center of earth...

[wstrege]

first,i am not a physics study, though i did have a class in high school 5 years ago.

with that said, i am wondering why it is a common belief to think of a solid nickel-iron core at the center of the earth. gravity is the attraction of matter to matter. so the all the matter of the earth is pulling us down. well, if i were at a point where there is matter pulling equally(or close to it) in all directions there would be effectively no gravity. this point/area would be near the center on the earth. Therefore there would be no pressure there and no reason for a solid mass in the center.

[RyanJ]

first' date='i am not a physics study, though i did have a class in high school 5 years ago.

with that said, i am wondering why it is a common belief to think of a solid nickel-iron core at the center of the earth. gravity is the attraction of matter to matter. so the all the matter of the earth is pulling us down. well, if i were at a point where there is matter pulling equally(or close to it) in all directions there would be effectively no gravity. this point/area would be mear the center on the earth. Therefore there would be no pressure there and no reason for a solid mass in the center.[/quote']

 

Good reasonins though there is a solid mass within the center of the Earth caused by the preassure from all the material on top of it

 

What you said would be true for the very center of the Earth but the core is well very big. This means that there will be gravity acting twards it and trying to compress it - adding to the preassure resulting in a solid mass

 

This has been proved by various methods one of the most interesting involving propegation of earthquake shoch waves through the interior.

 

And also don't forget that there are two layers to the core, an outer and an innter! The outer is liquid and the inner is solid

 

Cheers,

 

Ryan Jones

[wstrege]

Good reasonins though there is a solid mass within the center of the Earth caused by the preassure from all the material on top of it

 

there only reason there is pressure at all is because of gravity itself, it wouldn't matter how much stuff there is if there is no force acting on it, as i propose. if anything, stuff closer to the center would have the gravity of all the materials surrounding it pulling it toward the surface

[wstrege]

imagine stripping off the 1/2 of the earths mass. so you are left with a mass with half the gravity, right? now pile all that stuff back on top; yes that stuff is being pulled down too but at the same rate you were at that level. remember that the mass above you is also acting on you, pulling you up, to a lesser extent, but still acting on you and the ground that was just covered up...

[RyanJ]

there only reason there is pressure at all is because of gravity itself, it wouldn't matter how much stuff there is if there is no force acting on it, as i propose. if anything, stuff closer to the center would have the gravity of all the materials surrounding it pulling it toward the surface

 

True!

 

But what I said was this. If the center of Earth was small then there would be no gravity acting on some of it because its smaller relative to its center.

Because the Earths core is quite large (5100 to 6378KM for the inner core) gravity does act on it and thus there is preassure to keep it solid. its the same with the other planets though ther should be a point where a planets mas is sufficient to melt the core but not to keep it solid but on Earth this is not the case

 

This has actually been proven too.

 

Oh, and I forgot to say welcome to the forums

 

Some links:

 

http://www.livescience.com/forcesofnature/050414_earth_core.html

http://starryskies.com/articles/2003/08/earth.facts.html

 

 

Cheers,

 

Ryan Jones

[wstrege]

once again, i am challenging the current theories of the internal structure. you still have to account for the lack of gravity in the center area. remember the closer to the center of the mass you get the less gravity pulls you toward it.

[YT2095]

there would still be gravity pulling on you, it would just be spread even in all directions.

the only time gravity would be acting on you Least would be during the fall down that hole.

[RyanJ]

once again, i am challenging the current theories of the internal structure. you still have to account for the lack of gravity in the center area. remember the closer to the center of the mass you get the less gravity pulls you toward it.

 

But there would br gravity at the center... The center of mass is where all the gravity acts.

 

Because of the huge size of the core most of it would experience normal gravity and thus can have high compression and it therefor explaining why its solid even thought the temperature is greater than that of its melting point

 

If I'm not expalaing what I mean well - my applogies and I'll leave it to the experts to try and prove it

 

Cheers,

 

Ryan Jones

[YT2095]

lets consider an extreme, we have a hypothetical Gas Giant with 100x Earths gravity, and it also has a holow core that suddenly find yourself right in the Center of.

within seconds you`de be ripped apart and become as red paint on the walls of this cavern.

 

if it tied your hand to a truck and your feet to another truck and they slowly moved appart, you`de be lifted off the ground for a few seconds, this isn`t due to lack of Force, it`s Because of Force. the same would apply with gravity, but less Linear than 2 ropes and 2 trucks, it would be a full 360 even spread.

[wstrege]

i understand current theories, but i believe they are flawed because they do not consider varying degrees of gravity as one approaches the core.

[RyanJ]

i understand current theories, but i believe they are flawed because they do not consider varying degrees of gravity as one approaches the core.

 

If anything gravity increases preassure due to the fact your approching the center of gravity and have more mass being pulled twards you.

 

You can't argue with facts, it is proven that the center of the Earth is solid by earthquake seismology (And the studdy of wave propegation through the Earth).

 

Cheers,

 

Ryan Jones

[wstrege]

YT, your truck example is good. you remove the person tied to the ropes, just tie the trucks together with an infinitely strong rope. now put the two trucks apart by the length of the rope. now both trucks pull in opposite directions at the same time and the rope will not move at all, because the net force is 0

[wstrege]

as mass is closer to the core, the mass at that depth and all mass above that specific depth is being pulled down at at some constant acceleration. at the surface of the earth it is 9.8 m/s/s . as you travel deeper into the earth that number will lessen, approaching 0.

[RyanJ]

as mass is closer to the core, the mass at that depth and all mass above that specific depth is being pulled down at at some constant acceleration. at the surface of the earth it is 9.8 m/s/s . as you travel deeper into the earth that number will lessen, approaching 0.

 

I've seen threads like this on other forums, there is gravity at the center of the Earth and the center of the Earth is solid!

 

Links:

 

http://www.scienceforums.net/forums/showthread.php?t=15792

http://www.scienceforums.net/forums/showthread.php?t=7174

http://www.newton.dep.anl.gov/askasci/env99/env002.htm

 

Ryan Jones

[timo]

with that said, i am wondering why it is a common belief to think of a solid nickel-iron core at the center of the earth.

I dunno. Analysis of shock waves play a role in that, afaik. But then, I didn´t even know the core was solid.

 

gravity is the attraction of matter to matter. so the all the matter of the earth is pulling us down. well, if i were at a point where there is matter pulling equally(or close to it) in all directions there would be effectively no gravity. this point/area would be near the center on the earth.

Yes.

Therefore there would be no pressure there and no reason for a solid mass in the center.

Nope.

Just because there´s no gravitational force working you can´t conclude that there´s no pressure. Spacecrafts would be a very unhealthy place if there was no pressure in them, for example. In the case of spacecrafts the pressure is due to the walls that won´t let the air escape into void. In the case of your earth core it´s the mass around the center of earth (which experiences a gravitational force) that excerts pressure on it.

[CanadaAotS]

Dont forget the fact that the Earth has a large magnetic field and it has to be powered by something (the iron core would do well with this).

 

BTW - All of Earth's Mass is centered on the center. The matter above you would not pull on you it would push you. Thats why when you have several thousand km's of dirt above your head it causes extreme pressures lol.

[YT2095]

YT, your truck example is good. you remove the person tied to the ropes, just tie the trucks together with an infinitely strong rope. now put the two trucks apart by the length of the rope. now both trucks pull in opposite directions at the same time and the rope will not move at all, because the net force is 0

 

no, your perversion of my example makes it ridiculous, my point (and a very simple one it was) is that although gravity is pulling you down before the trucks pull, when they Do pull you now have 3 forces acting upon you, trucks 1 and 2 and gravity.

now imagine Infinate trucks on everysingle particle of you all pulling in opposite directions (the full 360 degrees) you`de be ripped appart.

well the same thing would happen in an extreme planet with a hollow core, we`re lucky that on Earth the most we`ll feel naturaly is 1G, and so you Would float in the dead center and probably be no where near as uncomfortable as the Truck example.

 

in conclusion, gravity would STILL BE pulling on you in all directions, you`de have Escaped nothing, least of all Gravitational effect

[timo]

Oh, I only read the initial post before replying so I forgot this important one: You´re wrong YT.

The only force relevant when "infinite trucks pull on everysingle particle of you all pulling in opposite directions" is the net force (the sum). If it´s zero for every single particle, then every single particle experiences zero force.

As a matter of fact, it is a very important property of forces that you can arbitrarily split them up or sum them up as long as the sum of them remains unchanged. The prime example for an application is a ball rolling down a ramp where you split up the gravitational force into one parallel to the ramp and one perpendicular to it.

 

Take for example the classical electromagnetic force: Humans consist of a whole lot of electrons and protons. We´d probably blast each other over the distance from here to england if the attraction of my protons on your electrons wasn´t cancelled out by my electrons (might be a funny calculation, btw).

[YT2095]

if you`ve understood my example in the way you`ve stated then Yes you`re correct and I agree, however you have MISunderstood my example entirely, renedering your post useless.

 

think 2 trucks (yes it`s a little bit Linear in design but serves well as an example) gravity still acts upon you when the trucks have you suspended.

 

now imagine that in a 360 and less linear way, you`re in the dead center of this cavern in the middle of Earth, yes you`ll float, but only because you`re being pulled equaly in ALL (360 degrees) directions.

 

THAT is about as simple as I can explain it without throwing my hands in the air and giving up on this thread entirely.

[timo]

^^ Ok, I seem to have misunderstood you. Actually, it was the following statement that made me think you´re on the wrong track:

lets consider an extreme' date=' we have a hypothetical Gas Giant with 100x Earths gravity, and it also has a holow core that suddenly find yourself right in the Center of.

within seconds you`de be ripped apart and become as red paint on the walls of this cavern. [/quote']

Perhaps you could explain what you meant by above. Because the net gravitational force in above example (given the planet has a spherical symmetric mass distribution and the cave is spherical) would be zero for all of your atoms.

[YT2095]

the net gravitational force in above example (given the planet has a spherical symmetric mass distribution and the cave is spherical) would be zero for all of your atoms.

 

the pull on your head would be one direction (directly above) the pull at you feet would be in the 180 opposite direction (below) and same for right and left.

you`de be HELD by gravity, you wouldn`t be Unaffected by it, you`de just be pulled equaly in all directions at the same time, having the Visual effect of no Gravity.

 

now when you Fall down this hole to get there, THEN you`ll not experience the effect of Gravity, same with Skydiving.

[timo]

the pull on your head would be one direction (directly above) the pull at you feet would be in the 180 opposite direction (below) and same for right and left.

No. That´s what I was trying to tell you. The net force on each and every particle -regardless whether it´s the whole body, an arm or just an atom- is zero.

There was a thread about the gravitational field of a spherical symmetric mass a few days age where Swansont and me were topping each other with details a bit. Maybe I´ll find it and you believe this thread more than my words....

 

EDIT: There you go: http://www.scienceforums.net/forums/showthread.php?t=15720

 

Your position is at a certain radius. As long as the problem is spherical symmetric, the only matter relevant for gravitational attraction is that which is in the volume with a radius smaller than yours as the rest cancels out. Since you were talking about a hollow core, this mass is zero. This is true for both your head and your leg.

[YT2095]

if you assume perfect symetry and employ an asymetrical body (literaly a Body (human)) then the forces will NOT and never will be EVEN

[timo]

With "spherical symmetric" I meant the planet, of course. You don´t really expect the gravitational force of a human body on itself to have much influence, do you?

I´m not sure if it will impress you much but please let me state the following:

I can only keep such a posting frequency as we have it now because I have actually done such calculations to quite some extend during my first two years of studying (gravity and electrostatics are quite similar for these kind of problems). I wouldn´t be so quick with my responses if I wasn´t quite certain about what I say. So please take a moment to think about the physical situation a bit. I´ll also think about whether I maybe misunderstood your posts.

 

Try to forget the gravitational attraction of the human body on itself. Then, consider each atom of the human body as seperate. Hopefully, you´ll see that the net gravitational force on that atom is zero. Then, try to understand that it´s zero for each and every atom of the human body.

[YT2095]

Try to forget the gravitational attraction of the human body on itself. Then, consider each atom of the human body as seperate. Hopefully, you´ll see that the net gravitational force on that atom is zero. Then, try to understand that it´s zero for each and every atom of the human body.

 

I cannot comply, it`s not within the parameters set by the original post and would be subject to OFF TOPIC regulations.

 

although your arguments isn`t flawed, you may as well be talking about the best way to cook an egg, it simply does Not apply here in this thread.