26 January 2011

A percentage of reality

Today a full day of physical work; gratifyingly tired. I am reduced to sitting on the floor to write as I don’t have the heart to shift either of the cats who are inhabiting the newly arrived chairs. His and hers, crashed out next to the stove. (I think that M + T, the kind chair donors, will feel that this is the appropriate hierarchy of users.) 
It’s dark and tonight’s scene is illuminated only by the light from the laptop screen and numerous flames, both naked and encased behind the mica windows of the aforementioned sizzling stove.

The book lies open at a page showing the title of section 2.3.
Phase of a propagating wave and its wavevector.
I can’t tell if it’s merely the rhythm of the words, or a combination of that with their subtle rhyme and alliteration, but I cannot help but roll the phrase around in my mouth for a while, feeling its sound. It feels good. And visually the veve (vera verity?) embedded in the last word is somehow both alien, and yet unspeakably perfect. 
Yesterday I spent much of the day with the book, revisiting things that I had glancingly encountered previously. I was making notes, reading around, and more fully understanding ideas that were being described to me. I realised I’d previously totally overcomplicated the notion of phase. What is phase? (– it helps, when dealing with this question, not to worry about wave particle duality implications, but just to consider light in terms of its wave properties - in my experience this shifts the understanding from mind-bendingly impossibly complicated to really pretty straightforward). It also helps to consider that the time element involved is fundamental – phase is the proportion of a periodic waveform that passes some reference point after a time t. Simple. So, on I skipped, frankly even feeling a little bit smug at how readily it was all going in this time. But.
Amazing that the simple act of turning a page can move one from lackadaisical absorption and regurgitation of information, into utter incomprehension. That thin layer from page 13 to page 14 has a sharp edge, and is followed by some maths. I stumbled around with a number of the equations, which I didn’t follow but felt that I should, and which culminated with the rather uncompromising words:
“Clearly this implies that:
r = 1
and that r is also complex and hence a phase shift is imposed on the reflected wave.”
I’m afraid the only thing clear to me at that moment was that clarity and I had parted company. (Maybe this ‘clearly’, as with other transparencies, is a relative term, and I simply had some kind of nonlinear response to the information such that my optical density increased with the intensity of the mathematics). But I do not wish to infer that the writings of Reed and Knights (or “the boss” as the former is currently known among intimate company) are in any way at fault – only moments earlier I had been applauding the inclusiveness of their fundamental introductions to various aspects of the subject. No, rather it was that the brain of the resident artist was not at its best, and seemed to fall at what is shamefacedly probably quite an easy hurdle.
An urgent injection of low brow was required so I returned to wiki, in an effort to ease the pressure on my head. 
The wiki silicon photonics page is not exactly what I would describe as low brow, and when I reach the statement that two-photon absorption “ ...is related to the Kerr effect, and by analogy with complex refractive index, can be thought of as the imaginary-part of a complex Kerr nonlinearity.[8] At the 1.55 micrometre telecommunication wavelength, this imaginary part is approximately 10% of the real part.[42]”, I decide that my efforts into comprehension of this realm are probably done for the day. I take a morsel of comfort from thinking that at least I get a little of what a wavelength of 1.55 microns implies, but my brain falters at trying to compute how one can calculate the size of an imaginary nonlinearity, let alone as a percentage of reality.

19 January 2011

Intrinsic mediocrity

I must admit that a few months ago I wouldn’t have envisaged the pleasure I would garner from time spent with “Semiconductor Devices, Physics and Technology” by S.M. Sze (whose name has such a delicious plethora of connotations attached). Admittedly this evening the pleasure is somewhat enhanced by warm murmurings from the newly-fixed stove (just in time for the cold weather this week, and after the dully unatmospheric electronic heating of Christmas), and a glass of a really rather nice Merlot. However, delving into the world of physical chemistry has a new glow these days, which it has acquired through the light of a desire to understand it, rather than it being an educational formality. But more of insights resulting from (Mr, Ms, Dr, Prof...?) Sze’s words at a later date.

I spent this morning sitting out on the deck, in the unstinting sunshine, finishing reading The Periodic Kingdom, and frankly now have a more fundamental understanding of the nature of chemistry than ever before, thanks to the combined work of Peter Atkins, who wrote the book, and Martin Blissett at the ATI who suggested / loaned it to me. (The more detailed reference for those who are interested is Atkins, P; The Periodic Kingdom, a journey into the land of the chemical elements; 1995; Weidenfeld &Nicolson, London). I have been doing some investigations into group IV chemicals over the last weeks (although P Atkins has now informed me that to comply with the IUPAC I should no longer refer to them as that, rather calling them group 14 chemicals, as proposed by the chemists’ committee), since this group contains, among other interesting things, silicon. Silicon, which is the subject of a significant chunk of my current intellectual and artistic endeavours, is a semiconductor (more about them anon), and as such is fundamental in the world of contemporary technology. But today the striking interest, to a biologist at least, is that carbon is also a group IV (or 14) element, and as a result of its properties as a member of that group has qualities that are indispensable for its role in living organisms. I’m going to quote Mr Atkins directly here, as I am taken with his description:
“... the overarching power of carbon to participate in molecule formation, a power that results in such complexity of structure and collaboration that the alliances it forms become alive and can reflect upon themselves [I think he’s talking about us here]. The essential reason for this latent power... is carbon’s intrinsic mediocrity, it’s lack of self assertion. ... it is neither an aggressive shedder of electrons, as are elements to [its] left, nor is it an avid receiver, like the atoms to its right. Carbon is mild in its demands on the alliances it makes. Moreover it is even content with its own company, and can make extensive liaisons with itself, forming chains, rings and trees of atoms. ... By being in the middle, undemanding and not particularly generous, it can spin lasting alliances rather than hasty conspiracies.”

I am under the impression that statistics, at a gross level, will always reduce the impact of extraordinary outliers by attempting to constrain them with the middling throng. As a result average will always be average, no matter how amazing it really is (although maybe I’m skewing this argument to a normal distribution). This notion saddens me, as I (along with the devil) see the wonder in the detail. And yet today I have been taking real pleasure from the thought that a fundamental prerequisite of life as we know it is the passivity of this rather unexciting element; that intrinsic mediocrity is one of the primary components responsible for the bickering goldfinches on the bird feeder, the snowdrops and violets that are pushing up in the garden, bursting with spring, the fire that warms me as I write.

11 January 2011

A photon of understanding

Fabulous date today. 11.1.11

I had hoped, among these words and lines, to track something of the acquisition of knowledge; to observe the process of my learning and pin it, splayed wide, onto this page. But it seems it is insidious, like love, and all of a sudden it is there, with the subtle details of how it arose forever smudged into hazy history. Not that I yet fully understand what it is that I go there to learn, but I believe I am further along that path than I had realised; the words I now read have new thoughts and meanings attached, my view has shifted. And as I tumble down this rabbit hole I see jars and objects on the shelves as I pass that contain wonderous galaxies of ideas and notions, the names of which, scrawled on their labels in myriads hands, I am beginning to recognise, and am able to envisage the taste of. (And yet I know I have a long way to travel before I land, with the bump cushioned I hope, at the end of this mysterious trail.)

I attended a lecture by Goran Mashanovich a few weeks ago, a senior member of the silicon photonics research group. (He is very interested in the process of learning, and uses contemporary, interactive methods in his lectures to encourage it, with the result that he teaches well and scores extremely highly with his students in their feedback). Anyway, I am out of practice at maths and have almost no knowledge of electronic engineering so the lectures of his I’ve attended have basically been beyond my comprehension (in this latter one he spoke of tea and pie circuits, which I’m afraid sounded more like social interactions, to me, than technological advancements). The maths of it was pretty straight forward (so it felt; so he later assured me) and yet still beyond my current capability (though not, I believe, beyond past capabilities), and I came away at the end of the lecture under the impression that I had nearly grasped it.

There was a girl on my fine art degree who made paintings about the sense of being able to feel proximity of objects in darkness, for example walking along a dark corridor and having a sense of the presence of the adjacent wall. I found her work intriguing, and was much taken with the notion of this sense. Somehow I left Goran’s lecture carrying what felt like an analogous feeling – that of almost understanding. I know that I did not understand it, and yet I felt that the point of absolute comprehension was close at hand. Is it possible to determine that? The degree of learning. Does understanding work as a smooth linear progression, where partial understanding is a real entity, decipherable as a distinct part of a bigger thing? Or is it attained in discrete units (photons of understanding?), in which case there is no such thing as partial understanding, and without having received a full photon of it (seeing the light?) one is none the wiser. 

Or is it, maybe, that photons work the other way, and even though at the moment at which a whole one is absorbed (etc) there occurs a luminating epiphany of some sort, nonetheless exposure to a partial one can still provide a sense of light to the receiver?

10 January 2011

Directional transparency

Transparency (and, as it transpires, this is also true of honesty) is not, after all, an absolute thing. It is a matter of the energy gap, apparently. My energy gap is such that I am transparent to X-rays and cosmic rays, but light and heat do not penetrate too far into me.

The passage of light (and other radiations) through things, or their absorption by things, relies on spaces of the right size being available for photons to be acquired as they interact with the thing. If they are not absorbed these radiations either pass on through (for example high energy cosmic rays) or bounce back off the thing being subjected to them. Light in the visible range bouncing off and scattering from things results in us being able to see them – the basis of visual observation. The leaves of the geranium on my windowsill absorb all but the green portion of the visible spectrum (and use this light for photosynthesis); the unused green light is reflected and scattered away, giving the appearance of a green leaf. The flowers of this fragrant wonder, however, absorb all but a beautiful deep crimson, a colour presumably used to entice aerial suckers to come and interact with the soft, velvety petal, to feed on the nectar offered up, and thus to pollinate the plant.

Optical fibres are made of silica (SiO2), which is transparent to visible light. Pure silicon is transparent to electromagnetic radiation of wavelengths greater than 1.1 micron, which is in the infrared, but is not see through in the visible range. Silicon is electrically ‘very good’, but this lack of visible transparency can, I believe, cause problems for those hoping to integrate electronics and optics in silicon.

Glass is transparent in the visible spectrum, so we can see through it (and thus use it for windows), and has a manipulating transparency to infra-red light, as a result of which we make greenhouses out of it and use it for passive solar heat gain in houses. (I must admit that I am unclear as to how heat can pass through a window one way but then not be able to get back out again – directional transparency? Imagine if the same thing happened with the visible light, my greenhouse would become brighter and brighter internally through the course of a sunny day (although I’m not sure we’d be able to see that light from outside the greenhouse – it would be blinding to walk into though), and then slowly the radiance would dissipate and diminish over night, as the light seeped back out into the surrounding dark).

4 January 2011

Invisible light

I walked from Trevan Point to the Rumps in the cold northerlyish wind yesterday; patchy sunlight between thick cloud, lowering to bright rays over the sea and a beautiful sunset. Seeing the colours of the burned-black gorse, fresh yellow flowers, bright turquoise of the wintery sea and myriad greys in the sky got me thinking about the light illuminating the scene. I always envisage visible light as colourless, and yet in reality it is comprised of all colours - every single conceivable shade is included in that transparent ray (or particle) that whistles past me, and of which a small portion is bounced back from the surface of the world to my receptors.

Funny that the light by which we see should be referred to as visible when it is, to us, invisible light.

First day of a new term today, for many; back to the process of learning, of knowledge acquisition, of education.