LSD-1 Love Our Live Planet!

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Vital Statistics…

Earth is the third planet from the Sun and the fifth largest:

orbit: 149,600,000 km (1.00 AU) from Sun

diameter: 12,756.3 km

mass: 5.9736e24 kg

Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic. There are, of course, hundreds of other names for the planet in other languages. In Roman Mythology, the goddess of the Earth was Tellus – the fertile soil

In Greek mythology Gaia was “terra mater” – Mother Earth).

It was not until the time of Copernicus (the sixteenth century) that it was understood that the Earth is just another planet.

Earth, of course, can be studied without the aid of spacecraft. Nevertheless it was not until the twentieth century that we had maps of the entire planet. Pictures of the planet taken from space are of considerable importance; for example, they are an enormous help in weather prediction and especially in tracking and predicting hurricanes. And they are extraordinarily beautiful.

Layer After Layer, After Layer…

The Earth is divided into several layers which have distinct chemical and seismic properties:

0- 40 km. – Crust 40- 400 km. – Upper mantle 400- 650 km. – Transition region

650-2700 km. – Lower mantle 2700-2890 km. – “D” layer 2890-5150 km. – Outer core 5150-6378 km. – Inner core

The crust varies considerably in thickness, it is thinner under the oceans, thicker under the continents. The inner core and crust are solid; the outer core and mantle layers are plastic or semi-fluid. The various layers are separated by discontinuities which are evident in seismic data; the best known of these is the “Mohorovic Disconti­nu­­ity“ between the crust and upper mantle.

Hotter than the Sun???

The Earth core is probably composed mostly of iron (or nic­kel/iron) though it is possible that some lighter elements may be present, too. Temperatures at the center of the core may be as high as 7500 K, hotter than the surface of the Sun. The lower mantle is probably mostly silicon, magnesium and oxygen with some iron, calcium and aluminum. The upper mantle is mostly olivene and pyroxene (iron/magnesium silicates), calcium and aluminum. We know most of this only from seismic techniques; samples from the upper mantle arrive at the surface as lava from volcanoes but the majority of the Earth is inaccessible. The crust is primarily quartz (silicon dioxide) and other silicates like feldspar.

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