Wednesday, April 11, 2012

The blessed valley of Sight

[15 Apr: Fixed typo, makes it even more incredible. Thanks, Nirmal!]

So, Facebook acquired Instagram for a billion dollars. Naturally (oh how I love this word, verily the Prince of Segues!), this leads one to ponder the preponderance of visual media over all other senses. Just look at how advanced our visual transactions are - we read (highly non-linear and asynchronous), see pictures, see nuances in colors, see videos (somewhat more linear and synchronous), etc. Sometimes we do a multi-layered visual transaction all at once - imagine seeing a movie with subtitles, with a scene having elements of black-and-white and selective color, with some elements changing and others stationary in time. A typical news cast involves all these - an anchor, a infographic still, a video, feed, a scrolling ticker below, etc.

In contrast, our aural transactions are primitive. We are confined to pretty much one kind of listening, and only very few of us are trained to recognize pitch and tone. That's the equivalent of only a tiny population being trained to read. Even for those, it is mainly a linear, synchronous kind of input. The most multi-layered it can get is someone speaking with music, but even then our resolution rapidly drops as more elements are added.  Our olfactory (smell) transactions are even more primitive. There's hardly any creative expression with smells, and pretty much all of us are at a very primitive level. The visual equivalent might be a population which can't just not read, but one where most can't even see more than vague blobs of color.

All this can lead to interesting questions of how this came to be, and how it could change in the future. One of the first steps in answering the former is to ask, how is it that our eyes see what they see?

There are many ways to interpret that, but one way is to focus on the electromagnetic frequencies that the eye is sensitive to. It turns out that pretty much every eye, in every organism in existence, is sensitive to approximately the same band of EM frequencies! Some insects can see farther into UV etc., but these changes in range are very tiny compared to the total part of the spectrum we're blind to. How come there is this extraordinary uniformity?

One theory, a very convincing one, is that the eye as an organ evolved when all organisms still lived underwater and had not yet crawled onto land. Water blocks out pretty much the entire EM spectrum (which is why you can't have RADAR under water) except for a tiny window between 400nm and 700nm. All eyes are sensitive in this range, because an organism would be fatally disadvantaged if it didn't evolve to see and compete. After they began moving onto land, there was no incentive for organisms to see any further than this range, because every other organism (competitor) saw only in this range!

The EM attenuation curve in water is amazing.

The attenuation curve drops 1000 orders of magnitude just around the visual range. Think about it, 1000 orders of magnitude! The range between a subatomic particle and the diameter of the visible universe is just around 40 orders of magnitude. Even if you measured the diameter of the visible universe in Planck lengths, you'd still be stretching at just around 60 orders of magnitude! There isn't much in this universe that changes that much, and even less where this change makes such a manifest impact, like be the cause of our ability to see.

One can very nicely motivate a creationist mindset by twisting cause and effect a little bit: How amazing it is that water's physical property has this incredible feature, that allows us to see! Surely, you can't explain away a 1000 orders of magnitude drop just around our visual range as chance - it sure feels like someone put it there, just so that we can see!

This reminded me of this Abstruse Goose comic, and yet again of the famous, iconic, beautiful Pale Blue Dot video. It is humbling, isn't it, that our window to the world rests precariously perched on one of the most stupefyingly rare features of a physical property of water?

Groucho Marx is said to have said, "Life is just the whim of several billion cells to be You for a while". A vanishingly temporary wisp of low entropy, man "appears as a somewhat ridiculous strutting animal, shouting and fussing during a brief interlude between infinite silences."

Right, we were talking about the Instagram story, and how it is is so amazing. [/condescending Wonka :P]


[1] I found most stuff about the eye in this very nice paper by Russell Fernald on the evolution of the Eye. That in turn I found when randomly browsing wikipedia and following the references in the Eye article.

[2] The keenly perceptive reader would have noticed that water's attenuation reaches the same low value as it does in the visual range at around 10^3 Hz and below. This corresponds to the long-wave radio range. Some underwater animals apparently exploit this, and use it for sensing! However, because of this extreme low frequency, the resolution is also low. Even large-sized objects cause huge diffraction distortions because the wavelength is several tens kilometers.


Siddhartha Banerjee said...

And a cheer for Bertrand Russell for one of the greatest sentences ever!

Very nice piece, sir!

KVM said...

Humbled, master. And the piece where that sentence comes from is one of the finest I have read! 

Ishan said...

Nice one mate - enjoyed a blog entry after a long time.

shak said...

KVM!! Brilliant as always!! 

Nirmal Raj said...

Oh, and I must add:

The intensity of non-absorption increases by 1000 orders of magnitude? All right, NOW I'm freaking out.
I must scratch my logic that such drastic tuning can be observed only in High Energy Physics.
Nature 1, Nirmal 0. 

Douglasclark64 said...

FYI, attenuation drops from 10^4 to 10^-2 dB/m which is only 6 orders of magnitude.

KVM said...

The decibel is a logarithmic scale. 6 orders of magnitude on the decibel scale is 1000 orders of magnitude on the amplitude scale. For a quick contrast, the range of human hearing, which is considered quite large, spans only about 120 dB - just two orders of magnitude. Virtually any instrument you can find has a range not much larger than this. 

kollseu said...

there have cheap and fast gold was RS Gold at

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