Bad Science in Newspaper Article: Mosquito v. Raindrop

[Hornblower]

See this Washington Post article:

http://www.washingtonpost.com/nation...plV_story.html

Mechanical engineer David Hu and a team of colleagues at Georgia Tech were pondering a mosquito's ability to take a direct hit from a falling raindrop uninjured. Following is a quote from the article:

Hu and his colleagues hypothesized that due to the insects’ low mass — about two milligrams, compared with a raindrop’s mass of up to 100 milligrams — the raindrop loses very little speed and momentum upon encountering the mosquito and thus imparts very little actual force to it.

That sort of reasoning would be like arguing that a 10000-lb truck striking a pedestrian would pack a lesser wallop than a 250-lb linebacker at the same speed, which we know not to be the case. The mosquito can take a sudden impact-induced velocity change that would be hard on a human because, like any small creature, it has the strength to mass ratio in its favor. If the body tissues are similar, the stress-bearing strength of the whole body is proportional to the square of the linear size, while the mass is proportional to the cube.

It's a shame when professional scientists and engineers have such lapses in entry-level physics, or when ill-informed writers misquote them.

[NEOWatcher]

See this Washington Post article:

the raindrop loses very little speed and momentum upon encountering the mosquito and thus imparts very little actual force to it.

That was in our local paper the other day. I don't remember it being that awkwardly worded, and it's not online, so I can't follow up on my memory. So; this could be the reporter's interpretation.

What makes it worse though is that further on, it's not really a straight-forward impact.

The team concluded that the raindrops deform and largely bypass the much smaller bodies of the mosquitoes.

Sounds more like if I got in the way of a flock of a thousand geese.

[spjung]

I have the paper. They calculate the force of a raindrop hitting an unyielding surface to be 10,000 dyn. A direct hit on the body of a flying mosquito imparts only about 600 dyn (300 x g). This knocks them down 5-20 body lengths. The authors do say that the exoskeleton allows the mosquitoes to survive.

[Jens]

I read the article a couple of days ago, but I got a different impression. I didn't think they were arguing so much about the mosquito being hurt by the raindrop as about how its flying would be affected. There was something about how far a mosquito was made to drop, maybe 13 body lengths if I remember correctly. So it was more about aerodynamics than about damage to the body.

[profloater]

I also read about it in New Scientist and the technical point is the way the Mosquito interacts with the raindrop because of its hairy microstructure, it reduces the impact by elongating the time of interaction and breaks free to fly again. The reason for the interest is for small flying robots that have to face the same issues flying in the rain.

[grapes]

Small flying robots?! Run!

[Hornblower]

This is starting to look a lot like misquoting and oversimplification by the Washington Post writer.

[headrush]

Here's the BBC's take on the story from 4th June.
They also link to PNAS.

[quotation]

Small flying robots?! Run!

Nowhere to run to...nowhere to hide:/ http://www.networkworld.com/community/node/80845

[Zentisan]

Here's the BBC's take on the story from 4th June.
They also link to PNAS.

"There is a philosophy that if you don't resist the force of your opponent, you won't feel it," he explained.

"That's why they don't feel the force; they simply join the drop, become one item and travel together."

Mosquitoes and Tai Chi! Well, you come across something new everyday.
Anyway, since they did invest so much time and energy on it, it would have made sense to at least keep at it till a mosquito bearing droplet touched down. Perhaps then we would have known that mosquitoes prefer rarer air or the dark side of the leaf when they sense rain.

[John Mendenhall]

Sigh. I was hoping the raindrop would impart enough energy to vaporize the mosquito.

[Jens]

... the force ...
...the force...
mosquitoes prefer ... the dark side ...

Sorry for selectively quoting, but I don't really know what to add.

[Zentisan]

Sorry for selectively quoting, but I don't really know what to add.

Everything within the " " was from the BBC's article, not mine.
They say all the mosquitoes managed to fly off. Not even one hit bottom. That's inconclusive or a very brief study.

[BigDon]

I find it amusing that the main problem with small flying spy robots are small flying predators.

[BigDon]

Grapes. the big break-through in small spy robots came with the discovery that surgically implanting various hardware into caterpillers just before chrysilasation allows the insects body to adjust around the implanted devices without harm.

There do exist radio controled butterflys.

[spjung]

Everything within the " " was from the BBC's article, not mine.
They say all the mosquitoes managed to fly off. Not even one hit bottom. That's inconclusive or a very brief study.

They did two tests with live mosquitoes. The first was in a 20-cm tall cage with a water jet simulating rainfall at terminal velocity. Six mosquitoes in the group were hit by the jet and didn't hit bottom. The second experiment was in a 10-cm tall cage with water dropped at a slower velocity. There they observed 17 hits, again with no mosquito hitting bottom.

[headrush]

Grapes. the big break-through in small spy robots came with the discovery that surgically implanting various hardware into caterpillers just before chrysilasation allows the insects body to adjust around the implanted devices without harm.

There do exist radio controled butterflys.

Hi BigDon, I've really enjoyed your posts about life on and under the flight deck. Would you consider radio controlled butterflies "bad" science ? (obviously I've moved the emphasis to "bad" there.)
Cheers.

ETA, I like your pragmatic approach in the previous post too, "small flying predators", heh.

[BigDon]

Hi BigDon, I've really enjoyed your posts about life on and under the flight deck. Would you consider radio controlled butterflies "bad" science ? (obviously I've moved the emphasis to "bad" there.)
Cheers.

ETA, I like your pragmatic approach in the previous post too, "small flying predators", heh.

I can honestly say that's a judgement call. And one I'm not qualified to make.

[John Mendenhall]

I can honestly say that's a judgement call. And one I'm not qualified to make.

Weekly World News headline: Bedbug Return Linked to CIA Spy Activity!

[publiusr]

Small life-forms are more resistant as it stands. drop an ant from a skyscraper and that's one thing. Drop me and its another. I guess we need to work on even bigger raindrops to kill the mosquitos, or we could use this: http://www.gizmag.com/mosquito-laser/11266/

Somehow, I think that small flying drones won't be as resistant to raindrops as these little buggers.