How many ways to find North can we think of?

[Colibri]

@Limmin

For a while it seemed my dog, when doing her duty, would align herself in a particular direction such as North. Further observations revealed she aligned herself in a cardinal direction, sure, but not always the same one. I think she aligns herself with nearby roads or the walls of the house, which pretty much always are parallel with a cardinal direction.

Actually, scientific studies have show that dogs do align north-south when defecating. A lot of other animals also align along magnetic lines:

It has long been suspected that animals such as turtles and birds use magnetoreception to navigate, but it is becoming increasingly obvious that many other animals sense magnetism too, seemingly when they’re doing very little. Insects like to align their bodies along a north-south axis, as do sleeping warthogs, fish in tanks, nesting house mice and foxes on the hunt.

In certain areas of Australia you can use the so-called magnetic termite mounds.

[steepone]

@Quercus

I don’t think that’s actually true in general.

It only works if both shadows are the same length (which means they were before and after local noon). What you need to do is get the stick, mark a shadow at some point in the morning, and draw a circle around the stick the same distance as the shadow length. Then wait until the afternoon shadow is just on the circle. Mark that shadow and connect them and you have a pretty good east-west line.

It works whatever the length of the shadows, if you mark several points rather than just two they will all be on the same straight east-west line

the only caveat is that you need to do it on a level piece of ground, the youtube video below explains it more clearly

Sun Compass Shadow Stick Method

[Quercus]

[quote=“steepone, post:62, topic:842251”]

It works whatever the length of the shadows, if you mark several points rather than just two they will all be on the same straight east-west line

the only caveat is that you need to do it on a level piece of ground, the youtube video below explains it more clearly

[/QUOTE] The board just went through this discussing the kidnapping question from 538's friday puzzler. For some reason, a bunch of people have put this idea up on the web (that all shadow points lie on one east-west line) . But if you think about say, summer in the northern (mid-latitude) hemisphere, it's pretty clearly not true, no matter what the random person on YouTube says. In northern hemisphere summer, the day is longer than 12 hours. From the perspective of the ground, the sun rises to the north of east, climbs up as it goes south until local noon when the sun is due south (but, outside of the tropics never ever gets directly overhead), then it sinks as it keeps swinging around, and setting north of due west.

So the tip of the very early shadow is so the southwest of the stick. The noon shadow is due north, and the almost-setting shadow is pointing southeast. There’s no way all three of those shadows can be on the same line. And there’s no way either the sunrise or sunset shadows can form an east-west line with the noon shadow.

If you do the experiment close to noon, and you’re not precise enough with marking the shadows, it’s pretty easy to convince yourself (and others) that the shadow tips lie on the same line, but thinking about a full day makes it clearly impossible. Only when two shadows are the same length (and therefore the same amount of time before and after local noon) do the tips form a perfect east-west line.

[journeyman_southpaw]

If you can figure out which way is to the poor part of town, that way is probably east.

[Colibri]

@journeyman_southpaw

If you can figure out which way is to the poor part of town, that way is probably east.

Maybe in the UK, according to that study, at least, but according to The Master in the US it’s often to the south. (I’m also nonplussed by the allegation in that article that the poor part of New York City is to the east. That’s not true either in Manhattan or the city as a whole.)

[cmyk]

@Quercus

The board just went through this discussing the kidnapping question from 538’s friday puzzler.
For some reason, a bunch of people have put this idea up on the web (that all shadow points lie on one east-west line) . But if you think about say, summer in the northern (mid-latitude) hemisphere, it’s pretty clearly not true, no matter what the random person on YouTube says. In northern hemisphere summer, the day is longer than 12 hours. From the perspective of the ground, the sun rises to the north of east, climbs up as it goes south until local noon when the sun is due south (but, outside of the tropics never ever gets directly overhead), then it sinks as it keeps swinging around, and setting north of due west.

So the tip of the very early shadow is so the southwest of the stick. The noon shadow is due north, and the almost-setting shadow is pointing southeast. There’s no way all three of those shadows can be on the same line. And there’s no way either the sunrise or sunset shadows can form an east-west line with the noon shadow.

If you do the experiment close to noon, and you’re not precise enough with marking the shadows, it’s pretty easy to convince yourself (and others) that the shadow tips lie on the same line, but thinking about a full day makes it clearly impossible. Only when two shadows are the same length (and therefore the same amount of time before and after local noon) do the tips form a perfect east-west line.

I took a few mins and used a physically-based sun system in my CG app (Cinema 4D) to cast virtual shadows. I chose Chicago for the latitude (~42°N). Then I used this method to measure the shifts between the Autumnal Equinox (Sept 21) and likewise for the Winter Solstice (Dec 21).

The results are what you seem to say, however the drift from true East/West is only about 5°… so it’s still a rather effective method.

Here’s a link to a screenshot I took (jpeg).

The red lines are true East/West. The green lines are what the shadow sticks give.

Note how straight the result around the equinox. Interesting.

[cmyk]

I also just tried measuring for June (Summer Solstice). I kind of got the inverse curve of winter, unsurprisingly, but it was a much shallower curve, and the drift was about ~8°.

[thorny_locust]

@Colibri

Actually, scientific studies have show that [URL dogs do align north-south when defecating.

Interesting. I’d swear mine mostly aligned east to west, though they weren’t entirely consistent about it.

Around here: locate the nearest Finger Lake. It’ll point approximately south to north. Find a road sign or village, and figure out which side of the lake you’re on. Done.

– having a few years ago, due to a claim that came up on the snopes boards, spent some time paying attention to whether cattle all face the same way in a field, and having concluded that (not surprisingly for a herd species that needs to watch for predators) they don’t; I suppose I’ll now be paying attention to whether they tend to be facing north, south, east, or west. The one sample I noticed yesterday were aligned mostly east/west, though with exceptions. I’ll try to remember to report back when I’ve got a batch more observations.

[Quercus]

@cmyk

I took a few mins and used a physically-based sun system in my CG app (Cinema 4D) to cast virtual shadows. I chose Chicago for the latitude (~42°N). Then I used this method to measure the shifts between the Autumnal Equinox (Sept 21) and likewise for the Winter Solstice (Dec 21).

The results are what you seem to say, however the drift from true East/West is only about 5°… so it’s still a rather effective method.

Here’s a link to a screenshot I took (jpeg).

The red lines are true East/West. The green lines are what the shadow sticks give.

Note how straight the result around the equinox. Interesting.

If you’re drawing lines between the end of the shadow at 9:00 AM CST and 15:00 AM CST, that’s probably not going to be true east-west. To get true east-west you want to be equal amounts of time before and after local solar noon (when the sun is highest and due south), which is not necessarily the same moment as 12:00 in the area’s time zone. Again, in the field you don’t need a clock, just use two times where the shadows are the same length.

[cmyk]

@Quercus

If you’re drawing lines between the end of the shadow at 9:00 AM CST and 15:00 AM CST, that’s probably not going to be true east-west. To get true east-west you want to be equal amounts of time before and after local solar noon (when the sun is highest and due south), which is not necessarily the same moment as 12:00 in the area’s time zone. Again, in the field you don’t need a clock, just use two times where the shadows are the same length.

I drew a line between 3 hours before noon and 3 hours after. I think as long as you get pretty close to local solar noon, as your center-point, you’ll get a decent result.

[TriPolar]

Even with a compass you’ll need to know where you are and how far off magnetic north is from polar north.

[cmyk]

Missed the edit window to say:

But yes, you appear to be right. So long as you get shadows of equal length on either side of noon, you’ll get true north. But I guess that’s the trick is determining when local noon actually is.

[Isamu]

@TriPolar

They’ll be pointed south, but not exactly 180 degrees opposite of due north.

I can find it at night from the North star, but I usually know north and south without any help. East and west go wrong when I am on the west coast. Something in my mind wants the nearest ocean to be east of me.

North, she is in Australia.

[Isamu]

@panache45

Find your location on a map. Usually, north is toward the top.

Unless you are in Japan where they don’t follow that convention. Instead they try to intuit what would be the most useful orientation for the reader. It sucks if you’re not used to that.

My contribution: In Japan go to a train station and find the North exit and compare that to the South exit, and you should get some idea of where North is. Maybe. Sometimes.

[Colibri]

@TriPolar

I can find it at night from the North star, but I usually know north and south without any help. East and west go wrong when I am on the west coast. Something in my mind wants the nearest ocean to be east of me.

Panama would really screwy you up then, since counterintuitively the mountains and both coasts run east-west (and there’re places where the sun rises out of the Pacific and sets on the Atlantic.)

[Pardel-Lux]

@panache45

Find your location on a map. Usually, north is toward the top.

Don’t try this in Barcelona. Hereis a typical example, North is about 2 o’clock. They usually put the sea to the east(ish) on the lower part of the map.

[Pardel-Lux]

@RitterSport

I know I’ve read this before, but where? Damn you, where!!?? It sounds like Douglas Adams or Terry Pratchett to me. Dave Barry?

Richard Feynman

[Quercus]

I just thought of another not-that-actually useful one. It requires being in an area that was glaciated recently (in geological terms; so last hundred thousand years or so), had a variety of bedrock hills that were small enough to be completely covered by the glacier and not change the glacier’s general north-south advance. Much of New England fits the bill; I’m not sure where else.

In these areas, the bedrock hills will be generally smoothly sloped on the north side (where the glacier polished them smooth as it flowed over) with cliffs on the south side (the flowing glacier pulled rocks off the north side as it flowed over/past).

[TriPolar]

@Colibri

Panama would really screwy you up then, since counterintuitively the mountains and both coasts run east-west (and there’re places where the sun rises out of the Pacific and sets on the Atlantic.)

That would be a problem. I hope they don’t have any canals down there because I’d likely drive right into one.

[Treppenwitz]

Out on the bike today I got the chance to put some of this into practice. The weather forecast was way off, and I spent a long time trying to figure out where the weather was coming from – hence my trying to gauge direction as I rode.

These were the methods available to me over about 10 or 15 pretty rural miles of the ride:

[ul]
[li]Solar panels (just once, oddly)[/li][li]Satellite TV dishes (all the time)[/li][li]Weather vanes (twice) – we haven’t had that, I think, and they make it almost too easy as they label the cardinal points [/li][li]A herd of cows (if you believe the weather vanes, the cows were headed south as they grazed. Oops.)[/li][li]Churches (two) and graves/headstones[/li][li](Very briefly) the sun [/li][li]At no point did I come across a dog taking a crap, which is unfortunate because there’s a loadstone joke just begging to be made. Also, I would love for it to be a practical method, but this experience suggests it is not.[/li][/ul]

Conclusion – on a heavily cloudy day, TV satellite dishes are your best bet. By a distance.

j

PS: it occurs to me that this use of the word “load” may be a Briticism. If it is, I apologise.