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Scientists think our solar system formed out of a great cloud of collapsing gas and dust. Earth’s original surface is thought to have been cratered like the moon. Approximately 70 percent of the Earth’s surface is covered with water.

The Earth’s shape is slightly flattened at the poles and slightly bulging at the equator. The Earth’s imperfect shape is primarily a result of its spinning motion. The following are sources of heat when the Earth first formed: Compression by overlying materials Bombardment by meteorites Decay of radioactive isotopes

The approximate temperature of the Earth’s inner core is 6000 Kelvin. The Earth turns on its axis. Earth moves around the sun in a single plane. Earth’s axis is slightly tilted.

Earth’s orbital plane is almost a perfect circle, however it is slightly skewed.

Because the Earth is not a perfect sphere an object weighs less at the equator than at the poles. A Foucault pendulum provides evidence of Earth’s rotation.

In the middle of the beautiful entrance hall of the Steno Museum you can see a version of the French physicist, Léon Foucault's (1819-68) famous pendulum experiment. Foucault in Pantheon, Paris

This is Foucault's Pendulum This is Foucault's Pendulum. It was used as evidence that the earth was rotating and thus placed in the center of the (then named) Temple for Science and Reason as a testament to the success of science in explaining the natural world.

Starting the Foucault Pendulum in the building of the National Academy of Sciences and the National Research Council at Washington; this instrument demonstrates the rotation of the earth.

Click the Earth to observe evidence of Earth turning about an axis.

During an earthquake in Pymatuning, PA in 1998, a Foucault's pendulum acting as a seismoscope scribed this incredible work of earthquake art.

Coriolis effect, length of day, and direction of sunrise are all a direct result of Earth’s rotation. Seasons are caused by the Earth’s elliptical orbit around the Sun.

Earth’s greatest speed of rotation occurs at the equator. Two locations separated by 1 degree of longitude differ in solar time by 4 minutes. The number of worldwide standard time zones is 24. Travelers crossing the International Date Line change their calendar by one day.

The approximate location of the International Date Line is the 180th meridian. Parallax of nearby stars provides evidence that Earth moves around the sun. Earth is closest to the sun on or about January 2. The Earth’s seasons are caused by revolution of Earth around the sun and tilt of Earth’s axis.

Earth’s rate of revolution is very close to 1 degree per day. 1 degree per day would give us a 360 day year. We actually have closer to 365.25 days in a year.

A: Inner core Solid iron and nickel B: Outer core Liquid iron and nickel C: Mantle Solid of iron, silicon, and magnesium with liquid properties. D: Crust Thin, rigid layer of lighter rocks. Includes the Earth’s surface.

Essay Earth has slowly been losing heat since its formation. Discuss the reasons why heat loss varies over Earth’s surface. Some rock types lose heat more quickly than others. The thickness of the crustal rock varies from place to place. The percentage of radioactive material in rocks varies.

Essay Every fourth year, the calendar year is 366 days long. Using your knowledge of Earth’s revolution , explain why such a leap year is necessary. What would happen to the calendar compared to the seasons if leap years were not observed? Earth revolves around the sun in a little more than 365 days. The extra partial day would add up over time, causing the seasons to gradually shift dates.