Naked Science Forum
General Science => General Science => Topic started by: thedoc on 02/05/2013 00:30:02
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Andy Rendle asked the Naked Scientists:
Hello,
I'm based out of Victoria, Canada, but I often find myself working along the river system in the Amazon for weeks at a time, around 2 degrees south.
I download and then enjoy your podcasts stored on my blackberry when far far out of cel range, for hours travelling along the various rivers.
I learned to find the North Star up in Canada, pretty much learned the same time as my five year old daughter.
Down in the jungle though, I have always wanted to figure out how to orient north. I've sat around campfires with local first nations peoples telling them about how that wonderful cloudy streak across the sky is a benefit only they have which we don't in the north, and I hear their philosophies on our place in the universe.
But no matter how many places I look in research, the more pragmatic matter of finding our north or south seems so complicated.
Is there not an easier way for us amateurs to find it quickly, while also focussing on not being pulled into the river by the boa or being in the wrong end of a huge herd of wild boar stampeding through the forest?
Regards,
Andy Rendle
What do you think?
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You can find an approximate North by noticing where the sun is, and then in the morning North will be to your left and South to your right, or in the afternoon North to your right and South to your left. In the middle of the day the sun will pass to the North of you in May June July or to the South of you in November December January. You do not need access to open sky; you should be able to tell from the general brightness where the sun is.
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At night time you have a 50/50 chance that the southern cross is in the sky. Imagine that the cross is a kite with a tail four times the length of the kite. The tip of the tail is at the South Celestial Pole, which at 2°S will be pretty close to the Southern horizon.
Here in Melbourne the cross is in the sky all of the time, and that is a sure method of finding the SCP, and hence the direction of South.
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Here's a sure-fire method (http://modernsurvivalblog.com/survival-skills/how-to-use-a-watch-as-a-compass/), but it requires the use of a rare, antique device called an analog wristwatch. (jk) The link gives one method for the northern hemisphere and another method for the southern hemisphere, so you being at the equator, you're basically screwed. (jk again, but perhaps not really) Here's another twig-and-watch method (http://www.compassdude.com/no-compass.shtml) and other methods.
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Or you could use... a compass?
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When it's too overcast to see the sun or shadows, you can often use moss, algae or lichens a few feet up on the trees as a rough guide, as they tend to prefer shadier, damper environments. The Natural Navigator (http://www.naturalnavigator.com/find-your-way-using/plants) site has some details on navigating without a compass.
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There are tribes in the Amazon which don't have words for left or right, but where they use north, south, east and west instead. They learn from an early age to keep track all the time of their orientation, but no one seems to have worked out how they do it. If you live in dense forest, most of the time you'll only get glimpses of the sky when looking directly upwards, but that could be enough to do the job. http://en.wikipedia.org/wiki/Haidinger%27s_brush (http://en.wikipedia.org/wiki/Haidinger%27s_brush) may be the key to what they are doing. If you're reading this on an LCD screen, try tilting your head 45 degrees to one side and stare at a white bit of the screen for 20 seconds, then tilt your head 45 degrees to the other side and stare at the white bit of screen again - your eyes can detect polarised light, and it works on a blue sky so long as you're looking reasonably far away from the sun (so midday in the jungle is no good).