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This experiment will take place on Sunday, June 21, 2009 at 5:46 Universal Time. How do I translate Universal Time into my time?
As many of you know, I work at a planetarium. I'm conducting a GLOBAL experiment to calculate the size of the Earth and the "Axial Tilt" using simple tools.
To conduct this part of the experiment, all you need to do is to hold a meter stick vertically, with one end touching the ground. Measure the length of the shadow cast by the stick and (if possible) record the direction using a compass.
To measure the axial tilt of Earth st solstice (June 21st) you must measure the angle of the Sun above your local horizon at Noon. Noon is defined as the point that the Sun is highest in the sky and will be around 1 pm for those in Northern hemisphere with daylight savings time.
Probably the easiest way to measure the Sun's angle above the horizon is to take a stick, make sure its vertical and standing on a surface that is flat (use a plumb line and spirit level to check), and measure the length of the shadow it casts at Noon. Now draw a right angled triangle with the vertical side being the length of the stick, the horizontal side being the length of the stick's shadow and use a protractor to measure the angle the line joining the vertical side to the horizontal side makes with the horizontal side. This gives you the angle the Sun is above your horizon.
To work out the axial tilt you need to take the angle you measured, add to it your latitude and subtract 90.
Eg if you live at latitude 60 and you measure the Sun to be at 53.5 degree above the horizon at noon June 21st the axial tilt of the Earth will be:
It would nice to have as many people post their results as possible. If you don't know your latitude, just provide your city and country and I'll use Google Earth to calculate the rest.
As many of you know, I work at a planetarium. I'm conducting a GLOBAL experiment to calculate the size of the Earth and the "Axial Tilt" using simple tools.
To conduct this part of the experiment, all you need to do is to hold a meter stick vertically, with one end touching the ground. Measure the length of the shadow cast by the stick and (if possible) record the direction using a compass.
To measure the axial tilt of Earth st solstice (June 21st) you must measure the angle of the Sun above your local horizon at Noon. Noon is defined as the point that the Sun is highest in the sky and will be around 1 pm for those in Northern hemisphere with daylight savings time.
Probably the easiest way to measure the Sun's angle above the horizon is to take a stick, make sure its vertical and standing on a surface that is flat (use a plumb line and spirit level to check), and measure the length of the shadow it casts at Noon. Now draw a right angled triangle with the vertical side being the length of the stick, the horizontal side being the length of the stick's shadow and use a protractor to measure the angle the line joining the vertical side to the horizontal side makes with the horizontal side. This gives you the angle the Sun is above your horizon.
To work out the axial tilt you need to take the angle you measured, add to it your latitude and subtract 90.
Eg if you live at latitude 60 and you measure the Sun to be at 53.5 degree above the horizon at noon June 21st the axial tilt of the Earth will be:
(60 + 53.5) - 90 =
113.5 - 90=
23.5 degrees
113.5 - 90=
23.5 degrees
It would nice to have as many people post their results as possible. If you don't know your latitude, just provide your city and country and I'll use Google Earth to calculate the rest.
