Yesterday, JR Minkel tweeted this:
@jrminkel The most striking science analogy I've ever heard:
The link leads to a brief excerpt from an NPR story in which Johns Hopkins neuroscientist David Linden says,
If there were a giant with her head in Baltimore and her toe off the coast of South Africa and she was bit by a great white shark on the toe on Monday, she wouldn’t feel it until Wednesday and she wouldn’t jerk her toe until Saturday.
That is to say, the human neuron response is slow. And Linden could have just said that. But instead, he chose to illustrate the point with planet-sized humans and pesky sea predators. The analogy works for two reasons.

First, Linden picked length and time scales more familiar to humans than nanometers and nanoseconds. When we accidentally touch a hot surface, our decision to remove our flesh from the heat seems almost immediate, if not involuntary. Electrical activity travels between our neurons at tens of meters per second; covering a distance of a few billionths of a meter takes only a few trillionths of a second. That is really freaking fast. Saying that it is slow would seem counter-intuitive, and the point would be lost.

However, without having to know the exact distance between Baltimore and South Africa, most of us understand that it is pretty far. But we also know that an airplane can make the trip much more quickly than two or three days. Our [slow] powers of [neurotransmitted] deduction lead us [eventually] to the logical conclusion.

Secondly, Linden doesn't compare apples to oranges. He likens the speed of (actual) neurons to the speed of (hypothetical giant) neurons. He doesn't add an extra layer of complexity by comparing the speed of neurons to drag-car racing or an ostrich. I think this is a very valuable point--one I remember learning in a science journalism course a few years ago from a guest speaker (whose name I cannot remember for the life of me, and for which I apologize because I'd love to give credit where credit is due!). She talked about reporting on hard-to-fathom concepts, such as nanotechnology or the cosmos, and made this suggestion as we looked for analogies and metaphors to help describe our subjects.

She gave us one particular example: if you gathered all the alcohol in Jupiter's atmosphere, you'd have enough to make a stiff drink. As in Linden's case, she just as easily could have stated explicitly that there were but a few ounces of alcohol on a planet 1300 times the volume of Earth (which we know has no shortage of the stuff). But she drew an analogy between atmospheric alcohol and drinking alcohol, and it was fun to imagine the contents of the Jovian planet reduced to the confines of a shot glass.

The art of analogizing is tricky to say the least. In a blog post, science writer John Rennie calls Linden's description "wonderful," then proceeds to pick it apart, leaving it up to his readers to determine whether the giantess's neural transmission speeds would really be as slow as Linden claims. (To be fair, Rennie does admit he's being kind of a killjoy, and that the analogy really is great.) And if you read the rest of the original NPR story, Linden likens the evolution of the brain to an ice cream cone--assembled first by a scoop of lizard brain, followed by a scoop of mouse brain, topped by a scoop of primate brain--which works on some levels, but not nearly as well as the giant analogy (see my second point).

There are plenty of tired, cliche, and flat-out bad analogies out there. As someone who writes regularly about ultra-small and ultra-fast science, I have grown weary of the obligatory "one hundredth the thickness of a human hair"-type descriptors that editors demand in order to "provide context." So I give you Analogy Watch, which I hope will serve as a resource for creative and enlightening ways to explain any type of science.

If you've come across any particularly intriguing science analogies (especially if they came from a scientist during an interview!) please include them in the comment section. Insightful critiques of really horrible analogies are fair game, too, as it is important to see what works, what doesn't, and why. But as I hope this thread will eventually function as a resource, please refrain from citing only bad/cliche analogies or repeating ones that have already appeared.

As a final aside, I would like to give a nod to Ivan Oransky, whose Embargo Watch blog has become somewhat of a meme among the science writing community and undoubtedly influenced the name of this thread.