“Maybe” Isn’t News

It’s been published several places, but you’ve probably seen this headline:

expansionheadlineIf you’ve been following me for a while, you know where this is going:

No, these physicists haven’t actually shown that the Universe isn’t expanding at an accelerated rate.

What they did show is that the original type of data used to discover that the universe was accelerating back in the 90’s, measurements of supernovae, doesn’t live up to the rigorous standards that we physicists use to evaluate discoveries. We typically only call something a discovery if the evidence is good enough that, in a world where the discovery wasn’t actually true, we’d only have a one in 3.5 million chance of getting the same evidence (“five sigma” evidence). In their paper, Nielsen, Guffanti, and Sarkar argue that looking at a bigger collection of supernovae leads to a hazier picture: the chance that we could get the same evidence in a universe that isn’t accelerating is closer to one in a thousand, giving “three sigma” evidence.

This might sound like statistical quibbling: one in a thousand is still pretty unlikely, after all. But a one in a thousand chance still happens once in a thousand times, and there’s a long history of three sigma evidence turning out to just be random noise. If the discovery of the accelerating universe was new, this would be an important objection, a reason to hold back and wait for more data before announcing a discovery.

The trouble is, the discovery isn’t new. In the twenty years since it was discovered that the universe was accelerating, people have built that discovery into the standard model of cosmology. They’ve used that model to make other predictions, explaining a wide range of other observations. People have built on the discovery, and their success in doing so is its own kind of evidence.

So the objection, that one source of evidence isn’t as strong as people thought, doesn’t kill cosmic acceleration. What it is is a “maybe”, showing that there is at least room in some of the data for a non-accelerating universe.

People publish “maybes” all the time, nothing bad about that. There’s a real debate to be had about how strong the evidence is, and how much it really establishes. (And there are already voices on the other side of that debate.)

But a “maybe” isn’t news. It just isn’t.

Science journalists (and university press offices) have a habit of trying to turn “maybes” into stories. I’ve lost track of the times I’ve seen ideas that were proposed a long time ago (technicolor, MOND, SUSY) get new headlines not for new evidence or new ideas, but just because they haven’t been ruled out yet. “SUSY hasn’t been ruled out yet” is an opinion piece, perhaps a worthwhile one, but it’s no news article.

The thing is, I can understand why journalists do this. So much of science is building on these kinds of “maybes”, working towards the tipping point where a “maybe” becomes a “yes” (or a “no”). And journalists (and university press offices, and to some extent the scientists themselves) can’t just take time off and wait for something legitimately newsworthy. They’ve got pages to fill and careers to advance, they need to say something.

I post once a week. As a consequence, a meaningful fraction of my posts are garbage. I’m sure that if I posted every day, most of my posts would be garbage.

Many science news sites post multiple times a day. They’ve got multiple writers, sure, and wider coverage…but they still don’t have the luxury of skipping a “maybe” when someone hands it to them.

I don’t know if there’s a way out of this. Maybe we need a new model for science journalism, something that doesn’t try to ape the pace of the rest of the news cycle. For the moment, though, it’s publish or perish, and that means lots and lots of “maybes”.

EDIT: More arguments against the paper in question, pointing out that they made some fairly dodgy assumptions.

EDIT: The paper’s authors respond here.

5 thoughts on ““Maybe” Isn’t News

  1. Amir

    The news got another thing wrong – there is a difference between “no acceleration” and “no cosmological constant”. In a universe without cosmological constant, there will be a deceleration of cosmic expansion. The Nielsen et al paper found that deceleration is rejected strongly by the data, and no acceleration fits it weakly (an of course positive acceleration is the most likely case). The paper says that the “no acceleration” scenario requires further investigation, and that maybe it could be due to the viscosity of the galaxies fluid or something.

    In short, if we only look at possibilities coming from a model, this new statistical data still proves that dark energy exists.


  2. Lubos Motl

    Hi Tetragraviton, I completely agree with these comments of yours about the “zero Lambda story”. But as a person who hasn’t been interested in the climate science journalism, as far as I know, you are a good recipient of the question: Do you agree that the climate fearmongering is pretty much all about analogous “maybe” stories?

    The polar ice may be gone by 2016 or, in 2016, by 2030. Life may disappear by 2050. Eating hamburgers may make hurricanes stronger etc. etc.

    If you agree that those stories should be non-stories as well, why haven’t you been concerned by those? I feel that the science journalism is ultimately a “single job” and very bad habits from reports on one discipline automatically affect the way how these journalists write about everything else, too.


    1. 4gravitonsandagradstudent Post author

      Health journalism is probably the paradigm example of this kind of thing. “X both causes and doesn’t cause cancer” is a stand-up comedy cliche on par with “what’s the deal with airline food”.

      The reason I don’t comment on this sort of thing in climate journalism is the same reason I don’t comment on its presence in the much more prolific field of health journalism: it’s not my field.

      I’m not interested in saying much more on this topic.


      1. 4gravitonsandagradstudent Post author

        Note that this blog, in general, has a “no politics” policy. Comments that go too far into political argumentation will be deleted. If you find that a comment was deleted, consider if you can rephrase it without political content.


  3. ohwilleke

    “I post once a week. As a consequence, a meaningful fraction of my posts are garbage. I’m sure that if I posted every day, most of my posts would be garbage.”

    FWIW, I post about 60-100 blog articles about physics a year, and while many are certainly of little value in the long run of things, the supply of worthwhile things to post about tends to be seasonal. During a week when a couple of important scientific conferences are going on at the same time, there can easily be eight or ten worthwhile topic to post on. During lulls in the release of new scientific discoveries, writing a good post often requires reviewing some recurring theme in a line of research that isn’t particularly timely or returning to a story that was missed during a surge.



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