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Guru

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4 year old boy stumps 38yr old man...

02/25/2008 11:43 PM

....again.

My son asked me why moths do not fly toward the sun and/or moon.

I have not answered him yet.


cr3

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#1

Re: 4 year old boy stumps 38yr old man...

02/26/2008 3:01 AM

As I understand it, they fly a path trying to keep the angle between them and the light source constant. So with a light sufficiently far away, the angle won't change significantly as they fly a straight path.

This doesn't explain why they fly towards a light, but would explain them orbiting a nearby light source. Presumably they 'like' the light (observe flying insects in a dull room attracted to the window). So they end up on a path which near-enough keeps the angle constant, but increases their perceived brightness. With a distant light source, getting a fly-mile nearer wouldn't increase the brightness.

(I think!)

You could maybe explain it as being like a string joining the insect to the light source (for the orbiting), then add that they like it bright.

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#2

Re: 4 year old boy stumps 38yr old man...

02/26/2008 5:38 AM

they are hard-wired to follow a logarithmic spiral towards the moon, if there is an artificial light source they mistake this for the moon but reach it. Turtle hatchlings make the same mistake and head for the bright city lights, instead of the moon (over the sea). Maybe humans do too?

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#4
In reply to #2

Re: 4 year old boy stumps 38yr old man...

02/26/2008 10:28 AM

Hux is correct in why they fly toward the moon (light). The reason they don't fly toward the sun is they're sleeping during the day to avoid being eaten by birds.

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#3

Re: 4 year old boy stumps 38yr old man...

02/26/2008 6:54 AM

What a powerful question.

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#5

Re: 4 year old boy stumps 38yr old man...

02/26/2008 3:29 PM

In theory they believe that moths use the moon for navigation. In order to fly a straight line they keep the moon in the same spot in their vision. When another light source interferes they are drawn to it in confusion. Trying to keep the light oriented in the same way they start to circle it.

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#6
In reply to #5

Re: 4 year old boy stumps 38yr old man...

02/27/2008 1:22 AM

Your quote is great, but if it's true I'll be dead fairly soon. ffeJ

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#7
In reply to #6

Re: 4 year old boy stumps 38yr old man...

02/27/2008 2:41 AM

True, if you go towards the light, then you must be dead.

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#14
In reply to #7

Re: 4 year old boy stumps 38yr old man...

02/27/2008 9:28 PM

Either that or a train is coming straight at you...

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#8

Re: 4 year old boy stumps 38yr old man...

02/27/2008 2:51 AM

Light from the moon is effectively at infinity so keeping the bearing to the moon constant will give a consistent direction over land, ie they can navigate. A candle is not at infinity, but they did not evolve in a candle using world, so they try to use it for navigation and using a close light source as if it was at infinity gives a neat and apparently suicidal spiral into the flame.

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#9

Re: 4 year old boy stumps 38yr old man...

02/27/2008 8:14 AM

I think that in the day they sleep, or they dont have enough power in thier wings to travel above a limited level towards the sky.In the night they might not be able to see the light of the moon.Like in the our case,we see the stars tingling bcaz they r so distant away that our sense of sight does not work.Similarly to their limited eyesight they may see the moon as a distant star and thus do not fly towards the moon.

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#10

Re: 4 year old boy stumps 38yr old man...

02/27/2008 2:12 PM

My guess is that infrared radiation from the moon is mostly absorbed by Earth's atmosphere and the night-flying moths don't see it. Perhaps someone could release some moths into a darkened room containing a heated iron and an ultaviolet lamp surrounded by heat shielding plastic film. My next guess is that the moths will be attracted to the dark, heated iron and that they won't see the ultraviolet light.

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#11
In reply to #10

Re: 4 year old boy stumps 38yr old man...

02/27/2008 2:21 PM

Mercury vapour lamps are among the commonest form of moth trap attractant - and they emit very little IR (and quite a bit of UV unless properly filtered).

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#12

Re: 4 year old boy stumps 38yr old man...

02/27/2008 4:25 PM

simple answer to a simple question:

Neither the sun nor the moon emit ultraviolet TUNGSTEN light. Try using a photographic light meter to measure light exposure from the sun and the moon. The moon emits no light at all, and the sun is so bright a moth is blinded. (shine a light into your eyes at night, at close range then try walking towards it; it would be ludicris). Moths follow low radation tungsten light, contrary to popular belife a moth will fly into the light and die. Light a candle on a night moths are out and see how many of them fly into the heat of the candle light...(none)

Ultraviolt tungsten light mimics light produces by flowers.

Apples are a fruit, so is an orange but totally diffrent things.

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#13
In reply to #12

Re: 4 year old boy stumps 38yr old man...

02/27/2008 5:06 PM

Golly!

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#15
In reply to #12

Re: 4 year old boy stumps 38yr old man...

02/29/2008 5:56 PM

The moon emits no light, true, nor does the Earth, we see by the light reflected from the sun. If moths were blinded by sunlight we wouldn't see them by day. Since moths do fly at night they are more likely to see moonlight than have eyes that are only adjusted to the light reflected by flowers from the sun that has just blinded them.

Moths evolved in a world where lights at night were the moon, stars, forest fires or volcanoes. Keep the moon, which is at optical infinity at a constant bearing of 30 degrees (or any acute angle) and you will fly a straight line (given the distances moths fly). They can therefore navigate by the moon or stars. Light a candle, which moths do fly into, and a moth keeping a 30 degree bearing will follow a predictable spiral to a depressing end.

There is nothing wrong with the moth's system, it just evolved in a world without night lights and thinks they are a moon at optical infinity. which just proves you are more intelligent than a moth.

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