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On Thu, 03 Sep 2009 09:14:41 +0100, Invisible wrote:
> Rain water isn't chemically pure. (Depending on pollution levels.) Once
> the pylon gets wet, it's entire surface is covered in a continuous sheet
> of water, which also covers all of the cables. So why don't they short
> out?
Because the bare wire isn't exposed, it's insulated. And in order to
short out, you have to have a path for electrons to flow. Arguably it
would take a pretty strong rainstorm to give the current someplace to go
to.
Jim
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Warp <war### [at] tag povrayorg> wrote:
> Darren New <dne### [at] sanrrcom> wrote:
> > One thing I haven't figured out is why poisonous prey animals (frogs,
> > butterflies, etc) wind up being brightly colored.
>
> AFAIK the bright colors work as a warning signal. Predators learn to
> distinguish the poisonous prey by their color.
>
> It would make little sense to just have poison but otherwise look edible.
> Both predator and prey get killed. With a warning color both live.
>
> (By this logic it would follow that some species mimic the color of
> poisonous species. I wonder if there are examples of this.)
>
> --
> - Warp
The viceroy butterfly mimics the poisonous monarch butterfly for protection from
predators. Its fairly common among many species.
http://en.wikipedia.org/wiki/Batesian_mimicry
Isaac.
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On Thu, 03 Sep 2009 09:07:32 +0100, Invisible wrote:
>>> Are mushrooms poisonous on purpose, or by accident?
>>
>> That implies a will behind their creation. And not all mushrooms are
>> poisonous. Take the ones that I had on my hamburger last night.....
>> ;-)
>
> No it doesn't.
Yes, it does. "On purpose" implies an intelligence is behind their
creation, purposefully making them the way they are.
> Did mushrooms evolve to be poisonous because that's advantageous
> somehow? Or do they just happen to be poisonous to animals because of
> their unusual chemistry?
Perhaps some of both.
Jim
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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> One thing I haven't figured out is why poisonous prey animals (frogs,
>> butterflies, etc) wind up being brightly colored.
>
> AFAIK the bright colors work as a warning signal. Predators learn to
> distinguish the poisonous prey by their color.
This clearly works poorly if the prey is so poisonous they kill the predator
with one meal.
> It would make little sense to just have poison but otherwise look edible.
> Both predator and prey get killed. With a warning color both live.
So which evolved first? At some point, you're poisonous enough to make the
predator sick, but bright enough to be easily found? I understand the
hand-waving explanation. It's the details I don't really follow.
> (By this logic it would follow that some species mimic the color of
> poisonous species. I wonder if there are examples of this.)
Yes, quite a few. Both monarch butterflies (and their immitators) and that
kind of snake with the red/black/yellow stripes whose name I forget springs
to mind.
http://en.wikipedia.org/wiki/Batesian_mimicry
Oh, there's the snake. GIYF. Can you tell which is poisonous and which
isn't? Notice the different order of the stripes.
http://www.pestproducts.com/images/coral.jpg
http://www.pestproducts.com/images/sckng.jpg
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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On Thu, 03 Sep 2009 10:06:55 +0100, Stephen wrote:
> So it is much simplier
> and cheaper for overhead cables to be left bare and make sure that there
> is a lot of space between them.
Weird, over here, the power lines are insulated....
Jim
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On Thu, 03 Sep 2009 17:37:20 +0200, Stephen <mcavoysAT@aoldotcom> wrote:
> Actually it is quite hard to ignite petrol from a petrol pump with a
> naked flame.
That depends on the flame.
> Besides having a LEL (Lower Explosive Limit) petrol has an Upper
> Explosive Limit (UEL) where above that level the gas/air mixture is
> too rich to burn. In the open air the gas/air mixture goes from too
> rich to too leen very quickly. I once saw a petrol pump attendant put
> a lit cigarette into the mouth of a full petrol tank.
http://www.intuitor.com/moviephysics/mpmain.html#cigarettes
--
FE
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On Thu, 03 Sep 2009 17:55:43 +0200, Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
>> AFAIK the bright colors work as a warning signal. Predators learn to
>> distinguish the poisonous prey by their color.
>
> This clearly works poorly if the prey is so poisonous they kill the
> predator with one meal.
It works perfectly if the predator does not eat the prey himself, but
instead feeds his offspring with it.
--
FE
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Jim Henderson wrote:
> Well, maybe not now, but when I was in college, PS101 was colloquially
> referred to as "Bonehead Chemistry". ;-)
Yes. It should be noted (for those outside the USA's idioms) that many 101
courses were targeted at people who were not planning to take another course
in the subject. A literature major might take Computers 101, while a
computer science major might take Sociology 101.
Hence, if someone says "Geez, you should know that, that's 100-level stuff"
that's why. (Note that "100-level" means all the 101, 102, etc courses.)
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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Fredrik Eriksson wrote:
> It works perfectly if the predator does not eat the prey himself, but
> instead feeds his offspring with it.
<laugh> For some definition of the word "perfectly" I suppose. :-)
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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On Thu, 03 Sep 2009 09:09:25 -0700, Darren New wrote:
> A literature major might take Computers 101
This is a good point - the CS101 class where I went to school was
basically a class on using an office suite ("Enable" was what the
software was called - wonder how many people here have heard of it and/or
used it) and software like Harvard Graphics to build presentations.
Jim
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