Bamboo – the grass that can be almost anything.

So what can I toss into a stir-fry, play a tune on, build scaffolding out of or put on a shirt made from? The answer is bamboo – the fastest growing member of the grass family. Right now I have several hand towels made of bamboo and a bag of bamboo shoots in the freezer. I'm debating planting some in my front yard (although it never looks healthy in neighboring yards so I might not) and flooring my house in it. Bamboo sounds like a miracle plant, but like everything it has a downside.

Wikipedia tells me that grasses can be considered the most important plant group. This group includes the grain and cereal crops people cultivate for food, wild grasses eaten by livestock or other animals, as well as bamboo, from which almost anything can be made. Bamboo shoots can be eaten, they are very tasty in a stir fry and they can be fermented into a sweet wine. Like other grasses, when bamboo is harvested it is cut, not dug up, so growing bamboo can add stability to soils and prevent erosion while producing a viable harvest.

Pesticides are not commonly used when cultivating bamboo. There are a few pests out there that like to munch on bamboo (I suppose pandas would be one), but they can be dealt with manually by cutting out the infested stems. Once the bamboo is harvested, pests become more of an issue. To prevent this, some large-scale operations treat the bamboo with a mixture that can include DDT. Dark flecks in the bamboo is often a hint that that bamboo has been treated this way. Once harvested, bamboo needs to cure. There are many ways this is done from soaking in water for months to burning techniques – it can even stored vertically and allowed to dry naturally. So, now the bamboo is ready to go.

Paper could be made through techniques mastered by the Chinese eons ago. Flutes could be made; I love the haunting sound that a bamboo flute can emit – it seems unearthly. Since I have no musical ability, I won't be making my own flute even though many websites exist to tell me how.

Bamboo fiber is becoming more and more available and is often touted as an eco-friendly option. Is it better than other fibers available? The answer is maybe; it depends how it was made. Bamboo can be made into fiber by two methods. The first, eco-friendly option is similar to how flax and hemp fiber is extracted. Stalks are crushed. Then natural enzymes take over breaking the fibers down more. Finally, the fibers can be combed out and used. The second method is essentially the same as how rayon is made from cotton. Harsh and toxic chemicals are used to break down the stalks and mechanical spinners extract the fibers. The label on my hand towels only say they are made from bamboo, not which method was used in the making of them.

If the first method is used, bamboo has a lot going for it. Like other natural fibers it is biodegradable. From the same sized space, bamboo produces ten times more fiber than cotton while requiring significantly less water. A website selling bamboo clothing says that bamboo fabric is soft (which is true of my towels), anti-fungal, anti-static and even cuts out most harmful UV rays. So, if you need a new shirt bamboo produced the right way is a great option. However, I don't recommend you throw out all your cotton shirts and replace them with bamboo - sometimes the most environmentally sensible option is to get the most wear and use out of the things you already have. But when your cotton shirts wear out, go shopping for a naturally prepared, bamboo shirt.

Drifting Spiders

I've been reading Rachel Carson's 'The Sea Around Us' after discovering it among my books during my recent move. My grandfather gave it to me when I first expressed interest in ocean science many years ago. The book was actually presented to him in the 50's as recognition of meteorological measurements he took as a mariner. When I first was given the book I started reading it, but didn't finish so when I found it this time I thought it was time to sit down and read the whole book.

In her chapter on island formation, this intrigued me:

So bare and desolate that not even a lichen grows on them, St Paul's Rocks would seem one of the most unpromising places in the world to look for a spider, spinning its web in arachnidan hope of snaring passing insects. Yet Darwin found spiders when he visited the Rocks in 1833, and forty years later the naturalists of H.M.S. Challenger also reported them, busy at their web-spinning.

Spiders? How did they get there? St Paul's Rocks are near the equator right in the middle of the Atlantic Ocean. Discovered by the Portuguese navy in 1511 by accident, that is by crashing into them, these islands are now part of Brazil. They jut up from the ocean floor 800 km off the coast of South America, and are made up of 15 small islands and rocks with a highest point of 17 m. This group of islands is one of the few places (Iceland is another) where the mid-ocean ridge breaks the surface. Currently, the Brazilian Navy has a science station and a lighthouse on the islands.

On the 16th of February, 1832 the H.M.S. Beagle stopped at St Paul's Rocks and Darwin had an opportunity to explore. His inventory of life included: 2 types of sea birds (boobies and noddies), a type of large crab, a fly, a parasitic tick (preying on the birds), a moth that survived by eating feathers, a beetle, a woodlouse and lots of spiders. He also observed that not a single plant or lichen could be found, since that time mosses and grasses have found their way to the island, probably helped by people.

Not including the crab, the only life form on the island that can't fly or hitch a ride is the spider. No spider can fly, even though there is an Australian spider called the flying spider. Flying spiders are tiny with pretty blue and green iridescent colouring. Their abdomens have flaps that can be extended allowing them to glide when they leap, increasing their range. But even an ability to glide wouldn't help spiders colonize remote islands.

Young spiders are forced to move away from their parents and siblings to avoid competing for food and other resources with them. To begin their journey, a spider climbs to a high point, and then point its abdomen into the air. It releases a long filament of silk that is picked up by the wind, taking the little spider up into the sky. Drifting spiders have been found thousands of meters above the remote Hawaiian Islands. Or according to Rachel Carson:

Airmen have passed through great numbers of the white, silken filaments of spiders' 'parachutes' at heights of two to three miles.

Drifting is a great way to travel as it requires no energy expenditure from the spider. I wonder how many of these drifting spiders eventually find a suitable home?

Sidewalks - where worms commit suicide on wet days

I walk to and from work, a round trip of 6 km or 3 km each way. It isn't a long walk, but, enough time for a little exercise and lots of thinking before I get to the office. The walk home allows me to unwind. Since I live in an urban area, the sidewalks are paved the whole way. Everyday, I see weeds poking up through cracks, worms committing suicide on rainy days, and the changing colour between wet and dry concrete.

A paved sidewalk probably wears out my shoes and knees faster, but, do sidewalks make us safer? Apparently the U.S. Department of Transportation has studied this (I'm sure other nations have looked at this as well). They found that the presence of a sidewalk, along with the speed limit, reduced the likelihood of a vehicle hitting a pedestrian by 88.2 percent – as a pedestrian, that's a big difference.


On a rainy day sidewalks look darker than when it's dry. Concrete is a matte surface, which is not shiny at all. Light is reflected diffusely off a matte surface, scattering in all directions as shown in the diagram. Dry concrete looks rather featureless and the same from all angles.

When the concrete is wet, a thin coating of water forms a smooth and glossy layer on top. A portion of the incoming light is reflected by the water layer, meaning less light reaches the concrete. The concrete now looks darker because less light reaches it to be absorbed. As an added feature, multiple reflections within this thin water layer highlights surface features in the wet concrete that can't be seen when it's dry. When the weather is frosty, a near invisible slippery film of black ice can form, which looks just like wet pavement and is a result of the same optical tricks.

Frost heave can create cracks in the concrete as can roots of nearby trees. I suspect small earthquakes could also form cracks. Once there is a crack, plants move in and take advantage of this new growing space. Ultimately they widen the cracks and more plants move in, creating a cycle that can destroy a sidewalk. Where I live dandelions and chamomile seem to thrive in these cracky environments.

So, why do so many worms commit suicide on sidewalks? When it rains, the worms' underground home fills with water. Since worms breathe through their skins, to avoid drowning they come up to the surface. Once in the air they can breath again. If they wander about and end up on the sidewalk they may not find their way back into the ground again, ultimately drying up when the sun comes out or forming a robin's lunch. Good for the robin I guess.

Cadmium

I was working out of my office yesterday, in a building that is basically a line of industrial workshops. I was doing some necessary but messy work and when I was done I swept out my workspace. The floor was dusty and by sweeping I put that dust into the air and no doubt breathed some of it in. It turns out that in one of the workshops at the end of the building is contaminated with cadmium. I doubt that sweeping the floor at the other end of the building exposed me to much, but I have worked with cadmium paints in the past so I did some looking into its toxicity.

Discovered in the 1800's, cadmium is a metal that has a bluish-silver look to it. It is soft and easily manipulated and can be a byproduct of zinc production. Since our bodies have no use for this metal, it is toxic to us even at low concentrations. To me the scariest part is that cadmium bioaccumulates – there has been reports of cadmium poisoning from crops downstream of mines. Ingesting it over a long period of time can result in kidney disease and various types of cancer – but inhaling cadmium fumes can be fatal relatively quickly.

Even with its scary side, cadmium is interesting stuff. I first encountered cadmium as a pigment component; it makes brightly coloured yellows, oranges and reds that last for centuries without losing their original bright hue. These shades replaced older, not light-fast pigments such as vermilion (mercury sulfide). Cadmium has also been used as a corrosion-resistant coating for steel and as a stabilizing compound in plastics.

Because of its toxicity, cadmium use is in decline. There are now non-toxic replacements for the cadmium pigments, it has been phased out of plastics and many of its other uses. Currently, most of the cadmium produced goes into nickel-cadmium batteries, which leaves a worry of how these batteries are disposed of.

Playing With Fire

I remember making candles when I was a kid. We filled empty and cleaned food cans with paraffin wax – the stuff that comes as a opaque block about the size of a deck of cards. The cans were then put into a bath of boiling water until all the wax melted. A few crayon stubs were added to each can, creating an array of colours. I tied a thick piece of cotton string, destined to be the wick, around a pencil for easy dipping. Next, I started dipping. With each dip another layer of wax clung to what was already there, increasing the diameter of the candle-to-be. I rotated through the colours, creating what must have been gaudy candles. When the candle was thick enough to stand on its own, the fun part began: we could light them.

A flaming match held to the exposed end of the wick has enough heat to vaporise wax within the wick and react with the oxygen in the air. Within moments a teardrop-shaped yellow flame flickers to life. The heat from the candle's flame melts the wax, and the melted wax is drawn up by the wick, sustaining the flame. At its hottest, a candle's flame can reach 1400 degrees Celsius. What is actually happening? Heat vaporizes the wax creating a gaseous cloud where the combustion takes place. Combustion is a series of chemical changes that converts molecules into new combinations – however this process isn't totally efficient resulting in the production of heat and light. Light, along with its cousin heat, are part of the electromagnetic spectrum and signify the release of excess energy.

Candles used to be one of the main ways to create artificial light. However, compared to an incandescent light bulb, a candle produces 100 time less light, which is probably why candles are now mostly used to set moods, conduct rituals and provide light in power outages. I don't often light candles, after all they are one of the leading causes of residential fires and they put soot and chemicals into the air I breathe. Some candle shops are so over-scented I can't even stand being in them: I can't imagine what my house would smell like if I burned their candles! But, when I do have a reason to light a candle, I enjoy watching the flickering flame – I find something about it quite mesmerizing.

One of the discoveries from experiments conduced in space is the importance gravity has in the formation of a flame. Here, in my mundane earth existence, when I light a candle the hot gases formed are less dense than the air around them, and so they rise in a process of natural convection into the familiar teardrop shape. This natural convection hinders complete combustion, so soot forms which makes the flame yellow. Out in my funky futuristic spaceship, where there would be no gravity (unlike the spaceships on TV), natural convection wouldn't occur, and I would get a perfectly spherical flame. In space, my flame would require ventilation or it would smother itself. Its temperature would be evenly distributed and combustion would be complete, so soot would not form. The flame would be bluer and more efficient.

Another effect of gravity on a candle's flame is the flickering. The frequency squared of a flame's flickering is proportional to the force of gravity over the diameter of the candle. Meaning that a candle with a smaller diameter would flicker at a faster rate than one with a larger diameter. So a candle on another planet (with different gravity) would flicker at a different rate than the same candle on earth. A candle on my spaceship wouldn't flicker at all (I would have to be mesmerized by its pretty spherical blueness instead).