You Know You Are Living In The 21st Century When.....

[Maximius]

The absolute king of vision though is the mantis shrimp (a stomatopod crustacean), which has 16 classes of colour pigment (hexadecochromatic), and more than 8 polarisation classes. Mantis shrimps have by far the best vision of any animal, with a visual range from 300nm to over 700nm (ultraviolet to deep infrared). Its eyes are very complex and sophisticated, and allow the shrimps to see with great clarity in a huge range of depths and water conditions.

 

If anyone was curious...

 

Thats really wild. WHen you say the best vision, do you also mean in terms of distance? I thought the raptors had the best eyes.

[obscurus]

Well, I mean in terms of overall sophisticatedness (I made up a word I think). The mantis shrimp has pretty poor distance vision. They are small animals that like to get very close to their prey before making a move, and they don't go out in the open too much, so distance vision is not so important for them. Raptors do indeed have the best vision when it comes to seeing detail from a distance, they have ~5 times the density of cones as humans. They also have two foveas in each eye, and a special organ called the pecter which keeps the vitreous humor supplied with oxygen and nutrients, that only birds have. A typical hawk can spot a mouse from over a thousand metres, and can pick out very well camoflaged prey. Birds also have a much larger proportion of their brains devoted to vision than humans. Different animals specialise at different things, but in terms of being reasonably good at seeing a bit of everything, we humans are quite well off.

 

 

Here is what a human sees: http://www.ratbehavior.org/images/WaterLily.jpg

 

And (approximately) what a rat sees:

 

http://www.ratbehavior.org/images/WaterLil...GreenCBblur.jpg

[Domarius]

I wonder what ultraviolet light looks like?

 

The donor was brain-dead, but there is an ethical question regarding whether a relative can authorise the removal of the face of a brain-dead but still living person.

Yeah I figured she was already dead, I just felt more concerned about what happened to her than the suicidal drug addict. @Spar, It's good to know there's a solid difference between comatose and brain dead.

[obscurus]

The only way to find out is to have your lenses removed and/or replaced. Whether or not your brain could interpret the new information is another question, as people need to sort out visual stimuli very early in life to be able to make sense of the light the eyes receive. People who were born blind, but have surgery to fix their eyes later in life usually have problems in interpreting what they see - it is just a chaos of colours and shades, because their brain has not wired itself to interpret that sort of information. Often the ears will take over the visual cortex in a person born blind, allowing them to interpret sounds as images, giving them very good spatial awareness through hearing alone. Interesting how the brain will compensate and redistribute its resources...

 

But if your brain could interpret UV, you would be surprised at how different the world looks. some things that look black under ordinary light might look very bright or flourescent under UV. Some objects that are opaque to visible light can be transparent to UV, so if you could see in UV, you might be able to see through things you couldn't see through before. Alot of flowers have very vivid patterns under UV filters, and rat urine sticks out under UV light (rodents can see UV light and use it to mark territories with UV flourescing urine).

 

Some fabrics are highly transparent to parts of the infrared spectrum, notably nylon swimsuits, and some video cameras have a night vison mode that picks up that wavelength, and such cameras have been used to vouyeristically capture invasive footage of beechgoers, revealing far more than the unsuspecting swimsuit wearer thought... I think such cameras are no longer available for that reason, and some countries, such as Japan, have laws regulating what parts of the light spectrum you are allowed to film in to prevent people from making unseemly videos at swimming pools and beaches.

[Domarius]

As soon as you mentioned "some things may become transparent", I immediately remembered some photos I saw from japan of girls wearing tops that became seethrough with a special lens. Just as you described in the last paragraph.

 

That was all a very interesting read.

 

I wonder if in the future we will mod ourselves to see UV, just like we innoculate ourselves against certain viruses as a "must do" thing.

If so, I'm sure there would be big changes in the textile industry. Hehe.

[Ishtvan]

I had a phsyics prof who claimed that getting surgery to expand visible spectrum is not unheard of in the military. I find that a bit hard to believe though, since at the time any invasive eye surgery would have disqualified you from jumping from planes AFAIK, because there's a danger of detachment or something when the air is rushing past you during a jump. So you can be a super-stealth commando who can see UV, but you'll have to take a boat or car to get behind enemy lines.

 

@Obscurus: How does sensitivity to a number of polarization states help from an evolutionary perspective? I know you can tell direction somewhat with polarization by looking at the sky, because different parts of the sky have different average polarization due to the angle of the sun and atmospheric scattering. How does it help aside from that though? The light from the sun incident on most things is effectively randomly polarized; do we look at that many materials that filter polarization upon reflection?

 

Also, what do you mean by sensitivity to polarization states? Angle of linear polarization, handedness of circular/eliptical polarization, or what?

 

300nm 700nm (ultraviolet to deep infrared)

To nitpick, 700 nm is not deep infrared. It's barely into the near infrared (NIR). Mid-far IR is more like 5-10 microns, and I'm not sure but I think deep infrared is around 1 THz, just before the "microwave" region, which is kind've a misnomer since the wavelengths are ~10cm. Just saying.

[OrbWeaver]

I think there are some humans that have extra colour receptors - women who are carriers for BOTH red-green and yellow-blue colour blindness end up with an extra frequency of cone, IIRC.

[sparhawk]

Quite interesting. Thanks.

[Maximius]

I had a phsyics prof who claimed that getting surgery to expand visible spectrum is not unheard of in the military. I find that a bit hard to believe though, since at the time any invasive eye surgery would have disqualified you from jumping from planes AFAIK, because there's a danger of detachment or something when the air is rushing past you during a jump. So you can be a super-stealth commando who can see UV, but you'll have to take a boat or car to get behind enemy lines.

 

I spent six years in the U.S. army and Ive known special forces and similar whackos, I never heard anything about that. THe people who would need such treatments are, as you point out, not going to fuck with their vision, which has to be 20/20 or better to get into combat arms training let alone the specialized branches like Green Berets etc. Unless the surgery was so routine that no one thought a second about it, which seems unlikely since Ive never heard about it before this post.

[OrbWeaver]

I don't think that seeing UV would be all that useful.

 

Seeing infra-red, that's a different matter. All matter gives off some varying amount of IR radiation, so seeing in this part of the spectrum would indeed give you the abilitiy to see in what other people would consider absolute darkness.

[Ishtvan]

Yes, seeing in the IR is useful. Fortunately we have cameras nowadays that do that fairly well without having to cut open your eye.

[obscurus]

@Obscurus: How does sensitivity to a number of polarization states help from an evolutionary perspective? I know you can tell direction somewhat with polarization by looking at the sky, because different parts of the sky have different average polarization due to the angle of the sun and atmospheric scattering. How does it help aside from that though? The light from the sun incident on most things is effectively randomly polarized; do we look at that many materials that filter polarization upon reflection?

 

Also, what do you mean by sensitivity to polarization states? Angle of linear polarization, handedness of circular/eliptical polarization, or what?

To nitpick, 700 nm is not deep infrared. It's barely into the near infrared (NIR). Mid-far IR is more like 5-10 microns, and I'm not sure but I think deep infrared is around 1 THz, just before the "microwave" region, which is kind've a misnomer since the wavelengths are ~10cm. Just saying.

 

 

To be honest, I don't understand light polarisation that well, so I'm not sure I can explain it properly. It refers to the angle of linear polarisation, but I think the mantis shrimp can detect elliptically polarised light as well. Most aquatic animals (fish, molluscs, crustaceans) can detect polarisation of light in one form or another. As I understand it, mantis shrimps use their ability to see variously polarised light to correct for distortion introduced by the water at different temperatures and conditions. Polarised light seems to be very important for some animals (pretty much all birds see polarised light). Quite how they interpret this information is not entirely clear. Many experiments have been done with polarised light that show how acutely aware many animals are to it. Detecting polarised light also seems to be a way to enhance contrast somehow. Mantis shrimp also use highly complex patterns of reflection and flourescence in mating, and it is important for them to see this, as they normally live in deep, dark, murky water. It also uses light polarisation to detect light reflected off the scales or other hard shiny parts of its prey. For many animals, sensing various angles of light polarisation is more important than colour.

 

Mantis shrimps are also have the fastest reflexes of any animal. Some use their hammer-like forelegs to stun prey by lashing out with them with the force of a .22 calliber bullet, at 50m/s and 10,400G of acceleration. If you picked one up and you weren't careful, it could easily split your thumb or fingers open. Other species have forelegs modified to form spears, which they use with similar speed. They are also quite intelligent and long lived as crustaceans go, and can learn and remember surprisingly complex things. Some species mate monogamously, and can stay together for over 20 years. They are probably the creature I find most fascinating....

 

http://oceanexplorer.noaa.gov/explorations...media/fig1.html

http://oceanexplorer.noaa.gov/explorations...media/fig3.html

 

http://www.nwf.org/nationalwildlife/articl...&articleID=1114

 

Whoops, I'm a biologist, not a physicist, thanks for correcting my whoopsie on the infrared wavelength. My reference actually said well beyond 700nm, it didn't say how much beyond that was (I'm guessing they haven't acurately determined it yet). Most biological references call this infrared, becasue few animals can see much of this part of the spectrum. After looking at some references, I see that usually we define infrared light as between 700nm and 1mm. Humans can see down to about 690nm, but only very dimly, as we are warm blooded and we actually emit enough IR in our eyes to cancel the IR light out. This is why night vision goggles have to protrude quite a bit from the head of the wearer - the heat emmited by the head would interfere with the goggles otherwise.

 

I can't see any application for humans in the military seeing UV, though you would be able to see quite a bit of interest, like distubed vegetation perhaps, it wouldn't have much utility in combat. I've never heard of the military modifying eyes by surgery to see UV.

 

Infrared light has far more use for military purposes. A forensic scientist on the other hand, would get great utility out of seeing UV...

[OrbWeaver]

It always amuses me when creationists spout "What use is half an eye?"

 

Apparently quite a lot of use since our own eyes are less than half as good as many other animals.

[sparhawk]

This reminds me a bit of the argument why anyone would have memory being swapped to discs, since everybody knows that discs are so slow (especially some ten years ago).

 

If the decisions is to NOT run an application at all, which you urgently need, or run it painfully slow, what would you decide? Obviously a painfully slow application preferable to no application at all.

[obscurus]

It always amuses me when creationists spout "What use is half an eye?"

 

Apparently quite a lot of use since our own eyes are less than half as good as many other animals.

 

 

Indeed. In fact, many eyes in the animal world do little more than tell the difference between night and day. Eyes in the animal world range from a simple collection of photosensitive cells to the sophisticated trinocular hyperspectral eyes of mantis shrimps, or the extrreme zoom eyes of eagles. "half" an eye is tremendously useful for most creatures, and yet some posess very well developed eyes that are entirely useless. For example, ther are cave dwelling fish that have no use for eyes, yet they have them. Strangely, they couldn't use them even if there was light to see - their eyes are covered over with scales, making them functionally blind. Not a very intelligent way of doing it, but very typical of what you can expect from an evolutionary process.