Good communication

What is the shape of a raindrop? Going by the common raindrop symbol, you might think it’s round on the bottom and pointy on the top. In actuality, they are spherical when small, and become more pancake-shaped at larger sizes. The biggest raindrops make parachute shapes before breaking up into smaller drops (see video). So that’s an interesting, if not particularly useful, scientific fact.

So the next question is, do you feel misled by the raindrop symbol? Are you incensed by the misinformation?

So this is another one of those posts where I look back at the atheoskeptical movement, and talk about things that have bugged me for a long time. I’m thinking back to an old skepticism website, which used this as its symbol:

alt: raindrop symbol with a circle and slash symbol.

The website still exists, although it feels extremely dated now, to the point that I feel bad about picking on what is obviously some old professor’s work of love. But anyway, if you click on the symbol, it shares an anecdote in which a weatherperson justifies their use of the inaccurate raindrop symbol, saying that it is “good communication”. The page goes on to say,

This page is dedicated to the proposition that:
it is better to communicate good information than to offer misinformation in the name of good communication

My first reaction is that this seems like a rather petty thing to complain about. Although people may be misled about the shape of raindrops, there aren’t exactly a lot of raindrop-shape-related decisions we make in our everyday lives. I can only ever see this coming up in an educational setting, where the teacher would explain the truth about raindrops to a mildly surprised audience. Which I can only imagine enhancing students’ engagement with the subject.

But here I am complaining about a decade-old website, so perhaps I better not talk about petty.

The problem isn’t so much that it’s petty, it’s that raindrop shapes are presented alongside a competing concern–good communication–and the competing concern is dismissed out of hand. Was this a thing that skeptics used to do all the time, obnoxiously prioritize factual accuracy over communication? Well, judging by the number of terrible science talks I have attended, it’s at least a common attitude among scientists.

It’s funny, because both factual accuracy and communication are both aimed at the same goal: truth. In order to propagate truth, we need to have the truth in the first place, and then we need to communicate it to other people. Communication isn’t even a competing concern, it’s more like… another aspect of the exact same concern.

Perhaps the real difference in opinion between the professor and weatherperson is which truths they choose to prioritize. The professor was more concerned with the truth of raindrop shapes, whereas the weatherperson is more concerned with the truth of what the weather will be like tomorrow. But why is one truth more important than the other? What about all the other weather-related truths that nobody is prioritizing, such as why raindrops are shaped that way, or what is the statistical meaning of “chance of rain”?

One last thought I have, is that the raindrop seems to have a sort of “artistic truth” to it. My impression upon seeing rain is not seeing a bunch of spherical droplets, but rather elongated lines. That’s because raindrops fall very fast, and the shape is smeared across the line of motion. “Smear”, I recently learned, is a concept in animation used to convey motion. Without any smear, the raindrop would look motionless, which is definitely not scientifically true about raindrops. So maybe the raindrop shape was an accurate representation all along, and we just needed to talk to artists to explain how the truth was encoded.


  1. Rob Grigjanis says

    This touches on a pet peeve of mine; the ubiquity in pop-sci of virtual particles. One example: Hawking radiation.

    In his 1975 paper, Hawking devotes a couple of paragraphs, out of 20+ pages, to a ‘picture’ of what is happening, involving a virtual pair of particles outside the event horizon, one of which has negative energy but can tunnel into the black hole, and the positive energy particle ‘escapes to infinity’ as radiation. None of this has anything to do with his calculations, and he does point out that the picture “should not be taken too seriously”.

    So: does this ‘picture’ qualify as good communication, or perhaps as “artistic truth”? Well, it got people talking about Hawking radiation, up to a point. But it’s hard not to conclude that Hawking’s goal was to get people talking about Hawking,

  2. brucegee1962 says

    As you point out, we can’t really see raindrops as they are falling from the sky.

    Where we can see them, however, is when they are accumulating in some elevated flat, pointed, or bowl-shaped object, running beneath it, and dripping down (eaves, stalactites, icicles). Then they definitely do take the teardrop shape. So, actually, do tears if they are allowed to drip from one’s face. So since we can easily observe these events, and we can’t easily observe rain, and the “teardrop’ shape doesn’t appear many other places in nature, it makes perfect sense to associate them.

  3. says

    @brucegee1962 #2,
    Yeah, there are a few alternate explanations for the raindrop symbol, one being the shape of drips from an icicle or faucet, and another being tears on a face. I don’t want to push the “smear” interpretation too hard. The raindrop symbol is certainly inaccurate in a certain sense, and more to the point, people get an inaccurate impression from it.

    It does, however, accurately communicate “rain”, so *shrug*. The website’s “manifesto” about good science vs good communication did not compel me.

    @Rob Grigjanis #1,
    I had to look it up, and found an article by Ethan Siegel explaining how Hawking radiation really worked. Hmmm… yes, I have to conclude that the standard explanation is just wrong. And to be honest, it never really made much sense in the first place (antiparticles don’t have negative mass!).

    I feel this is different from the raindrop symbol, because the raindrop symbol is communicating something accurate, i.e. a forecast of rain. Hawking’s vulgarization of Hawking Radiation does not seem to communicate anything accurate.

  4. Rob Grigjanis says

    Siggy @4: I haven’t read A Brief History of Time, so didn’t know Hawking had tried to further peddle his virtual pair picture. I guess the “shouldn’t be taken too seriously” in his paper was tossed out at the prospect of selling books.

    antiparticles don’t have negative mass!

    Virtual particles can certainly have negative energy. The negative energy particle tunnels beyond the event horizon. There, the time coordinate becomes spacelike, its momentum 4-vector becomes timelike, and it becomes a ‘real’ particle, even though its energy is negative relative to distances far from the black hole. That’s Hawking’s handwaving, anyway.

Leave a Reply
