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.
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
To be fair to Wikipedia, they cite their source for that claim. And the source is...
...(drumroll!)...
NASA
This is where the serious fun begins.
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.
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?
I agree that the nature of science is that we will definitely need to improve on our findings and get higher and higher levels of accuracy. That is to be expected.
What I find worrying is the range of correction that needs to be applied and also the fact that the correction takes this long - especially considering that the group was able to arrive at a value which is *twice* the older value by just spending a little bit of time studying the data.
The questions it raises are:
1. How is it that the Milkyway was considered to be 6000 light years wide? When someone made this claim, wasn't the data ever rechecked by anyone? If someone with a spreadsheet can come up with this new value of 12000 light years just by spending a few hours studying it, why was it not done earlier? What happened to peer-review - was it ever conducted? If this isn't an indication of incompetence at some level among a few people involved in setting this value, what is?
2. Scientific findings will, no doubt, be modified as new things come to light. However, corrections are normally meant to be just a few % off the initial value. 100% change is not an improvement - it means that the initial value was astoundingly and absolutely wrong. What is staggering about this is the fact that the new value was not calculated based on any *new* finding - but rather it was found just by recalculating based on the *already* existing data.
3. What implications does this have on other findings?
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.