core of earth

JonC · 8 Oct 2006 at 18:04

Mickey_D said:
snip

Aaaaargh!!!!!!

Centripetal/centrifugal forces DO NOT EXIST!!!

All you are doing is adding up forces and saying "I'll call this X".

When you swing a bucket, you exert a force because you are accelerating an object, in order to get it to spin in a circle. There is no "Escape Attempt force", or "Restrain" force, they are the result of other forces at work. This is where the misconception comes from.

As Psyk said, it's like accelerating in a car.

Psyk · 8 Oct 2006 at 18:04

Slam62 said:
isnt it true that nobody really knows whats in the earths core so he could be right, a big lump of iron sounds a bit unlikely, isnt it some sort of reaction ala the sun?

Stupid asking really as no one knows

I think there are many people that have a pretty good idea of what's there

There are radioactive isotopes in there too which is what keeps things nice and toasty down there.

growse · 8 Oct 2006 at 18:04

Slam62 said:
isnt it true that nobody really knows whats in the earths core so he could be right, a big lump of iron sounds a bit unlikely, isnt it some sort of reaction ala the sun?

Stupid asking really as no one knows

No, it's a big lump of hot solid iron under a lot of pressure. Of course we can't go down and have a look, but the experimental evidence suggests it's a big solid lump of hot iron under a lot of pressure. If it walks like a duck, and has feathers like a duck, and it quacks like a duck..... etc.

growse · 8 Oct 2006 at 18:07

JonC said:
Aaaaargh!!!!!!

Centripetal/centrifugal forces DO NOT EXIST!!!

All you are doing is adding up forces and saying "I'll call this X".

When you swing a bucket, you exert a force because you are accelerating an object, in order to get it to spin in a circle. There is no "Escape Attempt force", or "Restrain" force, they are the result of other forces at work. This is where the misconception comes from.

As Psyk said, it's like accelerating in a car.

Centrepetal acceleration *does* exist (Centrifugal *does not*). Without it, the bucket would go flying off in a straight line (Newton I). In the bucket model, without mavity and air resistance, the bucket will maintain the same velocity. In order to pull it round into a circle, you need to exert a force on it which is constantly perpendicular to the velocity vector. This won't affect its speed in any way (it's perpendicular), but it will affect it's direction. This, acting inwards, is the centrepetal force.

VaderDSL · 8 Oct 2006 at 18:10

Slam62 said:
isnt it true that nobody really knows whats in the earths core so he could be right, a big lump of iron sounds a bit unlikely, isnt it some sort of reaction ala the sun?

Stupid asking really as no one knows

We know shed loads about the core of the Earth, mainly the composition and state of the core.

We know the core has a solid interior, and that the outer core is molten. Geologists use seismic waves to map out the interior of the Earth.

Basically, there are shadow zones on opposite sides of the Earth to where Earthquakes propogate out from, as S & P waves (with different properties) are deflected, and absorbed by different boundaries within the Earth's core.

For example S waves (shake waves if you will) will not travel through liquids, and is deflected at certain points through the Earth's core. So you get areas on the opposite sides of the globe, from about 104 degrees and beyond.
It's basic Geology

From Wikipedia

Slam62 · 8 Oct 2006 at 18:14

tbh that all sounds pretty much like using long words to be vague, a few hard lumps with a molten bit around the outside with a cool crust.

Well the molten bit with a cool crust i worked out for my self, so now the detail of the rest boils down to some lumpy bits.

Doesnt sound like shed loads to me.

Efour · 8 Oct 2006 at 18:15

hhaha noobs :O

I hate talking about geology.

easy to understand version

growse · 8 Oct 2006 at 18:17

Slam62 said:
tbh that all sounds pretty much like using long words to be vague, a few hard lumps with a molten bit around the outside with a cool crust.

Well the molten bit with a cool crust i worked out for my self, so now the detail of the rest boils down to some lumpy bits.

Doesnt sound like shed loads to me.

We kinda know what it's made of, roughly how hot it is, how dense it is, how big it is, probably how viscous the liquid is, how much pressure it's under. It's quite a lot actually. Slightly more than just 'vague'.

Psyk · 8 Oct 2006 at 18:17

Slam62 said:
Doesnt sound like shed loads to me.

There's much more evidence for it than that. There are many ways to know about things we cannot see with our own eyes.

JonC · 8 Oct 2006 at 18:19

growse said:
Centrepetal acceleration *does* exist (Centrifugal *does not*). Without it, the bucket would go flying off in a straight line (Newton I). In the bucket model, without mavity and air resistance, the bucket will maintain the same velocity. In order to pull it round into a circle, you need to exert a force on it which is constantly perpendicular to the velocity vector. This won't affect its speed in any way (it's perpendicular), but it will affect it's direction. This, acting inwards, is the centrepetal force.

It is the resultant force, due to you exerting an electromagnetic force on the rope, etc etc etc...

http://en.wikipedia.org/wiki/Fundamental_force

It is not a force in it's own right.

growse · 8 Oct 2006 at 18:23

JonC said:
It is the resultant force, due to you exerting an electromagnetic force on the rope, etc etc etc...

http://en.wikipedia.org/wiki/Fundamental_force

It is not a force in it's own right.

Oh, I see what you're getting at - It's not a fundamental force (one of the 4 etc). True, on a very very "back to basics" level

I misunderstood and thought you were saying that centrepetal force is the sum of a bunch of other non-fundamental forces, acting in different directions, which it isn't. It's exerted by the central object and the medium and, as you say, is the result of probably mostly electromagnetic forces in the case of the rope.

An even simpler model would be an orbit of one point mass around the other. Here the centrepetal acceleration is a single force - mavity, which is fundamental. If you don't have point masses, you've got to effectivly sum over every atom in one mass having an effect on every atom in the other mass. End result is still the same - the moon doesn't travel in a straight line.

Psyk · 8 Oct 2006 at 18:26

growse said:
An even simpler model would be an orbit of one point mass around the other. Here the centrepetal acceleration is a single force - mavity, which is fundamental.

But is mavity really a force? (sorry, just read the wikipedia link

)

Slam62 · 8 Oct 2006 at 18:28

Cripes i was only asking as earlier this year i went to the nat hist museum with the kids and there was some sort of special expo thing about the earth and when you got to the bit about the core it all seemed a bit conjectural.

As per a lot of 'science' theories, they are presented to people as facts even though they are conclusions drawn from other known facts.

A bit like the weatherman saying its going to rain when he's not a hundred percent certain.

Even different densities to me dont mean we know whats going on under our feet.

For instance why is the rock molten under the crust what is generating the heat
obviously it must be some sort of exothermic reaction (nuclear fusion) i doubt we could ever find out for sure.

but we dont really know or if we do we're not saying

At the end of the day, understanding the earths core is way out of our league

Psyk · 8 Oct 2006 at 18:35

Slam62 said:
Cripes i was only asking as earlier this year i went to the nat hist museum with the kids and there was some sort of special expo thing about the earth and when you got to the bit about the core it all seemed a bit conjectural.

As per a lot of 'science' theories, they are presented to people as facts even though they are conclusions drawn from other known facts.

A bit like the weatherman saying its going to rain when he's not a hundred percent certain.

Even different densities to me dont mean we know whats going on under our feet.

For instance why is the rock molten under the crust what is generating the heat
obviously it must be some sort of exothermic reaction (nuclear fusion) i doubt we could ever find out for sure.

but we dont really know or if we do we're not saying

At the end of the day, understanding the earths core is way out of our league

Science doesn't deal with certainties, it deals with probabilities. We aren't 100% sure of anything at all. But there are some things we can be 99.9999999% sure of. The nature of the earth's core is something that current science is fairly sure of, even though we don't know it with a 100% certainty.

If it looks like a duck, quacks like a duck, has feathers like a duck, it's probably a duck. But there's a slim chance it's something else.

Slam62 · 8 Oct 2006 at 18:39

aah well i'm an engineer, i deal with certainties

Amp34 · 8 Oct 2006 at 18:46

Efour2 said:
hhaha noobs :O

I hate talking about geology.

easy to understand version

That article is wrong on a few facts, the mantle isn't moltern or liquid, it is solid. The only liquid part of the earths interior is the outer core and magma plumes.

Jambo · 8 Oct 2006 at 18:57

I don't buy it to be honest.

I reckon there is a secret world of aliens in The Core. How they laugh at the outer people.

growse · 8 Oct 2006 at 19:03

Slam62 said:
aah well i'm an engineer, i deal with certainties

Bah, daft engineers. Blind to the realities of the modern world

aardvark · 8 Oct 2006 at 19:08

Slam62 said:
Cripes i was only asking as earlier this year i went to the nat hist museum with the kids and there was some sort of special expo thing about the earth and when you got to the bit about the core it all seemed a bit conjectural.

As per a lot of 'science' theories, they are presented to people as facts even though they are conclusions drawn from other known facts.

A bit like the weatherman saying its going to rain when he's not a hundred percent certain.

Even different densities to me dont mean we know whats going on under our feet.

For instance why is the rock molten under the crust what is generating the heat
obviously it must be some sort of exothermic reaction (nuclear fusion) i doubt we could ever find out for sure.

but we dont really know or if we do we're not saying

At the end of the day, understanding the earths core is way out of our league

the evidence so far points to the heat in the core simply being left over from the formation of the planet - there is also the friction caused by the rotation (its beleived that the core rotates faster than the rest of the planet) and i wouldn't be suprised if the magnetic fields have a significant effect and a number of other theories (one involves nuclear fission - but thats regarded as a pretty dodgy theory).

its pretty obvious that the core is made from an iron/nickel combination - a lot of the subtle details are still not known though.

Amp34 · 8 Oct 2006 at 19:21

A lot of heat in the core is due to residual heat but by no means all. Radioactivity Uranium>lead etc. is a well established and thought out theory. It helps confirm the age of the earth too. Simply put the if it was just residual heat the earth could only be a couple of hundred million years old not the 4.57 billion it actually is.