Earth gets its name from the old English word ‘eorthe’ meaning ground. It is the only place in our solar system that can sustain life and which is attributed to many factors, including its distance from the Sun. Earth is at a distance that allows water to form as a liquid giving us the oceans from which life began. Our strong magnetosphere is created by our large iron core and the momentum of the planet, without it, solar storms would’ve destroyed any chance life long ago.
At the Equator: 6,378 km or 3,963 miles
At the Poles: 6,356 km or 3,949 miles
Average: 6,371 km or 3,959 miles
Circumference of the Earth: 40,075 km or 24,901 miles around the equator and 40,007 km around the poles.
The Earth’s Mass 5.9736×1024kg
Earths Volume is 108.321 x1010
The Radius of Earth’s core is 3,485 km
The Outer crust is a solid crust of rock less than 0.3 % of the Earths centre. The second layer is molten rock that has been heated by the radioactivity of the core and the pressures acting upon it. The next layer down is a massive sea of molten iron about the size of the moon. It is the hot molten metal sea moving towards the surface and then sinking again in a giant whirlpool that creates the Earth’s gigantic magnetosphere that protects us from most dangerous cosmic rays and solar flares. But new understanding of these fluid iron whirlpools are showing that the Earth doesn’t have a solid north and south magnetic poles but the poles move slightly and constantly. More alarmingly is that a part of our magnetosphere appears to be weakening and has been for some time. The phenomenon is being closely measured by scientist and they have named the phenomenon called the South Atlantic anomaly. The Hubble telescope seems to be showing possible affects of this when it passes through the south Atlantic anomaly it is being bombarded by cosmic particles that are getting through the weakened magnetosphere. These particles on occasion are causing interference with the Hubble telescope and have caused a loss in communication.
It means that the movement of the core could, over 1-10 thousand years, cause the poles to flip entirely but the gradual change may produce some very strange effects on earth such as two north or south poles simultaneously. Evidence has been found that the Earth’s poles have changed and flipped on many occasions and chances are will continue to do so.
The most recent discovery made possible by studying the seismic waves sent through the earth during earth quakes. The data showed that within the sea of molten metal and in the very centre of the Earth is a very large solid mass of an iron, nickel alloy slightly smaller than the moon. New experiments using iron-nickel alloys show that the centre is likely to contain giant crystals up to 10 km in length that grew in the direction of the poles. This explained another mystery which was why shockwaves seemed to travel faster north to south as opposed to east to west. It is now believed that these giant crystals act as a conduit increasing the speeds of the shockwaves travelling North and South.
It seems as if it would be impossible for man of machine to journey to the centre of the Earth as the pressure and temperature continues to increase and it is believed that the temperature increase by about 20 degrees centigrade for every kilometre travelled towards the Earth's centre which is believed to be 3000 times that of the surface
In 1975 two papers were published with a new theory that would change our picture of how Earth was formed and its relationship with our moon. One paper by William K. Hartmann and Donald Davis and another by Alfred G. W. Cameron and William Ward were written to explain why the moon has such a small metallic core which seems to be abnormal to the other celestial bodies in our solar system. The theory is called ‘The Giant Impact Hypothesis’ and is now regarded as the most plausible explanation for the structure of our moon and Earth.
For many years physicists tried to explain how the moon was formed but these theories didn’t fit with what we now about planetary formation, then in the 1970’s two pairs of physicists working on the problem came to the same conclusion.
The theory is that late into the formation of Earth while it was still a hot molten void it was struck by another planetary body about the size of Mars. The other planet hit what would become Earth on one side but with enough force to cause our spin and sheer off most of the crust. This sent the smaller planet spinning around with a tail of its own crust following. Both planets span around each other before coming together once more.
When the bodies collided for a second time their large iron cores fused together with most of the crust forming around the outside of this newly formed planet. Some crust was ejected into close orbit where it began to coalesce into the moon.
This theory explains why Earth has such a large core and why the moon is mainly made of silicon rock like our crust. It is still only a hypothesis as many experiments required to prove it conclusively would be very difficult to perform but all data collected including radioactive dating shows that the Earth and moon formed between 50 – 100 million years after the rest of the Solar system.
Image credit NASA
Illustration of a solar storm shedding vast amounts of radiation towards Earth which is protected moderately by its magnetosphere (a magnetic barrier created by the huge iron core and the Earth’s rotation)
Ref:
http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=446
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