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Posted by George on May 7, 2005, 3:06 am
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>
>>
>>> In numerous tests, twins are able to communicate flashcards "psychically"
>>> with greater than 60% accuracy..
>>> Not all, but some.
>>>
>>> Have you two ever participated in one of those tests?
>>
>> No, but then, when I took psychology and anthropolgy in college, I read
>> papers that showed that a 50% success rate can be duplicated randomly, so I
>> don't really have any faith in anyone having "psychic" abilities. I've
>> probably now opened a can of worms, and expect to see a lot of argument over
>> the issue. Sorry about that.
>>
>
> Naah, wrong group, we would have to move the thread to another group... 8)
That's good. I don't want to be responsible for starting a flame war. This
newsgroup is too useful to see it trashed.
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Posted by Mislav on May 6, 2005, 3:53 am
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In most part I agree with you that red color doesn't penetrate deep into
water. But I don't agree that fish cannot see red color. As CheezWiz said
laser produces a single wavelength of light about 632 nm for red light.
Why do percula clowns have transition between red and white with black line?
Surely it isn't just esthetics, it must have some evolutionary reason. It
seams that other fish must see it, otherwise it wouldn't develop black
color.
>>So what it is more likely responding to is not the color itself, but the
>>movement (of something that to it appears like a shadow) of the lazer dot
>>as it is moved around in the aquarium.
My sailfin chases the dot trying to eat it. He perecieves it as a food. If
he sees that something is moving he must see the red color of laser pointer
'cose it is only single wavelength.
Mislav
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Posted by George on May 6, 2005, 5:47 am
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> In most part I agree with you that red color doesn't penetrate deep into
> water. But I don't agree that fish cannot see red color. As CheezWiz said
> laser produces a single wavelength of light about 632 nm for red light.
> Why do percula clowns have transition between red and white with black line?
> Surely it isn't just esthetics, it must have some evolutionary reason. It
> seams that other fish must see it, otherwise it wouldn't develop black color.
It is for camouflage. Like I said in a previous post, "Rhodopsins, which are
also found in all other vertebrate animals, are a dark reddish color. Like deep
growing red algae, the rhodopsin pigment absorb the only wavelengths that
penetrate the water column: greens and blues. Therefore,
the rhodopsin, like the algae, reflects the light it does not absorb - which is
generally the red wavelengths of light. 632nm is nearly orange (625nm). Our
eyes are more sensitive to red, so we see the lazer light as red, not as
orangish red. I know all of this is hard to understand, but one look at how
certain fish look in UV gives you a much better understanding of how fish
actually see each other and the world around them.
>>>So what it is more likely responding to is not the color itself, but the
>>>movement (of something that to it appears like a shadow) of the lazer dot as
>>>it is moved around in the aquarium.
>
> My sailfin chases the dot trying to eat it. He perecieves it as a food. If he
> sees that something is moving he must see the red color of laser pointer 'cose
> it is only single wavelength.
>
> Mislav
>
Fish are territorial. A bass will strike at a lure passing close by more often
out of defensive behavior than out of hunger. And they could really care less
what color it is. The color is more for the lure owner than the fish. Fish
have rods (for black and white) and cones (for color) like we do. Because the
rhodopsin generally do not absorb red light, what your fish is probably seeing
is grayscale, like a shadow flittering around in the tank. It sees this strange
gray/black "thing", this dot scurrying about in its territory and it chases it,
just like a bass will strike a lure that gets thrown into its territory.
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Posted by CheezWiz on May 6, 2005, 8:40 am
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"
Safety.
Care should always be taken, especially with children, when using a laser
pointer. Exposure to a couple of seconds of the laser beam will cause only
temporary "spots" in front of the eyes. Even small children do not focus on
the sun because it is uncomfortable and the same is true of the laser
pointer beam. But the power is great enough to damage the eye if someone
stares directly at it long enough. Of the millions of pointers sold, the FDA
knows of only 2 cases which have caused serious eye injury and none have
resulted in permanent blindness. In these two cases, the victim stared
directly at the beam for 10 seconds or more. Insurance companies are perhaps
the best gauge of danger, since their financial well-being depends on
identifying dangerous products. The premium for laser pointer insurance is
no more than for office chairs.
"
> Is it safe to use a red laser pointer for the tank? I'm getting tired of
> saying to hubby "See the shrimp? Ok - see the knob next to him.. Now go
> straight over to the little hole in the rock and down about an inch..."
> It would be much easier to use the pointer but I don't want to disturb the
> critters.
>
> --
> Ann R
>
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