Ready, Set, GO!!! The Equinox is near!!!

The Equinox (spring equinox for the North, autumn equinox for the South) will come in three days, so the Sun already is very close to the East at dawn and to the West at dusk. So, everyone that believes in a flat Earth can honestly do the easiest experiment yet devised, with absolutely no chance of a conspiracy meddling in your quest for validation.

Instructions are simple:

• Do not look at the Sun directly. A horizontal piece of cardboard with a vertical stick in the middle will give you a precise shadow to measure without burning your eyes. But be careful ensuring that the stick is vertical.
• Measure both the azimuth at dawn and dusk. The difference between them is not dependent on the difference between magnetic and real North.
• Log the azimuth measurements and the time and day of the measurements, and the latitude of your location in this thread.
• If you cannot do the measurements exactly at dawn and dusk or on March 21, it is not important. Just log your information precisely

If you find a big difference between the expected and the measured values (say, more than 200 degrees of difference between dusk azimuth and dawn azimuth readings) you can publish your results and become in a few years the next Nobel Prize winner. Just publish your results many times in many periodicals and magazines and you will be eventually taken seriously. Nobody can stop every periodical from showing your evidence.

Im willing to give it a go, why not.  However I do not know what readings I should expect at my particular coordinates.  I am at Lat: 39.3  Rounded to the nearest 10th.  If I have time I will conduct the experiment on saturday.  I would like to add, that using magnetic north may not be the best method for determining the azimuth.  Perhaps as part of the experiment, the night before, true north needs to be determined, by marking the direction to polaris with some chalk.  That should be the 0 degrees point for all measurements during the experiment.

Perhaps as part of the experiment, the night before, true north needs to be determined, by marking the direction to polaris with some chalk.

That ought to be a fun exercise.

heh, why not, it certainly isn't required, but it would be nice to see if you get different readings.

heh, why not, it certainly isn't required, but it would be nice to see if you get different readings.

Protip: I cannot see Polaris.

If you use a powerful telescope, you should be able to restore polaris to your view. 

I admit my mistake, apologies.  Couldn't you determine the southern celestial pole?

I admit my mistake, apologies.  Couldn't you determine the southern celestial pole?

I could try that. It's kind of difficult as it has no distinguishing feature near the pole. There are ways of locating it from the surrounding stars, but I don't know that they would be particularly accurate tools for measurements such as these.

Even polaris is not exactly on the NCP.  I think it is about a half degree away, circling around it.  About the radius of the moon I think.

Should we be noting the azimuth of the sun, or the shadow it creates?  Sorry I am new to this.  Where's rig navigator when you need him?

Im willing to give it a go, why not.  However I do not know what readings I should expect at my particular coordinates.  I am at Lat: 39.3  Rounded to the nearest 10th.  If I have time I will conduct the experiment on saturday.  I would like to add, that using magnetic north may not be the best method for determining the azimuth.  Perhaps as part of the experiment, the night before, true north needs to be determined, by marking the direction to polaris with some chalk.  That should be the 0 degrees point for all measurements during the experiment.

The beauty of this experiment is that you do not need to know where the true North is and the latitude of the observer is irrelevant except if it is very close to one of the poles.

For example, if the magnetic North is at a bearing of 10 and the Earth is really round, your measurements will be 260 and 80, plus or minus a few degrees of error, and the difference between the two will be 180. In either model the point exactly between the Sun at dawn and the Sun at dusk will be the true North.

If you are able to see the Sun at dawn and dusk your latitude is fine. If not, you should do a correction of about +8 for every hour after dawn and -8 for every hour before dusk.

Even polaris is not exactly on the NCP.  I think it is about a half degree away, circling around it.  About the radius of the moon I think.

Should we be noting the azimuth of the sun, or the shadow it creates?  Sorry I am new to this.  Where's rig navigator when you need him?

Don't worry about Polaris.

Place the compass directly in the middle of the shadow, rotate the shell of the compass so the red side of the needle points to the big N. The azimuth is the reading you get in the direction of the stick. A very thin stick would be best. Please make sure the stick is vertical.

OIC, will do.  Ensuring the stick is vertical will be difficult, especially if it is thin (less room for a level).  Any advice on how to level the stick?  I doubt the parking lot outside my apartment is perfectly level.

If you hang a weight from a string, you could use that as your stick, string is very thin and the weight will ensure it hangs vertically.

If you hang a weight from a string, you could use that as your stick, string is very thin and the weight will ensure it hangs vertically.

Good idea. But the precision we intend to achieve is not so impressive, so if the string or stick is within two degrees of vertical we can live with that. The compass itself has some two or three degrees of error anyway unless it is an expensive, sophisticated model.

Don't forget to allow for magnetic declination (the fact that the magnetic north pole is not located at the geographic north pole).

This is a magnetic declination calculator.  It may or may not have your city in the list, but I'm sure you can google your latitude and longitude to figure out what kind of adjustment you need to make.  here in Vancouver, BC my magnetic declination is 17? 43' East, so by my understanding, I need to adjust my compass 17? 43' West to find true north?

http://geomag.nrcan.gc.ca/apps/mdcal-eng.php

When is the equinox again?

When is the equinox again?

Google is your friend...
http://en.wikipedia.org/wiki/Equinox

Google is not my friend anymore, we had a falling out

Don't forget to allow for magnetic declination (the fact that the magnetic north pole is not located at the geographic north pole).

This is why we take both measurements at dawn and dusk. Both measurements are skewed by the same amount, so the difference between them is not affected.

When is the equinox again?

March 21, but for the precision we are expecting, measurements from a few days before to a few days after the equinox are quite usable. Just include the day you did the measurement. If the FE model is right, the difference between azimuth at dawn and azimuth at dusk will be more than 220 degrees in Europe and the US, and about 270 degrees for us near the Equator.

When is the equinox again?

Try reading the OP.

When is the equinox again?

I will correct myself slightly. According to http://aa.usno.navy.mil/data/docs/EarthSeasons.php the equinox falls on March 20, at 11:44 AM universal time. But a day or two (or three) does not make a difference big enough to make a flat Earth seem round, or viceversa.

In fact, any day is good, year-round, but the maths required to interpret the data is more complicated.

I will correct myself slightly. According to http://aa.usno.navy.mil/data/docs/EarthSeasons.php the equinox falls on March 20, at 11:44 AM universal time.

That's the middle of the night over here. I'll see what I can do in terms of recording sunset tomorrow night and sunrise on Saturday morning, but there are too many trees around here to get a really clear shadow close to sunrise/sunset.

I'll try and remember, I just don't like the thought of getting up before 6:30

I'll try and remember, I just don't like the thought of getting up before 6:30

Solution: just stay up late partying.

I will probably make the experiment. The sunrise at my home will be at 6:45am. I'm going to buy a compass hehe.

Here are the results for my experiment on sunrise:

March 21st, 2009
Latitude 46,8°N
Longitude 71,3°W

Sunrise 06:45 EDT
Azimuth: 94°

yeah I didnt wake up..

I forgot completely.

Here are the results for my experiment on sunrise:

March 21st, 2009
Latitude 46,8°N
Longitude 71,3°W

Sunrise 06:45 EDT
Azimuth: 94°

Thank you for your data. Please repeat the experiment at sundown; it is not important that the result might be from another day. Having the other measurement gives us a reasonable idea of the errors and precision of the experiment.