreading out and cooling down, for about the last sixteen billion years. This sounds very idyllic, and for a long time, the steadily expanding universe has been thought of as the way the universe behaves.

Some scientists however, were bothered that our universe may be a one-off, never to happen again.

They speculated that if there was enough overall gravitational field in the universe, then the expansion, caused by the Big Bang, would eventually succumb to the gravitational field, and, after reaching its limit, would eventually collapse back in on itself, forming a super, hyper-black hole, which would then become an unimaginable singularity, spontaneously exploding and causing the next Big Bang, and the next universe. This idea is called the Oscillating Universe Hypothesis.

Scientists tended to favour this idea, because it gave the possibility of continuation, rather than eventual decay.

Can you imagine the horror on leading scientist’s faces, when they fed their numbers into their equations, and the numbers came up short of what they expect? Not just a little short, but it appeared that 95% of the universe was missing. What you see and can detect in the universe, is only 1/20th of what is needed to make the Standard Model work.

By a stroke of genius, the scientists involved, said that the missing matter must be there, we just can’t see it, and because you can’t see or detect it, they gave it a name, and thus it came to pass, that the idea of dark matter was born, and great was the rejoicing in the scientific community.

Dark matter is the theoretical, missing mass that is thought to pervade our universe, and is needed to make the mathematics work. You cannot observe dark matter, detect it, taste it, smell it, or perform any other known form of analysis on it. It exists solely to make the equations of The Standard Model of the Universe work.

It is supposed to have a gravitational field 19 times greater than the rest of the universe put together, and yet, there have only been speculative glimpses as to its existence. It seems that dark matter is as elusive as a clear picture of a UFO.

Dark Matter: What’s new?

 

Left: The sky during a three-hour interval prior to the detection of gamma ray event GRB 130427A. Right: A three-hour interval starting 2.5 hours before the burst and ending 30 minutes into the event, illustrating its brightness relative to the rest of the gamma-ray sky. GRB 130427A was located in the constellation Leo near its border with Ursa Major, whose brightest stars form the familiar Big Dipper. Image courtesy of NASA/DOE/Fermi LAT Collaboration.

Left: The sky during a three-hour interval prior to the detection of gamma ray event GRB 130427A. Right: A three-hour interval starting 2.5 hours before the burst and ending 30 minutes into the event, illustrating its brightness relative to the rest of the gamma-ray sky. GRB 130427A was located in the constellation Leo near its border with Ursa Major, whose brightest stars form the familiar Big Dipper. Image courtesy of NASA/DOE/Fermi LAT Collaboration.

Earlier this year, a study was made using publicly available data from NASA’s Fermi Gamma-ray Space Telescope. Independent scientists at the Fermi National Accelerator Laboratory (Fermilab), the Harvard-Smithsonian Center for Astrophysics (CfA), the Massachusetts Institute of Technology (MIT) and the University of Chicago have developed new maps showing that the galactic center produces more high-energy gamma rays than can be explained by known sources and that this excess emission is consistent with some forms of dark matter.

“The new maps allow us to analyze the excess and test whether more conventional explanations, such as the presence of undiscovered pulsars or cosmic-ray collisions on gas clouds, can account for it,” said Dan Hooper, an astrophysicist at Fermilab in Batavia, Ill., and a lead author of the study. “The signal we find cannot be explained by currently proposed alternatives and is in close agreement with the predictions of very simple dark matter models.”

Renewed speculation over the existence of dark matter has arisen this week because a cosmic ray detector on the International Space Station has detected some immensely powerful cosmic rays, which, scientists think, could only be created by two bodies of dark matter colliding, or a spinning magnetic supernova remnant called a pulsar. Would anybody care to place bets as to the origins?

Dark matter may or may not exist. One thing is very clear. In the history of science, there have been several times when the Standard Model has been under pressure, and an undetectable substance has been ‘created’ to fill the gaps in the abilities of current observers; Phlogiston, Caloric, and The Ether are but three examples. Could it be that dark matter is the 21st Century’s Phlogiston? Invented by capable minds to fill the gap, until we can really learn what is actually going on?

So, dark matter or not, the Standard Model is flawed, and this isn’t a problem because the model is always evolving and becoming more refined. What was a simple mystery today gets thoroughly explained by the next generation of scientists.

Whatever the point of view, dark matter sceptic or dark matter acceptor, dark matter is here to stay (for now), but what it actually is, is anybody’s guess. Careful observation and painstaking research will find it out and show its true nature.

What I will guarantee though, is that once truly discovered, its true nature will be weirder, more fascinating, and more wonderful than we ever thought possible. Because the Universe has a habit of doing stuff like that…

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Ralph Carr
Ralph Carr