Slashdot Mirror
Milky Way Is Twice the Size We Thought
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.
Yeah, it comes with "%30 MORE!" now.
Obesity is everywhere.
Wikipedia says it's only 1000 light years thick.
So until now everyone was just measuring the radius of the Milky Way?
This is a good reminder how you're supposed to dig down to the raw data and validate that. I remember reading in one of Richard Feynman's books about a similar case, some conclusion or data appeared well supported, because a lot of the research papers were supportive of the idea, but it turned out that they derived what they said based on a single source.
The case here is similar, it's a good reminder how science is about data, validation and facts not about authority. You're supposed to check your data, check your facts and try to avoid making implicit assumptions.
It takes a man to suffer ignorance and smile
Be yourself no matter what they say
So I read the article (yeah, yeah - I know...I was bored) and I hope the spreadsheet software used wasn't Excel - we all know how well that counts.
The Mothership
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)
Now you guys tell me!
What the Fudge man, I have been eating Snickers all this time thinking I'm getting more chocolate! Now I find this out?
What we're seeing now is middle age spread.
"Nine times out of ten, starting a fire is not the best way to solve the problem." - my wife
Well, if we're expecting that the universe is actually 75 to 95 percent dark matter based on the
SAME KIND OF FLAWED DATA, perhaps we are underestimating the amount of matter we actually CAN see.
I always wondered how exactly they determined how much matter was in the universe, indirect evidence or not.
Seems like there may be few assumptive leaps there, upon which we build our entire cosmological understanding.
If the 'missing' matter is actually regular matter that we haven't found, or have found and discounted,
the search for dark matter will be even more in vain than it appears to be already. Can we stop looking?
That famous scientist may have allowed himself to get carried away a bit. What it means is that there was no clean breakthrough article. Rather, evidence gradually accumulated. What it does not mean is that the connexion is "perhaps true", certainly not in the current stage where effective medicines exist.
On the other hand it's good practice to have roundup articles that go over the evidence.
Use something a layman could understand OK?
Say, how many Library of Congress, or elephants, have we got here?
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
Galaxy Song
Spoken: Whenever life gets you down Mrs. Brown,
And things seem hard or tough,
And people are stupid, obnoxious or daft
And you feel that you've had quite enough...
Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour,
That's orbiting at nineteen miles a second, so it's reckoned,
A sun that is the source of all our power.
The sun and you and me and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at forty thousand miles an hour,
Of the galaxy we call the 'Milky Way'.
Our galaxy itself contains a hundred billion stars.
It's a hundred thousand light years side to side.
It bulges in the middle, sixteen thousand light years thick,
But out by us it's just three thousand light years wide.
We're thirty thousand light years from galactic central point.
We go round every two hundred million years,
And our galaxy is only one of millions of billions
In this amazing and expanding universe.
The universe itself keeps on expanding and expanding
In all of the directions it can whizz
As fast as it can go, the speed of light, you know,
Twelve million miles a minute and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger all down here on Earth.
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.
...We are told that the sun's light takes approx 8 minutes to reach us, but now we know that the distance involved is twice as much so therefore the speed of light must be approximately double what we thought! ...if the moon is twice as far away as previously thought, how come astronauts have landed successfully - in theory, they should get 'there' and be in the middle of nowhere ...UNLESS, of course they never went....AH HA!!!
AT&ROFLMAO
What I find disturbing is the fact that a number is this widely off and no one discovered it for such a long time! I can imagine deviation by x % or less where x
The split of Humans from the Apes pushed back by another 6 to 7 million years earlier than previously thought based on molecular genetics. The difference from the earlier estimate of around 5 to 6 million years is therefore over 100%
http://www.news24.com/News24/Technology/News/0,,2-13-1443_2169361,00.html
Whenever life gets you down, Mrs. Brown,
And things seem hard or tough,
And people are stupid, obnoxious or daft,
And you feel that you've had quite eno-o-o-o-o-ough...
Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour,
That's orbiting at nineteen miles a second, so it's reckoned,
A sun that is the source of all our power.
The sun and you and me and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at forty thousand miles an hour,
Of the galaxy we call the "Milky Way".
Our galaxy itself contains a hundred billion stars.
It's a hundred thousand light years side to side.
It bulges in the middle, sixteen thousand light years thick,
But out by us, it's just three thousand light years wide.
We're thirty thousand light years from galactic central point.
We go 'round every two hundred million years,
And our galaxy is only one of millions of billions
In this amazing and expanding universe.
(Animated calliope interlude)
The universe itself keeps on expanding and expanding
In all of the directions it can whizz
As fast as it can go, at the speed of light, you know,
Twelve million miles a minute, and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger all down here on Earth.
If you violate copyright, do it right.
"Our galaxy itself contains a hundred billion stars. It's a hundred thousand light years side to side. It bulges in the middle, sixteen thousand light years thick, But out by us, it's just three thousand light years wide."
This is not a sig
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).
SIERRA TANGO FOXTROT UNIFORM
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?
These posts express my own personal views, not those of my employer
Perhaps the differences in quoted thicknesses are the result of different definitions of the edge?
TFA says: "The team's results were presented in January this year at the 211th meeting of the American Astronomical Society in Austin, Texas." but there's no indication of where the results have actually been published in a peer-reviewed journal so that one could read the paper for oneself. I looked on the AAS site and couldn't find anything there either. So, pending access to a detailed published per-reviewed account of their work, I'm reserving judgement as to how valid the claim is.
So every time someone forget to divide by 2 , he is going to claim he came up with a major discovery ??
I am an astronomer, so first some background: The Milky way has several components: young stars, old stars, dust and various components of gas. They all have different thicknesses. There is no single "thickness". One of these components (warm ionized gas) has been measured to have a thickness larger than expected. This measurement has not been confirmed by others, nor (I think) published yet.
Despite this complexity, this discussion thread is awash with arguments, confusion, wild speculation, suggestions that dark matter might be wrong etc. etc. OK, fine, this is slashdot, that's what slashdot is for.
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?
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.
As the island of our knowledge grows, so does the shore of our ignorance.
You really CAN get stuff on the net to double your size.
***GUARANTEED increase your galaxy by 6,000 light years***
thick and sturdy clusters. ladies love dark matter. hawking beautiful einstein copernicus keppler cassini
jplab buzz lightyear wormhole
[sorry--I couldn't resist]
I might know what I'm talkin' about, but then again, this is Slashdot...
does this effect Dark Matter, Missing Mass calculations so that they balance now? (or are a smaller magnitude?)
Lifes a game play to win!
Now I have to pack an extra suitcase.
It must have been something you assimilated. . . .