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Our future, our universe, and other weighty topics

Thursday, October 20, 2016

A Second Bullet in the Chest of Dark Matter Theory?

The phrase “caught with your pants down” means to be found in an embarrassing situation. This is exactly what has happened to the swaggering overconfident theorists who have been telling us for decades that many a cosmic mystery can be explained by postulating the existence of dark matter.

For decades such theorists have said the behavior of galaxies cannot be explained merely by the gravitational attraction of ordinary visible matter. So, we have been told, there must be some kind of additional matter, an invisible matter, what is called dark matter. No one has ever produced direct observational evidence for such dark matter, and the Standard Model of physics does not include dark matter. But our dark matter theorists have insisted that there is indirect evidence for dark matter, and have even dogmatically asserted that the universe is 26.8% dark matter. This type of unwarranted precision about an unknown has struck many as being an absurd case of theoretical overconfidence.

Now a new study has cast grave doubt on whether dark matter even exists. (Interestingly, a recent article in Astronomy magazine states, “Scientists now know that dark matter comprises some 84 percent of the universe’s material,” which is so far off from the other estimate it makes you wonder whether someone's just picking numbers out of a hat.)

As reported here and here, the new study found that the rotation speed of galaxies correlates very strongly with the amount of visible matter in galaxies. In other words, if you know how much visible matter is in a galaxy, you can accurately predict the rotation speed of that galaxy. Such a relation is all but impossible to explain under dark matter theories. As astrophysicist David Merrit says, “Nothing in the standard cosmological model predicts this and it is almost impossible to imagine how that model could be modified to explain it, without discarding the dark matter hypothesis completely.”

 The new study seems like a bullet in the chest of dark matter theory. And it may be the second bullet in the chest of dark matter theory. In August scientists announced findings about a distant galaxy called Dragonfly 44. This galaxy seems to have about roughly the mass of our galaxy, but only emits 1 percent of the light our galaxy emits. So astronomers stated that this Dragonfly 44 galaxy seems to be 99.99% dark matter. But such a conclusion raises the question: how could some galaxy get to be 99.99% dark matter, if dark matter is only about five times more common than regular matter? Our cosmologists have been telling us that dark matter is about five times more common than regular matter, and that the two are mixed throughout the universe. If two things are mixed together in a five to one ratio, we should not expect that you would have some local concentration that contained 99.99% of the first thing. A galaxy that is 99.99% dark matter seems no more likely than there might form over a town a lethal patch of the atmosphere that is 99.99% nitrogen and only .01% oxygen, something that would cause you to die of oxygen starvation.

Our scientists talk dogmatically about dark matter, and present arguments for its existence. But such arguments typically involve some underlying assumptions such as the following:
  1. The only force acting to determine the structure of galaxies is gravitation.
  2. Gravitation acts in the simple way that matches our formulas for gravitation, rather than in some more complicated way.
Since such assumptions are dubious, the case for dark matter is very doubtful. What we observe is a universe behaving in strange, mysterious ways. Our scientists try to make things look less mysterious by making precise estimates of the composition of the universe. It would be much more honest if such scientists admitted that we do not understand such things.

From a philosophical perspective, it is entirely possible that the universe is zero percent matter. All that we have direct knowledge of is what goes on in our own minds. Philosophers such as George Berkeley have presented reasonable scenarios of a “mind only” universe in which matter exists only as something perceived within a mind.

Let us imagine a savage living on some remote island in the Pacific ocean. The savage knows nothing of modern science and technology, and he often finds his little world to be a frightening place, particularly when there are thunderstorms. Yet the savage has one consoling thought: he thinks that the local witch doctor knows almost everything. But one day something surprising happens: the savage sees a distant jet airplane passing by the island, something he has never seen before. Bewildered, the savage goes to the witch doctor, and asks him to explain this wonder. “Oh that,” says the witch doctor. “That was just a big insect.” Now the savage is relieved. He can still believe that the witch doctor is a lord of understanding.

No doubt our cosmologists will try to explain away this latest cosmology anomaly in some similar way. Once society has anointed a figure as a great “lord of understanding,” such a figure will almost never say, “You know, I really don't understand these matters.”

But if our cosmologists were to be candid, they would cross out their dogmatic “composition of the universe” pie charts, and replace them with a frank diagram looking like the lower chart below. 

composition of universe
 Postscript: A new scientific paper notes that "no explanation exists so far for the observed dearth of dwarf galaxies in the local universe compared to the large number of dark matter halos predicted by" dark matter theory.

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