[extropy-chat] FWD [Skeptic] Re: Looking for examples of naturally evolved X-ray vision?

Terry W. Colvin fortean1 at mindspring.com
Wed Jan 18 07:27:43 UTC 2006

On Jan 17, 2006, at 8:10 PM, Terry W. Colvin fnarded:

> I was helping my daughter come up with some ideas for a school  
> science project and I stumbled onto a couple unknowns.
> Animals have evolved a wide variety of abilities to seek food and  
> avoid predators. Echo-location, color vision, and compound eyes are  
> just a few. All provide important information regarding the  
> immediate surroundings. My daughter asked me why the visible light  
> spectrum IS the visible light spectrum. After all, animals hear at  
> a wide range of frequencies that humans cannot, so why not have the  
> same thing occurring in vision? Are there animals with X-ray vision?

The "visible light spectrum" refers to humans.

Two reasons most of life on Earth is anchored on the "visible" spectrum:

1. the atmosphere is not transparent. Solar X-Rays, Gamma, and UV do  
not have much intensity on the surface. See:

2. there isn't much functional benefit: there are no biological  
emitters or reflectors of X-rays. It would be like turning plants and  
animals into glass.

Other animals have extended or shifted visible ranges, as you expect.  
Insects and some other invertebrates see well into the UV, as do some  
Aves. Many vertebrate predators see into the IR.

This is a useful piece of trivia when I talk about applications of  
organic chemistry. Specifically: brighteners and whiteners. These are  
chemicals that are added to detergents or paper to make the objects  
appear brighter. The way they work is that they absorb light from  
many wavelengths and reflect in the visible spectrum, achieving  
greater light intensity than you would expect in ordinary daylight.

One side effect of this phenomenon is that they can sometimes reflect  
intensely in the UV range as well but we don't see it. Insects,  
however, see it like a beacon and this explains why when you're  
hiking in a group sometimes there's that one unfortunate kid who's a  
bee magnet. Think black light in reverse.

Those white flowers are only white to us. To bees, they're a palette  
of the most beautiful colours in the world. The flowers evolved to be  
pollinated by insects, not to benefit human aesthetics.

If your kid's looking for a science topic, this is has been popular  
in the past: "bee's-eye view of the world."

As an interesting philosophical aside, there's an example of how  
facts can be used to back any argument if you close one eye and  
squint enough: I feel that this invisible world is evidence that the  
universe is not designed with humans in mind. My Mennonite friends  
consider this evidence that the world so obviously has a creator. I  
don't see the connection, myself.


Graeme Kennedy

"Only a zit on the wart on the heinie of progress." Copyright 1992, Frank Rice

Terry W. Colvin, Sierra Vista, Arizona (USA) < fortean1 at mindspring.com >
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