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I love this trick. You can also do this using your hands if you know roughly what time it is. For example, if it's sunny out, place your arm in your shadow, pa

by kije 4y ago

I love this trick. You can also do this using your hands if you know roughly what time it is. For example, if it's sunny out, place your arm in your shadow, parallel to the ground. Keep it there. This arm represents the current time (say, 10 O'clock). Look at your shadow and point your other arm out, parallel to the ground, and adjust it until the arm's shadow points at "12 O'clock" relative to your first arm (in your shadow). Clap your hands together, and you're pointing north!

soperj 4y ago
You'd be pointing South no? Or is this for the southern hemisphere?
- kije 4y ago
  Compare it to the parent article and you'll see what I mean. If you are the center of the watch and you put your hand in your shadow, it will face the direction opposite of the hour hand in the article. If you adjust your other hand to face 12 O'clock relative to that hand, it would be at 6 O'clock if you're going by the article. So the direction is flipped. When you clap your hands together, you'll be facing North instead of South.
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zmgsabst 4y ago
Doesn’t N or S reverse at noon? Imagine (for simplicity) that we have 6a to 6p with solar noon at 12p. Then if I put my right arm in my shadow at 6am and my other arm 180 degrees from it, then I’ll be facing South. If I do the same thing at 11 am, I form a big wedge with my right arm on the NW side, again facing South. But at noon that changes: the sun is directly South from me, so my right arm is North and my other arm is in the same spot, so I turn around to face North. From there, my right arm is on the NE side, and my left arm makes a widening wedge as I face North — until at 6pm, I’m standing with my right arm facing East and my left arm opposite it, facing North.
- HillRat 4y ago
  Yes -- the article doesn't explain this, but in the morning you use the clockwise side of the hour hand to find south, and in the afternoon the counter-clockwise side (IIRC).
- mckeed 4y ago
  It doesn't work at 6:00 unless you know which way to face. At 11am you should have a small wedge, and your left arm should be in the shadow, in order to not point both arms straight behind you. At 1pm your right arm will be in the shadow for the same reason, so you're still facing north.
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  - bigiain 4y ago
    At sunrise or sunset, it's pretty obvious which way east or west is. At least to a first approximation. For a second approximation you'll want to interpolate between the equinox and solstice and use that to approximate an allowance for the ~24 degree tilt of earths rotation axis. That second approximation error is there for all times that are not midday, but reduce to zero as you approach midday. A third approximation might be to allow to the offset between your local timezone and solar midday. Where I am (Sydney) we are fairly close to the middle of the +10 and +11 timezone boundaries, so solar noon is within a few minutes of timezones noon. Perth on the other hand is way out to the west of it's timezone, so solar noon there is almost 25 minutes off from timezone noon. So "watch north" in Perth will be about 7.5 degrees off "true north".

by kije 4y ago

soperj 4y ago

You'd be pointing South no? Or is this for the southern hemisphere?

kije 4y ago
Compare it to the parent article and you'll see what I mean. If you are the center of the watch and you put your hand in your shadow, it will face the direction opposite of the hour hand in the article. If you adjust your other hand to face 12 O'clock relative to that hand, it would be at 6 O'clock if you're going by the article. So the direction is flipped. When you clap your hands together, you'll be facing North instead of South.
- deleted 4y ago
  [deleted]

zmgsabst 4y ago

Doesn’t N or S reverse at noon? Imagine (for simplicity) that we have 6a to 6p with solar noon at 12p. Then if I put my right arm in my shadow at 6am and my other arm 180 degrees from it, then I’ll be facing South. If I do the same thing at 11 am, I form a big wedge with my right arm on the NW side, again facing South. But at noon that changes: the sun is directly South from me, so my right arm is North and my other arm is in the same spot, so I turn around to face North. From there, my right arm is on the NE side, and my left arm makes a widening wedge as I face North — until at 6pm, I’m standing with my right arm facing East and my left arm opposite it, facing North.

HillRat 4y ago
Yes -- the article doesn't explain this, but in the morning you use the clockwise side of the hour hand to find south, and in the afternoon the counter-clockwise side (IIRC).
mckeed 4y ago
It doesn't work at 6:00 unless you know which way to face. At 11am you should have a small wedge, and your left arm should be in the shadow, in order to not point both arms straight behind you. At 1pm your right arm will be in the shadow for the same reason, so you're still facing north.
- deleted 4y ago
  [deleted]
- bigiain 4y ago
  At sunrise or sunset, it's pretty obvious which way east or west is. At least to a first approximation. For a second approximation you'll want to interpolate between the equinox and solstice and use that to approximate an allowance for the ~24 degree tilt of earths rotation axis. That second approximation error is there for all times that are not midday, but reduce to zero as you approach midday. A third approximation might be to allow to the offset between your local timezone and solar midday. Where I am (Sydney) we are fairly close to the middle of the +10 and +11 timezone boundaries, so solar noon is within a few minutes of timezones noon. Perth on the other hand is way out to the west of it's timezone, so solar noon there is almost 25 minutes off from timezone noon. So "watch north" in Perth will be about 7.5 degrees off "true north".