Shape of the Earth

[Mohit Pandey]

What is the exact name given to the shape of the Earth?

I read somewhere that poles are not in proper shape. Please tell me about it also.:)

[Jay-qu]

I am not sure what you would call it either, its a sphere that bulges at the middle, ie its equitorial diameter is larger than its polar diameter. This is because of the spin :)

[ronthepon]

An oblate spheroid or something of that sort.

 

Umm... yeah. Here it is.

 

http://regentsprep.org/Regents/earthsci/units/introduction/oblate.cfm

[Boerseun]

Squashed ball?

[arkain101]

a flat dimension stuck in a gravity curve in space-time?

 

 

The poles are not at the very top and bottom. They fluctuate posistion, based on the action of the core inside the earth.

 

The magma core is massive and a large generator of magnetic field.

 

According to evidence the magnetic field flips poles from time to time (Tens of thousands of years -time to time-)

[Turtle]

a flat dimension stuck in a gravity curve in space-time?

 

 

The poles are not at the very top and bottom. They fluctuate posistion, based on the action of the core inside the earth.

 

The magma core is massive and a large generator of magnetic field.

 

According to evidence the magnetic field flips poles from time to time (Tens of thousands of years -time to time-)

 

NO; it is not flat.

NO; this only refers to the magnetic poles, not the geographic poles.

NO; the core is not magma, the mantle is.

Yes; the magnetic poles flip and wander, but NO, this has nothing to do with Earth's shape.

[Turtle]

I am not sure what you would call it either, its a sphere that bulges at the middle, ie its equitorial diameter is larger than its polar diameter. This is because of the spin :cup:

 

Earth's spin (rate of rotation) has little to do with the oblate speroid shape of Earth. The root cause is tidal bulge from the gravitational pull of the Moon.

There are also tides in the solid earth. The tidal bulge is about 1 meter high. The moon pulls up this tidal bulge on the earth, there is a time delay between the pull of the moon and the time when the tidal bulge reaches its maximum height. During this time the rotation of the earth carries this tidal bulge around the planet in the direction of rotation.

 

http://www.exo.net/~pauld/physics/tides/tidalevolution.htm

The calculus of tidal bulging:

http://scienceworld.wolfram.com/physics/TidalTorque.html

 

The Sun also effects a tidal bulge on Earth, but I'm still tracking down the amount. BBS

 

Addendum:

 

The moon, which is approximately 240,000 miles (386,240 km) from the earth, exerts a greater influence on the tides then does the sun, which sits 93 million miles (150 million km) from the earth. The strength of the sun's gravity is 179 times that of the moon's but the moon is responsible for 56% of the earth's tidal energy while the sun claims responsibility for a mere 44% (due to the moon's proximity but the sun's much larger size).

http://geography.about.com/od/physicalgeography/a/tides.htm

[arkain101]

NO; it is not flat.

joking

 

NO; this only refers to the magnetic poles, not the geographic poles.

thats what I said :cup: or at least meant.

 

NO; the core is not magma, the mantle is.

I stand corrected. Center of the earth creates magnetic field right? I realise now I am not sure what section exactly.

 

Yes; the magnetic poles flip and wander, but NO, this has nothing to do with Earth's shape.

Agreed. But they change posistion as I said.

[Turtle]

joking

Oh.;) :eek2: :doh:

 

I stand corrected. Center of the earth creates magnetic field right? I realise now I am not sure what section exactly.

More or less correct; the exact dynamics remain under scientific study and debate.

 

Agreed. But they [magnetic poles]change posistion as I said.

Just nod & smile. :cup:

[Turtle]

Squashed ball?

 

More like a squishing ball, and not to be confused with a squash ball. :cup:

[Mohit Pandey]

Is it called Geiod?

C.F. Gauss describes it as "mathematical figure of the Earth".

 

Which is the answer, oblate spheroid(according to ronthepon) or Geiod?

Tell me...................:doh:

[Qfwfq]

The term geoid means the equipotential surface which extends mean sea level. It is approximately an ellipsiod of rotation, with the two equal axes being greater than the unequal one. The exact geoid has local discrepancies due to inhomogeneity of the material, mountains and valleys etc. so the ellipsoid is called the theoretical geoid.

 

Earth's spin (rate of rotation) has little to do with the oblate speroid shape of Earth. The root cause is tidal bulge from the gravitational pull of the Moon.

:umno:

It is due exactly to rotation as JQ says, considering the composition of gravitation and the centripetal acceleration. The difference between the radius at the geographic poles and that at the equator is much more than 1 metre. The gradient of the moon's gravity field changes the geoid by less than a metre, something like half, and this can be amplified at coasts according to many dynamic factors.

[Turtle]

Earth's spin (rate of rotation) has little to do with the oblate speroid shape of Earth. The root cause is tidal bulge from the gravitational pull of the Moon.

:umno:

It is due exactly to rotation as JQ says, considering the composition of gravitation and the centripetal acceleration. The difference between the radius at the geographic poles and that at the equator is much more than 1 metre. The gradient of the moon's gravity field changes the geoid by less than a metre, something like half, and this can be amplified at coasts according to many dynamic factors.

 

:doh: Guess I was the one that spun out of control on this one! :doh: :hihi: Thanks Q.:hihi:

[Qfwfq]

:hihi: No problem Pal.

 

Another difference is that the alteration due to the :ebomb: is more egg-like.

 

This appears to be a very detailed source, though I haven't yet read it in detail.

 

Yep, as I thought, the difference in radius is some 20 km!

[saidevo]

The Earth spins at a rate of nearly 30 km/s. Its diameter is nearly 8,000 miles. Its inner core is located roughly 3,100 miles below the surface and has temperature in the range 5,000 to 6,000 deg.C. The outer core is located roughly 1,800 miles below, and the mantle with its temperature in the range 1,000 and 4,000 deg.C occupies an area from 37 miles below. The crust and the lithosphere extend to a depth of hardly 40 miles out of the radius of the Earth which is around 4,000 miles (just one percent). (http://en.wikipedia.org/wiki/Earth). The surface temperature on the Earth is within a range of, say 50 deg.C below and above zero.

 

Some questions arise with this composition:

 

1. Since heat dissipates faster, why hasn't all the heat at the core and mantle escaped through the atomic pores of the upper layers through the ways it propagates (conduction, convection and radiation), allowing Earth to cool down faster than it is doing? Taking into account the enormous volume of water on and under the surface, and the massive polar ice regions, heat dissipation should take place at a much faster rate. If the inner heat is sustained by pressure, how exactly does this pressure prevent heat dissipation, since we know that ether or space occupies everywhere (even inside the atoms) as a continuum.

 

2. If the center of gravity of the earth is at its center in the inner core, inasmuch as the solid rocky surface is hardly 1% of its radius (40 miles out of 4,000), and with the earth spinning very fast, why hasn't the crust and lithosphere collapsed to form a more compact shape? Since this is not happening, can it be right to say that there is no center of gravity but only a ring of gravity located half way down the solid outer surface (crust and lithosphere)?

 

3. In the dryer of a washing machine or in a cement-concrete mixture, because of the spin, the contents are thrown towards the rim, leaving a hollow portion inside with openings at the polar regions. Why shouldn't this happen for the Earth also, considering its eternal, tremendous spinning rate?

 

I would expect an answer that a layman could follow, free of mathematical equations.

[Boerseun]

The Earth spins at a rate of nearly 30 km/s.

The Earth spins on its axis at around 460m/s. The Earth orbits the Sun at around 30km/s.

 

This is easily calculated:

40,000km / 24 hours / 60 min / 60 sec = approx. 460 meters per second at the equator.

[Mohit Pandey]

Excuse me!

But I have not got the answer of the question which I have asked at the beginning till now.

Please spare some time for it.:)