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Frostbite Theater

Here's a Question! - What Shape Does the Sun Trace?

What shape does the sun trace in the sky over the course of a year?

Announcer: Frostbite Theater presents... Cold Cuts! No baloney!

Joanna and Steve: Just science!

Joanna: Hi! I'm Joanna!

Steve: And I'm Steve!

Joanna: Here's a question for you...

Steve: Suppose you were to, safely, photograph the sun over the course of a year from the same place, with the same framing, at the same time, adjusting for daylight saving time. If all those images were merged, what pattern would the sun make?

Joanna: Will it form a line segment aligned east to west?

Steve: Will it form a line segment aligned north to south?

Joanna: Will it trace out a circle?

Steve: Or, will it trace out something like a figure eight?

Joanna: Pause the video now if you'd like to think it over before we show you what happens.

Steve: If you keep track of where the sun appears to be at a specific time of day over the course of a year, you end up with an asymmetrical figure eight shape.

Joanna: This kind of plot is called an analemma. You might have seen it before... Sometimes, they'll put them on globes out in the middle of the Pacific.

Steve: An analemma's shape is determined by the tilt of the axis, the shape of the orbit, and where along the orbit Spring begins. So, Earth's analemma looks different than Mars' or Jupiter's, for instance.

Joanna: If you like, you can even make a version of this yourself. You don't even need a camera. Just find something like a flagpole and mark where the tip of its shadow falls on the ground at a particular time of day. Do this over the course of a year and you'll trace out a similar pattern.

Thanks for watching. I hope you'll join us again soon for another question!

Steve: Shadowlemma!

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