Light Pollution and Dark Skies

The world is full of the unintentional consequences of human activities. Light pollution is one of them. Where can you go to escape it?

We’re contending serious problems because of climate change, the release of chemical compounds into our environment that mimic hormones, the extinction of many, many species of animals and plants, and the list goes on. The overwhelming majority of these problems are unintentional. No one sat around thinking what a great idea it would be to lose a large portion of the earth’s biodiversity by accident. Light pollution is not on the same scale of problems as the present mass extinction crisis, but some species are badly affected by it (especially birds and insects). It has also been recognized as an issue of loss of cultural and scientific heritage.

On 5 December 2012, NASA released a series of images and videos of the earth’s surface as it looks at night, derived from photos taken by a NASA-NOAA satellite. The images have been dubbed “The Black Marble” and received a fair bit of press coverage (http://www.nasa.gov/mission_pages/NPP/news/earth-at-night.html). The images are beautiful, certainly, and you get a real sense of the mass – the spread – of the human population from them. We are truly a global species (David Suzuki has dubbed us a “SuperSpecies” – influencing the lives and fates of most, if not all, other species on earth).

They are also in a sense a map of “Dark Sky” areas – places where you can still hope to get a view of the night sky without the overwhelming warm glow of stray photons from street lamps, cars, highrises – well, you get the picture. Here’s Southern Ontario, a cropped view of one of NASA’s images, a stunning high-resolution composite covering much of North America (the source file is at: http://www.nasa.gov/images/content/712129main_8247975848_88635d38a1_o.jpg).

NASA Black Marble Cropped SO

Southern Ontario at night from space, cropped from a much larger image published by NASA in December 2012, part of the “Black Marble” project. Photo credit: NASA

So, where can you go in Southern Ontario to see dark skies? A great start are areas already designated as dark sky parks or preserves. Here are some main ones, plotted on an inverted version of the NASA photo:

 

Ontario Dark Sky Areas 2012

Prominent Dark Sky locations in Southern Ontario, plotted on an inverted image of the area from space at night. Dark areas represent highest concentrations of light pollution. Original photo credit: NASA

  1. Gordon’s Park, Manitoulin Island (the island follows practices to encourage a “dark sky” environment) –  Designated a Dark-Sky Preserve by the Royal Astronomical Society of Canada
  2. Bruce Peninsula Fathom Five National Marine Park, near Tobermory –  Designated a Dark-Sky Preserve by the Royal Astronomical Society of Canada
  3. Bluewater Outdoor Education Centre – Wiarton, ON
  4. Point Pelee National Park –  Designated a Dark-Sky Preserve by the Royal Astronomical Society of Canada
  5. Torrance Barrens – NE of Orillia. Designated a Dark-Sky Preserve by the Royal Astronomical Society of Canada in November 2012
  6. Lennox-Addington Dark Sky Viewing Area – about 60 km NNW of Napanee, ON

Other areas recommended by some sources include:

  • Binbook Conservation Area – about 16 KM south of Hamilton, a favourite site of the Hamilton Amateur Astronomers
  • Fingal Wildlife Management Area, 30 km from London, Ontario.
  • Bon Echo Provincial Park, 100 km north of Prince Edward County
  • Charleston Lake Provincial Park, west of Brockville

UNESCO has a dark skies designation program underway, noting that dark skies are of scientific and also of cultural value. Royal Astronomical Society of Canada is also promoting the idea of Urban Star Parks – but there seems to only be one designation so far, in New Brunswick.

Links:

Text © 2012, David Allan Galbraith
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Star Stuff? Try “Big Bang Stuff!”

One of the (deservedly) frequently quoted observations by my hero Carl Sagan is that we are all star-stuff. The chemical elements in our bodies – and everything we see around us on Planet Earth – were forged in exploding stars billions of years ago. This is a profound realization. It seems to me that doesn’t go far enough, however.

I started thinking about the origins of the elements in our bodies, and made a connection I haven’t seen elaborated before. To explain myself, I have to explain the origin of the universe first.

The 98 elements that occur in nature are divided up by astronomers into two groups: hydrogen and helium, and “metals:” all the other stuff. Hydrogen and helium were the products of the evolution of matter following the big bang. The “metals” were subsequently produced in a process dubbed nucleosynthesis: nuclear fusion taking place within stars (the process was worked out over half a century ago; the landmark paper is E. M. Burbidge, G. R. Burbidge, W. A. Fowler, F. Hoyle. 1957. Synthesis of the Elements in Stars, Rev. Mod. Phys. 29: 547). The proportions of these things are considered very important. The ration of hydrogen to helium in the observable universe is one of the hallmark tests for cosmology and models of the origins of the universe. Different models predict different ratios, and only the natural ration of about 76% hydrogen to 24% helium gets to decide which models fly.

The other stuff is used to characterize stars, with a measure called metallicity – the proportion of the stuff of the star that is not hydrogen or helium. For example, the metallicity of the sun is approximately 1.8% by weight. Put the other way, the sun is 98.2% hydrogen+helium by weight. This quantity is very helpful to astronomers as it’s a measure of the age of stars, among other things. The older the star, the higher the expected metallicity, as the metals are added by the very process of fusion. Looked at one way, it’s stellar pollution.

This started me thinking about human metallicity. There’s a nice summary on Wikipedia on the elemental composition of the human body (http://en.wikipedia.org/wiki/Composition_of_the_human_body). Here are the top ten elements and the percentage of the body, by weight and atomic proportion, that they represent:

  • Oxygen – 65% by weight but 24% by atomic proportion
  • Carbon – 18% by weight but 12% by atomic proportion
  • Hydrogen – 10% by weight but 63% by atomic proportion (!!)
  • Nitrogen – 3% by weight but 0.58% by atomic proportion
  • Calcium – 1.4% by weight but 0.24% by atomic proportion
  • Phosphorus – 0.78% by weight but 0.14% by atomic proportion
  • Potassium – 0.25% by weight but 0.033% by atomic proportion
  • Sulfur – 0.25% by weight but 0.038% by atomic proportion
  • Sodium – 0.15% by weight but 0.037% by atomic proportion
  • Chlorine – 0.15% by weight but 0.024% by atomic proportion

Ok, so what, I hear you say. Well, look at #3 in this list – hydrogen. Ten percent of our body mass is hydrogen, in chemical compounds like water, sugars, and all sorts of other things. However, two facts about hydrogen are important. First, it’s the lightest element there is, so 10% by weight is a big number by atoms. Second, hydrogen was not made by nucleosynthesis. It was made by the Big Bang itself – and sixty-three percent of the atoms in our bodies are hydrogen.

If we shift our attention away from overall proportions by mass and re-list things by number of atoms, we see a different picture of our own composition. Yes, we are star-stuff – but 63% of the atoms in our bodies have their origins in the Big Bang itself. These humble hydrogen atoms that are the majority population in our bodies – and are the most abundant stuff in the visible universe –  went through stars that exploded, but they came from the Big Bang. In a real sense, so did we.

© 2012, David Allan Galbraith

How does the Moon “Really Look?”

A few weeks ago a friend and colleague at Royal Botanical Gardens, Bill Kilburn, asked me a deceptively simple question. After looking at some of my photographs of the moon, he asked me what it really looked like. I had mentioned that the surface of the moon was actually very dark. Our natural satellite looks very bright to us at night, and it’s easy to over-expose a photo of the moon, especially if you set your camera to an automatic exposure setting.

Bill’s question challenged me to try to take a photograph of the moon that has an appearance more in keeping with our understanding of the moon’s natural reflectivity, or albedo. Before starting to take photos, I needed to think about the matter of light and exposure.

Normally, cameras are calibrated with one of several roughly equivalent systems of standardization regarding their sensitivity to light. The actual standards are established by the International Standards Organization, or ISO, and there are several ways that cameras are calibrated according to the standard. The standards were first established for photographic film, but today the standard (technically, it’s called ISO 12232:2006) applies to the camera itself: its complex systems of light-recording sensors and tiny computers that process the images they record.

The system is designed to allow photographers to match up the sensitivity (the “ISO number”), the shutter speed of the camera, and the aperture or “f-stop” to achieve a properly exposed image. For any given ISO number (higher numbers mean more sensitive to light), proper exposure will be a function of both the shutter speed (faster speeds mean less light gets in) and f-stop (higher numbers mean less light gets in). While that sounds complicated, there is a simple old photographer’s rule of thumb that applies very well: the “Sunny-16 rule.”

Sunny-16 states that on a sunny day, for any ISO number, the image of an object in sunlight will be correctly exposed if the f-stop is set to f/16 and the shutter speed is set to the reciprocal of the ISO number. Still sounds complicated? Here are a couple of examples:

  • If ISO=400 and the lens is set to f/16, then the correct shutter speed is 1/400.
  • If ISO=100 and the lens is set to f/16, then the correct shutter speed is 1/100.

Makes more sense now? Working from this idea, that a sunny scene should be properly exposed under the Sunny-16 rule, I reasoned that if I set my camera to ISO=400, shutter speed = 1/400 seconds, and aperture to f/16, then the image of the moon (which is fully exposed to the sun) should be recorded by the camera as though it was sitting in front of me on a sunny day. There is a big assumption in this, but really only one: that the full thickness of the earth’s atmosphere is actually as transparent to visible light as is a few dozen or hundreds of feet of air would be for a terrestrial scene on a sunny day.

So, armed with these three settings (IS0 400, 1/400 of a second and f/16) I set up my camera and telephoto lens and took some photos of the moon. Here is a frame recorded at that setting without any changes “post camera” to brightness or contrast:

The moon at is "really looks." Photographed on the morning of 6 December 2012 along Fallsview Road in Dundas, Ontario. The camera was set to ISO 400, shutter speed 1/400th of a second, and aperture of f/16. By the "Sunny-16" rule in photography, this should record how the moon would look if it was sitting in front of us on a sunny day.

The moon at it “really looks.” Photographed on the morning of 6 December 2012 along Fallsview Road in Dundas, Ontario. The camera was set to ISO 400, shutter speed 1/400th of a second, and aperture of f/16. By the “Sunny-16” rule in photography, this should record roughly how the moon would look if it was sitting in front of us on a sunny day… minus the blue sky of course.

The technical details of the moon’s brightness are available from NASA (http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html). There are a couple of ways of measuring the albedo, or reflectivity, of a surface, but either way, the moon reflects to us between 11% and 12% of the light that strikes it. This is similar to the albedo of slightly weathered asphalt. There are some areas on the moon that are darker, and some lighter, than this. The relatively new crater Aristarchus, for example, is considered to be the brightest feature on the moon’s surface.

It must also be noted that your own computer monitor or tablet may not display the image “exactly right.” Unless it’s been calibrated for brightness, the gray scales represented in the image may look a little different to you.

The same image, adjusted to bring out detail and make the moon look a little brighter, looks like this:

The western half of the moon, photographed before dawn on 6 December 2012, from Dundas, Ontario. This view is particularly good for tracing the history of astronomy in the names of the craters visible.

The western half of the moon, photographed before dawn on 6 December 2012, from Dundas, Ontario. Adjusted for brightness and contrast to appear more like the moon does to the naked eye than the image above. Note that there are details visible in the western part of the image (to the left) in the original copy that are washed out by this brighter view.

This is a bit more like we’re used to seeing it. Part of the difference lies in contrast at night. Once our eyes are dark-adjusted, we’re much more sensitive to light than we are in the day, and the moon – coal-dark as it is – appears much brighter than we think it does in the daytime.

© 2012, David Allan Galbraith

Enjoy Winter Solstice 2012!

It’s the moment of the Winter Solstice, an event that has both cultural relevance around the world and is an element of a real science (Astronomy). Read something meaningful today, like Ann Druyan and Carl Sagan’s “The Demon-Haunted World: Science as a Candle in the Dark.” (http://books.google.ca/books/about/Demon_Haunted_World.html?id=5QpLlsPPM_YC&redir_esc=y)

Today (21 December 2012) was hyped onto a cottage industry of world-wide catastrophe by a few self-interested charlatans who prayed on the gullible. It’s a very, very old story. Carl Sagan has been quoted as saying that extraordinary claims require extraordinary evidence. The whole proposition that an ancient Mayan calendar foretold that today would be the end of the world was based on less than evidence – just a misinterpretation of an ancient document. This was not the first time, or the last time, that whole industries will be built on taking ancient texts and cooling up some baloney about their inferred meaning for the future.

There is only one knowledge system that can make evidence-based predictions about the future, and that’s science. Furthermore, the method of science is dependent on putting out predictions and then testing them against nature. In science, a failed prediction just means that the hypothesis upon which it was based was falsified – it didn’t work, and we try again. In chicanery a failed prediction has no consequences, except that it’s further evidence that, as is attributed (without evidence that he said it) to P. T. Barnum, “There’s a sucker born every minute.” It’s sad. The universe is beautiful, mysterious, and rich beyond the imaginings of any of us, modern or ancient. Get to know it for itself. Look for yourself, ask questions for yourself. Get to understand. Reject what doesn’t work. And – surprise – you will be applying the scientific method yourself. It’s not about believing in anything except that the evidence you can trust is evidence that has passed the test of being put up against the touchstone of nature.

© 2012, David Allan Galbraith

Pine River Observatory is Up and Running!

I hope you enjoy your visit to Pine River Observatory. This blog will be used to post observations, photographs, and, generally, things astronomical. Over the coming weeks I will be updated and adding to the blog, including adding lots of photos and notes from months and years past.

The basic idea of Pine River Observatory is to put together a “virtual” and “mobile” observatory. Pine River, located on the west coast of Ontario south of Kincardine, is a lovely area with fairly good skies given that it’s along the shores of a major lake. Our family cottage is in the area. I can be found many summer nights with tripods, cameras, and telescopes, or sometimes just a lawn chair and binoculars, soaking up the sky.

In the future I am planning on organizing some sky watching events in the Kincardine area during the summer, or taking part in ones that might already be planned.

© 2012, David Allan Galbraith