Tuesday, September 27, 2011

Shedding Light

Something happened over the weekend; something wonderful. Something that many have been eagerly anticipating for some time now, and many will rejoice in for months to come. New Zealand was gifted an extra hour of sunlight in which to enjoy the evening. Oh sweet Amun, God above, your brilliance shall be basked in with added euphoria and duration. In short, I love summer. Nay, I despise winter. Perhaps that's unfair though, there are things about winter that I wouldn't want completely removed from my life. Wood fires crackling away while the rain sheets down the windows. Those crisp, sunny days when your dragon's breath hangs in the air as you wrap your scarf ever tighter. Snow gently settling on your skin as you try and convince yourself that it's not just regular sleet. There are some things that only winter can provide. However, there are things that I could do without. One thing in particular: a noticeable absence of daylight.
So it was that I found myself a week or so ago discussing the upcoming blessing that the Department of Internal Affairs was about to bestow upon us. I mentioned that I am always amazed how, sitting in the darkness at 7pm on a winter's night, it's hard to imagine a time where there is still light at 10pm. At some point during the fits of derisive laughter that subsequently surrounded me, I started to think that maybe those I was with didn't necessarily agree with my contemplation. It turns out they thought 10pm was a bit of an exaggeration. Never one to doubt myself in the face of unanimous doubt, I was convinced that it was, at most, an optimistic rounding error. Mostly because I clearly remembered thinking on one night last summer, at around 10pm, that there was still light where six months prior there had been none. I was unable to broaden their minds to the possibility, so it was dropped and the conversation moved on.
Not for me though. Never one to pass up an opportunity to procrastinate at work, I set out to prove, if possible, that the summer months ahead held more daylight hours than my disbelieving companions could fathom. Where else to start a search for such proof than the US Naval Observatory. If there's one thing the US do well, it's providing government websites that generate tables of data which can be openly interpreted to prove a point. I'd used such a service before when some insisted that sea temperatures had varied significantly since we were children (they hadn't; data not blogged).
Ferreting through the tabular possibilities, I chose to focus on three measures of 'light': sunset, civil twilight and nautical twilight. Sunset you should all know about already...I hope. Civil twilight can be defined as the limit at which terrestrial objects can still be clearly distinguished and outdoor activities can be carried out without further illumination. Nautical twilight is defined as the limit at which the horizon is indistinct, however ground objects may still be distinguishable. So, without further ado, I present to you a graph:

As you can see, 10pm may have been an optimistic rounding error. However, at the height of summer (light-wise, not temperature-wise), there is still enough light to distinguish ground objects at 9:53pm. I'd say that falls pretty damn close to my original contemplation. Good enough for me anyway. I can relax, safe in the knowledge that a little over 2 hours before we welcome in 2012, I will be able to walk outside, point to the ground and say, with absolute confidence, "that, my friend, is an object".

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