Noon at night

Full moon... and city reflection

Last week a big storm system moved through southern Ontario, dumping a pile of snow in its wake. I love being out in the country for snowstorms, both during and after. It doesn’t get much prettier than giant fat snowflakes falling against a backdrop of evergreens and red dogwood. Once the storm has passed the whole world is blanketed in a smooth sheet of pristine white, untouched, as yet, by little feet. All the branches are lined with snow, creating definition among the forest trees.

That night was a full moon, and as I was going to bed I stopped to admire the long shadows of the big maples in the front yard, cast across the sparkling snow. As I often do, I tried to capture the scene with my camera. Although an interesting image, I’m not sure it really did justice to the magical feel of it.

The sky in the picture is pinkish-purple. When I took the picture, standing at the window with the lights off, looking out over the front yard, it was most definitely dark. The above image was shot with a 15 second exposure, enough to try to capture the crispness of the shadows and the brightness of the snow. In using such a long exposure, I also managed to capture some of the ambient light being given off by the town to the south.

City of Light

It’s called light pollution, and it’s as common and wide-reaching as people are. Although in rural areas, such as my parents’ home, it can be very subtle to discern (most of the time it’s manifested to our eyes as simply a rosy glow along the horizon), in the big city it can be incredibly bright. One lightbulb may not cast a lot of light on its own, but when you combine hundreds of thousands all together… Well, think of it as the difference between the candles on the cake brought in for your niece’s 6th birthday party versus those on your uncle’s 60th. You could probably illuminate the room with your uncle’s cake. The above photo of the city of Toronto, taken from a distance at night, really gives you an idea of the effect. The glow of the lights hangs over the city like a layer of smog.

Today we got another big dump of snow. If you believe what they said on the evening news, it could be record-breaking for amount of snowfall in a single day for the Toronto area (I’m sure places north and west of us would scoff at the paltry amount). It continues to snow even now, having begun before dawn today. It should be done by the time people are heading out to work tomorrow, but it will be a considerable accumulation.

City light reflection

Because it’s still snowing, it’s overcast. Clouds throw another wrench into the mix as far as light pollution goes. The above photo was taken using a similar 15 second exposure as the top photo, pointed out the side window instead of the front, but still generally toward the south. Instead of the pale pinkish-purple sky of the first image, however, we have a deep, vibrant orange. The trees are darker because there was no moon to illuminate them, but the sky is glowing. You can also see the streetlight at the home across the road (private, installed by the homeowners when they first moved to the country, for security I guess; it’s the only one on the street), and a thin ribbon of light as a car drove by during the long exposure (which I think is neat).

Clouds have excellent reflective properties, both of light and of heat, which is why overcast days are often warmer than clear, sunny days. They reflect a lot of the warmth trapped in the atmosphere back down to earth. Similarly, they also reflect a lot of the light cast on them from urban centres. If you’re out walking at night, particularly near town, you’ll find it easier to navigate on overcast nights than on clear ones because of this.

Light pollution in Toronto

This effect is amplified when you’re inside the light source. Our apartment sits over the garages of the building, and the floodlight illuminating the small parking lot also casts a lot of light on the surroundings. This is particularly noticeable after a good snow, such as in the above photo, taken last week. It can be so bright it almost seems like dawn. The exposure for the above photo was a paltry 1.6 seconds. I started washing the image out if I went any longer than that.

Light pollution in Toronto

This photo was taken looking south (from the west-facing windows) toward the lake from the apartment. There’s a very noticeable darkness on the horizon over the lake. I suspect (although I don’t know for certain) that this is the delineation between the clouds over the city, casting back all the light, and those over the lake, where there is no light to cast back.

(stars as seen looking lakeward from Tommy Thompson Park on the Toronto lakeshore; long exposure, of course)

When I was a kid I would go out stargazing with my dad, picking out the constellations from the dark starry sky. The big city and neighbouring local towns have all grown since then, and with the increased night light, the stars are fewer and harder to see. This change is noticeable to me, even within my relatively short lifetime, and I find it sad to think of what the sky will be like in another 20 years. When I travelled out to British Columbia a couple years ago, I lived in a small trailer in the bush in the Okanagan Valley. The sky resembled, to quote Incubus, “a backlit canopy with holes punched in it.” It was gorgeous, and something quite unlikely to be seen with any regularity in the Toronto area again.

In summer 2003 the eastern seaboard suffered a “Big Blackout”, and cities were completely darkened, treating their residents to a light show the likes of which probably many of them had never seen. On March 29 this year, at 8pm, Toronto will participate in Earth Hour, a one-hour event where (ideally) the city will turn its lights out on a scale approaching the Big Blackout. The idea behind this is to make a statement to governments and other powers that be on energy usage and climate change, and related environmental issues. Although it’s still a month and a half away, pencil it in on your calendar on March 29 to turn your lights off then head outside to enjoy the sky.

Icicles in reverse

Ice cube spike

About a year ago, in late winter, Blackburnian called me into the kitchen to show me a bizarre ice cube he’d discovered in the tray in the freezer. It looked like a normal cube, except that at one side, sticking out of the top at a slight angle, was a narrow spike of ice about an inch long. It was the strangest thing, looking a little like the little back-splash of water when a droplet hits the surface, frozen in ice. But obviously that wasn’t possible, so my hypothesis was that a hair had fallen into the cube while it was still liquid, and the water molecules had frozen up its length in a capillary action (where the chemical bonding properties of the water molecule cause it to crawl up a surface a little). Although I could see no hair inside, I’m blonde and figured it was just hidden. After all, what else could cause such a bizarre structure?

This afternoon I opened the freezer door to pull out tonight’s dinner to thaw, and happened to notice a freshly-frozen ice cube tray on the freezer door. And within this tray was – you guessed it – another ice cube spike. Well, what are the odds that another invisible hair had fallen into the cube tray? Particularly since I so rarely fill it, and Blackburnian has dark hair. So this time I did some poking around. Sure enough, it seemed to be a fairly common observation – under the right conditions.

Ice cube spike
(last year’s ice spike)

Water begins freezing at the edges of its container (the banks of a pond, or the sides of the ice cube tray), where the solid acts as a catalyst (remember the frost?). As the top freezes inward, it creates a little hole in the surface of the ice. At the same time, the ice cube is also freezing along the sides and bottom (doesn’t happen in a pond, but in small, contained bodies of water where the cold reaches all sides, all sides freeze at the same time). Ice is less dense than water, and takes up more space than the water does when it melts. So as the ice cube is freezing from the bottom and sides, the still-unfrozen water inside is getting squeezed out through the hole in the top of the surface.

Like an icicle grows through the addition of more ice as the water droplets running down the outside freeze, so the ice spike grows as more water is pushed up through the hole and freezes at the edges, creating a narrow tube or straw, through which more water is pushed and subsequently freezes. Some ice spikes can grow quite long if the pressure is slow and steady, and the temperatures mild enough to result in slow freezing speeds of the tube. The tube closes off when either the inside of the cube is completely frozen (no more water to force out), the temperature gets too cold (the water on the spike freezes faster than in the cube and seals it off), or the walls of the tube narrow beyond a certain point (where the water coming up forms a bridge between the walls instead of adding to the walls as it freezes).

Ice cube spike

You’d think that given the nature of an ice cube this ought to be seen more frequently, but it actually takes fairly specific conditions to produce the effect. For one, the water needs to be distilled, or low in dissolved solids (such as salts and minerals, typically found in most well or city water). The salts and minerals in the water will act as a catalyst to freezing so that the ice isn’t growing only from the walls of the tray (and therefore isn’t creating the same pressure on the water inside), although not all of these dissolved solids affect ice formation in the same way. We use a Brita filter, and it’s possible that it had removed enough of the minerals out of these couple ice cubes to encourage the spike to form.

Your freezer also needs to ideally be just below freezing – cool enough to encourage the water to freeze, but not so cold that it will freeze quickly. However, ice spikes will also form under “supercooling” situations, where lukewarm or room-temperature water is placed in a very cold environment (-10 to -20 oC, such as outdoors in winter, or in a freezer, particularly chest freezers which maintain colder temperatures) and is brought to freezing rapidly. In these cases a slightly different sort of ice crystal forms on the surface creating sheets of thin ice, including some that jut into the water below. These crystals, like those in snowflakes, form 60 degree angles creating a triangular opening in the surface, and the sheets hanging into the water form the base of the ice spike as it grows, often resulting in strange angles depending on the way the sheet was hanging.

The Discovery Channel’s show Daily Planet aired a segment a few years ago on the phenomenon after it was sent in by a viewer in Courtenay, BC, who discovered a spike in her birdbath. This site, by Professor Stephen Morris of the University of Toronto, also has a lot of information and links to photos and other sites.

You can try making your own ice spikes simply by freezing distilled water (not tap water!) in an ordinary ice cube tray in your freezer. Good luck and have fun!