Thought Experiment, need opinions

This topic is locked from further discussion.

Avatar image for RedentSC
RedentSC

1243

Forum Posts

0

Wiki Points

0

Followers

Reviews: 0

User Lists: 0

#1  Edited By RedentSC
Member since 2013 • 1243 Posts

So, basically

At the centre of the earth, we have a solid core and an outer liquid core. All the gravity we feel on the surface is due to the mass of the earth 'below' us (relitivty)

Now at the centre of the earth, the only gravity that should be there would be pulling 'outwards' (away from the centre in all direction) as this is where the mass of the earth now resides.

Now, as the pressure (in the case we are taaking about anyway) present in the core of the earth is only there due to the huge amount of weight placed in it (due to gravity) then would there be an empty sphere at the centre of the planet? a little ball shapped hole with no gravity? as all the gravity should be acting in the oposite direction you'd assume (as all the mass that bends space time to create the gravity is now "above" the centre of the core. More to the point the gravity will be acting at the same strength in all directions, creating what we would assume to be an empty sphere.

Its a hard thing to describe but hopfully you get my drift

Any thoughts from any sciencey people on here?

Avatar image for SaintLeonidas
SaintLeonidas

26735

Forum Posts

0

Wiki Points

0

Followers

Reviews: 2

User Lists: 0

#2 SaintLeonidas
Member since 2006 • 26735 Posts

No.

Avatar image for RedentSC
RedentSC

1243

Forum Posts

0

Wiki Points

0

Followers

Reviews: 0

User Lists: 0

#3 RedentSC
Member since 2013 • 1243 Posts

Can you justify you response? If not then it's meaningless.

Avatar image for SaintLeonidas
SaintLeonidas

26735

Forum Posts

0

Wiki Points

0

Followers

Reviews: 2

User Lists: 0

#4 SaintLeonidas
Member since 2006 • 26735 Posts

@RedentSC said:

Can you justify you response? If not then it's meaningless.

You don't seem to have a full understanding as to how gravity, mass, etc. works. There cannot be a gravityless hole/sphere in the center of a planet - no thought experiment needed for this...just basic science.

Avatar image for RedentSC
RedentSC

1243

Forum Posts

0

Wiki Points

0

Followers

Reviews: 0

User Lists: 0

#5  Edited By RedentSC
Member since 2013 • 1243 Posts

@SaintLeonidas: OKay, so if i don't have a basic understanding of General Relitivity (which i never claimed i did) please explain why this is not possible. as mass bends spacetime, in the direction of the centre of mass. when at the centre of the earth, the centre of mass is not the centre of the earth (reletive to me)

Is this not correct? and if not, explain why its not. you cannot just dismiss an hypothosis without expliantion, you may as well just say "god made it that way"

I'm not trying to prove you wrong, i just want evidence or an explination either way. As my "basic" A-Level understanding of physics clearly doens't cut the mustard, where as your clearly does

Avatar image for SaintLeonidas
SaintLeonidas

26735

Forum Posts

0

Wiki Points

0

Followers

Reviews: 2

User Lists: 0

#6 SaintLeonidas
Member since 2006 • 26735 Posts

@RedentSC said:

@SaintLeonidas: OKay, so if i don't have a basic understanding of General Relitivity (which i never claimed i did) please explain why this is not possible. as mass bends spacetime, in the direction of the centre of mass. when at the centre of the earth, the centre of mass is not the centre of the earth (reletive to me)

Is this not correct? and if not, explain why its not. you cannot just dismiss an hypothosis without expliantion, you may as well just say "god made it that way"

I'm not trying to prove you wrong, i just want evidence or an explination either way. As my "basic" A-Level understanding of physics clearly doens't cut the mustard, where as your clearly does

So you are throwing a theory out into the world, that you admit is based only on your limited knowledge of the principles at play - and want others to prove or disprove why you are wrong? I can most definitely dismiss a hypothesis if the presenter has presented anything that can be dismissed by basic science. There are no gravity-less spheres in the middle of large bodies of mass. Just can't happen. Just a dense center - and if the force of gravity is large enough, then the opposite of what you say is true, the mass gets compressed and so dense it becomes a black hole...which has an inescapable level of gravity.

Avatar image for comp_atkins
comp_atkins

38662

Forum Posts

0

Wiki Points

0

Followers

Reviews: 3

User Lists: 0

#7  Edited By comp_atkins
Member since 2005 • 38662 Posts

the theory i assume would be technically accurate for a perfectly spherical object with uniform density throughout but the due to the way stars / planets and anything with significant mass their centers would be very dense and thus not devoid of matter/gravity

however for example if you could theoretically drill a wide hold through through the earth from crust to crust and jumped in once you passed the center of the planet you would essentially be falling "up" back towards the crust. given air resistance would slowly eat away at your speed ( assuming there is air in there ) you would oscillate back and forth in the tube until eventually reaching an equilibrium at the center of the planet. you would be "weightless" but that doesn't mean there is no gravity, just that the forces would pull on you equally in all directions and cancel each other out, giving the impression of no gravity

Avatar image for LJS9502_basic
LJS9502_basic

178810

Forum Posts

0

Wiki Points

0

Followers

Reviews: 0

User Lists: 0

#8 LJS9502_basic
Member since 2003 • 178810 Posts

Do your own homework....

Avatar image for dave123321
dave123321

35553

Forum Posts

0

Wiki Points

0

Followers

Reviews: 0

User Lists: 0

#9 dave123321
Member since 2003 • 35553 Posts

The science people will know.

hey lj, you should come to tdh

Avatar image for SaintLeonidas
SaintLeonidas

26735

Forum Posts

0

Wiki Points

0

Followers

Reviews: 2

User Lists: 0

#10 SaintLeonidas
Member since 2006 • 26735 Posts

@comp_atkins said:

the theory i assume would be technically accurate for a perfectly spherical object with uniform density throughout but the due to the way stars / planets and anything with significant mass their centers would be very dense and thus not devoid of matter/gravity

however for example if you could theoretically drill a wide hold through through the earth from crust to crust and jumped in once you passed the center of the planet you would essentially be falling "up" back towards the crust. given air resistance would slowly eat away at your speed ( assuming there is air in there ) you would oscillate back and forth in the tube until eventually reaching an equilibrium at the center of the planet. you would be "weightless" but that doesn't mean there is no gravity, just that the forces would pull on you equally in all directions and cancel each other out, giving the impression of no gravity

Tunnel through earth theory has never made much sense to me. If you managed to survive the temps - there should still be gravity pulling from other directions - perpendicular to the tunnel - either collapsing it or pulling the person falling against the side. Even IF you managed to somehow create a hollow sphere in the center of a planet, the walls of which are strong enough to support the mass above, the force of gravity would still pull into a single point.

Avatar image for comp_atkins
comp_atkins

38662

Forum Posts

0

Wiki Points

0

Followers

Reviews: 3

User Lists: 0

#11 comp_atkins
Member since 2005 • 38662 Posts

@SaintLeonidas said:

@comp_atkins said:

the theory i assume would be technically accurate for a perfectly spherical object with uniform density throughout but the due to the way stars / planets and anything with significant mass their centers would be very dense and thus not devoid of matter/gravity

however for example if you could theoretically drill a wide hold through through the earth from crust to crust and jumped in once you passed the center of the planet you would essentially be falling "up" back towards the crust. given air resistance would slowly eat away at your speed ( assuming there is air in there ) you would oscillate back and forth in the tube until eventually reaching an equilibrium at the center of the planet. you would be "weightless" but that doesn't mean there is no gravity, just that the forces would pull on you equally in all directions and cancel each other out, giving the impression of no gravity

Tunnel through earth theory has never made much sense to me. If you managed to survive the temps - there should still be gravity pulling from other directions - perpendicular to the tunnel - either collapsing it or pulling the person falling against the side. Even IF you managed to somehow create a hollow sphere in the center of a planet, the walls of which are strong enough to support the mass above, the force of gravity would still pull into a single point.

the tunnel would work ( obviously assuming we live in a universe where it could actually be built, hence the "thought experiment" part ). there would be gravitational forces from all sides of the tunnel as well but they would exert the same magnitude of force in each direction towards the walls of the tunnel. a faller would have a force pulling them to the left and an equal force pulling them to the right effectively "cancelling" each other out.

as far as the hollow center i'm not so sure. i think IF you had a perfectly spherical planet and IF the density of the planet was uniform throughout ( so that the distribution of matter and hence gravitational attraction is equal ) and IF you somehow managed to hollow out the center again in a perfect sphere, could support the pressure around it and plopped a person inside it you basically have the same situation as the tunnel where the person would have equal forces pulling on them in all directions, effectively being weightless.

Avatar image for foxhound_fox
foxhound_fox

98532

Forum Posts

0

Wiki Points

0

Followers

Reviews: 13

User Lists: 0

#12 foxhound_fox
Member since 2005 • 98532 Posts

The force of gravity effects all things.

The "round ball" at the core of the Earth is made up of iron atoms that all have their own individual force of gravity.

Science barely understands how gravity actually works, we just can measure the force and include it in models of physics.

Avatar image for RedentSC
RedentSC

1243

Forum Posts

0

Wiki Points

0

Followers

Reviews: 0

User Lists: 0

#13  Edited By RedentSC
Member since 2013 • 1243 Posts

@comp_atkins: thanks for being one of the few that actually bothered to engange in an intelectual conversation here. People seems to be missing my point. its an Idea.. i very much doubt there is a sphere at the centre of the earth, for reason others have described (pressures and density). However this is a thought experiment, not a thesis... so why do people (not yourself) just laugh at me for even suggesting somthing?

@SaintLeonidas said:

@RedentSC said:

@SaintLeonidas: OKay, so if i don't have a basic understanding of General Relitivity (which i never claimed i did) please explain why this is not possible. as mass bends spacetime, in the direction of the centre of mass. when at the centre of the earth, the centre of mass is not the centre of the earth (reletive to me)

Is this not correct? and if not, explain why its not. you cannot just dismiss an hypothosis without expliantion, you may as well just say "god made it that way"

I'm not trying to prove you wrong, i just want evidence or an explination either way. As my "basic" A-Level understanding of physics clearly doens't cut the mustard, where as your clearly does

So you are throwing a theory out into the world, that you admit is based only on your limited knowledge of the principles at play - and want others to prove or disprove why you are wrong? I can most definitely dismiss a hypothesis if the presenter has presented anything that can be dismissed by basic science. There are no gravity-less spheres in the middle of large bodies of mass. Just can't happen. Just a dense center - and if the force of gravity is large enough, then the opposite of what you say is true, the mass gets compressed and so dense it becomes a black hole...which has an inescapable level of gravity.

Show me the basic science that wont allow this then... and it will all be done. Otherwise, you are just throwing out hot air. At least i attempted to explain why this might be possible in theory, and not just say "it can't happen" .... thats not the scientific way, you may as well say god made it that way.....

Exactly, we know that gravity can warp spacetime to the point of a singularity, we understand this. but we are talking about a though experiement here, not an actual theory. I do not have a university education in Physics however i do in Mathematics and Trig, which allows me to understand the broad concepts of general relitivity.

Now, once again, i agree that there will be no void in the centre of the earth, fair enough, but lets take a smaller astronomical object, like say, an small (perfectly sperical) body in space. Would gravity act in such a was as to product this void? Matter gets crushed at the centre of this hypothetical object yet but only (and ONLY) in the direction of the centre of mass that is creating the warping of spacetime, which in the case of the centre of this sphere... is outwards, not inwards. Therefor all the gravity is acting to "pull" anything at the centre outwards, as there is nothing in the centre to "pull" it inwards.... even if there was one atom at the centre of this "void" then it would get pulled to the walls of this void.

Soo... Once again (and for the last time) this is a thought experiement, no need to have ago at my scientific credentials. have a go at the arguement, not the messenger.

Avatar image for SaintLeonidas
SaintLeonidas

26735

Forum Posts

0

Wiki Points

0

Followers

Reviews: 2

User Lists: 0

#14 SaintLeonidas
Member since 2006 • 26735 Posts

This being a thought experiment doesn't protect it from scrutiny - and as I said before, you proposed it and so it is up to you to prove how it would be possible.

Anyway, no idea where you are getting this "outward" force from. If gravity is pulling towards a singularity, then there is no outward force. Just like in a black hole. If it was a sphere, then all the mass would be pulled towards a single point in the center- hence why the center of a large object is so dense. There would be nothing pushing outward - if it did them the object would be unstable. Gravity, from say the northern end of an object wouldn't cross over that from the southern end - both ends counteract and meet at the middle...if one end had a stronger force of gravity, then the structure would warp/break up until the gravity was uniform or stable. Even if you somehow created a hollow sphere in the middle of a planet - it wouldn't be "gravity-less". You might " float" and experience weightlessness as you do in space - but that isn't because there is no gravity - like in space you would still be subject to gravity - just in this case you would "float" at the point of the singularity because gravity is equal in all directions from you center of mass.

Avatar image for davillain
DaVillain

55899

Forum Posts

0

Wiki Points

0

Followers

Reviews: 0

User Lists: 5

#15  Edited By DaVillain  Moderator
Member since 2014 • 55899 Posts

I Recommend you watch the movie call, The Core. [And it's on Netflix I do believe]

Avatar image for SaintLeonidas
SaintLeonidas

26735

Forum Posts

0

Wiki Points

0

Followers

Reviews: 2

User Lists: 0

#16  Edited By SaintLeonidas
Member since 2006 • 26735 Posts

@davillain- said:

I Recommend you watch the movie call, The Core. [And it's on Netflix I do believe]

Avatar image for davillain
DaVillain

55899

Forum Posts

0

Wiki Points

0

Followers

Reviews: 0

User Lists: 5

#17 DaVillain  Moderator
Member since 2014 • 55899 Posts

@SaintLeonidas said:

@davillain- said:

I Recommend you watch the movie call, The Core. [And it's on Netflix I do believe]

Avatar image for kriggy
kriggy

1314

Forum Posts

0

Wiki Points

0

Followers

Reviews: 3

User Lists: 0

#18  Edited By kriggy
Member since 2008 • 1314 Posts

Because gravity is a centripetal force there is no way you can have a void in the middle. A centripetal force pulls everything towards the center, which means that the center is the most dense place in the sphere.

What you are talking about is a sort of exploding force in the middle, you can experiment this by yourself outside, place a large firecracker on the ground and cover it with light objects (like ping-pong balls). What will happen? Well the balls will start flying in all directions. You are referring to a force that breaks atoms apart. Therefore your scenario is completely impossible.

Avatar image for comp_atkins
comp_atkins

38662

Forum Posts

0

Wiki Points

0

Followers

Reviews: 3

User Lists: 0

#19  Edited By comp_atkins
Member since 2005 • 38662 Posts

for further reading, check out the shell theorem.

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

  1. A sphericallysymmetric body affects external objects gravitationally as though all of its mass were concentrated at a point at its centre.
  2. If the body is a spherically symmetric shell (i.e., a hollow ball), no net gravitational force is exerted by the shell on any object inside, regardless of the object's location within the shell.

Again, this wouldn't occur naturally because planets are not perfectly spherical objects and are believed form through an accretion process which would ensure a hollow center would be impossible.

Avatar image for dylandr
dylandr

4940

Forum Posts

0

Wiki Points

0

Followers

Reviews: 19

User Lists: 0

#20 dylandr
Member since 2015 • 4940 Posts
@davillain- said:

@SaintLeonidas said:

@davillain- said:

I Recommend you watch the movie call, The Core. [And it's on Netflix I do believe]

I still love you babe!