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"Dark Matter" Observed
An anonymous submitter writes: "The space news site Space Flight Now has an article about the first direct "observation" of so called dark matter. Galaxies appear to have more gravitation (mass) than we can currently observe. The theory of dark matter tries to explain this missing mass by the existence of massive bodies too faint to detect. These bodies include everything from dim stars to exotic particles called WIMPs. The previously dark matter, a dwarf star, was detected when it passed in front of a brighter blue star, creating a gravitational lens. It is thought that there are many more like it out there creating all that extra gravity, we just can't see them." Wired has another story; or see the European Space Agency's original article.
The fate of the universe is held by dark matter. Without dark matter, there is insufficient gravity to bind all matter together forever. If there is enough dark matter, with its attendant gravity, then eventually the universe will collapse back onto itself. Probably the end result of that would be another Big Bang.
What a pair of choices.
So long and thanks for all the fish . . . !!!
The observed object is a dwarf star. It is luminous. This article should have been titled "Confirmation that one of the MACHO objects is not Dark Matter".
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It was indeed Bohdan Paczynski who wrote the first paper about that specific phenomenon, if I recall correctly, the paper was titled "Microlensing on small optical depths". And indeed, he was the one who invented the term "microlensing".
However, I'm more concerned with "extragalactic" microlensing. The funny thing is that stars in remote galaxy can cause microlensing of even more remote quasars. This was first discussed by Chang and Refsdal in an article in Nature, December 6 1979.
The great thing about this is that in galactic microlensing, there are very few MACHOs between us and the stars, so you would have to watch a lot of stars (millions), whereas in extragalactic microlensing, there will be lots of stars, so microlensing events happen all the time. You only need to separate it from the intrinsic variations of quasar...
Now, galactic microlensing has been a so much bigger field of study than extragalctic microlensing, we haven't really got that much attention. In part, it can be becuase galactic microlensing gives so much more solid results, but then, it is just addressing what's going on in our backyard, while the extragalactic microlensing really deals with the universe... :-)
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I can COMPLETELY believe the idea that dark matter is just regular matter that isn't being illuminated or is not emitting enough radiation for us to detect! But it seems that this, the most obvious explanation, is the last one that physicists want to believe.
I used to work in a research institute that had a lot of physicists in it, and I think most of them would prefer the mundane explanation. However, they would not rule out wild possibilities, and the minority that preferred the wild possibilities would not rule out mundane explanations.
I think that your problem may be with the reporting of science, which I agree sucks. One thing I have learned (rather painfully) upon my transition from research science to industry is that scientists operate and think very differently from the way journalists think. The journalist tries to translate what the scientists are saying into what he and/or she thinks is the language of most people. This causes distortion, for two reasons:
I dealt with a lot of journalists during my 13 years as a research scientist, and I cannot think of a single instance where the journalist got the story even approximately right. The worldview of the journalist is simply too different from the worldview of the scientist. Very, very few scientists are gifted enough with words to provide alternate explanations, and even when they do, they are usually ignored by people who have read a lot of journalistic reviews of science and love to tell the scientists that they're wrong.
Scientists love to toss around wild guesses and argue fiercely about them. The reason they do this is that this process stimulates imagination and the generation of hypotheses, which give hints on what to look for. The sky is just too big simply to passively look around and gather evidence that you will synthesize later. That approach might be ideal if we had an infinite number of scientists, but we don't. The next best thing is to have a diverse community of scientists, each looking for a different thing. Most may be looking for mundane explanations, but a few will be following wild hairs. This is not a bad thing, because whether the wild hairs turn out to be supported or unsupported, knowing this information reduces the number of ideas that have to be considered. Eventually, if we're lucky, a consensus eventually emerges. But, remember, this is the first observation of a class of objects, not the last.
So, some people will be looking for A, and some will be looking for B, etc. Some of them will get evidence that confirms their guesses; some will not, but all will contribute to the sum of knowledge.
It's a bit like doing detective work. You can't just put cameras everywhere and feed the output into a massive algorithm that solves all possible crimes. Instead, you have to follow leads, guesses, hunches, etc. The only difference in science is that a lot of scientists are doing it, and they tend to keep each other honest.
Now, the journalist wants to make a good story, above all. The mundane does not make a good story. Neither does the concept of a working hypothesis, a guess, or a hunch. So, the journalist (or ESA public relations department or whatever) writes a dramatic story focusing on the exciting bits.
Then, finally, when it gets to the readers, they conclude that something is an Explanation from On High, when it is really nothing of the kind. That's just what happened to it in the process of translation through the journalist.
One thing about science that usually doesn't get around is that the scientist is always in doubt. No scientist is really, deep down, 100% sure of anything. He and/or she may be close to 100% sure, but that isn't a trivial difference; it's a vast chasm in a philosophical sense. This is a very difficult thing to learn, and some scientists forget it. The best scientists, however, do remember it, and some are articulate in describing it, such as Richard Feynman. It isn't a need that most people have to deal with at all, and so explanations tend to be ignored.
For the notion of "dark matter," nobody is even close to 100% sure about anything. The whole need to look for dark matter is because, without it, the equations and predictions relating to the big bang look ugly and unbalanced. That may seem like the flimsiest of reasons, until you remember that radio and relativity were developed as a result of precisely that kind of aesthetic judgement of Maxwell's equations. It could all turn out to be totally wrong, which leads to another poorly understood aspect of science: the most effective evidence is that which is against an idea, not for it. However, the best way we know of to find evidence against an idea is to look for evidence for an idea. This is another psychological trick: if you are emotionally attached to an idea, you will try much harder to show it is correct, and a failure to do so means more than a failure of a casual effort. If you do unintentionally distort evidence to support your hypothesis (this happens all the time, far more than outright fraud), there is always somebody else who will poke holes in your ideas. This is good, not bad, but it's very hard to translate that into the language of most people, where auditors are the enemy, not friends.