Astronomers Find Star-Less Galaxy 608
Wohngebaeudeversicherung writes "Astronomers have discovered a galaxy about 50 million lightyears away from earth that appears to be composed entirly of dark matter. This galaxy, dubbed VIRGOHI21 is rotating like a real galaxy, at speeds only explainable through massive amounts of matter, thought no single visible star could be detected."
Dark Matter (Score:2, Interesting)
Dyson/Matroska Spheres? (Score:3, Interesting)
Isn't this what they've been telling us to look for for years now - the entire energy output of a galaxy caught and channelled for use by an intelligence that has spread throughout it's own galaxy?
Re:Black holes? (Score:3, Interesting)
Also, is it possible that there was once a star, but now there isn't.
Could they be rotating around something cold and solid, or something not burning bright enough to be visible at these distances
Comment removed (Score:2, Interesting)
I've figured out dark matter (Score:5, Interesting)
Okay, that's an enormous (and highly unlikely) exaggeration, but I *have* thought of an interesting possibility. A Dyson Sphere surrounding several stars (or in a Type 3 civilization, an entire galaxy) would block visible light - the problem is it would glow in the infrared, so it wouldn't really be dark. Black holes are dark, but they tend to fling stuff around, and matter sucked into them gives off bursts of energy before they disappear.
The solution: a dark bubble. At the center of our galaxy there is a supermassive black hole, which is (according to some estimates) roughly three million solar masses. A civilization putting a bubble around it would have 1 (earth) gravity a little beyond the orbit of Pluto, perhaps 40-45 A.U. or so. The problem is that you still would need to stick some stars around it to supply energy, and a Klemperer rosette would be pretty noticeable.
Well, light falling onto a blackhole blue shifts, increasing its energy. Increase the bubble enough (remember, we're talking a civilization that can harness the energy of a galaxy), and the mass of the bubble itself starts to warp space around it. There comes a point where the size of the bubble and the mass that makes it up can be just under the Schwarzschild limit - a bit more massive and it would be a black hole - even without a central singularity. For humans, we'd want a bubble that has a surface gravity equal to earth's, and a blue-shifted energy equal to the average output from our sun.
As a back-of-the envelope calculation, using v^2=2*g*R, where v is the escape velocity, g is the gravitational attraction at the earth's surface, and R is the radius from the center of mass, and setting v=c (the speed of light) for the maximum size, you get a bubble with a diameter just a bit under a light-year across (354 light days, if I figured correctly). The surface area would be about 3 square light-years, 2.6 x 10^26 square kilometers, or 5.2 x 10^17 times the surface area of the earth. The mass would be equivalent to 1.5 trillion suns - roughly twice the mass of our galaxy. Assuming you use buckytubes as the material of choice, you'd have a shell 7000 kilometers thick of solid buckminsterfullerene.
Of course, this is the absolute maximum size and mass just before it becomes a black hole, so the actual construct would be a bit smaller and less massive, balancing surface gravity and blue-shifted energy hitting the surface. You'd also want to carve out mountain ranges and oceans for a bit of variety - a galactic Kansas would be kind of boring. For safety reasons, you would have to stick these bubbles in the empty space between galaxies, or just use all of the mass in one large galaxy (you'd have to be careful, though, to keep relativistic rocks from flying at the completed project). You'd have a sky that would look kind of like a slow-moving aurora, perhaps -- infrared would be shifted into visible light, visible stars would have their peak shifted to ultraviolet -- especially since the gravitational warping would slow down time considerably compared to the rest of the galaxy.
To detect them, you'd have to aim telescopes at the "empty" parts of the sky and see if there was any gravitational lensing. If something was there that was far too massive to be a neutron star but didn't have the characteristics of a supermassive black hole, that could be a sign of it. The largest ones would have the gravitational mass of a large galaxy, so if a supercluster appears to be missing a galaxy's worth of stars that stellar motions demand, it might not be exotic matter but instead bubbles of normal matter from some vast engineering project.
Of course, it might be too early in the evolution of the universe for a type 3 civilization to appear, or you might not be able to make a buckytube bubble big enough that would also support its own weight, so exotic forms of matter might still be necessary. One thing's for certain, though - a bubble like this would make Ringworld look as spacious as a phone booth.
Re:Anyone Question the Existence of Dark Matter? (Score:5, Interesting)
It was easy to disprove the existence of aether with the Michelson-Morley experiment. Had that experiment not been possible it would have been very premature to jump to the conclusion that there is no aether. When it comes to dark matter, there is no easy experiment to disprove its existence and so it would be very rash to conclude that our understanding of gravity, which has worked extremely well for us for hundreds of years, is wrong.
Re:Dark matter is sciences god (Score:4, Interesting)
Serious scientist DO say when they have no idea.
Dark matter indicates that there is a whole field of physics out there and that we're in the state of peaking through the keyhole atm, before opening the door. BTW, this is what the article states, just worded differently when it says something about starting to understand things.
Perhaps just "Dark Current Mode" plasma (Score:1, Interesting)
http://www.electric-cosmos.org
If you read it all the way through you see that "Dark Matter" is just a hack to explain objects like this.
Re: Dyson/Matroska Spheres? (Score:5, Interesting)
It increased thermal conversion effeciency by 50%, making me the envy of all the other Spheriods.
Re: Dyson/Matroska Spheres? (Score:4, Interesting)
Re:Intelligent Life! (Score:5, Interesting)
But is it really Dark Matter? (Score:5, Interesting)
It may be unusual that none of this hydrogen has ignited in a fusion reaction, but that doesn't change the fact that hydrogen atoms are baryonic matter, quite common here on earth. (There are quadrillions of them in my body right now.)
Later, TFA says "according to cosmological models, dark matter is five times more abundant than the ordinary (baryonic) matter that makes up everything we can see and touch."
So this object is "dark" in the sense that it doesn't emit visible light, but it's not Dark Matter.
Or am I missing something here?
Re:Not Black holes (Score:4, Interesting)
Re:Dark matter is sciences god (Score:3, Interesting)
Further, bear in mind that Isaac Newton lived at a time when the church was under greater state control than was typical throughout its history and even received special treatment from the Church of Englad (courtesy of the King) such as the decree - still in effect today, currently on Stephen Hawking - that the Lucasian professor need not take Holy Orders, something nobody else can do. Furthermore, Newton's findings on gravitational fields did not directly challenge any particular belief held by the church.
The notion that science benefits significantly from religion is idiotic. It suggests in a subtle manner that the reason scientists succeed is that they're given baseless conclusions to smash, but that's not the case. Copernicus didn't go looking to beat up the Ptolemic model for the universe and didn't even want to accept his own findings. Galileo didn't go looking to beat up the Geocentric model of the universe. Einstien even rejected some of his discoveries - which are now turning out to be accurate to varying degress - with the famous quip "god doesn't play dice".
Religion is a crutch for people who want to know the "why" of something but don't want to go to all the trouble of following the "how" backwards long enough to get a real answer. People wouldn't be religious if they were clear, critical thinkers because the idea of making non-time-sensitive judgements on faith is an absurd thing born of ignorance and fear. Taking on religious beliefs is like wandering around in the dark and coming to a pit in the floor. Religious people would just back up and take a running jump not know how wide or deep it. Smart people would run some tests like dropping pebbles into it to depth test and trying to determine the width before they jumped. Rare is the case where you'd be forced to simply jump on faith and not be stupid for doing so such as, for example, because you are being chased by a wild animal or something.
Re:Not Black holes (Score:4, Interesting)
A collection of Matrioshka Brains (Score:3, Interesting)
This would qualify as a Kardashev Type III civilization.
But don't suggest this to the astronomers or astrophysicists because they are so friggen sure that the universe is *dead* and nothing they observe could be explained by the activity of advanced technological civilizations... They obviously haven't read any of the work by the Lineweaver group pointing out that 75% of the stars in the galactic habitable zone are older (in some cases much older) than the Sun. [Ref: astro-ph/0401024 [arxiv.org]].
Roll the open source and nanotechnology development efforts forward by a few hundred million years and project what the universe would look like...
Let's get it straight (Score:3, Interesting)
I do not think the word "theory" means what you think it means. A scientific theory is a thesis that has been proven by numerous experiments, has many peer-reviewed papers published exploring it, and is generally accepted as "truth" by the scientific community.
A (layman/religious) "theory" is a guess that could be disproven at any moment, and which has no basis in fact, except the coincidental.
Now then, when we debate a scientific theory, we know there is a large body of work that supports the theory. We can reference it, and we can reproduce the experiments. When we debate a religious theory, it generally comes down to who can shout the loudest, because there are NO reproducible experiments, and precious-few peer-reviewed papers (How many angels can dance on the head of a pin? Discuss.)--certainly not in any respected journals.
As for the desirability of "testing religious theories" there is really no point. As one of my profs put it, If someone comes to you with a 'proof that any angle can be trisected', it doesn't matter how long the proof, how elegant the introduction, how many sources cited, or how clear the abstract. There is no point in reading it, because you know somewhere, buried deep in the discussion, there is a tiny error that renders the entire proof meaningless.
Re:I've figured out dark matter (Score:2, Interesting)
If I understand it correctly, matter being sucked into a black hole emits blue-shifted light, this is true, but only if you're observing it from the outside. I believe an observer near the event horizon would see the light without any blue or red shift.
Additionally, a spacefaring civilization would be reluctant to make their home so deep inside a gravity well. It would require way too much energy to do even the simplest satellite launch.
You also run into a lot of problems with time-dilation and tidal forces. If I'm not mistaken, your clocks run slower than the rest of the universe, so it might make for a nice retirement home, but nothing more.
The gravitational gradient would be so steep that tidal forces would mess you up. Imagine your feet experiencing much more gravity than your head. That is, assuming, any body/device you build can withstand that much gravity.
And, of course, it's very unstable. Should any matter fall in, suddently you become a black hole. oops. Likewise, should any matter fall to the center and make a singularity you suddently end up in an unstable, type-II dyson sphere around a black hole. Even if you have time before you fall in, see above for gravity wells.
So, I'm not sure it works, at least not for harnessing background radiation as you seem to want to do, and even if it did, it would be too risky for a long-lived civilization to want to invest in.
Re:Not Black holes (Score:2, Interesting)
These temperature fluctuations in the Cosmic Background Radiation as thought to indicate the size of the irregularities that once scattered the CMB photons (essentially the light from the big bang) in the very early universe. Once the universe cooled enough for hydrogen atoms to be stable, the CMB radiation would no longer be scattered, so the size of the temperature fluctuations tell us about the density variations of the early universe.
Those density variations are interesting becuase they're enough by themselves to lead to galaxy formation, as density variation tends to increase over time.
The first peak shows that the universe is nearly flat. Open and closed are both within the error bars (anyone else suspicious that the universe is exactly flat?).
The second peak, according to this theory, measures the mass of baryons as a fraction of the total effective mass (mostly energy at that point) of the universe, and the third peak the ratio of all matter to the effective mass of matter+energy in the universe.
What I can't follow is why the second peak is baryons only, but the third peak is all matter. It seems to me that if both baryons and non-baryons have mass and gravity there would be no way to distinguish between dark baryons and dark non-baryons. The presentaiton doesn't seem to explain that.
I'm not seeing how the CMB data is evidence for non-baryonic dark matter.
Re:Have you seen the bombing of Nagasaki? (Score:2, Interesting)
Re:religion and politics in US (offtopic) (Score:3, Interesting)
I personally admit that sometimes I act like a zealot; I do it when I confront religious zealots. I am not savvy enough to argue from first principles with someone who argues from religious faith. I don't think it's good, I just think it's less bad than leaving their viewpoint unopposed. Which isn't to say that I think their views are not valid; I think they are. But I think they're often misapplied. I can see how two wrongs don't make a right, and that maybe when someone says something obviously trollish I should laugh it off-- but the national atmosphere in the US since the day after 9/11 has me thinking that people say a lot of things, and that even false or weak statements can be accepted if unopposed. I don't have the chops to push back against the conservative republican movement, so I like to imagine that I can have a social impact by keeping my liberalness "loud and proud", at least here.
Also, I think some of this behavior is primate- or mammal-territorial .. I think of slashdot as a place where I'm (somewhat) shielded from people who hate science, hate liberals, hate nerds. And I feel that in a very small way I can perpetuate that safe space for people like me by rebutting things that infringe on it. I don't go out of my way to bash the religious, but I *do* go out of my way to confound people who say things that bash liberals or scientists, because I identify with those groups.
I believe that religion is a useful and meaningful part of human knowledge, like philosophy or science or history.
Blah! I have to leave work now.
I have a gmail invite, you can have it if you want.