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> 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?
Both.
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triple_r wrote:
> Invisible <voi### [at] dev null> wrote:
>> Why do overhead cables never flap around in the wind?
>
> They do, so of course they're designed to minimize that. Tension will increase
> the natural frequency of the cable, hopefully well above the vortex shedding
> frequency.
Vortex shedding frequency?
WIN!
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Darren New wrote:
>> Come to think of it, why doesn't rain short out power cables?
>
> Because power system engineers aren't stupid enough to put them close
> enough together a raindrop will bridge them.
I was thinking more of when everything has been covered in a continuous
layer of water...
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>> Why do some people like the X-Files?
>
> Because it's cool. The whole UFO "I want to believe" mantra as well as
> the "Trust no one" conspiracionist theories were all around in the 90s...
I just don't see the point.
Each episode, something happens which makes absolutely no sense. It's
not that it's "mysterious", it's just nonsensical. Molder and Scully
investigate. A series of utterly incomprehensible events occur. It turns
out that the conspiracy was actually a conspiracy to create a conspiracy
that would make people think the conspiracy was actually a conspiracy
about a conspiracy to create a conspiracy. But then that turns out to be
wrong too. And after about an hour of abject failure to make any kind of
weakly comprehendable sense, the show ends.
WTF?
I mean, seriously. Any moron can write a bunch of gibberish that doesn't
make sense. But where's the entertainment in that?!
>> Are mushrooms poisonous on purpose, or by accident?
>
> On purpose. They know you'd eat them otherwise.
I see...
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Invisible wrote:
>
> I was thinking more of when everything has been covered in a continuous
> layer of water...
How pure the rainwater even is? Pure water (H2O) doesn't lead
electricity (at least not very well), the usual water you get from tap
ain't pure, it has all kinds of particels within it, including metal
ones. I'd *guess* the rainwater hasn't got as much metal particels as
the water already on the ground and doesn't lead electricity as well.
Anyway, the smart people have calculated that the space between electric
wires is enough, even on hard storms. :-)
-Aero
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Eero Ahonen wrote:
> How pure the rainwater even is?
Depends on the local pollution levels. (Ever hear of acid rain?)
> Pure water (H2O) doesn't lead electricity (at least not very well)
In our lab, we measure water purity by electrical conductivity. The
higher the resistence, the purer the water...
...which is kinda silly really, given that the impurities that affect
resistence are the least relevant to the work we do.
> the usual water you get from tap
> ain't pure, it has all kinds of particels within it, including metal
> ones. I'd *guess* the rainwater hasn't got as much metal particels as
> the water already on the ground and doesn't lead electricity as well.
I would suggest that the ionic compounds disolved in tap water have a
*much* more significant effect than any hypothetical "metal particles"
it may contain...
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scott <sco### [at] scottcom> wrote:
> > Come to think of it, why doesn't rain short out power cables?
> Because air with rain in it is still an insulator?
Ok, there's definitely something here I'm seriously not understanding.
What does rain or water have *anything* to do shorting out power cables?
I don't get it.
Heck, there are power cables at the bottom of the sea. So what? What does
that have to do with anything?
It feels like everybody is writing like power cables were bare metal wires
with nothing covering them. Why?
--
- Warp
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> I was thinking more of when everything has been covered in a continuous
> layer of water...
Are you sure that every part between the pylon structure and the cable can
get wet to form a continuous path? It seems to me like part of the design
of the insulator is to keep other parts dry:
http://en.wikivisual.com/images/3/33/Pylon.detail.arp.750pix.jpg
Even if it does *all* get wet, it's going to be a really thin layer of
water, and even non-pure water is not a particularly good conductor, if you
do the math the resistance probably comes out pretty huge.
BTW, that photo also shows the dampers attached on the cables either side of
the fixing point.
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On Thu, 03 Sep 2009 09:14:41 +0100, Invisible <voi### [at] devnull> 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?
There are insulators between the cables and pylons so there is no path for the
electricity to flow there. The conductors are spaced far enough apart so that
the electricity cannot jump between them. This is called engineering. ;)
--
Regards
Stephen
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Invisible <voi### [at] devnull> wrote:
> I mean, seriously. Any moron can write a bunch of gibberish that doesn't
> make sense. But where's the entertainment in that?!
I don't think everybody can write scripts of that quality. It requires
expertise and talent.
And some people like fiction for entertainment. If you don't like it,
that doesn't mean nobody else souldn't like it either.
--
- Warp
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On 3 Sep 2009 04:41:30 -0400, Warp <war### [at] tagpovrayorg> wrote:
> It feels like everybody is writing like power cables were bare metal wires
>with nothing covering them. Why?
Because they are uninsulated.
http://en.wikipedia.org/wiki/Electric_power_transmission
--
Regards
Stephen
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Stephen <mcavoysAT@aoldotcom> wrote:
> Because they are uninsulated.
> http://en.wikipedia.org/wiki/Electric_power_transmission
I don't get it. Is that rubber around the cables a non-insulator?
I don't see bare copper here:
http://en.wikipedia.org/wiki/File:Electric_transmission_lines.jpg
--
- Warp
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> It feels like everybody is writing like power cables were bare metal
> wires
> with nothing covering them.
That's how they are actually:
"While overhead lines are usually bare conductors, rarely overhead insulated
cables are used, usually for short distances (less than a kilometer)."
from
http://en.wikipedia.org/wiki/Overhead_power_line
Insulating them for longer runs just needlessly reduces the amount of
current they can take without overheating.
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>> 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?
>
> There are insulators between the cables and pylons so there is no path for the
> electricity to flow there.
Indeed. This is why it works when they're dry.
However, when those insulators are covered with a continuous layer of
water...
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On 3 Sep 2009 04:56:16 -0400, Warp <war### [at] tagpovrayorg> wrote:
>Stephen <mcavoysAT@aoldotcom> wrote:
>> Because they are uninsulated.
>
>> http://en.wikipedia.org/wiki/Electric_power_transmission
>
> I don't get it. Is that rubber around the cables a non-insulator?
>I don't see bare copper here:
>http://en.wikipedia.org/wiki/File:Electric_transmission_lines.jpg
You won't see copper as aluminium is used. KISS I assume that rubber or a man
made insulator would deteriate over time in such exposed conditions. Also as
Scott said the cables are under a lot of tension that would add to the cost of
connecting them without dammaging the insulation.
I have worked on underwater equipment (not power transmission) and I can tell
you that it is not easy to keep water out of things. 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.
--
Regards
Stephen
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On Thu, 03 Sep 2009 10:06:46 +0100, Invisible <voi### [at] devnull> 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?
>>
>> There are insulators between the cables and pylons so there is no path for the
>> electricity to flow there.
>
>Indeed. This is why it works when they're dry.
>
>However, when those insulators are covered with a continuous layer of
>water...
Look at the insulators, they are a strange shape. That shape ensures that they
are not covered with a continuous layer of water. Magic, isn't it :)
--
Regards
Stephen
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scott <sco### [at] scottcom> wrote:
> > It feels like everybody is writing like power cables were bare metal
> > wires
> > with nothing covering them.
> That's how they are actually:
> "While overhead lines are usually bare conductors, rarely overhead insulated
> cables are used, usually for short distances (less than a kilometer)."
Ok, maybe it's just different here (and basically everywhere else I have
been), or they are really good at making it *look* like the cables are
covered in black rubber. I certainly was fooled.
Do they paint them like that?
--
- Warp
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scott wrote:
>> I was thinking more of when everything has been covered in a
>> continuous layer of water...
>
> Are you sure that every part between the pylon structure and the cable
> can get wet to form a continuous path? It seems to me like part of the
> design of the insulator is to keep other parts dry:
>
> http://en.wikivisual.com/images/3/33/Pylon.detail.arp.750pix.jpg
How do you figure that?
> Even if it does *all* get wet, it's going to be a really thin layer of
> water, and even non-pure water is not a particularly good conductor, if
> you do the math the resistance probably comes out pretty huge.
You're aware that those cables are carrying several *million* volts?
Still, perhaps all that current would just vapourise the water - and
then it wouldn't be there any more...
> BTW, that photo also shows the dampers attached on the cables either
> side of the fixing point.
Well, this stuff clearly works - it's just a mystery to me *why* it
works. ;-)
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> Ok, maybe it's just different here (and basically everywhere else I have
> been), or they are really good at making it *look* like the cables are
> covered in black rubber. I certainly was fooled.
>
> Do they paint them like that?
It's just the dull grey of aluminium oxide you are seeing on the outer
surface. If you looked close and polished them a bit you'd see nice shiny
aluminium :-)
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>> I mean, seriously. Any moron can write a bunch of gibberish that doesn't
>> make sense. But where's the entertainment in that?!
>
> I don't think everybody can write scripts of that quality. It requires
> expertise and talent.
It takes expertise and talent to write scripts which *make sense* and
are *interesting*. The X-Files lacks both of these qualities in spades.
[OK, you can argue about whether or not something is "interesting". But
whether something makes sense or not is pretty objective. It's hard to
find something interesting when it's unintelligable gibberish.]
> And some people like fiction for entertainment. If you don't like it,
> that doesn't mean nobody else souldn't like it either.
Sure, fair enough. I'm just puzzled as to why such a low-quality show
was so absurdly popular.
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>> Are you sure that every part between the pylon structure and the cable
>> can get wet to form a continuous path? It seems to me like part of the
>> design of the insulator is to keep other parts dry:
>>
>> http://en.wikivisual.com/images/3/33/Pylon.detail.arp.750pix.jpg
>
> How do you figure that?
Well they're like mushrooms stacked on top of each other, so presumably the
narrow bit right up inside the mushroom "cap" stays pretty dry, unless the
rain is going upwards.
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> It takes expertise and talent to write scripts which *make sense* and
> are *interesting*. The X-Files lacks both of these qualities in spades.
>
> [OK, you can argue about whether or not something is "interesting". But
> whether something makes sense or not is pretty objective. It's hard to
> find something interesting when it's unintelligable gibberish.]
Did you consider that maybe some people *can* understand it?
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"scott" <sco### [at] scottcom> wrote:
> > Ok, maybe it's just different here (and basically everywhere else I have
> > been), or they are really good at making it *look* like the cables are
> > covered in black rubber. I certainly was fooled.
> >
> > Do they paint them like that?
>
> It's just the dull grey of aluminium oxide you are seeing on the outer
> surface. If you looked close and polished them a bit you'd see nice shiny
> aluminium :-)
I think if you look at anything against a bright sky it will look matte black,
even if it's mirror-polished.
And isn't alumina pretty much transparent at the thicknesses it's likely to
reach in ambient conditions?
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>> It takes expertise and talent to write scripts which *make sense* and
>> are *interesting*. The X-Files lacks both of these qualities in spades.
>>
>> [OK, you can argue about whether or not something is "interesting".
>> But whether something makes sense or not is pretty objective. It's
>> hard to find something interesting when it's unintelligable gibberish.]
>
> Did you consider that maybe some people *can* understand it?
Some tiny minority of the population, perhaps. But that wouldn't explain
it being so popular.
[Alternatively, I am drastically more stupid that the vast majority of
the human population - an unlikely but plausible hypothesis.]
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> And isn't alumina pretty much transparent at the thicknesses it's likely
> to
> reach in ambient conditions?
Having had a car with bare aluminium panels, I can tell you that it quickly
goes dull grey if you don't polish it :-) I have no idea what the thickness
is, but it certainly is visibly very different.
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Invisible <voi### [at] devnull> wrote:
> >> I mean, seriously. Any moron can write a bunch of gibberish that doesn't
> >> make sense. But where's the entertainment in that?!
> >
> > I don't think everybody can write scripts of that quality. It requires
> > expertise and talent.
> It takes expertise and talent to write scripts which *make sense* and
> are *interesting*. The X-Files lacks both of these qualities in spades.
You are now confusing two things:
What you are talking about is "coming up with an interesting idea for a
story" (or what you consider being an interesting idea) versus writing a
good script for a TV series episode.
Even if someone has a wonderfully ingenious idea for a script, that doesn't
mean he has the knowledge, expertise and talent to write a script that can
actually be used to film an interesting episode.
A script requires more than just an idea. You need a lot more around it.
You need dialogue, you need events to progress through the story, you need
to describe the settings so that the people making the episode can stage
the scenes... Just having a good idea is certainly not enough to write a
good script.
On the other hand, even a mediocre idea can be turned into a good script
in expert hands. Moreover, just writing a script good enough to be filmed
in the first place requires expertise. Not everybody is able to do that.
Most people could perhaps *learn* to do that with time and hard work, but
most people are certainly not born with the innate ability.
> [OK, you can argue about whether or not something is "interesting". But
> whether something makes sense or not is pretty objective. It's hard to
> find something interesting when it's unintelligable gibberish.]
Just because you find it "unintelligable" (sic) gibberish doesn't mean
that everyone else does.
Knowing that to you all C programs and all regular expressions are
unintelligible gibberish, I'm kind of not surprised.
--
- Warp
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Invisible <voi### [at] devnull> wrote:
> Some tiny minority of the population, perhaps. But that wouldn't explain
> it being so popular.
Actually there's a contradiction there.
--
- Warp
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scott <sco### [at] scottcom> wrote:
> It's just the dull grey of aluminium oxide you are seeing on the outer
> surface. If you looked close and polished them a bit you'd see nice shiny
> aluminium :-)
What stops the aluminum from oxidizing all the way through?
--
- Warp
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"scott" <sco### [at] scottcom> wrote:
> > And isn't alumina pretty much transparent at the thicknesses it's likely
> > to
> > reach in ambient conditions?
>
> Having had a car with bare aluminium panels, I can tell you that it quickly
> goes dull grey if you don't polish it :-) I have no idea what the thickness
> is, but it certainly is visibly very different.
Ah, fair enough, I must be thinking of something else.
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On Thu, 03 Sep 2009 10:13:50 +0100, Invisible <voi### [at] devnull> wrote:
>You're aware that those cables are carrying several *million* volts?
No.
--
Regards
Stephen
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On 3 Sep 2009 05:39:36 -0400, Warp <war### [at] tagpovrayorg> wrote:
>scott <sco### [at] scottcom> wrote:
>> It's just the dull grey of aluminium oxide you are seeing on the outer
>> surface. If you looked close and polished them a bit you'd see nice shiny
>> aluminium :-)
>
> What stops the aluminum from oxidizing all the way through?
Aluminium oxide. Aluminium is so reactive that it almost instantly forms a skin
of aluminium oxide which insulates it from the surrounding air stopping it from
oxidising further.
--
Regards
Stephen
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Warp <war### [at] tagpovrayorg> wrote:
> scott <sco### [at] scottcom> wrote:
> > It's just the dull grey of aluminium oxide you are seeing on the outer
> > surface. If you looked close and polished them a bit you'd see nice shiny
> > aluminium :-)
>
> What stops the aluminum from oxidizing all the way through?
The initial oxide layer. It slows further oxygen access to the bulk beneath.
Aluminium oxide is particularly effective at this - many high-temperature
alloys are designed with this phenomenon in mind.
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Invisible wrote:
>
> You're aware that those cables are carrying several *million* volts?
>
Where is that kind of voltage used?
The biggest powerlines in Finland are carrying 400kV.
-Aero
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Invisible wrote:
>>> Why do overhead cables never flap around in the wind? Come to think
>>> of it, why doesn't rain short out power cables?
>>
>> Those cables are pulled rather tight, also take a close look at high
>> tension wires, they'll have some funny looking thing hanging off of
>> them that looks like some sort of paddle, This also helps with the
>> wind. And they're too far apart to short out in the rain. Fresh water
>> is actually not a great conductor, and air is even a worse conductor.
>> Submerge them in salt water, and they'll short for sure.
>
> 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?
>
Right, but think of the impedance and the distances the electricity
needs to travel. It's not chemically pure, and may be mildly conductive,
but the layer is thin, and not continuous. There's enough resistance to
current that it doesn't flow.
>
> [Actually, apparently peppers are hot due to an antifungal toxin...]
Hmm, and I thought it was to discourage mammals from eating them, since
some mammals can actually destroy the seeds before they're "deposited"
> Seems plausible, I guess...
--
~Mike
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Invisible wrote:
>
> You're aware that those cables are carrying several *million* volts?
>
At most about 500kV. Typically 250kV. ;) Not millions.
>
> Well, this stuff clearly works - it's just a mystery to me *why* it
> works. ;-)
Physics is why it works ;)
--
~Mike
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Bill Pragnell wrote:
> The initial oxide layer. It slows further oxygen access to the bulk beneath.
> Aluminium oxide is particularly effective at this - many high-temperature
> alloys are designed with this phenomenon in mind.
The oxide layer also doesn't flake off like, say, iron oxide. So no
fresh metal is exposed.
--
~Mike
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scott schrieb:
>> Why do overhead cables never flap around in the wind?
>
> Actually they do, it's just it's usually very fast and very low
> amplitude flapping. Imagine holding out a stretched violin string in
> the wind, it's not really going to flap is it?
Indeed, in strong wind you can actually hear such cables "sing".
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>>> Why do overhead cables never flap around in the wind?
>>
>> Actually they do, it's just it's usually very fast and very low
>> amplitude flapping. Imagine holding out a stretched violin string in
>> the wind, it's not really going to flap is it?
>
> Indeed, in strong wind you can actually hear such cables "sing".
I don't know about that, but I *do* know that there's a particular
petrol station I sometimes go to, situated under a ****ing huge set of
pylons. As soon as you get out of the car, all you can hear is an
unearthly crackling sound... I can't describe it, but it's really
quite... worrying.
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Invisible wrote:
> I don't know about that, but I *do* know that there's a particular
> petrol station I sometimes go to, situated under a ****ing huge set of
> pylons. As soon as you get out of the car, all you can hear is an
> unearthly crackling sound... I can't describe it, but it's really
> quite... worrying.
Haha... There's a park near where I live that was basically turned into
a park to make use of land that would otherwise be unusable due to the
power lines. 2 sets, one (I'm guessing, here) a 100kV and the other at
least 250kV (I can only tell one caries a lot more power, one has twin
lines for each phase)
Standing under the twin-line set is creepy as hell. They crackle and
buzz quite audibly. The other lines, are very quiet, they don't make a
sound.
--
~Mike
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> Standing under the twin-line set is creepy as hell. They crackle and
> buzz quite audibly. The other lines, are very quiet, they don't make a
> sound.
Mmm. Petrol station. No naked flames. Switch off engine. No mobile
phones. Bzzzzzzzzzzz.
That can't be good(tm)!
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scott wrote:
>> 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?
>
> Both.
One thing I haven't figured out is why poisonous prey animals (frogs,
butterflies, etc) wind up being brightly colored.
If you're trying to avoid being eaten, it would seem that being hard to see
is a benefit whether you're poisonous or not.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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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
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scott wrote:
> Anyway, take 200 metres of this stuff (which I make weighs 10 tons):
> http://www.csunitec.com/saws/new-river-band-saw.html
Cool. It doesn't really look that big from the ground, does it?
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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scott wrote:
>> It feels like everybody is writing like power cables were bare metal
>> wires
>> with nothing covering them.
>
> That's how they are actually:
Phone lines used to be bare wire too, and you can sometimes see that (at
least in the USA) running next to train tracks (it tends to look greenish).
Of course, when they invented ways to insulate the wires, they could start
bundling them and/or running them underground.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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>> 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.)
Hoverflies look very like wasps, but have no venom.
False nettles look like stinging nettles, but lack a sting.
I couldn't give you a name, but I'm pretty sure there are snakes which
are harmless yet mimic deadly ones...
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On Thu, 03 Sep 2009 15:43:01 +0100, Invisible <voi### [at] devnull> wrote:
>> Standing under the twin-line set is creepy as hell. They crackle and
>> buzz quite audibly. The other lines, are very quiet, they don't make a
>> sound.
>
>Mmm. Petrol station. No naked flames. Switch off engine. No mobile
>phones. Bzzzzzzzzzzz.
>
>That can't be good(tm)!
Actually it is quite hard to ignite petrol from a petrol pump with a naked
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.
I would not do it myself, though. ;)
--
Regards
Stephen
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On Thu, 03 Sep 2009 09:23:03 +0100, Invisible wrote:
> Each episode
How many (and which ones) did you watch?
Jim
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On Thu, 03 Sep 2009 10:27:43 +0100, Invisible wrote:
> Some tiny minority of the population, perhaps. But that wouldn't explain
> it being so popular.
If it was popular, then by definition it was understood by most of those
who watched it. This is not an implementation of your "alternative
hypothesis", as it has nothing to do with intelligence.
Escapism can be good for some people, and for some people, the show
worked for that.
Jim
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On Wed, 02 Sep 2009 23:05:32 -0700, Chambers wrote:
> 101 isn't usually the "for noobs" section, but rather the "first course
> appropriate for college" level.
Well, maybe not now, but when I was in college, PS101 was colloquially
referred to as "Bonehead Chemistry". ;-)
Jim
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On Thu, 03 Sep 2009 09:06:16 +0100, Invisible wrote:
> Jim Henderson wrote:
>
>> Maybe the first unis that did this figured people were Pascal-based
>> rather than C-based. (Pascal, IIRC, starts arrays at '1', C starts at
>> '0').
>
> As *I* remember, Pascal arrays start at whatever index you tell them to
> start at. (E.g, you can make the first index be 17 if you want...)
>
> VAR stuff : ARRAY [17..21] OF INT;
I was thinking positions for a string. In Pascal, using the string
"abcdef", position 1 is "a". In C, it's position 0.
Jim
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