Tag Archive: ArkFab


There is a companion article exploring the issue from the perspective of environmental monitoring over at ArkFab.

Human influence on the environment has increased dramatically over the last 10,000 years, to the point that some geologists have argued that human reworking of the earth defines a new geologic age, The Anthropocene. (Zalasiewicz et al, 2008) Much of the focus has been on relatively robust, tangible changes in biogeochemistry. Examples include:

  • megafaunal extinction, accelerated erosion (Zalasiewicz et al, 2008) and nitrogen fixation resulting from the spread of intensive subsistence patterns
  • the loss of stratospheric ozone resulting from the release of novel chlorofluorocarbons

However, fleeting and less tangible effects are also important. Two examples are:

  • the light pollution resulting from urbanization and transportation infrastructure
  • changes in the acoustic environment resulting from direct addition of sonic energy and memes, as well as indirect sources.

A year-long composite view of the earth at night, showing human light generation. White lights are cities; blue lights are fishing boats; green lights are natural gas flares, and red lights are ‘ephemeral light sources’, interpreted as fires. Image from  NOAA National Geophysical Data Center – click for source + discussion.

Light pollution, the scourge of urban astronomers, is a well-accepted phenomenon with serious consequences. A 2004 review begins:

In the past century, the extent and intensity of artificial night lighting has increased such that it has substantial effects on the biology and ecology of species in the wild. We distinguish “astronomical light pollution”, which obscures the view of the night sky, from “ecological light pollution”, which alters natural light regimes in terrestrial and aquatic ecosystems. Some of the catastrophic consequences of light for certain taxonomic groups are well known, such as the deaths of migratory birds around tall lighted structures, and those of hatchling sea turtles disoriented by lights on their natal beaches. The more subtle influences of artificial night lighting on the behavior and community ecology of species are less well recognized, and constitute a new focus for research in ecology and a pressing conservation challenge. (Longcore & Rich 2004)

The amount of sonic energy released by human activity is recognized as an urban nuisance as well as an occupational safety concern. It also has recognized ecological effects: urban European robins have begun singing at night, when they have less acoustic competition. (Fuller et al 2007) Frogs have begun changing the pitch of their croaks in order to talk over traffic noise (Paris et al 2009)  In addition to sonic energy, human activity has released sonic memes into the environment. A meme is a self-replicating information pattern; jokes and computer viruses are two examples of memes. A person or computer acquires a meme and then spreads it, through retelling or infected emails. Sonic memes, such as ambulance sirens and cellphone ringtones, have been picked and repeated by songbirds. (Stover 2009) This is very interesting: human memes, the basis of Richard Dawkins’ ‘extended phenotype’ concept, have organically extended into other animals’ extended phenotype. (Recent reports of dolphins mimicking human speech are also very interesting in this context. The reverse flow also occurs, as animal communications are repackaged as ringtones or ambient music.)

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A companion article at ArkFab shares my thoughts on peer review in regards to this project and DIY/community/citizen science in general. 

At long last, the much-anticipated booklet, “CO2 Trouble: Ocean Acidification, Dr. Everett, and Congressional Science Standards” is available and approved for human consumption! Download and share HERE (or at Scribd HERE).

In this document, I have bundled, updated, and expanded my series of essays debunking the congressional testimony of Dr. John Everett regarding the environmental chemistry of carbon dioxide.

It has been designed to be a fairly short (less than 30 pages, including images, appendicies, etc.) and accessible read. It has been challenging but fun to write; I have had to learn a lot about GIMP, Python, Scribus, social networking, and of course ocean acidification to get to this point.

It was also very useful for me as an opportunity to go back through my earlier remarks and double-check my work. For example, I later realized that the documentation which Dr. Everett provides for his CO2 data in part two is ambiguous: Although the citation for the rate data is referred to as “Recent Global CO2”, the URL provided links to the longer record as measured at Mauna Loa Observatory. This confusion had led me in the past to make incorrect claims about some of the figures he presents. Ultimately it was inconsequential to my argument, but it was frustrating to have to deal with such ambiguities. On the other hand, this led me into comparing the Mauna Loa record with the global record (Appendix B) which was an interesting exercise.

In researching this project, I also came across new phenomena I wasn’t previously aware of. For example, while I was calculating historical rates of CO2 change, I ran though the 1000-year Law Dome record and saw this:

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DIY Spectro FAQ

Apparently a lot of people were interested in my spectrophotometry project! It was picked up by several websites including BoingBoing and HackADay. An update is long 0verdue [ed: HERE], but first some answers to questions I got. A few things I should have mentioned (the -photometer actually uses a transmission diffraction grating, which is what you see in those glasses that put rainbows on everything, [eg, these.] They work slightly differently but the principle is the same.) I also left a lot of detail out because I didn’t think people would be interested. Here’s the dirt:

What about the width of the light source? [BB#3; TO comment from James]

As it happens, the shape of the light source is one of the factors effecting the resolution of the device. When a beam of light hits the diffraction grating, ‘copies’ of it get reflected at different angles, and thus get projected to different locations. If the beam is thick, then the red copy of the beam will also be thick, and will overlap significantly with the orange copies. If the beam is very wide, there will be so much overlap that all colors overlap in the middle of the spectrum, and you get a white blur edged with red and blue.

The width of the light source limits the resolution of the device; a thinner light source gives a higher resolution, because there is less overlap between the 'projections' of each color. In extreme cases, there will be significant overlap of most of the spectrum, and the colors will recombine to form 'white' light everywhere except the red and violet edges. Of course, the smaller the slit, the less light gets through...

You reduce this overlap by making the beam thinner. I do in fact do this; it is unpictured but there is a beam-narrowing slit in front of the spectrophotometer, similar to the one in the spectroscope. The ideal setup is an infinitely bright light behind an infinitely thin slit, but this is difficult to accomplish on a DIY scale, though two razor blades can be a good approximation. I used double-layered electrical tape with a ~1.5mm slit cut in it, further narrowed with bits of aluminum. Also, although a smaller slit means higher resolution, it also lets less light through, which can lead to detector sensitivity issues.

You need to remove baseline detector response! [BB#5]

I did ;D What Anon is saying is that it doesn’t make sense to claim that these data are an absorption spectrum: Continue reading

DIY Spectro

UPDATE: There is a newer, more automated version of this project here, and an FAQ section here.

For the last while I have been concentrating on a project: developing an easily built spectrophotometer for low budget and DIY laboratories.

At the subatomic level, light is made up of entities called photons. Photons are electromagnetic vibrations; the speed at which they vibrate (in vibrations per second) determines the color of the light. Red light has a relatively slow vibrational frequency, while purple light has a faster one. The frequency also determines the energy that the the photon has: the faster a photon vibrates, the more energy it has. A photon of violet light has more energy than a photon of red light.

White light, like that from a halogen lamp, contains photons of a lot of different frequencies. However, you can use a prism or a diffraction grating to break that light up into its component colors, to get the familiar rainbow:

 

The spectrum of a halogen lamp

The above image is from a spectroscope I built during development. It’s made from bamboo, duct tape, pieces of beer cans, and an old CD: the perfect combination of steampunk, cyberpunk, and drunkpunk.

 

I did this spectroscope myself.

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