If Dark Matter Can't Be Seen, What About Ghosts?
September 13, 20166:28 AM ET
Over the last few decades, scientists have built a new picture of the universe where about 95 percent of its stuff comes in a "dark" form (27 percent being dark matter and 68 percent being dark energy). But what exactly do physicists mean when they talk about something being "dark?"
Well, basically, they mean the dark stuff acts a lot like a ghost in a horror movie. You can't see the dark matter and dark energy — but you know it's with you because it messes with the things you can see.
It's important to understand that dark matter and dark energy are different "things," in the sense we've inferred their existence through different kinds of phenomena. This means they go bump in the night with stuff we can see in different ways.
Dark matter was discovered decades before dark energy by looking at how galaxies rotate. It was Vera Rubin's famous work in the 1970s that showed pretty much all spiral galaxies were spinning way too fast to be accounted for by the gravitational pull of the their "luminous" matter (the stuff we see in a telescope). Rubin and others reasoned there had to be a giant sphere of invisible stuff surrounding the stars in these galaxies, tugging on them and speeding up their orbits around the galaxy's center.
Kind of sounds like those ghostly kitchen drawers doesn't it?
Dark energy was discovered 16 years ago, when observations showed the expansion of the universe (known since Edwin Hubble in the 1920s) was accelerating. Once again, a form of invisible stuff was invoked to explain the motions of the visible stuff. In this case, dark energy was made accountable for nature's heavy foot on the cosmic gas pedal.
So how do physicists and astronomers get away with claiming the existence of cosmic ghosts (dark matter and dark energy) when they would probably roll their eyes at descriptions of the more terrestrial haunted-house kind?
The answer is data, its prevalence and its stability.
There are literally thousands of studies now of those rotating-too-fast galaxies out there — and they all get the same, quite noticeable result. In other words, data for the existence of dark matter is prevalent. It's not like you see the effect once in a while but then it disappears. The magnitude of the result — meaning its strength — also stays pretty consistent from one study to the next. The same holds true for studies of dark energy.
This is quite different from the many attempts, over more than a century, to get coherent, repeatable, large, signal-to-noise data on paranormal activity (a million episodes of Ghost Hunters not withstanding).
Another key point is that evidence for dark matter pushing around the luminous stuff we can see pops up in lots of places other than the rotation of galaxies. It's needed to explain the bending of light in gravitational lenses and it's needed to understand the clustering of zillions of galaxies on the universe's largest scales. In other words, the ghostly dark matter is part of a dense web of observations and their explanations. There isn't just one reason to "believe" in dark matter.
But here is the rub. For years now, people have been looking for direct evidence of dark matter. This is the equivalent of seeing a ghost with your own eyes rather than seeing the kitchen drawers it keeps opening. After a whole lot of work, no one has found conclusive evidence for a dark matter particle (dark energy is different kind of story in terms of direct searches).
It's still early in the game but, at some point, if nothing is found, scientists may have to re-evaluate their "belief" in dark matter. In that case, they will have to come up with other explanations for the bumps we know we're hearing in the night.
the science behind ghost hunting __________
Exposure to certain types of EMF can lead to physical and psychological side effects like paranoia, nausea and a belief that one is having profound experiences. In the 1980s, a Canadian psychologist named Dr. Michael Persinger created a famous "God Helmet" that placed electromagnetic emitting coils around a subject's head. Once the helmet was activated, the wearer's temporal lobes were pounded with EMFs. More than four out of five of the people who had this happen reported feeling a presence of some kind in the room with them, including on some occasions visions of God.
infrasound, which paranormal investigators have also claimed is a sign of ghostly doings. Low-frequency infrasound, like EMFs, are all around us, and they can have a seemingly enigmatic effect on our minds and bodies as the audio frequency ranges below the normal human hearing range. Everything from the movements of tectonic plates beneath our feet to the rumbling of thunder clouds in the sky can produce low-frequency infrasound. Depending on the origin and nature of the sound, people who are exposed may experience headaches, dizziness and nausea, as well as psychological effects like anxiety and a feeling of dread. Research suggests that infrasound helps inspire, or at least reinforce, perceptions of paranormal encounters.
"I have a foreboding of an America in my children's or grandchildren's time," Sagan wrote, "when the United States is a service and information economy; when nearly all the manufacturing industries have slipped away to other countries; when awesome technological powers are in the hands of a very few, and no one representing the public interest can even grasp the issues; when the people have lost the ability to set their own agendas or knowledgeably question those in authority; when, clutching our crystals and nervously consulting our horoscopes, our critical faculties in decline, unable to distinguish between what feels good and what's true, we slide, almost without noticing, back into superstition and darkness."
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