sundial directions?

[kittynh]

My daughter has to make a small sundial for school. She was thinking it would be cool to make a wrist sundial. Any good directions or sites out there for this?

[Brown]

Have her watch "The Flintstones."

Seriously, one of the problems with a wrist sundial would be orienting it correctly. You might want to have her build it on top of a water-filled compass with a leveling bubble, so that she can orient the sundial properly in the north-south direction, and hold the sundial level.

Most sundials are on fixed pedestals, and don't have to be reoriented. A portable sundial, however, would have to be reoriented with every reading.

As for marking the time of day, she can discover this herself by experimentation. Have her build a sundial, and mark where the shadows points at noon, two o'clock, four o'clock, etc. Of course, the sundial will have to be oriented the same way for each measurement. Also, have her use standard time, not daylight time. At noon (standard time), the shadow should basically point north.

[Earthborn]

North American Sun Dial Society (http://www.sundials.org/)

Cosmic Gnomon (http://www.cosmicgnomon.com/index.htm)

Some fairly easy projects for portable sundials (http://www.sundials.co.uk/projects.htm)

[kookbreaker]

If you can build something like this (http://www.stanleylondon.com/sundialcomp.htm) in watch form, you've got it made.

[Brown]

The concept of using the World Wide Web to find information for building a sundial... why, it's almost enough to make me want to use one of the "irony" smilies.

[tedly]

Try thisEleanor of Aquitaine (http://www.leevalley.com/garden/page.asp?SID=&ccurrency=3&page=10050&category=2%2C42191%2C42189)

[Grommitt]

I can see a few problems with a wrist model sundial.

1. It would have to be large enough to be able to see the
markings on the face. The smallest possible dial would
be awfully awkward for wearing on the wrist.

2. The 'pointer' would have to stick up the proper amount
which adds to the awkwardness of it.

3. The rig would have to include a leveling device of some kind
(bubble).

4. It would have to include a magnetic compass.

5. The user would have to orient the arm each time so that it
was level and pointing in the proper TRUE direction
(magnetic North + or - the magnetic variation for the
users longitude).

6. The arm would have to be held VERY steady to get a good
indication on a device small enough to wear on the wrist.

If she can design a sundial to overcome all this, I will be the first one to buy one!

I have to give her credit for thinking of a wrist model sundial. Encourage her to have a go at it and let us know how it works out.

[Crossbow]

Actually, there is a good bit that can be done with sundials and sundial implements.

For example, if one knows the local time, then one can determine ones longitude. One can also use certain types of CADD software to model how buildings and structures will look under solar lighting throughout any day of the year, or throughout the whole year.

Sundials and such may seem simple, but there is actually a great deal of science behind him, so your daughter has one cool project in mind.

[whitefork]

On an unrelated note, you can use a watch to find north:The Watch Method

Point the hour hand of the watch towards the sun and bisect the difference between the hour hand and 12. This gives you South, so North is directly opposite. eg if it is 10 o'clock, South will be at 11 o'clock and North at 5 o'clock, assuming your watch's hour hand is still pointing to the sun!
http://www.aircadetcentral.com/site/essentials_expeds_north.asp

[richardm]

I own a rather nice pocket sundial that is about the right shape and size for a wristwatch. The gnomon (the bit that casts the shadow) is hinged to fold flat out of the way, and it has a compass needle to show the right way to hold it.

It is a replica of one found on the Mary Rose, a Tudor warship. So all the problems have been overcome for quite a while! I can probably get you a picture of its face if it's any use to you.

[richardm]

Originally posted by Grommitt
I can see a few problems with a wrist model sundial.

1. It would have to be large enough to be able to see the
markings on the face. The smallest possible dial would
be awfully awkward for wearing on the wrist.

3. The rig would have to include a leveling device of some kind
(bubble).

4. It would have to include a magnetic compass.

5. The user would have to orient the arm each time so that it
was level and pointing in the proper TRUE direction
(magnetic North + or - the magnetic variation for the
users longitude).

6. The arm would have to be held VERY steady to get a good
indication on a device small enough to wear on the wrist.



The problem with these objections is - they're not really problems. You'd never need a sundial to give you astonishing accuracy - neither do many wristwatches. "Good enough" is normally good enough for most people, who tend to round times up to "about five to ten" sort of precision anyway.

"Small dials" - have you seen the size of some women's wristwatches? :D

3 and 4 together - yes, you'd need a compass to get yourself in the right alignment to the sun, and you can use the same needle to ensure that the sundial is adequately level; if it's swivelling, it's level enough.

5 - again, how much accuracy do you need from a wristwatch?

2 and 6 - I possess a pocket sundial, and I can assure you it's perfectly straightforward to hold your arm steady enough. Certainly, you have to stop what you're doing to unfold the gnomon and read it, but then again, remember those early digital watches where you had to press and hold a button to turn on the display?

Of course, you can only use it outside on sunny days, which automatically restricts the usefulness.

I'd think making such a thing would be quite a fun project - sorting out the markings, materials, and so on. Although portable sundials are an old invention, I don't believe I've ever seen a wristwatch version; I'm also prepared to believe that many people have never heard of the portable sundial in the first place, outside of the Flintstones!

[tedly]

Sorry guys, Eleanor's ring sundial is still the most elegant solution. Levelled by hanging on a string, south determined by the light falling on the back. No compass, no level, and a bit smaller than the watch on my wrist.

[Rolfe]

Didn't they find a nice portable sundial when they were excavating the ruins of the abortive Darien Scheme?

Rolfe.

[Skeptical Greg]

Originally posted by Grommitt
I can see a few problems with a wrist model sundial.

1. It would have to be large enough to be able to see the
markings on the face. The smallest possible dial would
be awfully awkward for wearing on the wrist.

2. The 'pointer' would have to stick up the proper amount
which adds to the awkwardness of it.

3. The rig would have to include a leveling device of some kind
(bubble).

4. It would have to include a magnetic compass.

5. The user would have to orient the arm each time so that it
was level and pointing in the proper TRUE direction
(magnetic North + or - the magnetic variation for the
users longitude).

6. The arm would have to be held VERY steady to get a good
indication on a device small enough to wear on the wrist.

If she can design a sundial to overcome all this, I will be the first one to buy one!

I have to give her credit for thinking of a wrist model sundial. Encourage her to have a go at it and let us know how it works out.


Sheesh!! Save it for when someone wants to help their kid with a demonstration of cold fusion....:rolleyes:

[ceptimus]

More convenient than carrying a compass and spirit level would be to use a wristwatch to find the correct time, and then turn the sundial around till the shadow falls on the correct mark.

[xouper]

richardm: 5 - again, how much accuracy do you need from a wristwatch? Depends on where you are. In Chicago, there's very little difference between magnetic and true north. In Boston, the deviation is about 15 degrees. In Vancouver, BC, the deviation is about 25 degrees.

[richardm]

Originally posted by xouper
Depends on where you are. In Chicago, there's very little difference between magnetic and true north. In Boston, the deviation is about 15 degrees. In Vancouver, BC, the deviation is about 25 degrees.

Hmm, interesting point; I hadn't considered that. I wonder how you could overcome that? Rotating bezel on the compass, and a data book, perhaps, Or is that heading into the realms of madness?

[Brown]

Here is a science project that I would like to see someone do. I'd even like to perform it myself. The problem is that it requires a lot of effort and dedication, and a lot of space (e.g., a parking lot). Also, you have to be careful about who you tell about the project, because people (being jerks) will vandalize it if they know what you are doing.

Here's what you do.

Plant a pole in the ground, and fix it (e.g., with concrete) so that it cannot move. On the top of the pole, have a mast with a small ball on the top of it.

On every sunny day, at exactly the same Universal time, paint the spot on the ground at which the small ball makes a shadow. (If you do not have a sunny day in which the ball casts a crisp shadow, skip that day.)

Observe the path that is created by the shadow of the ball. What path do you expect it to take?

[daver]

Originally posted by Brown
Here is a science project that I would like to see someone do. I'd even like to perform it myself. The problem is that it requires a lot of effort and dedication, and a lot of space (e.g., a parking lot). Also, you have to be careful about who you tell about the project, because people (being jerks) will vandalize it if they know what you are doing.

Here's what you do.

Plant a pole in the ground, and fix it (e.g., with concrete) so that it cannot move. On the top of the pole, have a mast with a small ball on the top of it.

On every sunny day, at exactly the same Universal time, paint the spot on the ground at which the small ball makes a shadow. (If you do not have a sunny day in which the ball casts a crisp shadow, skip that day.)

Observe the path that is created by the shadow of the ball. What path do you expect it to take?

Something like this? http://antwrp.gsfc.nasa.gov/apod/ap030320.html

[xouper]

Brown: Plant a pole in the ground, and fix it (e.g., with concrete) so that it cannot move. On the top of the pole, have a mast with a small ball on the top of it.And the really cool thing about many large parking lots (at schools and malls) is that they have already done this for you, usually in several places, so you can choose the lampost that's most convenient for your experiment.

[Brown]

Originally posted by daver
Something like this? Yup, that's what I'd expect, except the marks would be on the ground rather than up in the sky. (Also, painting marks on pavement requires less tech skill than photography.)

Edited to add: This Link! (http://www.analemma.com/Pages/framesPage.html)

In the move "Cast Away," Tom Hanks uses a projection of the sun through a hole in rocks as his calendar. Notably, the path of the sun follows the figure-8 analemma. However, the sun's projection would follow this path only if Tom Hanks had a working watch, and he noted the position of the projection at a consistent time of day.

[arcticpenguin]

Lawdy mae, we're sending a sundial to Mars! (http://athena.cornell.edu/kids/sundial.html)


The Mars Exploration Rovers will carry the first-ever interplanetary sundial. This martian sundial will also be used to calibrate Pancam, the panoramic camera on the rovers.

I found a link to this on Slashdot.

[arcticpenguin]

http://www.sciencedaily.com/releases/2003/11/031121071707.htm


Sullivan, a University of Washington astronomy professor, is teaming up with television personality Bill Nye, "the science guy," and The Planetary Society on EarthDial, a project to get schools, community organizations and individuals around the world to build their own sundials and display them on the Internet using 24-hour webcams.

Their hope is to have a broad sample of sundials from each time zone, illustrating the difference in shadows between the northern and southern hemispheres and the equator. The plan is to display the images together on a single Web site during the working life of two Mars landers, Spirit and Opportunity, that are scheduled to land on the red planet in January.

Both Spirit and Opportunity are equipped with sundials, referred to as Marsdials, that were largely designed and fabricated at the UW.

[geni]

Originally posted by Diogenes



Sheesh!! Save it for when someone wants to help their kid with a demonstration of cold fusion....:rolleyes:

A lump of palladium two beakers and some deuterium. Whats the problem?