A question for the physicists.

[Karl]

If I were to drill a hole through the planets core and out the other side. Then I dropped an Apple down the hole, (assume a heat proof Apple that would disintegrate under pressure but could deform).

 

What exactly would happen ? Would it be crushed by gravity until it was more dense, but tiny ? Would it beginning falling fast and then more slowly as it reached the centre. Would it just bob about at the centre ?

[EmeraldHead]

Planets are hollow

[Karl]

Planets are hollow

I suggest to you that they aren't.

[blackstar212]

If I were to drill a hole through the planets core and out the other side. Then I dropped an Apple down the hole, (assume a heat proof Apple that would disintegrate under pressure but could deform).

 

What exactly would happen ? Would it be crushed by gravity until it was more dense, but tiny ? Would it beginning falling fast and then more slowly as it reached the centre. Would it just bob about at the centre ?

It would fall all the way through and then go back and forth losing a little height each time until it comes to a rest at the center. I would not think it would deform as long as it did not touch anything (the walls) on the way down

[Karl]

It would fall all the way through and then go back and forth losing a little height each time until it comes to a rest at the center. I would not think it would deform as long as it did not touch anything (the walls) on the way down

Interesting. You think the velocity would stay constant right up to the centre and inertia would carry it beyond the centre- conservation of momentum in other words.

 

If you look at the definition of a 'field' it says there are different numbers at every different point. In other words the field is 'strongest' at the centre. I only say that because that is implied in the definition, not necessarily because I agree with it. I quite like your conservation of momentum theory, I don't know if that's what would occur in a field of differing numbers though.

[blackstar212]

Interesting. You think the velocity would stay constant right up to the centre and inertia would carry it beyond the centre- conservation of momentum in other words.

 

If you look at the definition of a 'field' it says there are different numbers at every different point. In other words the field is 'strongest' at the centre. I only say that because that is implied in the definition, not necessarily because I agree with it. I quite like your conservation of momentum theory, I don't know if that's what would occur in a field of differing numbers though.

The apple would hit maximum velocity when it hits the center then as it passes the center would begin to decelerate. It is called harmonic motion if I remember correctly.

[Karl]

The apple would hit maximum velocity when it hits the center then as it passes the center would begin to decelerate. It is called harmonic motion if I remember correctly.

Yes I get it in 3 D. It is effectively trying to orbit and moving in a spiral towards the centre. Like a decaying AC waveform but looking along the wave itself it is a spiral until it becomes a single point/straight line between the peak amplitudes.

[Karl]

This is a pleasant respite from the philosophy. :-)

I await Brian's input as this is effectively the field thread I promised to create, but brought down to terms the layman can grasp :-)

[Marblehead]

The apple would hit maximum velocity when it hits the center then as it passes the center would begin to decelerate. It is called harmonic motion if I remember correctly.

Just for the purpose of adding complexity:  Would this also happen with an object entering a Black Hole?

[Karl]

Just for the purpose of adding complexity:  Would this also happen with an object entering a Black Hole?

should be the same, the acceleration would be greater of course, the maximum velocity close to the speed of light ?

[blackstar212]

Just for the purpose of adding complexity:  Would this also happen with an object entering a Black Hole?

Not at all. The object would be stretched incredibly thin because of the massive gravity. There would be no apple as we know it. It would eventually end up as a singularity

Edited August 26, 2016 by blackstar212

[Brian]

This is a pleasant respite from the philosophy. :-)

I await Brian's input as this is effectively the field thread I promised to create, but brought down to terms the layman can grasp :-)

Oh, but this is philosophy! This is what is called natural philosophy.

 

The primary flaw in your reasoning here, Karl, (besides the obvious -- that you think you've logic'd-out a "gotcha") is that you believe the planet is an object.

 

Chew on that for a bit and I'll be back...

[silent thunder]

oops, sorry, (belch) y'all were planning to use that apple as some thing?

[Brian]

Just for the purpose of adding complexity:  Would this also happen with an object entering a Black Hole?

 

 

should be the same, the acceleration would be greater of course, the maximum velocity close to the speed of light ?

 

 

Not at all. The object would be stretched incredibly thin because of the massive gravity. There would be no apple as we know it. It would eventually end up as a singularity

Just as one might wisely learn the fundamentals of music -- developing a working understanding of notes and scales and tablature, for instance, before tackling Schubert's Symphony Number 9 in C Major, one might want to have a grasp of gravity as we experience it before jumping (pun intended) into a black hole.

 

That said, blacikstar212 clearly has the right idea, both about apples & the Earth as well as relativity and the phenomenon commonly known as a black hole.

[Karl]

Oh, but this is philosophy! This is what is called natural philosophy. ;)The primary flaw in your reasoning here, Karl, (besides the obvious -- that you think you've logic'd-out a "gotcha") is that you believe the planet is an object.Chew on that for a bit and I'll be back...

I haven't any thoughts on the subject. It's a scientific question. It isn't a gotcha. Bloody hell dude you are suspicious of what is a straightforward request to understand at a level I'm comfortable with.

 

I can ask questions and this has nothing at all to do with philosophy. You stay on your own side of the fence. ;-)

 

The planet clearly is an object, so is the Apple.

 

There is an acceleration we perceive it, there is an object with a nature we know it. I don't know what the nature of the object is I can only see causality in operation, the Apple accelerates in a direction, potentially towards the centre of the mass ? I have no way to confirm the centre of mass, or the objects trajectory, it hits the ground and that's all I see. It falls towards rather than away from, I see that. I've done the experiments that show the acceleration at 9.81 m/s/s. I know that it requires a very high velocity to escape the gravity well, much higher than the velocity of that Apple falling-that makes sense in a force equation way.

 

Are there gravity wells in space without objects in them, or in reverse, objects with no gravity ?

 

I don't know the answer, which is why I'm asking. I prefer an answer to a puzzle. I never liked puzzles much or those that design them.

[Brian]

If I were to drill a hole through the planets core and out the other side. Then I dropped an Apple down the hole, (assume a heat proof Apple that would disintegrate under pressure but could deform).

 

What exactly would happen ? Would it be crushed by gravity until it was more dense, but tiny ? Would it beginning falling fast and then more slowly as it reached the centre. Would it just bob about at the centre ?

 

 

It would fall all the way through and then go back and forth losing a little height each time until it comes to a rest at the center. I would not think it would deform as long as it did not touch anything (the walls) on the way down

 

 

The apple would hit maximum velocity when it hits the center then as it passes the center would begin to decelerate. It is called harmonic motion if I remember correctly.

Yes, it is an example of harmonic oscillation, much like a child on a swing or a weight on a string. The falling object* would experience a centripetal (center-seeking) force which would be proportional to its distance from the center of the Earth. As such, it would continue accelerating (albeit with decreasing intensity) as it approaches the center and then the acceleration would reverse direction and increase as the apple moves away from the center.

 

If you were to drop the apple from a significant distance above the surface of the Earth, the force of gravity would increase as it approached the surface and would then start to decrease. Crossing the center, the force would reverse direction (centripetal, remember) and would increase in magnitude until the apple passed the surface again, at which point the magnitude would start to decline again. Regardless of whether dropped from right at the surface or from a distance outside the Earth surface, the thing (neglecting effects from the motion of the Earth itself) that would slowly diminish its motion until it finally comes to rest at the center would be the friction of air resistance.

 

It is perhaps worth mentioning that the Earth would feel the same force and would move in a very similar fashion but on a scale relative to the ratio of the masses involved. From the apple's perspective, it would be standing still and the Earth would be bouncing up and down around it.

 

*But... but... but... Didn't I just say in a previous post that believing the Earth is an object was a mistake? But surely that would apply to the apple as well? Yes, I did -- and don't call me Shirley. The key (as is so often the case) is understanding the fundamentals rather than memorizing rules and equations. This allows one to recognize that a model can be useful even though wrong (all models are wrong, BTW) and to flexibly apply different models as appropriate to a given situation.

[Brian]

I haven't any thoughts on the subject. It's a scientific question. It isn't a gotcha. Bloody hell dude you are suspicious of what is a straightforward request to understand at a level I'm comfortable with.

 

I can ask questions and this has nothing at all to do with philosophy. You stay on your own side of the fence. ;-)

 

The planet clearly is an object, so is the Apple.

 

There is an acceleration we perceive it, there is an object with a nature we know it. I don't know what the nature of the object is I can only see causality in operation, the Apple accelerates in a direction, potentially towards the centre of the mass ? I have no way to confirm the centre of mass, or the objects trajectory, it hits the ground and that's all I see. It falls towards rather than away from, I see that. I've done the experiments that show the acceleration at 9.81 m/s/s. I know that it requires a very high velocity to escape the gravity well, much higher than the velocity of that Apple falling-that makes sense in a force equation way.

 

Are there gravity wells in space without objects in them, or in reverse, objects with no gravity ?

 

I don't know the answer, which is why I'm asking. I prefer an answer to a puzzle. I never liked puzzles much or those that design them.

Ah, but you clearly demonstrate that you do have thoughts on the subject, and that you have reached firmly engrained conclusions which happen to be patently wrong!

 

We typically treat massive bodies ("massive" meaning those with mass rather than ones which are particularly massive, if you follow me) as point objects with all the mass located at the "center of mass" or "center of gravity." In most cases, with seemingly discrete bodies with some separation between them, for instance, this model works splendidly! It does a superb job with speeding bullets or orbiting satellites or pendulums, for example. Once you dig a hole and lower something into it (among other scenarios), however, the model is revealed to be a gross simplification.

 

The gravitational force experienced is not the result of a massive body called "the Earth" but the vector summation of all the overlapping forces generated by the incomprehensible number of individual particles which compose the phenomenon commonly referred to as "the Earth" on each of the incomprehensible number of individual particles which compose the phenomenon commonly referred to as "the apple." Every single electron, quark, neutron, etc. -- all in constant motion relative to each other. Add ALL of these individual forces up for a given instant (we'll leave propagation delays and the fallacy of simultaneity out of the discussion for now) and you have the effective gravitational force. This becomes significant once the apple is inside the Earth because now some of the particles are pulling the apple away from "the center of the Earth" rather than towards it! This is why the effective gravitational force (the "real" force the "apple" experiences) decreases as it falls inside the Earth.

 

As a side note, the effect would hold true if the planet were a hollow shell, too...

[Brian]

I haven't any thoughts on the subject. It's a scientific question. It isn't a gotcha. Bloody hell dude you are suspicious of what is a straightforward request to understand at a level I'm comfortable with.

 

I can ask questions and this has nothing at all to do with philosophy. You stay on your own side of the fence. ;-)

 

The planet clearly is an object, so is the Apple.

 

There is an acceleration we perceive it, there is an object with a nature we know it. I don't know what the nature of the object is I can only see causality in operation, the Apple accelerates in a direction, potentially towards the centre of the mass ? I have no way to confirm the centre of mass, or the objects trajectory, it hits the ground and that's all I see. It falls towards rather than away from, I see that. I've done the experiments that show the acceleration at 9.81 m/s/s. I know that it requires a very high velocity to escape the gravity well, much higher than the velocity of that Apple falling-that makes sense in a force equation way.

 

Are there gravity wells in space without objects in them, or in reverse, objects with no gravity ?

 

I don't know the answer, which is why I'm asking. I prefer an answer to a puzzle. I never liked puzzles much or those that design them.

Out of curiosity, are you composing your posts on an Apple product which keeps capitalizing the word?

 

As to the bolded questions, general relativity says that gravity wells are a deformation of spacetime and Einstein's famous example is a continuously accelerating elevator -- the condition inside that elevator car would be indistinguishable from gravity. An object with no gravity is simply a massless object.

[Karl]

Out of curiosity, are you composing your posts on an Apple product which keeps capitalizing the word?As to the bolded questions, general relativity says that gravity wells are a deformation of spacetime and Einstein's famous example is a continuously accelerating elevator -- the condition inside that elevator car would be indistinguishable from gravity. An object with no gravity is simply a massless object.

It's not the product is the habitisation of flash cards. On which was written 'Apple'.

 

Im going to have to think on this a bit, you have given me a lot of information with this and your last post. I assume a massless object is a contradiction in terms ?

[joeblast]

. I assume a massless object is a contradiction in terms ?

Not at all, it all depends on how its vibrating

[thelerner]

As to the bolded questions, general relativity says that gravity wells are a deformation of spacetime and Einstein's famous example is a continuously accelerating elevator -- the condition inside that elevator car would be indistinguishable from gravity. An object with no gravity is simply a massless object.

I don't think we need to get Einsteinian on this one.  Keeping it simple, old school Newtonian, answers the question. 

Edited August 26, 2016 by thelerner

[Karl]

Ah, but you clearly demonstrate that you do have thoughts on the subject, and that you have reached firmly engrained conclusions which happen to be patently wrong! :)We typically treat massive bodies ("massive" meaning those with mass rather than ones which are particularly massive, if you follow me) as point objects with all the mass located at the "center of mass" or "center of gravity." In most cases, with seemingly discrete bodies with some separation between them, for instance, this model works splendidly! It does a superb job with speeding bullets or orbiting satellites or pendulums, for example. Once you dig a hole and lower something into it (among other scenarios), however, the model is revealed to be a gross simplification.The gravitational force experienced is not the result of a massive body called "the Earth" but the vector summation of all the overlapping forces generated by the incomprehensible number of individual particles which compose the phenomenon commonly referred to as "the Earth" on each of the incomprehensible number of individual particles which compose the phenomenon commonly referred to as "the apple." Every single electron, quark, neutron, etc. -- all in constant motion relative to each other. Add ALL of these individual forces up for a given instant (we'll leave propagation delays and the fallacy of simultaneity out of the discussion for now) and you have the effective gravitational force. This becomes significant once the apple is inside the Earth because now some of the particles are pulling the apple away from "the center of the Earth" rather than towards it! This is why the effective gravitational force (the "real" force the "apple" experiences) decreases as it falls inside the Earth.As a side note, the effect would hold true if the planet were a hollow shell, too...

I know some things, but my conclusions aren't fixed at this point. I can grasp the idea that we have all these particles with forces.

 

What are these forces exactly ? Presumably they exert there own fields, but they bond is far stronger than the Apple and the Earth. Why is that ? Why doesn't the apple just squash up into a homogenous conglomerate ?

 

I'm struggling to understand the last paragraph. Do you mean the particles above its decent are now working to pull the apple back up. Why wouldn't the apple go sideways and stick to the wall ?

 

A hollow planet ? I don't think I can get my head around something hollow which....Oh wait, I see, the apple would get attracted by all sides of the shell and rest at the null point inside the shell ? Have I got that right ?

 

LOL that's quite funny, I was wondering how the hell the shell would stop itself being attracted to itself and thefore just collapse, but it wouldn't if it was of the same thickness and density, presumably it would have to be perfectly spherical in every sense, but that's not possible in reality with a massive sphere - or is it ?

[Karl]

Not at all, it all depends on how its vibrating

If it's vibrating there must be an 'it' to vibrate ?

[joeblast]

If it's vibrating there must be an 'it' to vibrate ?

ah, but what is vibrating?

 

its only interacts if it resonates with certain fields....if it does not...*cough*neutrino*cough*

 

or in this case of gravity,

 

http://www.livescience.com/51584-weyl-fermions-created-lab.html

http://www.sciencealert.com/scientists-have-finally-discovered-massless-particles-and-they-could-radically-speed-up-electronics

Edited August 26, 2016 by joeblast

[Brian]

I don't think we need to get Einsteinian on this one.  Keeping it simple, old school Newtonian, answers the question.

That's the point -- an elevator is pure old-school Newtonian motion, it is indistinguishable from "real" gravity, and it helps to illustrate the concept which bridges from classical mechanics to general relativity. There isn't some artificial wall between classical natural philosophy and modern natural philosophy but instead a gradual maturation of our philosophical understanding of the behavior of nature. Karl introduced the ideas of massless gravity and gravityless objects, thereby moving the discussion, albeit briefly, beyond the supposedly mundane starting point of a falling apple.