Aim: To build a sundial.
Research: Video
Method:
- Cut around the outer edge of the Sundial diagram.
- Fold the centre vertical line up, and the 2 True South lines down to create a triangle (called the Gnomon) that stands vertically from the horizontal paper sundial face.
- Ensure the Gnomon stands vertically, at right angles to the sundial face.
- Place the Sundial flat and level, with the Gnomon (triangle) pointing toward the True South for the Southern hemisphere.
Results: ![](https://hhsshaheenf.edublogs.org/files/2023/10/IMG_20231026_140206-1-300x169.jpg)
Discussion:
A. The needle on the compass points to Magnetic North. Is that the same as the North Pole (Geographic North)? What is the difference?
B. The Earth spins once every 24 hours (one day). This makes it look like the sun is travelling across the sky. How many degrees does the sun travel each hour?
C. On our sundial, when it’s pointed True South, it will indicate that it is 12 noon when the Sun is highest in the sky. Is that correct?
D. If it’s not true, what time is Solar Noon today?
E. Does the sun rise at the same time every day? If not, why not?
F. Why do we have daylight savings in NZ?
G. We use Greenwich Mean Time to arrange the time zones around the World. Which country was the first to have a standardised time? And why?
Answers
A. A compass that uses magnets does not point towards the geographic North Pole.
B. The Sun stays at an angle of about 23.5° above the horizon throughout the day as it moves in a circular path. In 24 hours it completes a full circle of 360° which means it moves 15° every hour.
C. When the midday sun climbs highest, the sundial reads 12 noon and your local clock says 12 noon.
D. In most places on Earth, solar noon does not happen at 12 o’clock
E. The combination of Earth’s elliptical orbit and the tilt of its axis results in the Sun taking different paths across the sky at slightly different speeds each day.
F. longer summer evenings would mean fewer lights needing to be switched o
G. the USA had already chosen Greenwich as the basis for its own national time zone system.