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Mosquitos Have Little Trouble Flying in the Rain

Posted by Unknown on from the all-the-better-to-give-you-malaria dept.

sciencehabit writes with an interesting article about the (surprisingly not well studied) effects of rain on flying insects. From the article: "When a raindrop hits a mosquito, it's the equivalent of one of us being slammed into by a bus. And yet the bug will survive and keep flying. That's the conclusion of a team of engineers and biologists, which used a combination of real-time video and sophisticated math to demonstrate that the light insect's rugged construction allows the mosquito to shrug off the onslaught of even the largest raindrop. The findings offer little aid in controlling the pest but could help engineers improve the design of tiny flying robots." Bats, unfortunately, aren't so lucky: "...these furry fliers need about twice as much energy to power through the rain compared with dry conditions."

34 of 186 comments (clear)

  1. Impact energy not the same for small objects by Anonymous Coward · · Score: 4, Interesting

    A mouse could fall off a building and walk away. People, not so much. The smaller you are, the more resistant you are to long falls. It's why many dwarves become steelworkers.

    1. Re:Impact energy not the same for small objects by Drishmung · · Score: 5, Interesting

      You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes

      On Being the Right Size J. B. S. Haldane in 1928

      --
      Protoplasm. Quiet Protoplasm. I like quiet protoplasm.
    2. Re:Impact energy not the same for small objects by zero.kalvin · · Score: 4, Informative

      Force = dP / dt P = mass * velocity A mouse weights around ~20g , a horse around ~450kg. If we assume that both of them have the same velocity when touching the floor, the horse will experience a force that is ~22000 times higher. Easily explains the splashing... ( I could go more and calculate an approximation of the value force itself, but I think this is enough )

    3. Re:Impact energy not the same for small objects by linatux · · Score: 5, Funny

      Dropping a bus on a horse, a human or mouse at the bottom of a thousand-yard mine shaft will still wreck the bus. Wouldn't be good for the creatures either (probably kill the mosquito too).

    4. Re:Impact energy not the same for small objects by zero.kalvin · · Score: 5, Insightful

      AIUI, you assume wrong.

      I am aware of that, but I didn't want to complicate things, in case the reader was not a physicist. Sometimes simple assumptions can still give you a clear indication of what is going on.

    5. Re:Impact energy not the same for small objects by Sulphur · · Score: 5, Funny

      AIUI, you assume wrong. The horse's terminal velocity is considerably higer (and considerably more terminal) than that of the mouse.

      and thus you strengthen his point. The mouse wins with conservative estimates. The mouse wins by more when you take into account more detailed explanations.
      Maybe he should have said "even if you assume..."

      This is called the principle of conservation of mice.

    6. Re:Impact energy not the same for small objects by zero.kalvin · · Score: 5, Insightful

      Give me a break, I wanted to write that comment that was as short, as quick, and as simple as possible. My conclusion isn't wrong ( in the literal sense ), I just made a "very" conservative estimation ( we do that in physics ). The whole point was to show, that the difference between a mouse and horse isn't small, but rather gigantic. I was not going into assumptions of density and its uniformity, or whether we can assume animals as spherical or not, or of buoyancy and drag factors. Now I agree with http://science.slashdot.org/comments.pl?sid=2894703&cid=40216663 , I should have mentioned that I was doing a very conservative estimation and the number is actually much higher.

    7. Re:Impact energy not the same for small objects by FrootLoops · · Score: 5, Informative

      No, your two main assumptions are badly wrong.

      (1) The terminal velocities of larger objects is larger, and the effect is significant. The mouse hits the ground at a much lower speed than the horse.
      (2) The mouse and horse are not even remotely point particles so you should be considering pressure instead of force. You'd have to divide your 22000 number by the ratio of whatever bits land on the horse at once to the same for the mouse; this would be a fairly large number.

      To illustrate very approximately why larger objects have larger terminal velocities, consider two falling spheres of equal density, one of small radius and one of large radius. An object reaches terminal velocity when the energy it gains from gravity is perfectly canceled by the energy it has to give up to move air molecules out of the way. Let's compute each.

      Basic physics gives the first line of the following. Constant density and the definition of velocity gives the second, and the formula for the volume of a sphere gives the third.
      (energy gained from gravity)
      = (gravity constant) * (mass of object) * (distance it fell in a given time)
      = (different constants) * (volume of sphere) * (velocity of sphere)
      = (different constants) * (cube of radius) * (velocity of sphere)

      The other half is more approximate. The first line is pretty much trivial from the setup. The second line is from the formula for the surface area of a sphere and from the basic physics fact that the energy of an object is proportional to the square of its velocity. The rest is algebra.
      (energy lost to moving air out of the way)
      = (constants) * (amount of air moved per unit time) * (energy imparted to each molecule of air)
      = (constants) * [(surface area exposed) * (distance it fell in a given time)] * (velocity of sphere squared)
      = (constants) * [(radius squared) * (velocity)] * (velocity squared)
      = (constants) * (radius squared) * (velocity cubed)

      At terminal velocity, these two are equal. Simple algebra gives the answer from here.
      (constants) * (cube of radius) * (terminal velocity) = (constants) * (square of radius) * (cube of terminal velocity)
      (constants) * (radius) = (square of terminal velocity)
      (terminal velocity) = (constants) * sqrt(radius)

      The large sphere has large radius, so large terminal velocity. Incidentally this is the formula from the Wikipedia page I linked, though my assumptions were very, very approximate and are probably different from the ones used to derive it.

    8. Re:Impact energy not the same for small objects by Ragzouken · · Score: 4, Funny

      But your mouse remains safe, as predicted.

    9. Re:Impact energy not the same for small objects by Strider- · · Score: 4, Funny

      What about a spherical horse in a vacuum?

      --
      ...si hoc legere nimium eruditionis habes...
    10. Re:Impact energy not the same for small objects by quarkscat · · Score: 4, Interesting

      Aside: This is only tangentially relevant to TFA, but I hope it gets a pass from the moderators and not modded down as OffTopic:

      Preface: Bats are kind of like mice with flappable wings. One would expect that they would have that knack of flying, pretty much instinctively. One would not expect them to thwart Darwin's Law, survival of the fittest, by doing 'stupid' things while flying, but ...

      True Story: I was driving home from work one night and was only a block away from home in a residential neighborhood, when something fell out of the sky and loudly hit the hood of my car. I stopped, engine still running and headlights on, to get out and see what had happened. A bat, with it's wings wrapped around something or other, had fallen out of the sky. As I was contemplating retrieving the combo windshield squeegee / ice scraper from the trunk to brush this poor dead creature off my hood, it separated from what it fell from the sky with and flew away. Almost immediately, a second bat roused itself and flew from the hood in presumed pursuit of the first bat. The only thing that I could figure is that those 2 bats were copulating in mid-air, lost control, and plummeted down to earth and landed on my car's hood.

      I'm not a biologist, nor have I ever played one on TV, but it would seem that the act of 2 small mammals copulating in mid-air would violate the base instinct of survival that falling out of the sky might negate. Unless ... unless they routinely know that such a fall is non-lethal, and other base instincts kick into play. Kids. You let them out to run around without supervision in the evening after a big supper (of bugs), and the next thing you know, they're getting into trouble. And yes, there was a full moon that night.

      Question: (Directed to anyone who might actually know): Was I fortunate to see a common occurrence, something that very few people have an opportunity to see, or were those bats engaged in very risky behavior that they managed to survive?

      Inquiring minds want to know, and Bing has so few good answers.

    11. Re:Impact energy not the same for small objects by RivenAleem · · Score: 5, Funny

      Okay, there's only one way to settle this once and for all. BRB

    12. Re:Impact energy not the same for small objects by NFN_NLN · · Score: 5, Funny

      Force = dP / dt
      P = mass * velocity
      A mouse weights around ~20g , a horse around ~450kg. If we assume that both of them have the same velocity when touching the floor, the horse will experience a force that is ~22000 times higher. Easily explains the splashing... ( I could go more and calculate an approximation of the value force itself, but I think this is enough )

      Yes. But the real question is: What would happen to a bag filled with 22,500 mice (weighing a total of 450kg)?
      Would the mouse-bag make a splash like the horse? Or would each individual mouse walk away with a slight shock?

    13. Re:Impact energy not the same for small objects by Zorpheus · · Score: 4, Insightful

      Yeah but if you assume that they touch the floor at the same speed, the amount of energy to be absorbed per body weight is the same for mouse and horse. The force per body weight is even lower for the horse since it has longer legs and therefore more time to slow down. But also the ratio of the cross section of the legs to the body weight is worse, which makhttp://science.slashdot.org/story/12/06/05/0112252/mosquitos-have-little-trouble-flying-in-the-rain#es it worse for the horse again.

    14. Re:Impact energy not the same for small objects by zero.kalvin · · Score: 4, Interesting

      That's way more complicated. You are talking about an n-body ( n= 22500 ) dynamics, if I am not mistaken this can be best handled by fluid dynamics. But even that is based on a lot of assumptions, for example will the bag hold ? if yes then it will behave like the horse. If not, then it depends on how fast will it tear, and how will it tear! Try this, take a melon and throw it out of a 10 story building, then another melon in ten plastic bags, and another in 100 plastic bags, and throw them. The result will show you what I mean.

    15. Re:Impact energy not the same for small objects by NFN_NLN · · Score: 5, Informative

      The simplified answer was actually the next two sentences in the essay:

      'You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes. For the resistance presented to movement by the air is proportional to the surface of the moving object. Divide an animal’s length, breadth, and height each by ten; its weight is reduced to a thousandth, but its surface only to a hundredth. So the resistance to falling in the case of the small animal is relatively ten times greater than the driving force."

      You are debating a single sentence of an essay that is an amazing read to say the least. I highly recommend reading it: http://irl.cs.ucla.edu/papers/right-size.html

    16. Re:Impact energy not the same for small objects by BagOCrap · · Score: 5, Funny

      The whole point was to show, that the difference between a mouse and horse isn't small, but rather gigantic.

      Thank you, sir! This would never have occurred to me if you hadn't brought it up. Now I better understand why my parents would never give me a horse as a child; it wouldn't fit in the cage with the mice, and it would splash if I accidentally dropped it.

      --
      -- Chaos, panic, pandemonium... My job here is done!
    17. Re:Impact energy not the same for small objects by mysidia · · Score: 3, Informative

      A mouse could fall off a building and walk away. People, not so much. The smaller you are, the more resistant you are to long falls.

      Close.... the lower your mass to surface volume density; the more resistance you are to long falls.

      The most resistant objects to long falls are very large organisms that have very little mass, and therefore a higher ratio of surface volume to mass.

      The larger the object's horizontal cross-section w.r.t the ground, the greater the air resistance, the lower the velocity while falling.

      The lower the velocity towards the ground while falling, the lower the change of momentum at the point of impact.

      The lower the mass of the object, the lower the change of momentum at the point of impact with the ground.

      The lower the change of momentum at the point of impact with the ground, the lower the upward force that is exerted upon the object in the collission.

      The difference in damage between the two objects then depends on what the two different objects were constructed from. Different materials have different strengths; a titanium skeleton will probably fair better than something made out of fired clay.

    18. Re:Impact energy not the same for small objects by sco08y · · Score: 5, Funny

      Give me a break, I wanted to write that comment that was as short, as quick, and as simple as possible.

      You didn't even take relativistic affects into account. What if the horse and mouse are being dropped near a large mountain? And what about the possibility of quantum tunneling?

      You're just lazy and sloppy, that's all.

    19. Re:Impact energy not the same for small objects by TubeSteak · · Score: 4, Funny

      A man, a horse, and a mouse walk into a bar...
      "Barkeep," the man says "I need 3 pints of beer and access to your roof."
      "Here you are," the barkeep says as he gives him the beer and keys to to roof.

      Then he looks at the horse and asks "Why the long face?"
      The horse pondered for a moment and then replied

      "Well, basic physics gives the first line of the following.
      Constant density and the definition of velocity gives the second, and the formula for the volume of a sphere gives the third.
      (energy gained from gravity)
      = (gravity constant) * (mass of object) * (distance it fell in a given time)
      = (different constants) * (volume of sphere) * (velocity of sphere)
      = (different constants) * (cube of radius) * (velocity of sphere)

      The other half is more approximate. The first line is pretty much trivial from the setup. The second line is from the formula for the surface area of a sphere and from the basic physics fact that the energy of an object is proportional to the square of its velocity. The rest is algebra.
      (energy lost to moving air out of the way)
      = (constants) * (amount of air moved per unit time) * (energy imparted to each molecule of air)
      = (constants) * [(surface area exposed) * (distance it fell in a given time)] * (velocity of sphere squared)
      = (constants) * [(radius squared) * (velocity)] * (velocity squared)
      = (constants) * (radius squared) * (velocity cubed)

      At terminal velocity, these two are equal. Simple algebra gives the answer from here.
      (constants) * (cube of radius) * (terminal velocity) = (constants) * (square of radius) * (cube of terminal velocity)
      (constants) * (radius) = (square of terminal velocity)
      (terminal velocity) = (constants) * sqrt(radius)

      The large sphere has large radius, so large terminal velocity. Incidentally this is the formula from the Wikipedia page I linked, though my assumptions were very, very approximate and are probably different from the ones used to derive it.

      In summary, this asshole is going to shove me off a roof just to prove a point, physics says they'll both survive, but I'm fucked."

      --
      [Fuck Beta]
      o0t!
    20. Re:Impact energy not the same for small objects by Talderas · · Score: 3, Funny

      Excellent, so I can toss mice off the top of my building all day long and not have to worry about killing them.

      Suck it PETA. Throwing these mice is intrinsic to testing the catacopter.

      --
      "Lack of speed can be overcome. In the worst case by patience." --Znork
  2. Figures. by Anonymous Coward · · Score: 5, Funny

    You have to work your ass off to keep the things you like alive/going (plants, cars, house, etc), yet pests like mosquitoes, bankers, and politicians you just can't get rid of no matter how hard you try.

  3. The Wooden Wonder by rossdee · · Score: 4, Funny

    Yes, Mosquitos could fly in the rain. However they would have trouble dropping their bombs accurately and obviously the recon version wouldn't get good photos.
    The night fighter version would fare better with its radar, if there were any German bombers up there to intercept.

    But of course sometimes they had to fly in bad weather, such as just before D-Day.

  4. Re:/. editors: Too many games, not enough reality by maugle · · Score: 4, Interesting

    But the bus analogy is still wrong, because the entire point of the article is that the mosquito is not smashed by the raindrop. Instead the mosquito simply merges into and falls with the drop, then escapes before the raindrop hits the ground.

    So, it's more like phasing through the front of an oncoming bus, landing comfortably in one of the seats, then escaping out the rear before the bus plows into a concrete wall.

  5. Re:/. editors: Too many games, not enough reality by rgbrenner · · Score: 5, Funny

    *sigh* I don't understand these bus analogies. Can someone please give me a car analogy instead?

  6. Re:Why don't they? by siddesu · · Score: 5, Funny

    Not where I live. When it rains, it only makes them more vicious. And the hotter/wetter it gets, the worse they are. It is unbelievable, they fly in packs of five, four lift the blanket by the edges, one sucks. Then they change.

  7. Here's the video for it ... by knopf · · Score: 4, Informative

    http://www.pnas.org/content/suppl/2012/05/28/1205446109.DCSupplemental/SM01.mp4

    Cheers.

  8. Matter of chance by dutchwhizzman · · Score: 3, Insightful

    If mosquitos weren't able to deal with rain, there wouldn't be a lot of mosquito's. They need water to reproduce in so they live in predominantly wet areas. Evolution made the rain resistant mosquito's breed and the non resistant ones extinct. Horses don't often fall down steep cliffs, nor do humans, so there isn't a lot of reason for them to develop a resistance against that. Mice reach their terminal velocity rather quick, so if they survive a 2m drop, they are much more likely to survive a 200m drop, since the difference in velocity isn't that much.

    --
    I was promised a flying car. Where is my flying car?
    1. Re:Matter of chance by a_hanso · · Score: 4, Funny

      Stiiiinging in the raiiiin, I'm Stiiiinnning in the raiiiin...

  9. Tiny Flying Robots? by guttentag · · Score: 3, Insightful

    The findings offer little aid in controlling the pest but could help engineers improve the design of tiny flying robots.

    Great! Because I was just thinking to myself, "we really need more tiny flying robots. If I have to wait 20 years for the CIA to solve the raindrop problem and weaponize these things, I'll die of boredom before videos of them assassinating people with them show up on YouTube."

    Too heavy on the sarcasm? Fortunately I don't say stuff like this out loud.

  10. Re:/. editors: Too many games, not enough reality by rvw · · Score: 4, Funny

    But the bus analogy is still wrong, because the entire point of the article is that the mosquito is not smashed by the raindrop. Instead the mosquito simply merges into and falls with the drop, then escapes before the raindrop hits the ground.

    So, it's more like phasing through the front of an oncoming bus, landing comfortably in one of the seats, then escaping out the rear before the bus plows into a concrete wall.

    *sigh* I don't understand these bus analogies. Can someone please give me a car analogy instead?

    It's like a raindrop that hits a Yugo. The raindrop merges into the Yugo. The Yugo stops because the electricity fails. You get out, a little wet because of the leaking roof, but still OK.

  11. Effect of Rain on Mosquito Behaviour by hyades1 · · Score: 4, Funny

    In Winnipeg, it isn't that mosquitoes can't fly in the rain, they just don't like it very much. Usually, your basic Winnipeg mosquitoes just jack a car and drive to their next victim. If the driver's lucky, the mosquitoes will let him go instead of keeping him for an en route snack. If there's a dog or cat in the car...don't ask. It won't be seen again.

    --
    I've calculated my velocity with such exquisite precision that I have no idea where I am.
  12. Terrible analogy by LordNimon · · Score: 3, Insightful

    When a raindrop hits a mosquito, it's the equivalent of one of us being slammed into by a bus. And yet the bug will survive and keep flying.

    In other words, it's definitely not the equivalent being slammed by a bus.

    --
    And the men who hold high places must be the ones who start
    To mold a new reality... closer to the heart
  13. I routinely get smashed by giant bodies of water by Normal_Deviate · · Score: 3, Funny

    When I jump off a 10-ft diving board, a lake-sized glob of water smashes me at 20mph. Amazingly, I survive.