Question about why we see the spectrum we see?

Question

If the Sun emits deferents electromagnetics waves besides the ones includes in the visible ligth spectrum, why can we just see the visible spectrum and no others electromagnetics waves emited by the sun

Answer 1

This was explained to me years ago by my mentor in the science of vision.

There is a range of the sun's electromagnetic radiation that makes it through the atmosphere to the earth. A lot of UV radiation is blocked by the atmosphere ... which is a good thing as it causes havoc with DNA.

However, some UV still survives, but this high-energy radiation is harmful to delicate cells like the photoreceptors in the retina. So the cornea has evolved to filter much of this remaining UV out, and the photoreceptors are not responsive to light in this range.

As for the other end, the infrared (IR), this is radiation given off just by heat. This can be useful for night-time predators hunting warm-blooded mammals ... which is why some vipers have developed an organ for detecting IR. But for daytime animals, this IR radiation would be overwhelming ... as you walked around in the daytime environment, everything (rocks, ground, plants, even warm currents in the air) would be a *source* of radiation. If our eyes responded to all of this, our visual system would be overwhelmed with all this "light".

So there is an opimal range in which all visual systems on this planet will operate.

As for why our *exact* range, this is as much an act of accident ... it's just the range that was natural for the photopigments we developed. Other organisms see a slightly different range within that slightly wider range for terrestrial life.

Hope that helps.

Answer 2

We adapted and evolved. We gather information about our environment by observing it. The more information we get from those observations, the better we can survive in it. The range of frequencies in the electromagnetic spectrum called "visible light" provide the most amount of information about things the photons bounce around off of to our eyes. Just think if we could only detect ranges in the radio wave frequencies. Not much everyday useful information would be observed that way. Or microwave range. While that may make it cool to watch dinner cook, it still wouldn't be very helpful otherwise. Of course, having X-ray vision would help doctors and make clothing an optional human trait [which could be good or bad...think about it. :P]. If we didn't see the colors we do, just think what art would have been throughout history.
The most relevant thing is that not all of those types of radiation get through our layers of atmosphere in sufficient amounts to be useful for us even if we could detect them. We simply ended up using what worked best for us by adapting to it.

Answer 3

The Sun does emit radiance at different wavelengths, but because of the sun's temperature (~6000 K), most of the radiance it emits is in what we call the visible range - because it's the range we can sense. Having evolved on a planet bathed in light from a 6000 K Sun, we have evolved eyes that are most sensitive to the peak wavelengths of light from the Sun. In fact, the peak wavelength emitted by the Sun is at 0.55 microns (visible green), and this is the wavelength our eyes are most sensitive to.
It's an interesting question why we can't see in the UV or near infrared - maybe, given the size of our eyes and what we use them for, it wouldn't be evolutionarily stable or advantageous for us to see in these extended wavelength ranges.

Answer 4

I do not know why secretsauce's answer has a thumbs down because it's very good.

We developed eyes that see the most useful range of light wavelengths for us. There's not a lot of UV that gets through our atmosphere to see and as secretsauce said, it can be damaging to living tissue anyway. Much of the sun's IR is blocked by our atmosphere as well, and since humans are daytime creatures, the abundance of IR light emitted by everything around us would make it not very useful for seeing.

Answer 5

our eyes only see visible light. You cant see non-visible light because it is invisible. :P Birds can also see Ultraviolet rays, as an added colour. making visible light for birds a broader spectrum and theyr perception different from ours.

its similar to the 'why do things fall down' question. Items fall down because down is defined by the direction things fall too.

Answer 6

human vision is only sensitive to a limited range of wavelengths, which roughly coincide with the wavelengths that are the most intense components of sunlight. other animals have different spectral ranges but they don't go all that far outside the human range. presumably natural selection favors those light-detecting proteins that detect the most common forms of light. there is little advantage to be had in seeing x-rays.

Answer 7

Our eyes have evolved to work in this spectrum because focusing ultra violet or infra red would burn our retinas.
People who have had corneas removed due to cataracts con often see further along the blue end of the spectrum because the cornea naturally has a faint yellow tinge and acts like mild sunglasses.l

Answer 8

The other answers are decent. In addition, there are birds of prey and insects that see ultraviolet, so it's not like it's impossible or anything. Like someone already said, what more we could see in ultraviolet simply doesn't benefit us any. We don't need to.

Answer 9

just a matter of biology. its the only spectrum our eyes can see.