The Earth's Shape, Dimensions, and Internal Heat

Earth's Shape and Size

Recall the North Star diagram as a way of disproving that the earth was flat.
Why a sphere and not a circle?
- Weight of an object at several places on the Earth’s surface.
- The weight of an object measured in Newtons – changes with the distance from the center. (The less it weighs further from the center)
Imperfect Sphere?
- An object that weighs 195 newtons at sea level on the North Pole or South Pole will weigh 194 newtons at sea level on the equator.
- Earth is flattened at the poles, buldged at the equator
- This is all caused by the Earth’s rotation
True Name = Oblate Spheroid

Measurements of the Earth Notes
Eratosthenes’ method for finding circumference (276-195 BC)
Recall the Eratosthenes Lab!!!

Angle = distance 360 degrees circumference

- Circumference at the Equator 40,074 km
- Circumference at the Poles 40,007 km
- Diameter at the Equator 12,756 km
- Diameter at the Poles 12,714 km

Recall our notes on denisty.
Remember who we took the denisty of a small and large piece of the SAME rock.
Why did they have the same density?

What is an average density? Density = mass/volume (amount of material in a given space)

Heating an object can cause the object to have slightly lower density.
Cooling an object can cause the object to have slightly higher density.
Most material have their greater density in the solid state.
Water is an exception to this rule. It is most dense as a liquid.

There is an increase in 1 degree Celsius for every 40 meters in depth.
Direct temperature measurements are only available for a few thousand meters down. Temperature is estimated further.
If we continue at the 1 degree per 40 meters then what is the temperature of the center of the Earth (inner core)?
Use your class notes!!!

Contrary to this method, scientists believe that it is 7000 degrees Celsius.
- Evidence from the Earth's volcanoes

What makes the Crust hot? (Hint there are two theories!)

What are examples of some radioactive elements found in the earth?

What happens to our heat?

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