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Cool Science: Sun dials (VIDEO)

One of the earliest ways with which people have kept track of passing time, is with a sundial.

One of the earliest ways with which people have kept track of passing time, is with a sundial.

In fact, before mechanical clocks were possible, many tall buildings were built with enormous vertical sundials on them.

However, getting an accurate time out of a sundial requires both math and astronomy.

Many sundials are made in areas close to the equator, so they aren’t adjusted for the sun’s position at their new home in the north. 

To fix this, take a level and protractor, then adjust the sundial base until the wedge-shaped “Gnomion” part is at 48.4 degrees, with the higher end facing true north. 

Also, Thunder Bay is located near the western edge of our time zone.  

So the “solar time” will be off by a whopping 57 minutes!  The easiest way to adjust for this is to subtract the 57 minutes to the time whenever you’re looking at the sundial. 

Fortunately, if you’re making your own sundial from scratch, it is possible to build a dial that shows the correct time, using geometry! Just visit the Science North Facebook page to download a sundial diagram adjusted specifically for Thunder Bay.

However, the time shown on your sundial will rarely be exactly right.

The earth’s orbit around the sun is not a perfect circle, so it regularly “speeds up” and “slows down.”  

Plus, the angle of the earth itself changes with the seasons, which makes the sundial appear to be ahead or behind. 

Now that’s cool science!