Proof of the apple 'pulling' the earth?

[James R]

plane:

No. You are the wrong one.

Whether it be an egg or an elephant, the acceleration rate towards the earth is the same. The earth's mass determines the rate of acceleration towards the earth.

Understand that and I will go through the rest of your nonsense.

I understand, but read what I wrote again.

Let me explain it step by step to make it easier for you to understand. First, the acceleration of an object of mass m subject to any force F is:

$$a = F/m$$

From this, we see that the acceleration is determined by (a) the magnitude of the force applied to the object, and (b) the mass of the object itself. This is called Newton's second law of motion.

Now, Newton's law of gravity says that the force on mass m due to some other mass M at distance r away from m is:

$$F =\frac{GMm}{r^2}$$

where G is a fundamental constant of nature. This is the force that acts on mass m (and also on mass M).

Strangely, you seem to agree with this law, all of a sudden, because you implicitly rely on it in your previous post. Yet, all the time in this thread you have been trying to dispute it. I think you're confused, but I hope this post helps you sort yourself out.

Now, if F is the force that acts on mass m, then the acceleration of mass m is:

$$a = F/m = \frac{GM}{r^2}$$

Interestingly, the mass m cancels out, so that the acceleration of mass m is determined by its distance from mass M and the mass of M itself. This is something specific to gravitation, whereas before I was making a more general point about force.

Now, the important thing to notice is that Newton's law of gravity doesn't specify that M must be a greater mass than m. In other words, the above argument is valid regardless of whether m or M is the greater mass.

This invalidates your silly argument that if m is greater than M it won't accelerate at all towards M.

Since you appear to agree that both Newton's law of gravity and Newton's second law are correct, I will now be interested to see if you still want to try to refute the above analysis. Certainly, you'll look like a fool if you now go on to refute a fact you just relied on a moment ago to make your argument.

Well?

 

[plane]

No, you mean $$mg = \frac{GMm}{r^{2}}$$, which simplifies down to $$g = \frac{GM}{r^{2}}$$, so the acceleration, for any object, is proportional to the mass of the object creating the gravitational field.

Why did you ignore my last post plane? I commented that the things I'd talked about were observed : http://en.wikipedia.org/wiki/Center_of_mass#Barycenter_in_astronomy

We do see the Sun be affected by the gravitational effects of the planets. It orbits about a point above it's surface, the barycentre of the solar system. Pluto and it's moons also orbit a position above the surface of Pluto.

The back reaction of the smaller object on the larger one is seen. We see binary pulsars orbiting their barycentre, not the smaller one going around the larger one. As the ratio of the masses gets larger and larger, the back reaction gets smaller and smaller, because while the forces each experiences are the same, the resultant acceleration of the larger due to the smaller gets less and less.

The forces must be the same or else there would be an overall spontaneous resultant force on them, which would mean the total mass of the two objects is accelerating, all on it's own! But if they are experiencing equal and opposite forces then there is no resultant force on the system overall and so things like momentum conservation are obeyed.

If you are correct in your claims, why do we have such an excellent and experimentally verified grasp of mechanics?

No what I meant was if you set k.m.a = k.M/m/d x d you get a = k.M/d x d or, when you accept the inverse square law and repeated Cavendish experiments give you the same answer for k, you get knowledge that there is direct proportion between magnitude of gravity of a body and its mass.

After I posted I went to bed and remembered I hadn’t cancelled out one of the small masses but couldn’t be bothered correcting it. Was inebriated at the time.

The point is when the small masses take no part in the proportion, there is no legitimate reason to say they have.

I have not ignored your posts. I have said that if Newton’s law of gravity is structurally flawed, you have to look for other explanations of what it is currently believed to explain. I have also mentioned Tyco Brahe being drawn to astronomy by a precise prediction of when an eclipse of the sun would occur. At the time the sun was believed to be in orbit of the earth. Things are always going on in the universe, misapprehensions about reasons why all things are going on can easily occur.

Hope that helps. If you go back to post 136, you will see an explanation of how Newton derived his law of gravity out of F = k.m.a. To subsequently set k.m.a equal to k.m.a proves nothing except, as explained a direct proportion between mass and magnitude of gravity when you introduce different ways of measuring a.



James R, this reply to alphanumeric is relevant to you and pretty much covers where you are at.

From this, we see that the acceleration is determined by (a) the magnitude of the force applied to the object, and (b) the mass of the object itself. This is called Newton's second law of motion.

This just says that there is a problem with labeling gravity as a force. We know that all masses fall at the same rate. The mass of a falling object is not relevant to its rate of fall. Your (b) does not apply to a falling object. So that puts a question mark against the veracity of your (a).

With respect of gravity, it’s back to the drawing board for you. You are talking about a gravity logic that is proven to be counter to observation. All things subject to the same gravity fall at the same rate.

Best that you also go to post 136 and see that Newton has most plausibly derived his law of gravity from Galileo (F = k.m.a.) He knew the earth was subjecting the apple to that formula. Presumed the apple was subjecting the earth. Then introduced a = k.M/d x d and A = k.m/d x d and was left with twice with F = k.M.m/ d x d

But you can see, can't you, that various masses falling at the same rate tells you that it is incorrect to simply say that gravity is a force directed at mass? If you can't see that, not much I can really do for you.



First time for a while that I have come to this forum sober. You proud of me? More importantly do you understand that you are not giving due respect to unlike masses falling at a like rate.

Give that proper respect and you will see that your arguments about the mass of a falling body somehow being involved in its own rate of fall are just convoluted nonsese invented to try and make an original mistake correct.

 

[Vkothii]

But you can see, can't you, that various masses falling at the same rate tells you that it is incorrect to simply say that gravity is a force directed at mass? If you can't see that, not much I can really do for you.

Because different masses (that are much smaller than the mass of the earth) fall at the same rate, or accelerate as if the same force is applied, then there's a constant force due to the earth that will accelerate all bodies at the same rate (including the moon, asteroids, satellites we launch into orbit).

Actually anything that is a material body and so has mass, will accelerate towards the centre of mass of the earth, right?
But these bodies will only move along a path (that ends at the centre of the earth) if there's nothing in the way, right?
If the surface of either body is in the way, neither body will have a motion, but will be "at rest", wrt the centres of either, right?

Just trying to get some agreement here on what the subject might be, right? Not trying to "do anything for anyone" (considering I have said I won't be responding directly), just trying to make sense.
Right.

 

[Vkothii]

the mass of a falling body somehow being involved in its own rate of fall are just convoluted nonsese invented to try and make an original mistake correct.

The mass of a body is the mass of a body.
If it isn't falling, does it have any mass? Can someone who can't see what an equation is (they seem to be incapable of figuring that one side is either equal, or alternatively equivalent to the other side depending on a few things like the units used in the equation, say), construct a logical answer, as to why a body on the surface of a planet (like their human body that stands still occasionally), has no mass, no acceleration, or doesn't feel a force since it isn't moving...?

Well, I wonder what the answer might be, right?

 

[James R]

plane:

Since you haven't addressed the argument I put to you, there's no point in further discussion.

 

[Vkothii]

If a bottle of whiskey contains 750 grams of fluid, does drinking it increase the mass of the drinker? Do they then have a greater acceleration towards the centre of a local large concentration of mass?

If they drink two bottles, does the earth keep spinning?

Perhaps plane is investigating the possibility, and will let everyone know the answer in due course (when he's feeling better).

 

[plane]

plane:

Since you haven't addressed the argument I put to you, there's no point in further discussion.

Your argument

From this, we see that the acceleration is determined by (a) the magnitude of the force applied to the object, and (b) the mass of the object itself. This is called Newton's second law of motion.

The address

This just says that there is a problem with labeling gravity as a force. We know that all masses fall at the same rate. The mass of a falling object is not relevant to its rate of fall. Your (b) does not apply to a falling object. So that puts a question mark against the veracity of your (a).

If you and haven't the intellectual guts to enter an avenue of thought where you could end up wrong and prefer to cheap out with a false accusation, not my worry.

Much of science is the art of searching for your mistakes. I have quite succinctly pointed your mistake out here. Makes me the scientist for both of us I guess.

Cheers.

 

[Neddy Bate]

Hello plane,

I am not sure why you are not satisfied with all of the logical reponses provided so far. So, please allow me to try a less logical approach.

Next time you go to the produce section of your local grocery store, place an apple on a scale and measure it's weight. After converting the unit of weight to Newtons, that value represents the force (F) due to the acceleration of gravity (g), and the mass of the apple (m) in kilograms.

F=mg

Where g=9.8 meters per second squared (m/s/s).

Notice the apple's mass is considered here, but the mass of the earth is not considered directly. It is indirectly factored in to the given value of g. Likewise, the the distance to the center of gravity of the earth is also already factored into g.

To prove that the apple does in fact pull the earth, we can repeat the above "scale experiment" only in-reverse. Instead of weighing the apple on planet earth, we can weigh the earth on "planet apple".

Turn the scale upside down so that the earth is sitting on the measuring platform of the scale. You will have to reset the scale to zero to correct for the weight of the scale's internal mechanisms. Now place "planet apple" on the bottom surface of the scale (where the earth used to be) and take a measurement of the earth's weight on planet apple.

As before, convert this value to Newtons, and then using the new formula:

F=Ma

Where (F) is the force due to the acceleration of gravity (a), and the mass of the earth (M).

Unlike the first equation where the acceleration on earth was known, we do not know the acceleration on planet apple. Fortunately, we have a measured value for F, and we can look up M in an astronomy book to find that it is approximately 5.97x10^24 kilograms, so we can calculate the value of a.

Now you should be able to visualize that planet apple does have a tiny gravitational field that pulls the huge mass of the earth to its surface. If you wave your hand around planet apple, you will not be able to feel its gravity because it is so small. But rest assured that it is there, or else the earth would have floated right off of the measuring platform!

 

[plane]

Now place "planet apple" on the bottom surface of the scale (where the earth used to be) and take a measurement of the earth's weight on planet apple.

How do you know the earth places weight on the apple? Turning a set of scales upside down does not reverse what is measuring what.

That's hopeless, Neddy.

Just as hint, gravity is not a force. Gravity may be caused by force and may cause force, but gravity its self is simply an acceleration through space towards a centre of mass.

Your job is to have a penny drop.

Give you a hand. Mass places a force upon space in a direction away from mass.

The acceleration is through space in the opposite direction.

Explained gravity for you Neddy. Your lucky day. Sleep well.

 

[James R]

Just as hint, gravity is not a force. Gravity may be caused by force and may cause force, but gravity its self is simply an acceleration through space towards a centre of mass.

This is so imprecise as to be useless.

Is there any difference between gravity and the acceleration of a car along a road, using your definition? (Because both are accelerations through space towards a centre of mass of some kind.)

 

[Neddy Bate]

How do you know the earth places weight on the apple? Turning a set of scales upside down does not reverse what is measuring what.

That's hopeless, Neddy.

Well, I warned you that I was going to present a "less logical approach". I was hoping it might appeal to the rebel in you.

So, are you claiming that, if two masses are touching, except for a set of scales between them, the only valid way to interpret the weight measurement is to say that the large mass is attracting the small mass, and not the other way round?

Just as hint, gravity is not a force. Gravity may be caused by force and may cause force, but gravity its self is simply an acceleration through space towards a centre of mass.

Yes, it can be considered to be a constant acceleration at one elevation, for example, at sea level on earth it is 9.8 m/s/s.

I went to the grocery store and weighed an apple. It was appropriately about 1 Newton. So on "planet apple", the acceleration would be about 1/5.97x10^24 m/s/s. Quite a bit less than the 9.8 m/s/s of earth, but certainly not zero. Otherwise it would be immune to gravity and permanently weightless. Wouldn't you agree?

Your job is to have a penny drop.

Give you a hand. Mass places a force upon space in a direction away from mass.

The acceleration is through space in the opposite direction.

Explained gravity for you Neddy. Your lucky day. Sleep well.

Thanks, but I'm afraid that your explanation is still unclear. Why are you claiming that the acceleration goes in the oppsite direction to the force?

 

[plane]

So, are you claiming that, if two masses are touching, except for a set of scales between them, the only valid way to interpret the weight measurement is to say that the large mass is attracting the small mass, and not the other way round?

No. Not attracting but that is beside what you are trying to say.

The only valid interpretation is to say that the one that makes the scales accelerate (register) is accelerating towards the one that doesn't cause the scales to accelerate.

Thanks, but I'm afraid that your explanation is still unclear. Why are you claiming that the acceleration goes in the oppsite direction to the force?

Still your lucky day. This diagram explains gravity better than words

Didn't have to be a genius to work it out, either. Just an interest in the topic.

If you are going to say it's an errant diagram for some reason or other, hope you are able to put forward something about how the quantity of the earth does actually cause the earth to have what we refer to as gravity.

This is so imprecise as to be useless.

Is there any difference between gravity and the acceleration of a car along a road, using your definition? (Because both are accelerations through space towards a centre of mass of some kind.)

Just as a life tip James, you seem to be a chip on the shoulder poster. If you had of taken the entire post in context, you would have seen that the key point being made was the force is in the opposite direction.

I have taken the time to appreciate that your argument is that gravity is a force. If you are going to bother with posting, why not take the time to see just what the poster you are replying to is saying. Otherwise, why bother? You really owe me a poster to poster apology by now. Doesn't matter though. I'm just a happy chappy.

 

[Steve100]

No. Not attracting but that is beside what you are trying to say.

The only valid interpretation is to say that the one that makes the scales accelerate (register) is accelerating towards the one that doesn't cause the scales to accelerate.



Still your lucky day. This diagram explains gravity better than words

Didn't have to be a genius to work it out, either. Just an interest in the topic.

If you are going to say it's an errant diagram for some reason or other, hope you are able to put forward something about how the quantity of the earth does actually cause the earth to have what we refer to as gravity.



Just as a life tip James, you seem to be a chip on the shoulder poster. If you had of taken the entire post in context, you would have seen that the key point being made was the force is in the opposite direction.

I have taken the time to appreciate that your argument is that gravity is a force. If you are going to bother with posting, why not take the time to see just what the poster you are replying to is saying. Otherwise, why bother? You really owe me a poster to poster apology by now. Doesn't matter though. I'm just a happy chappy.

Why wouldn't the earth fall down the apple's space gradient then?

 

[James R]

plane:

You still haven't replied to my argument in post #161.

I assume you have no adequate response.

Enough said.

 

[Vkothii]

Does that diagram really say "space is forced into space around the earth"...?
That's real meaningful right there. How do you force space?

 

[plane]

Why wouldn't the earth fall down the apple's space gradient then?

The earth is not in the apple's space gradient. The apple’s space gradient is terminated where the earth and apple space gradients otherwise would be equal and opposite in magnitude.

plane:

You still haven't replied to my argument in post #161.

I assume you have no adequate response.

Enough said.

Enough by you I guess. This was posted.

Whether it be an egg or an elephant, the acceleration rate towards the earth is the same. The earth's mass determines the rate of acceleration towards the earth.

And you posted in your post 161

Strangely, you seem to agree with this law, all of a sudden, because you implicitly rely on it in your previous post.

You explain that. I could not fathom it. It was completely non-sequitur.

You may have been reading what I posted to steve 100 which was

g = k.m/d xd (I had an uncancelled out m in the post which has subsequently been explained (was drunk)) but it still doesn't explain why anyone would suddenly say that I posted Newton's law of gravity makes sense.

I will go through it for poor you.

Cavendish experiments.

m.g is set equal to k.m.M/d x d

The small masses are cancelled out.

g = k.M/d x d

Taking the inverse square law as a given, all that says is that there is a proportion between the mass that the acceleration is towards (M) and the mass of M.

In no way does an acceptance of g = k.M/d x d equal an acceptance of a small mass 'attracting' a large mass. The small mass takes no part in the equation.

I still advise you to go back to post 136 I think it is so as you can get a bit of a drift on how Newton came up with his law. At this stage you don't seem to have a clue as to where he got it from.

Incidentally, you are a very weak debater. Your enough said does not in any way challenge my diagram. Even less so when if we went back through the thread we could find a post where you state that no one knows how mass causes gravity. Or something to that effect. If you were for real, you would do better than your "enough said" when you first come across an idea of how mass causes gravity. You just don't seem fair dinkum to me. If you are I apologize but you come across as a waste of time. A few brains in your head but not using them for the good of the earth.

Does that diagram really say "space is forced into space around the earth"...?
That's real meaningful right there. How do you force space?

Archimedes principle is the way I have it. In part anyway. The presumption is space is a spontaneously existing particle.

This is probably proveable through the solar system. Not sure that I will ever acheive as much though.

 

[James R]

plane:

Cavendish experiments.

Maybe you ought to look those up.

g = k.M/d x d

Taking the inverse square law as a given, all that says is that there is a proportion between the mass that the acceleration is towards (M) and the mass of M.

Yes, and nothing in the equation says whether M is bigger or smaller than m.

A point I made earlier, and one you still haven't addressed.

In no way does an acceptance of g = k.M/d x d equal an acceptance of a small mass 'attracting' a large mass. The small mass takes no part in the equation.

Just to repeat, nothing in the equation says that M is a "big" mass and m is a "small" mass. M could be the small mass and m the big mass.

I still advise you to go back to post 136 I think it is so as you can get a bit of a drift on how Newton came up with his law. At this stage you don't seem to have a clue as to where he got it from.

Meh. Whatever. What matters is not where it came from, but whether it is correct.

Incidentally, you are a very weak debater. Your enough said does not in any way challenge my diagram.

Your diagram shows nothing useful. There's no need to challenge it.

Even less so when if we went back through the thread we could find a post where you state that no one knows how mass causes gravity.

Correct. And that includes you.

You just don't seem fair dinkum to me. If you are I apologize but you come across as a waste of time. A few brains in your head but not using them for the good of the earth.

Personal insults won't save your poor argument.

 

[plane]

plane:







Yes, and nothing in the equation says whether M is bigger or smaller than m.

A point I made earlier, and one you still haven't addressed.



Just to repeat, nothing in the equation says that M is a "big" mass and m is a "small" mass. M could be the small mass and m the big mass.

In Cavendish experiments, the small mass is always the one cancelled. Was just explaining to you all Cavendish experiments can be taken to mean.

Meh. Whatever. What matters is not where it came from, but whether it is correct.

So you agree that Newton's law of gravity was derived from Newton's second law. That means when the "law" is set equal to Newton's second law (with a different way of measuring acceleration), nothing of much consequence can be said.

We have m.a (newton's law of gravity where a = M/d x d) = m.a (Newton's second law where a is measured under laboaratory conditions).

What grand conclusion can you draw from that monsieur.

Your diagram shows nothing useful. There's no need to challenge it.

If it is right, it might be the most useful diagram to hit the planet for a long time. Not sure why you say an understanding of the relationship between mass and acceleration towards mass is not useful. Each to their own I guess.

Correct. And that includes you.

Wonder why I label you a waste of time do you? I am putting forward why I think a smaller mass falls towards a large mass, you say it is wrong without offering a reason why it is wrong. I am proving that you are a waste of time if nothing else.

Personal insults won't save your poor argument.

From this thread, in particular your reaction to the last diagram I posted, a very sound conclusion is you don't use your brains for the good of the earth. That is hardly a personal insult. Just an observation that can be backed up with facts.

If you want to post on, advise rigourlessly dealing 1/ with the smaller mass always being the one cancelled out in Cavendish experiments and 2/ the full implications of Newton's law of gravity being derived from Newton's second law. Cheers

 

[James R]

plane:

In Cavendish experiments, the small mass is always the one cancelled. Was just explaining to you all Cavendish experiments can be taken to mean.

Cavendish did the sensible thing and kept the larger masses stationary and the smaller masses accelerating in his experiments? Why? Because the larger masses will accelerate more slowly for the same force (a=F/m), and the accelerations involved are very small.

So you agree that Newton's law of gravity was derived from Newton's second law.

No. Newton's law of gravity is an independent law of nature. It cannot be derived from Newton's second law of motion. On the other hand, the reasoning process that led to Newton's law of gravity used the second law as a sensible rationale. And the law of gravity is compatible with the second law of motion, as it must be.

Not sure why you say an understanding of the relationship between mass and acceleration towards mass is not useful.

I don't say that. Please do not put words in my mouth. The fact is, we have a very good understanding of the relationship between mass and acceleration. It's called Newton's second law of motion.

I am putting forward why I think a smaller mass falls towards a large mass, you say it is wrong without offering a reason why it is wrong.

I explained very clearly in my very first reply to you why you are wrong. The fact that you haven't understood my explanation after a further 20 or so posts of further explanation is your problem, not mine.

I guess some people are uneducatable by choice.

 

[plane]

plane:



Cavendish did the sensible thing and kept the larger masses stationary and the smaller masses accelerating in his experiments? Why? Because the larger masses will accelerate more slowly for the same force (a=F/m), and the accelerations involved are very small.

Amusing. So this proves the larger mass accelerates towards the smaller mass. Perhaps at a later point of time you will start using your brain.

No. Newton's law of gravity is an independent law of nature. It cannot be derived from Newton's second law of motion. On the other hand, the reasoning process that led to Newton's law of gravity used the second law as a sensible rationale. And the law of gravity is compatible with the second law of motion, as it must be.

How was it derived then? You either know or you don't. Willing to put plenty of good money on you not having a clue on how Newton derived F = k.M.m/d x d

Sure bet.

I don't say that. Please do not put words in my mouth. The fact is, we have a very good understanding of the relationship between mass and acceleration. It's called Newton's second law of motion.

Almost feel sorry for you, as if I am playing with you. How does mass (the mass of the earth for example) cause an acceleration towards its self is what we are discussing. Newton's second law explains a relationship between an applied force, acceleration and mass. It does not explain how mass causes gravity, whether gravity be a force applied at a distance (you) or an acceleration through space (fundamental approach to gravity).

I explained very clearly in my very first reply to you why you are wrong. The fact that you haven't understood my explanation after a further 20 or so posts of further explanation is your problem, not mine.

Your first post did not deal with mass exerting force on space. Why post stuff that doesn't make sense. Mass exerting a force on space was not introduced until the black diagram a few posts back.

I guess some people are uneducatable by choice.

It's your choice. A truck can be driven through Newton's law of gravity. If you want to go to your grave believing education equals an apple pulling a planet, your choice. A coffin is a coffin is a coffin but your death when it happens will be the death a dishonest human being.