Spider plants

A spider plant inhabits a corner of my home office, in fact I can't remember a time when I didn't have a spider plant somewhere in my home. I poached this particular plant from an off-shoot of a friend's plant and it now has an off-shoot of its own. Based on my reading about spider plants, I think I'll pot up the new off-shoot and create another plant.

Spider plants, or Chlorophytum comosum, originally came from South Africa to become a very common house plant. Their tolerance to some neglect makes spider plants a great plant for busy folks. I don't know what spider plants look like in the wild, but mine is the typical domestic variety with long, spikey green leaves with a white stripe up the middle. I've also seen spider plants with solid green leaves. It isn't my prettiest plant - the tips of the leaves tend to go brown (I hear regular fertilizing can help prevent this) - but what the spider plant does for my indoor air keeps me growing them.

Nicely insulated houses, like mine, can have significantly more polluted air than the outside. In the winter, when windows and doors are kept closed, these air pollutants can build up. Fortunately, cleaning up indoor air has been extensively studied by NASA because an extended space mission can't possibly bring enough air for the whole trip – so the air needs to be cleaned and re-used (the same hold true for water in space).

In a house or office building the most common pollutants include carbon monoxide, formaldehyde and benzene – each comes with its own negative effects. Plants provide an easy, low energy way to remove air pollutants. Since this is not a new idea, a technical term exists – phytoremediation, which is defined as the use of plants to remove environmental pollutants or render them harmless. The most effective plants for dealing with air pollution include: philodendrons, golden pothos, spider plants and chinese evergreens. My spider plant can effectively remove lots of carbon monoxide. Some say a spider plant removes about 560 micrograms per hour of formaldehyde (ref). They go on to say that a spider plant can remove all the formaldehyde in a room in under 4 hours, but, it didn't provide any back up data so I'm suspicious.

More than just the plant does this good work, microbes found in the soil also aid in removing pollutants. To create an optimized plant filter combine the plant and its associated soil microbes with activated carbon* - a combination that is already available commercially.

There is another side though – some argue that plants as air filterers are not that effective in real world rooms (as opposed to controlled conditions in a lab). Plants also increase humidity in a room, which can lead to mold issues if you aren't diligent. I tend to have lots of plants – I enjoy seeing them and believe they improve air quality, although perhaps not as much as some say they do. I think a reasonable additional step is to also avoid adding chemicals to your indoor environment (like cleaning chemicals or particle board furniture) and to air out rooms whenever the weather permits.

*As a tangent – what is activated carbon? It's a small carbon chunk with an extremely rough and porous surface. This creates a huge surface area for the size of the chunk, according to wikipedia: just one gram of activated carbon has a surface area in excess of 500 square meters. This huge surface area is available to bind to pollutants (and other stuff).

A bit of space

Let's go on a rocket trip to the moon!
We take out own air and water.
We need special suits, too.
In the sunlight, the moon is hotter than boiling water.
In the shade, it is very cold.
From the moon, the sky looks black.
We cannon hear any sound.
The mountains stand sharp and clear.
There are no plants or animals.
Jumping on the moon is fun.
We can jump six times as far as on earth!

- from Sun, Moon and Stars, 1950 by Jeanette Smith

How our understanding of things change with time is always interesting. It was once believed (before telescopes) that the moon as a perfectly smooth heavenly body. By 1609, Galileo Galilei looked through one of his homemade telescopes at the moon and saw that it was not smooth. Over the next century the craters were mapped and named.

One of the motivations for William Herschel (1738-1822) for making bigger, better telescopes was to observe life on the moon - at one point he believed the moon teemed with life. Eventually, with one of his better telescopes, he discovered the moon wasn't inhabited - at least no cities were to be seen.

The above poem is from a children's book written back in 1950, before anyone set foot on the moon. This poem got it right. Within twenty years of its publication astronauts landed on the moon and found it to be a dusty airless place.

Insect wings

I'm fascinated by iridescence - I wrote about it here and here. A recent study of the iridescence of insect wings when viewed against dark backgrounds was conducted and the resulting pictures are fantastic. Check it out here or here.

Here is a photo I took yesterday of my jar experiment (I started it here). I'm now eleven days in and the water inside the jar still looks slightly yellow. I don't think there has been any change so far. Perhaps the jar should be moved into direct sunlight (which isn't possible in my office).

Another type of scattering

Clouds are mists drawn up by the heat of the sun, and their ascension stops at the point where the weight they have gained is equal to their motor power
- Leonardo da Vinci

The weather has changed outside. We had almost a week of beautiful but cold, sunny days. Now, clouds have rolled in, changing the sky from beautiful blue to drab gray. Have you ever looked up at a cloudy sky and wondered why the clouds are white? Alternately, have you ever looked at the foam of a dark beer and wondered how the foam could be white while the beer is dark? The answer lies in how light interacts with water droplets in clouds and tiny bubbles in beer foam.

The average size of a water droplet is between 0.01 and 0.02 mm, with the largest ones about 0.15 mm (from 'The Field Guide to Natural Phenomenon' by Keith Heidorn and Ian Whitelaw) and they are transparent. Cloud colour results from an optical phenomenon. Since water droplets are similar in size to visible light wavelengths, when light passes through the water droplets all wavelengths are affected the same way. This optical phenomenon is very different to the preferential blue scattering from gas particles in Rayleigh scattering that make the sky appear blue. The effect of scattering each wavelength of light in the same way is called Mie scattering after Gustav Mie, the German physicist who figured this out (there are others who independently came to the same conclusion but didn't get the phenomenon named after them). In Mie scattering all wavelengths scatter equally, making clouds appear white since all the wavelengths are present in the same amounts. In a thick bank of clouds, no direct light makes it through; instead all colour results from diffuse radiation. Thick clouds may appear in menacing shades of gray.

The foam atop of a freshly poured beer is composed of uniformly sized bubbles suspended in beer (from 'Does Anything Eat Wasps? And 101 Other Questions' edited by Mick O'Hare). Each tiny bubble is filled with air with a lower refractive index than the liquid around it. As a result, the bubbles act like magnifying glasses in reverse, where light that enters the bubbles is scattered in different directions – another example of Mie scattering. Reflections off the bubble's surface adds another layer of scattering. Both scattering effects created by each bubble is compounded in the foam. Since each wavelength of light is affected the same way, the fraction of light that makes it out will appear white, that is all wavelengths are equally present (The end result might be slightly yellow if the beer surrounding the bubbles absorbs some of the light).

Light hitting dust, smoke or pollen can also experience Mie scattering. This effect also explains why milk is white.

A new year and an experiment

When I woke up this morning there was a heavy frost on the ground. This photo is of the frost on the last of my kale – the same kale as this picture (I haven't eaten it yet, but will soon).

I've decided to conduct an experiment directly out of 'how to be an explorer of the world' by Keri Smith. It's exploration #52 – miniature ecosystem. What I've done is collect a jar of water out of my aquarium (I was doing a water change) and set it on my desk. I'm going to watch it to see if things grow. I'll post photos along the way.

On day two, all I have is slightly yellowed water.