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Mosquitos Have Little Trouble Flying in the Rain
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."
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.
On Being the Right Size J. B. S. Haldane in 1928
Protoplasm. Quiet Protoplasm. I like quiet protoplasm.
*sigh* I don't understand these bus analogies. Can someone please give me a car analogy instead?
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.
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).
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.
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.
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.
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.
Okay, there's only one way to settle this once and for all. BRB
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?
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
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!
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.