How we know the Earth is old

July 6, 2010 • 10:44 am

Over at Pharyngula, PeeZee describe new kerfuffles involving tea partiers and creationists who weasel about the age of the Earth.  He links to one of his earlier posts about Earth’s age, but I thought I’d add a useful link.  It’s a nice short paper by geologist Robert Hazen, “How old is Earth, and how do we know?” published in Evolution, Education and Outreach (online access is free).  All the dating methods are there: dendrochronology, varves, plate tectonics and—the method for determining Earth’s age—radiometric dating.  There’s a good list of references, too.

If you’re a teacher, or someone who just wants a short precis on how we know that life has been around more than the Biblical few thousand years, bookmark Hazen’s piece.  And, as I do, have a look at the journal from time to time.

34 thoughts on “How we know the Earth is old

  1. I do not believe access to this article is free online. I even registered, and it wanted me to buy the article.

    1. Hmmm. . . I accessed it without going through my university’s site. Trying putting the journal name in Google and then clicking on “current issue”, here. Let me know if it doesn’t work; it would be a damn shame if a journal intended for science educators charged $$ for its articles.

      1. It looks like this particular issue has “partial access”. The article you mentioned says “no access” on my end when I navigate inside the issue.

        Some of the issues do have full access, though.

      2. But did you access it from a university IP address? That’s often enough to get access through the institutional subscription. I used to get ADSL from the university and could access most journals from home too.

        1. That may be it, and if so I apologize for saying that access to the site was free. Springer has long been one of the most mercenary of science publishers, and I am appalled that they would charge $34 for science educators to get access to materials that are useful for teaching.

  2. Yep. $34…

    In my experience, Springer-Link is one of the least-likely publishers to allow open access to its journals, even archival issues.

  3. What about Bones, Rocks and Stars: The Science of When Things Happened? Available for $14 off of Amazon. Tunney’s a solid science writer. It’s short work that would be very accessible to HS students. Reads like a detective story.

    1. Yes, that’s a good book, one I recommend in WEIT. And it’s a lot cheaper than the $34 that Springer’s ripping you off for.

      $34 is OUTRAGEOUS for access. It would cost you 50 cents to Xerox it at the library.

      1. $34 is OUTRAGEOUS for access. It would cost you 50 cents to Xerox it at the library.

        But then you’d be a pirate. Do you really want to be guilty of raping and pillaging on the high seas?

        1. It’s kind of dumb, though. If they priced it at $10, there are 4 or 5 people here who would probably buy it, and they’d make $40 or $50 instead of $0. And you have to consider we’re not the only ones. I know the demand for these obscure journals and articles is low, but they might increase their sales from 100 to 500 people, which would increase their overall profit from $340 to $500 per article.

  4. Springer started charging for access to this journal at the beginning of this year. Damn shame considering it is such a valuable resource to high school teachers. I just hijack my wife’s University account to get my fix, but those who would benefit most are S.O.L.

  5. I haven’t access to Hazen’s paper (paywall), but to those methods when you discuss the many different methods you could add indirect methods.

    One would be estimating the Sun’s age on the stellar main branch since the planetary system is about as old. Another would be measuring the age of the Moon from Apollo or meteorite ejecta from Moon impactors, since we now know that the Earth-Moon system came about at roughly the same time from the same bodies.

    It isn’t as if this observation is a problem anymore.

    Btw, thanks for the resources! PZ links to an article that describes research correcting a problem in the astrobiology text book we study. W00t! (The CAI [calcium-aluminum–rich inclusions] age discrepancy: “other, less precise radioisotopes disagreed with the age derived from lead — but agreed with one another.”)

    – When in doubt, wait. The problem will usually go away.

    1. … from Apollo _samples_.

      But you know, sometimes the Apollo mission seems that old by now.

      Also I should add that the correlation sun-protoplanetary disk have been fairly well established by observations on exoplanets et cetera by now, but of course it is isn’t as certain as the other methods in an individual case. OTOH if the problem is about deep age vs YEC, it doesn’t help the later much to kvetch over a specific case.

  6. “Older than dirt,” is the answer I always give.

    If you want to have “fun” check out the transcripts of the Kansas Kangaroo Kourt back in 2005 during which each of the “experts” was asked a simple question: what is the age of the earth.

    You’d think it would be simple to answer 4.54 billion years, but to read the equivocation from the “experts” most of whom are young earth creationists is mind-boggling.

  7. If you look at the editorial in that issue, they mention the hiccup in free access:

    We have great news! After a temporary hiatus, when Evolution: Education and Outreach became no longer completely free online at, we are poised to come back free online—the better to serve our educational outreach mission.

    Thanks to the imagination, dedication, and hard work of Andrea Macaluso, Editorial Director, Springer Science + Business Media (and the founding genius behind this journal in the first place), we have made arrangements with the National Institutes of Health online library PubMed Central ( to provide our journal once again completely free online.

    As we write, the backlog at PubMed Central will require another month or so for E:E&O to appear. Our arrangement with PubMed Central requires a one-year embargo—meaning that as soon as the backlog clears, our entire Volumes 1 and 2 will appear on their website. In March of 2011, all four issues of Volume 3 (2010) will be added, and so forth.

    So give them a little time, they’ll be made available soon.

    1. Ah that explains it. Weird thing is that once I had trouble getting it from my institution, but then got on with no subscription at home. This time, however, both are shut down… Only for the moment apparently…

  8. Unfortunately the online access to the article “How old is earth and how do we know?” is not free. Even after registering for the site they wanted $34 for it. There are quite a few articles that are free, but this one does not appear to be one of them.

  9. Robert Hazen is, incidentally, a ridiculously over-accomplished person with a fuckton of musical activity and professional credits. Some circles of musicians know him primarily as a trumpet player (soloist and sectional) with a specialty in collecting and performing on “original” or “period” brass instruments:

    As far as those musicians know, Hazen is a musician first, and a writer of popular science books on the side — never mind he’s a professor of science who justifies his university position with research and journal publications!

  10. Interesting article, I’ll read it in full later (hurrah for institutional logins). It also seems that Hazen will eventually link to a pdf on his publications website (, although this particular article is not available yet. It’s still listed as “in press”, so perhaps he’s updated his site … ? One can always ask for preprints from the author directly, though he might be really busy…

    Related, and less than $34 (or $14, it seems), is Richard Fortey’s Earth: An Intimate History.

  11. Watching this video of Gibberson, accuse the “new atheists” of having an unsophisticated notion of god … is especially ironic given what president of one of the nations leading seminary schools is about to deliver him a massive smackdown.

    This really exposes just how bankrupt and dishonest Gibberson is. To make make it sound like Richard Dawkins is fabricating and “framing” all this stuff about God, when Dawkins is really just accepting that important and educated men like Mohler know what they are saying, and mean what they are saying.

    Gibberson on the other hand is off on a project to minimize the importance of origins, and creation itself, which is clear in his latest letter to Mohler (which includes a discussion of the speed of light among other basic facts), and he keeps accusing Mohler of misunderstanding the importance of “creation” as if they simply are not reading the book closely enough.

    Then, Gibberon leaves us with this “ground of being” stuff … and literally proposes that we drop the whole “creator” meme, because that would be like confusing God with a painter, and instead of what he really is which is a “sustainer”.

    Does the word “sustain” appear in Genesis? The word “destroy” seems to.

    If BioLogos is going to bring us this kind of fun with Evangelicals, can we get them to discuss the “historical” Noah? Is that metaphor too?

    We really need these guys … Jerry, could you please ask in your most sonorous voice, using all the cuddly words that they do, what, besides your excellent book, you can do to help?

    This is the most fun I’ve had since the Dover trial.

    Thanks, you rock.

  12. $34 for one article is very steep. You can get a whole book for that! If there was a nominal charge of $0.50 or $1.00, or 10 articles for $5.00 to minimise bank charges, I would be ok.

    It is obvious what academics should do about this – all other things being equal, choose a publisher who will allow access to your work to the widest audience for the least charge.

  13. Thanks Jerry for posting this link. As a person who does not have a scientific background it great to read such an article that allows for a basic understanding of how old the earth is. I think the most interesting evidence of all was the fact that all these different ways of dating our planet are complimentary to each. You really have to have your head buried in the sand not to accept this.

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