Douglas Scott wants to know: what’s the etymology of the term “cosmic variance”?
Since our web presence has made it harder to find out, and the OED offers no clues, I thought I would pose the question to you. Any one know when/where/by whom it was first used?
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Cosmic Variance is a group blog by people who, coincidentally or not, all happen to be physicists and astrophysicists:
Our day (and night) jobs notwithstanding, the blog is about whatever we find interesting — science, to be sure, but also arts, politics, culture, technology, academia, and miscellaneous trivia. We have similar outlooks on many things, widely disparate opinions about others, and will do our best to keep the discourse reasonably elevated.
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August 26th, 2005 at 7:38 am
Cheez, all the way back to 1999?:)Yes googled, I see what you mean.
When you try to estimate any quantity based on a restricted sample, then you expect some uncertainty between your estimate and the “true” underlying value. This is sometimes known as the sample or sampling variance. As you build up a bigger and bigger sample you expect this uncertainty to decrease (if everything is behaving nicely, it will go down like the square root of the number of samples).
http://www.astro.ubc.ca/people/scott/faq_intermediate.html
August 26th, 2005 at 8:46 am
http://en.wikipedia.org/wiki/Cosmic_variance
Hey, it’s not *that* hard — you only have to go down five results to get to a ripped-off Wikipedia article on the subject!
August 26th, 2005 at 10:32 am
Guys, I think we know the definition. Doug is looking for the origin of the term — who coined it?
August 26th, 2005 at 11:29 am
I believe that I have found its origin: a 1993 paper by Martin White, Lawrence Krauss, and Joseph Silk (ApJ 418:535). Quoting them:
Constrained to observe only one universe, there remains an irremovable uncertainty in our ability to relate certain CMB measurements, no matter how precise, to predictions of inflationary models … We term the induced uncertainty the “cosmic variance” …
August 26th, 2005 at 11:52 am
I’ve heard this mentioned as the original reference before, too, I think. If correct, Saucy Wench should get a prize of some sort! (Or is the “pleasure of finding things out” enough?)
-cvj
August 26th, 2005 at 11:53 am
The pleasure of finding things out certainly keeps me happy, but were I awarded a prize, I doubt that I would complain…
August 26th, 2005 at 12:13 pm
Saucy, excellent detective work.
Clifford, you are hereby appointed chair of the CV Prize Committee. Let us know how that goes.
August 26th, 2005 at 12:24 pm
Thank you sir!
-cvj
August 26th, 2005 at 1:15 pm
Wait. Isn’t anyone concerned as to why we aren’t mentioned in the wikipedia article yet?! This is most disturbing.
-cvj
August 26th, 2005 at 1:28 pm
Well, the thing about Wikis is that that’s easily remediable. Looks like someone’s already done it, in fact, although they linked to the wrong Sean Carroll.
August 26th, 2005 at 1:39 pm
Ha! That’s amazing. I did not see that there a week or so ago when I looked. I stand corrected.
How do you know it is the “wrong Sean Carroll”? He’s a multi-talented guy, you know!
-cvj
August 26th, 2005 at 3:05 pm
Am I blind? I don’t see any such reference. Perhaps one of our detractors has removed it, if it was there at one point…
August 26th, 2005 at 3:19 pm
It’s hiding there at the bottom.
August 26th, 2005 at 3:21 pm
Scroll down to the bottom of the entry for cosmic variance. I hadn’t noticed it before, either.
Eventually our blog will be the main entry, and the term of art will be relegated to a footnote.
August 26th, 2005 at 4:37 pm
Wait. Risa, we have detractors ? I’m living in La La land, I thought everybody was our friend.
-cvj
August 26th, 2005 at 4:51 pm
I swear it wasn’t there before. I think Clifford was able to woo whoever the detractors might have been. Sean’s identity has now been clarified in the wiki.
August 26th, 2005 at 4:54 pm
Woo, I like that image. Me going around woo-ing people with the sweet honey of mathematical peotry dripping from my lips…..
Byron beware!
-cvj
August 26th, 2005 at 5:23 pm
Oh boy. I’ve created a monster.
August 26th, 2005 at 5:36 pm
You’ve made me splurt coffee all over my lovely G5. Bad! Bad!
-cvj
August 27th, 2005 at 2:15 pm
Unless I missed something, one more remediation please to Wiki: the complete citation for the paper.
And you guyz/girlz, how clever you are. I just thought CV was a great name, which it is, of course, but now I know its provenance and like/appreciate CV even more. It is one of those demystifications, at least to amateurs like me, that rather than robs from its beauty, only adds to and underscores it.
August 27th, 2005 at 2:22 pm
Thanks. -cvj
August 28th, 2005 at 9:18 am
> It is one of those demystifications [..] that rather than robs from its beauty, only adds to and underscores it.
A nice definition of science in general ?
August 28th, 2005 at 7:34 pm
Are we really supposed to believe that CV has nothing to do with CVj? A coincidence? A likely story.
August 29th, 2005 at 2:41 am
Jill: – You might be on to something there….!
-cvj
October 6th, 2005 at 12:19 pm
So despite a bunch of replies, not much help here!
I certainly didn’t invent the term “cosmic variance”, and neither did my old friend Martin
White in that 1993 paper.
In CMB-land the idea goes back at least as far as Scaramella & Vittorio 1991 and Abbott &
Wise 1984. But neither of those sets of authors appear to have used the term in print.
If I search on ADS for abstracts with “cosmic variance”, the earliest I find is Buchert 1991.
I’m imagining that the term was used in the 1980s by people working on large-scale structure
and maybe velocity fields in particular (the local dipole tells you almost nothing about the
average universe because of cosmic variance). But I can’t find anything!
Maybe it’s just a term that was “in the air”, and no one was actually responsible for it?