Milky Way Is Twice the Size We Thought 301
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.
2x bigger (Score:3, Insightful)
Re:Wikipedia says 1000 (Score:3, Insightful)
Is this real information? (Score:3, Insightful)
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)
Dark Matter (Score:1, Insightful)
Re:Wikipedia says 1000 (Score:2, Insightful)
Re:Wikipedia says 1000 (Score:3, Insightful)
Re:Wikipedia says 1000 (Score:5, Insightful)
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.
Re:Wikipedia says 1000 (Score:5, Insightful)
Does this affect our estimate of the mass? (Score:3, Insightful)
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)
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.
Re:This may cost me my geek card... (Score:4, Insightful)
If you violate copyright, do it right [youtube.com].
1000 light years where? (Score:3, Insightful)
Re:Wikipedia says 1000 (Score:4, Insightful)
"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.
Interesting but premature? (Score:5, Insightful)
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)
Perhaps the differences in quoted thicknesses are the result of different definitions of the edge?
Re:Other instances of numbers widely off (Score:5, Insightful)
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.
Re:Wikipedia says 1000 (Score:2, Insightful)
That should say.. (Score:2, Insightful)
Re:The problem with Wikipedia (Score:5, Insightful)
Re:Other instances of numbers widely off (Score:5, Insightful)
Re:The problem with Wikipedia (Score:5, Insightful)
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:
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.
Re:The problem with Wikipedia (Score:5, Insightful)
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).
Re:The problem with Wikipedia (Score:5, Insightful)
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.
Re:The problem with Wikipedia (Score:1, Insightful)
Re:Other instances of numbers widely off (Score:5, Insightful)
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...
Dark Matter / Missing Mass (Score:2, Insightful)
Re:The problem with Wikipedia (Score:2, Insightful)
Re:Other instances of numbers widely off (Score:5, Insightful)
Re:Other instances of numbers widely off (Score:5, Insightful)
I fully expect to be modded down to oblivion for this and I honestly couldn't care less.
Re:Other instances of numbers widely off (Score:3, Insightful)
Re:Other instances of numbers widely off (Score:3, Insightful)
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.
Re:The problem with Wikipedia (Score:3, Insightful)
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.