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Space Science

Milky Way Is Twice the Size We Thought 301

Posted by kdawson
from the everything-you-know-is-wrong dept.
Peter writes to tell us about a research group at the University of Sydney in Australia, who in the middle of some calculation wanted to check the numbers everybody uses for the thickness of our galaxy at the core. Using data available freely on the Internet and analyzing it in a spreadsheet, they discovered in a matter of hours that the Milky Way is 12,000 light years thick, vs. the 6,000 that had been the consensus number for some time.
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Milky Way Is Twice the Size We Thought

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  • 2x bigger (Score:3, Insightful)

    by Feef Lovecraft (1231264) <feeferscat AT gmail DOT com> on Wednesday February 20, 2008 @04:06AM (#22485308) Homepage
    So until now everyone was just measuring the radius of the Milky Way?
  • by timmarhy (659436) on Wednesday February 20, 2008 @04:11AM (#22485344)
    that only confirms that wikipedia is not a reliable source.
  • by Thanshin (1188877) on Wednesday February 20, 2008 @04:13AM (#22485360)
    Is there any physical effect where a galaxy ends? Or are we just talking about an imaginary limit.

    How hard is it to map the galaxy? If we don't know where the stars are, we can't know the size. If we know, we don't need it; we can describe the actual, real, shape.

    Where's the flaw in my logic? (I hope it's in the part about the limit being imaginary, I like limits in Space like the heliosphere)
  • Re:A good reminder (Score:3, Insightful)

    by bandersnatch (176074) on Wednesday February 20, 2008 @04:16AM (#22485374) Homepage
    because like the internet is like TOTALLY a definitave source mkay?
  • Dark Matter (Score:1, Insightful)

    by Anonymous Coward on Wednesday February 20, 2008 @04:17AM (#22485390)
    Does this ruin dark matter? Perhaps our mass estimates for our own galaxy were off by a factor of 2.
  • by TapeCutter (624760) on Wednesday February 20, 2008 @04:37AM (#22485454) Journal
    People who depend on a single source are unreliable.
  • by Atario (673917) on Wednesday February 20, 2008 @04:58AM (#22485538) Homepage
    Not anymore! Hee hee!
  • by Jugalator (259273) on Wednesday February 20, 2008 @05:09AM (#22485582) Journal

    that only confirms that wikipedia is not a reliable source.
    This argument is getting sort of tiresome to me. In well written Wikipedia articles, key facts are often referenced today. This then becomes a blanket argument against Wikipedia as a whole, without caring for whether the information was well referenced or not. Often, it is. Sure, often it's not too, but IMHO, one need to check that out first.

    This time, you've already received your answer to why Wikipedia had this information, and it's in fact not a long time ago I've had to do the same.

    So, please guys, before you bash Wikipedia, check if there's a good reason to the discrepancy of the information. Surprisingly often, especially in articles receiving good attention like the one for our galaxy, there is.
  • by Jugalator (259273) on Wednesday February 20, 2008 @05:12AM (#22485598) Journal
    Ironically, Wikipedia is one among few encyclopedias that do this. Not for all facts, far from it, but for a fair number of facts. For example, Wikipedia has three references for the mass of the Milky Way, and you can also see which referenced were used for that sole claim. You won't be able to see that by using Britannica.
  • by dltaylor (7510) on Wednesday February 20, 2008 @05:17AM (#22485628)
    The spiral arms are thicker than we've been assuming. Does that mean that there are more stars and gas/dust clouds in the greater volume? If there are more, then the mass of the galaxy is higher, and with the relativistic adjustment recently adopted, there's less need for a "dark halo", or, at least, less of one required to balance the velocity of the outer stars. OTOH, if there's the same amount, then the density is less, which throws off the very measurement technique that they're using to derive the new thickness, since the less-dense interstellar medium will have less effect on the two wavelengths (yeah, I read the article).

    Anyone know of an online resource for the American Astronomical Society papers? I'd like to see what, if anything, they say about the density values for the WIM.
  • Re:A good reminder (Score:4, Insightful)

    by TapeCutter (624760) on Wednesday February 20, 2008 @05:24AM (#22485662) Journal
    The other reply is correct. It's not that everyone just assumed it's origin it's that everyone was uncertain about the origin. There was a hell of a lot of evidence collected for the CDC, WHO and others. Science is designed like that, nobody is ever 100% certain about anything.

    Some religious and political groups (where many claim/demand proof) use this systematic uncertainty to justify their particular perversions of common decency when science presents them with inconvienient evidence. The search for the origin of aids was a good example.

    Nobody is immune because nobody can keep up with everything. The comments on slashdot demonstrate that every day. Over the last 7-8yrs there has been a magnificent debate on slashdot over global warming. What once was marked troll is now insightfull, if nothing else I think most of the regulars (including me) know more about the science behind it than they did a few years ago.
  • by piquadratCH (749309) on Wednesday February 20, 2008 @05:35AM (#22485710)

    As a public service to the Slashdot community I'm going to blatantly violate copywrite and post the lyrics here so we can all see them after geocities melts down

    If you violate copyright, do it right [youtube.com].

  • by uhlume (597871) on Wednesday February 20, 2008 @05:41AM (#22485740) Homepage
    The NASA source doesn't specify at what radius the thickness is measured, leading me to believe that the "1000 light years" figure references an average, or representative, thickness. According to the summary (although curiously unmentioned in TFA) this new discovery seems to pertain specifically to the Milky Way's thickness at the Galactic core, where it is substantially thicker than at points located further down the arms (as illustrated in this side view [usra.edu]).
  • by Eivind (15695) <eivindorama@gmail.com> on Wednesday February 20, 2008 @05:43AM (#22485746) Homepage
    Technically, Wikipedia should never claim any spesific thing. They don't really have an opinion as such on the size of the MW or anything else. Yeah, I know, the article says "The Milky-Way is so-and-so big". But that should really be read as:

    "Our sources, given under this article, claims that the Milky-Way is so-and-so big" One could write it like that, but it'd become tiresome real quick.

    That information is by nessecity only at best as good as the sources.

    Besides; that's the way reality works in general. When somebody claims some fact it ALWAYS means that based on the sources that that person choose to believe (be it his own eyes or a scientific paper, or Fox-news) says so.
  • by syousef (465911) on Wednesday February 20, 2008 @05:43AM (#22485752) Journal
    From TFA with commentary:

    Proving not all science requires big, expensive apparatus, Professor Gaensler and colleagues...downloaded data from the internet

    No, this actually proves that you can reuse data gathered with large expensive apparatus. There's a difference. They couldn't have done this without expensive infrastructure that just happened to cost them nothing (or close to nothing) - ie. The original instruments and the Internet.

    The University of Sydney team's analysis differs from previous calculations because they were more discerning with their data selection. "We used data from pulsars: stars that flash with a regular pulse," Professor Gaensler explains. "As light from these pulsars travels to us, it interacts with electrons scattered between the stars (the Warm Ionised Medium, or WIM), which slows the light down.

    Well now wouldn't you want to explore why the data differs so much, before declaring your answer to be the correct one just because you verified your calculations are correct?

    My first thought is: Did they use some standard or average value for the density of the WIM? Could the discrepancy be because the WIM itself is not uniform through the thickness of the galaxy/

    This is definitely an interesting result and worth following up but rather than declare victory the real question is why is there such a large discrepancy with other data?

  • Define "edge" (Score:3, Insightful)

    by Dan100 (1003855) on Wednesday February 20, 2008 @06:03AM (#22485826) Homepage
    To measure the thickness of something, you need to know where it ends. The Milky Way isn't a solid object, so there must be some arbitary definition of the "edge" where the average density drops below a certain value.

    Perhaps the differences in quoted thicknesses are the result of different definitions of the edge?

  • by uhlume (597871) on Wednesday February 20, 2008 @06:44AM (#22486004) Homepage
    How is this modded "insightful"? Scientific models and methods improve, often building upon earlier models and methods. This isn't an indication of incompetence or malfeasance in the earlier science; it just means that we're getting better at it.

    Additionally, the revised estimate of the point of divergence of humans from primates as a result of newly-discovered fossil evidence isn't even remotely relevant to a case in which existing data has been re-interpreted to form a new conclusion.
  • by rastan (43536) * on Wednesday February 20, 2008 @07:49AM (#22486414) Homepage
    Wikipedia states the average thickness was 1000ly, not the maximum as discussed in the summary.
  • That should say.. (Score:2, Insightful)

    by mario_grgic (515333) on Wednesday February 20, 2008 @09:45AM (#22487140)
    We now think Milky Way is twice the size than what we had previously thought. Using "is" makes it sound like they actually know how big it is this time around.
  • by greginnj (891863) on Wednesday February 20, 2008 @09:56AM (#22487246) Homepage Journal

    But the same people (presumably) have also rushed off to edit Wikipedia! (I see a half dozen edits this morning, to add in the "new" thickness.) That's the part that I find incredible. And people really take Wikipedia seriously?
    You're right. God forbid some stupid fucking amateurs should be so passionately interested in your field that they would do something so counterproductive to your ivory-tower efforts as ... editing a Wikipedia article. It's not like they're part of the public that becomes more or less willing support funding for NSF or NASA grants, for instance. You should be able to get by on royal patronage just fine, without being troubled by the noise generated by hoi polloi.
  • by gfxguy (98788) on Wednesday February 20, 2008 @10:14AM (#22487394)
    It's what happens when one guy does a calculation and everybody else cites it... then it becomes "consensus."
  • by boot_img (610085) on Wednesday February 20, 2008 @10:37AM (#22487676)

    God forbid some stupid fucking amateurs should be so passionately interested in your field that they would do something so counterproductive to your ivory-tower efforts as ... editing a Wikipedia article

    I guess I should clarify. I have no problem with amateurs editing Wikipedia. But I do have problems with, as you say, stupid, fucking amateurs editing Wikipedia.

    For example, at the moment Wikipedia says:

    The disk of the Milky Way galaxy is approximately 100,000 light years in diameter, and is believed to be about 1,000 light years thick (average thickness),[8] with the center bulge's thickness recently discovered by University of Sydney researchers to be about 12,000 light years, contrary to the previously thought 6,000.[9]

    This is not correct. The Wikipedia editors have decided somehow that the 12,000 light year measurement refers to the center of the Milky Way (even though it does not state this anywhere in the U Sydney Press Release). As I said above, the 12,000 light year measurement refers not to a location but to a component, the Warm Ionised Medium or WIM.

    My point is simply that the quality of Wikipedia is only as good as the effort that editors make to understand a subject and edit appropriately.

  • by mysticgoat (582871) on Wednesday February 20, 2008 @10:58AM (#22487932) Homepage Journal

    You bet I take Wikipedia seriously.

    It is the largest and broadest source of information that has ever been available, any where, any time. It gives access to any of 2.25 million articles at incredible speed: it takes many times longer to phrase the Google query that identifies the relevant article than it does to fetch the text.

    Are the contents accurate?

    That's the wrong question.

    Are the contents useful?

    You bet they are, if you understand the context and know how to critically assess what you read. As with any encyclopedia, the most valuable parts of the articles are the references and citations to other works. Through those, a discerning reader can learn the major features of an unfamiliar field. Additionally, the Wikipedia article itself is a pretty good indicator of what the well informed non-expert believes he knows about any field. This is important: it wasn't so long ago that expensive surveys were the only tools for assessing lay knowledge about a field.

    Wikipedia is not authoritative. That does not diminish its value. For various reasons no encyclopedic collection is an authority on any subject (other than itself, and even that is often time-limited).

  • by greginnj (891863) on Wednesday February 20, 2008 @11:02AM (#22487992) Homepage Journal
    I'm perfectly willing to concede that you have expertise on this subject. Since you complain that

    the quality of Wikipedia is only as good as the effort that editors make to understand a subject and edit appropriately.
    why don't you become an editor and help it along? It's not hard at all. When talking about Wikipedia editors, there is no "them". Rather than telling Slashdot that Wikipedia could be better, you could be ... making Wikipedia better. If you put in appropriate footnotes and a clear explanation, especially once today's media frenzy dies down, you'll be lighting a candle rather than cursing the darkness. [Full disclosure, and odd coincidence: a while back, I made a minor edit for clarity to the article on "peculiar velocity" [wikipedia.org]. The article is still a stub -- feel free to check it out and improve it [wikipedia.org]. ]

    I can easily understand that talking about 'how thick the galaxy is' is a lot like the 'is Pluto a planet' dispute -- it's just shorthand for more complex issues that you could elucidate. For example -- you could provide a brief paragraph describing the controversy, and how different elements lead to different measures of a galaxy's thickness, and give those measures. You'd be, you know, educating. If you both care enough and know enough about a subject to be bothered by the Wikipedia article, that's a sign you should be improving it.
  • by Anonymous Coward on Wednesday February 20, 2008 @11:10AM (#22488094)
    I guess you're one of these morons. All he's saying is do a little research and try to work out what is really going on before you go and write an encyclopedia. The usual wiki-wankery happens when people change things too fast without getting a clear understanding of what's going on before they make the changes, and that's why it can never be taken seriously.
  • by zenyu (248067) on Wednesday February 20, 2008 @12:09PM (#22489014)
    My example about the dating of primate and human evolution was to prove that these type of huge "corrections" have occured even in other scientific fields as well. So what we know to be absolutely true today, can be completely off tomorrow.

    Scientists never know anything to be "absolutely true". Absolute truth is the domain of charlatans, liars and cheats.

    When geology started scientists proved that certain rocks in England were "millions of years old!", and postulated based on that that the earth might be "hundreds of millions of years old!". But those numbers seem quaint and even silly today. As new rocks were discovered we soon learned that they were billions of years old, and when we learned about plate tectonics we realized the Earth could be older than the oldest rocks we could find. Our guess as to what the milkyway even looks like are based on looking at other galaxies and then seeing similar structures in our own local neighborhood. We can't actually look at it like we look at other galaxies. We are inside of it; close by stars and dust obscure our view, and our vantage point is that of someone looking at a plane from the side.

    What we can see are 'standard candles', that is stars emitting light within a certain range based on our knowledge of nuclear reactions and our ability to calculate apparent mass and composition. This rests on nuclear reaction theory for stars of large mass that we can not test as easily as we can test say simple nuclear decay, and it also rests on a number of approximations for the amount of dust vs "dark matter" in the intervening space (once you know how bright the star is at it's surface, you then base it's distance from you on how bright it appears to you on earth; the stuff in between matters). Terms like "dark matter" and "dark energy" should be hints that we can be off by several magnitudes. If one star is somewhere between 5,000 and 10,000 light years away, while it sounds like a huge difference, the same approximations can tell us that another star is between 5 and 10 light years away.

    To put this in perspective, does it really matter if homo split off from ape 1 or 2 or 4 million years ago. Or, whether modern man is 50, 100, or 200 thousand years old? Even what happened in your day yesterday is not completely known to you. You have forgotten most of it, and what you do remember is colored by your dreams last night and your mind's ability to integrate it into what has happened before. But you'll make do with your imperfect knowledge of the day, this month you'll have an idea of how warm it was based on the weather this year + the fact that you don't remember it being an unseasonable day, and ten years from now you'll have an idea based on the season, and ten thousand years from now, people reading your description of your day will have an idea of the weather based on the season and climate. All are less accurate than if I had asked you yesterday how warm it was, but so long as you understand the data and it's approximate accuracy it is still useful. It's useful to have an idea of how long ago ape split off from man vs when modern man split off from other human species, but the day the month and the year isn't important when you're dealing with large numbers like this. The order of magnitude is all you need for any useful work. The processes probably took many years anyway. Except in the laboratory, speciation doesn't happen overnight...
  • by BloodSprite (557023) on Wednesday February 20, 2008 @12:12PM (#22489052) Homepage
    does this effect Dark Matter, Missing Mass calculations so that they balance now? (or are a smaller magnitude?)
  • by Nodlehs (860786) on Wednesday February 20, 2008 @01:02PM (#22489838)

    Now you will say that I could always revert the changes ... but that means that not only would I have to write the article, but constantly "maintain" and "protect" it as well. It's the latter prospect that is discouraging.
    If you have enough energy to check slashdot regularly, you have enough energy to check a wikipedia article once a week to see that information you obviously care about is maintained.

    On the other hand, if I were contacted by an editor to write for a "real/classical" encyclopedia, I could be assured that my hard work would be protected.
    Real? Because classic literature is NEVER wrong... And you are always right too? right? ...
  • by spun (1352) <loverevolutionary@@@yahoo...com> on Wednesday February 20, 2008 @01:17PM (#22490078) Journal

    I wonder where I've heard that word before.
    The one guy who calculated global warming is a myth, and all the dittoheads who parrot back the misinformation without any thought in their tiny, birdlike brians?
  • by pkphilip (6861) on Wednesday February 20, 2008 @01:43PM (#22490498)

    "Why do I feel your hidden conclusion from this is 'Jebus is teh g0d!'"
    Interesting that this was brought up. Questioning a "scientific finding" these days or even implying that there may be problems in how the scientific research is being conducted can bring all kinds of interesting people from the woodwork - it is an act about as sacrilegious as arguing before the pope during the dark ages that the sun is not, in fact, rotating around the earth.

    I fully expect to be modded down to oblivion for this and I honestly couldn't care less.
  • by PitaBred (632671) <slashdot.pitabred@dyndns@org> on Wednesday February 20, 2008 @01:59PM (#22490798) Homepage
    It's because you specifically noted primate and human evolution versus the theory of evolution in general, somehow implying that humans are special and outside the system, and you also used a fallacious argument about "Well, if we were wrong about one thing, we could be wrong about everything in science!". This is typically an argument of "Intelligent Design theorists", which is why the GPP brought it up. There have always been problems with scientific research in all fields being imperfect, because humans do it. Stating that you think this is some kind of new thing, or only new in your field of interest, is disingenuous.
  • by uhlume (597871) on Wednesday February 20, 2008 @04:36PM (#22493240) Homepage
    You have no evidence of such an occurrence in this case, and I'd challenge you to find conclusive and credible evidence of such a phenomenon in any other scientific consensus.

    Boldly-worded Slashdot write-up and subsequent rush to Wikipedia notwithstanding, all we have here is a brief article in a little-known Australian paper, vaguely referencing an as-yet unpublished study by a group of astronomers who seem (it's hard to say anything without reference to the study itself) to have re-interpreted existing data to support a finding contradictory to the current consensus, probably within a relatively narrow domain. A new consensus may or may not be built as other scientists independently verify or discredit the methodology and findings of the study. Sensationalistic headlines aside, a single new study does not automatically establish or dissolve consensus, nor should it. This is precisely what the process of scientific consensus is about, and why scientists (and others) rightly trust it.
  • by brian0918 (638904) <brian0918@g m a i l .com> on Wednesday February 20, 2008 @05:22PM (#22493876)
    "You just don't like to pay your bills."

    I'm fine with my bills. I'm even fine with a voluntary taxation system. I think if someone wants to donate their money to a cause, they should be free to do so. What I am not fine with is the plurality taking away my fundamental rights. Do you deny that we have such rights? Individual rights are the fundamental moral principle when men deal with one another. The majority may not --morally -- trample the rights of the minority or the individual. Democracy, to the extent it is good, is only good as good as its ability to protect individual rights.

How many NASA managers does it take to screw in a lightbulb? "That's a known problem... don't worry about it."

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