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Category / Hardware

CloudFTP and projects 14 November, 2011 at 1:48 am

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Blackle holes? 24 April, 2008 at 7:13 am

I’ve been reading about black holes recently, you know, those things that Hawking eats for breakfast, but Blackle is something else: a rebadged Google search, painted black “to save energy”, because the white background of the usual Google search pages uses too much power.

What the?.. Sounds like the kind of pseudo-scientific slight of hand or turn of phrase that might make the writings of the Saturday-morning-doorknocking witnesses on evolution (or lack thereof) seem plausible.

An LCD panel uses less power than an equivalent CRT (well, let’s say most of the time – there may be some extreme examples where this is not the case, but not that I know about). LCD = good. LCD screens work with a backlight – a white light behind the (sub-)pixels, which produce the coloured display we see by blocking some of the white light: if you block the red and the green, you’re left with blue. As a side note, now that I think of it, it’s ironic that this ‘emissive’ colour mixing property we typically associate with screens is, in a sense, actually an absorptive colour mixing technology! Perhaps it is better to think of it as transmissive, as opposed to reflective colour mixing (eg CMYK printing). Actually, though, the LCD’s white backlight is separated into red, green, and blue subpixels before the ‘liquid crystal’ part, so each LC cell only deals with one of red, green, or blue light, and it is our eyes that do the actual mixing (this is called optical mixing), such as is with pointillism or divisionism (chromoluminarism) of the impressionists in the art world.

An LED display (think big, like an outdoor display) has red, green and blue lights (maybe white as well), so is an RGB(W) display, for which one might expect having less lights on (ie more black and dark colours) to require less power. A LCD screen (such as in most laptops and most flat-panel displays) is, in a sense, a minus-RGB, or anti-RGB device, but does blocking the light take more or less power than letting it through? That I wasn’t so sure of, so I had a quick read of the technology behind LCD displays before keying the following message to Blackle via their contact page:

On LCD technology…

“The optical effect of a twisted nematic device in the voltage-on state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, these devices are usually operated between crossed polarizers such that they appear bright with no voltage (the eye is much more sensitive to variations in the dark state than the bright state).”

Given that most (if not all) LCD screens are probably twisted nematic devices, and producing black on such a device requires application of a voltage (, then surely displaying black instead of white uses MORE power, not less.

I’m sure you are already well aware of this, so am wondering why you don’t just drop the pretending that black screens use less power.

Do you really just not give a shit and it is about making money from the advertising?

Excuse my French (and, to the French, excuse my English; I’m aware that swearing in French is so much more expressive) – a liberty taken as this Blackle caper is apparently Aussie (based in Sydney), and it only seemed proper to show some local concern.

With a little more reading I got to the part about ‘vertical alignment’ LCD’s, which are black in the natural (no voltage applied) state. At this moment I don’t know if that is common, as compared to the opposite voltage requirement suggested earlier as being the most common. It is doubtful that I’m the first person to have such musings (maybe if I now go and do a search… just to, you know, save some energy). I’m supposing it is similarly doubtful that I will receive a particularly meaningful reply. If you ask me, using a bunch of computers (Blackle’s) to process and re-serve search results that have already been provided by a bunch of other computers (Google’s) sounds like using more power than any perceived, perhaps even imagined, display wattage saving.

Meanwhile, on the subject of black holes, I’m currently confused by the notion that a black hole is something that exhibits extremely high entropy. Evidently I wasn’t paying enough attention at some point… If an ice cube has lower entropy than the ice cube when it is melted (water), how can something even more dense, more localised (the probability of a particle being found far off in the universe), less able to change its arrangement with respect to the particles around it (er… this is a pretty vague assumption, given that things are supposed to be ‘weird’ in a black hole!), have higher entropy? Sneaking a peek just now on Wikipedia, I read,

Jacob Bekenstein and Stephen Hawking have shown that black holes have the maximum possible entropy of any object of equal size. This makes them likely end points of all entropy-increasing processes, if they are totally effective matter and energy traps. Hawking has, however, recently changed his stance on this aspect.

Hmm… I don’t know/understand Hawking’s original stance, nor his new one, but it’s nice to know I’m not the only one that isn’t so sure! :o)

-subpixel (subtractive-RGB!)