fwh

I am re-reading Robert Ornstein's "Multimind". Please comment on the accuracy of the following statement found on pp. 36.

"The eye, the inroad to the most complex and rich dimension of our experience, transmits less than 'one trillionth' of the information reaching its surface! We obviously cannot see what is really out there."

I have never seen the info quantified as such. Accurate?

scombrid

Our eyes miss most of the EM spectrum. As far as our eyes are concerned xrays and radio waves may not exist. Our eyes also aren't equipped to detect vibration. So it's true that our eyes don't record all of the "information" out there. However, that figure sounds to be of the "pulled out of ass for effect" sort. These assertions are usually made by somebody trying to use the "just because we can't see it doesn't mean that it doesn't exist" tack to convince you of the existense of Chi, ghosts, god, or anything else of the etheral rhelm unseen by the eye. However, the difference between these objects and EM radiation, sounds, etc... is that radio waves and sound, neither detectible by the eye are measureable by other means and even other body structures.

Jesse

I did a google search on "eye" and "fraction of photons" and turned up this pdf on telescopes--on p. 5 they define "quantum efficiency" as the "fraction of photons actually detected" and say that the human eye has a QE of about 0.01, which is a lot larger than one trillionth. According to this page, this means that "for every 100 photons that hit the retina, two or three of these photons will actually cause your retina to send a signal to your brain." Of course, not all photons that hit the lens are going to be successfully focused onto the retina, so this might lower the fraction of incoming photons that are detected even more (although I'm not sure if 'quantum efficiency' already takes this into account...I'm also not sure if it takes non-visible light photons into account, and if so what assumptions they make about the characteristic spectrum of light hitting the eye, i.e. the relative proportions of photons of different frequencies); also, each photon may not necessarily lead to a distinct nerve cell firing in the retina, and perhaps the brain does not pay attention to each distinct retina-cell-firing-event. Still, unless Ornstein provides a reference I'd take his figure with a grain of salt.

fwh

There is no reference to this particular statistic nor any further explanation. If I remember my statistic's class properly, 0.000000000001 is in danger of being statistically insignificant in relation to the computation of data.

The book itself seems to be well-referenced.

Undercurrent

I suspect that "trillionth" is here meant to mean "one over some really big, but unspecified, number", rather than 10^-12 in particular.

Deep Junior

"I can see, I can see I'm going blind..."
Blind - Korn (Good song, check it out sometime)

You guys see the movie Daredevil yet? It makes me want to put a blindfold on and run around in the rain...

Chrissyfly

from what i can remeber from alevel physics classes the visable part of the spectrum (the part the eye can detect) is only about
0.0000000000003% of the spectrum
also from what i can remeber of the Daredevil is that he can see infared which is part of the spectrum so any ideas how he sees any part of the EM spectrum while being blind? (i dont know if he sees this way in the movie but its what he could do in the cartoon/comic)

Gooch's dad

Its an interesting question....

Jesse, I'm fairly sure that the quantum efficiency number they're quoting only applies to the visible spectrum. But the sun's radiation peaks in the visible spectrum, too.

This PDF document has graphs of both the eye response and the solar spectrum. Looking at that spectrum, I'd take a wild-assed guess that the visible portion is maybe 1/10 of the power the sun radiates, total.

So we can take the .01 QE and it becomes .001. Still a long ways from .0000000001, or 1 x 10^-9 .

But there are other types of radiation other than EM radiation, and of course that radiation all carries information of some kind. Neutrinos, for example, are streaming through the eye (and the rest of us) at a pretty decent flux. As is other types of radiation, mainly cosmic rays such as gamma rays. These rays do carry a lot of information about the stars and galaxies they come from, and of course the eye doesn't register them.

But I have no idea of the relative flux of neutrinos and gamma rays, vs the visible light we see. I suspect it is quite small, and that is just based on the number of cosmic ray events I see on the Raman Spectrometers I work with (they use a cooled CCD camera which can register cosmic ray events).

Edit: Whoops, I forgot to mention non-solar EM sources, which are all over the place. If you walk under a high power transmission line, you may be getting a dose of low frequency EM radiation in the level of many watts (wild assed guess, again). How much goes through the pupil into the eye? Microwatts, at most. But that is comparable to the amount of visible light we normally see.

Then there are the various radio waves flying about, from sources like cell phones and cordless phones, etc.

-Kelly

Jesse

Gooch's dad:
But there are other types of radiation other than EM radiation, and of course that radiation all carries information of some kind. Neutrinos, for example, are streaming through the eye (and the rest of us) at a pretty decent flux. As is other types of radiation, mainly cosmic rays such as gamma rays. These rays do carry a lot of information about the stars and galaxies they come from, and of course the eye doesn't register them.

Gamma rays are a type of EM radiation, no? But maybe most of the gamma radiation on earth comes from things like cosmic rays rather than from the sun (that's suggested by the last paragraph of this page). And of course cosmic radiation contains all kind of other particles, although I don't know what fraction of them make it through the atmosphere (is our knowledge of the composition of cosmic rays based on looking at the EM radiation and inferring particle creation/annihilation events, or do the particles themselves reach the surface to be detected?)

Shadowy Man

Many cosmic ray experiments measure air showers produced by the actual cosmic rays. So, basically a high energy cosmic ray enters the atmosphere and hits a nitrogen atom or whatnot and produces a shower of particles, a lot of the times they are muons. These muons are either directly detected or the air shower can also produce visible light (Cerenkov radiation, perhaps?) and that flash is detected.

It's not exactly my area of expertise.

Neutrinos, of course, can go all the way through the Earth without even interacting. A few do, and those are detected in a couple of different ways. One type of cool experiment the University here is actually involved in... you put a bunch of downward facing photodetectors in the Antarctic ice and wait for neutrinos passing up through the Earth to hit an atom and cause a muon or something to come flying out at faster than the light speed in the ice, producing a flash of Cerenkov radiation. With a big enough array of these photodetectors you can get the angle of incidence and energy of the original neutrino. Cool stuff!!

As far as QE of the eye: QE usually just refers to the detector efficiency, so the efficiency of the eye's optics are most likely not included in that. It is also probably just an average of the eye's response in the visible part of the spectrum.

And I don't know off hand what the bolometric correction for the Sun is (i.e. what fraction of the total luminosity comes out in the visible part).



And we should probably all not quite sit so close to our monitors either!