Proof of the apple 'pulling' the earth?

[AlphaNumeric]

You are saying without hesitation in this post that the sun and earth apply equal force to each other.

Yes. It's measured. The Sun isn't set at the centre of the solar system, it orbits the barycentre of the solar system, which is the 'centre of mass' of all the planets and the Sun (as well as moons etc) added together and averaged over their interactions.

As I said to you before, we observe massive planets in distant solar systems not by seeing them but by seeing their influence on their stars. A planet 10 times the mass of Jupiter as close to the Sun as Mercury will affect the Sun a lot, enough to be seen light years away by technology we have at the moment. If there wasn't this mutual back reaction, we'd not see all the planets we do.

Then there's other systems which are gravitational and involve close-ish masses. The Moon, compared to the Earth, is very large. It's the second largest moon/planet ratio in the solar system (I'll get to the first in a moment) and so the Earth doesn't just have the Moon going around it, both of them orbit a point which is their 'centre of force', their barycentre. The Moon isn't large enough to make the centre of their mutual orbits to be above the Earth's surface.

However, the Jupiter/Sun system is! The Sun actually orbits a point above it's surface!! And the system with the largest moon/planet ratio is Pluto and Charon. They are very close is size and orbit about a point somewhere between the two of them.

See http://en.wikipedia.org/wiki/Center_of_mass#Barycenter_in_astronomy and the animations just below it.

So we have demonstrated proof that you're wrong.

 

[Vkothii]

Just wait for the echo...

 

[Steve100]

Just wait for the echo...

 

[plane]

Scientists gave up trying to explain things mechanically some time ago

Scientists should never give up on that chore. Not scientists if they do.

plane:







It's implicit in what we mean by the term "force". It's a definitional fact. Arguing it is, frankly, quite silly. To do so effectively, you really need to rework the whole notion of "force" - something you have so far made no attempt to do.

It's non implicit in quantity of mass being directly proportional to the rate of acceleration towards mass, James R. The greater the mass, the greater the rate of acceleration towards it. The moon 1/6 the gravity of the earth etc.


Your definition of force (anything that causes acceleration) lacks scientific substance.

That defines what force does. It doesn't define what force is. My definition is far better. It defines what force is.

Will try and teach you. Your idea of unequal masses causing equal forces is what you are trying to explain. Will try and help you.

Question.

Does the apple's gravity cause the earth to accelerate towards the apple faster than what earth's gravity causes the apple to accelerate towards the earth? Or vica versa?



Your answer, correct me if I am wrong, is the apple accelerates the faster because it has less mass.

 

[Vkothii]

That defines what force does. It doesn't define what force is. My definition is far better. It defines what force is.

So, we are finally going to learn after all this time (Galileo, Kepler, Newton, the Renaissance thing) what a force is, as well as what a force does; an independent (possibly using some brand new math) description of forces, distinct from those things - material bodies that we can't explain the existence of either - that forces are seen (by our eyes) acting upon somehow or other?

Fascinating, really, I'm all eyes.

 

[James R]

plane:

The greater the mass, the greater the rate of acceleration towards it.

Your definition of force (anything that causes acceleration) lacks scientific substance.

You're contradicting yourself. In the first quote here, you rely on Newton's definition of force to say that force is proportional to acceleration and mass (i.e. Newton's 2nd law). In the second quote, you claim you don't believe in Newton's definition of force.

So, which is it? Are Newton's laws of motion true or false? Time to decide.

Does the apple's gravity cause the earth to accelerate towards the apple faster than what earth's gravity causes the apple to accelerate towards the earth? Or vica versa?

The acceleration of the Earth towards the apple is less than the acceleration of the apple towards the Earth. That follows from Newton's second law and the fact that the force on the apple is equal to the force on the Earth (the point that you dispute).

What do you think the answer to your question is? And why?

Your answer, correct me if I am wrong, is the apple accelerates the faster because it has less mass.

Yes. a = F/m. Given the same F, the larger mass accelerates at a slower rate.

Do you believe in Newton's second law? Yes or no?

 

[Norsefire]

I thought we settled this. The apple does pull on the Earth;....all matter has gravity. However the gravity of the apple is insignifcant in comparison with that of the Earth.

 

[Steve100]

I thought we settled this. The apple does pull on the Earth;....all matter has gravity. However the gravity of the apple is insignifcant in comparison with that of the Earth.

The gravity is the same if we only consider the apple and the Earth.
The acceleration of the Earth is insignificant.

 

[Vkothii]

The gravity is the same if we only consider the apple and the Earth.

It's the same if you only consider the apple, too.
It's the same for both, $$ F_{apple} = F_{earth} $$

At least, it is if you sit in an orchard and watch apples and earths accelerate toward each other.

 

[plane]

So, we are finally going to learn after all this time (Galileo, Kepler, Newton, the Renaissance thing) what a force is,

I would say force is the exertion of matter upon matter.

plane:

You're contradicting yourself. In the first quote here, you rely on Newton's definition of force to say that force is proportional to acceleration and mass (i.e. Newton's 2nd law). In the second quote, you claim you don't believe in Newton's definition of force.

So, which is it? Are Newton's laws of motion true or false? Time to decide.

Time for who? I would say my decisions are made. Not sure that you have actually made decisions about Newton's work.

On your inquiry as to my position, some right, some absurd, and some not what they purport to be. (Newton’s third law should read to every force there is a like and opposite force, law of gravity absurd, first law of motion Newton’s second law under the condition of zero unbalanced force.)

You are saying if one element of Newton’s laws are right, all elements are. Doesn’t necessarily follow.

In the first quote I am relying in the earth having a greater rate of acceleration towards it because it has the greater mass. Newton’s second law is not in the picture. Drop the apple on the moon. It accelerates at a rate proportional to what? The moon’s mass. Force is not introduced. Acceleration is proportional to mass. That is all we have.

Look closely at my first quote and understand your mistaken reading on what I post. I make no mention of force. You read what I write and you bring force into it. If we are debating, as you say we are earlier in the thread, your standard of debating does not amount to much. If you want to say what someone says is wrong, deal with what they say.

The acceleration of the Earth towards the apple is less than the acceleration of the apple towards the Earth. That follows from Newton's second law and the fact that the force on the apple is equal to the force on the Earth (the point that you dispute).

More explanation. You are hiding your brain in the betwixt of Newton's work. A few posts back I said not worth your time replying. And I meant it. You haven't been able to answer how an the lesser mass of an apple applies the same force to the earth as what the earth does to the apple. The truth is you don't know and we both know that you don't, so why bother replying? I will try and teach you as per last post, I guess, if you do.

What do you think the answer to your question is? And why?

The apple accelerates towards the earth. The earth does not accelerate towards the apple.

Yes. a = F/m. Given the same F, the larger mass accelerates at a slower rate.

Around the circle we go. How the same F if the earth has more mass than an apple? You will never answer.

Do you believe in Newton's second law? Yes or no?

Ja. You? Has this link got it wrong. If Newton said gravity is proportional to mass and also that unlike masses apply an equal force to each other, he contradicted himself. No big deal, I guess, but he did.

Isaac Newton said that gravity is proportional to mass,

 

[Steve100]

The apple accelerates towards the earth. The earth does not accelerate towards the apple.

How do you explain, planetary wobble then? Or binary star systems etc.

Ja. You? Has this link got it wrong. If Newton said gravity is proportional to mass and also that unlike masses apply an equal force to each other, he contradicted himself. No big deal, I guess, but he did.

Where is the contradiction?

 

[James R]

plane:

What is it about Newton's law of gravity that you can't grasp? It involves two masses. Look:

$$F=\frac{Gm_1 m_2}{r^2}$$

In other words, the gravitational force acting on mass 1 is equal to the gravitational force acting on mass 2, and the magnitude of the force depends on the magnitudes of both masses.

You seem to think that gravitational force depends only on the mass of the larger object. But Newton's law of gravity plainly contradicts you, and you are offering no alternative formula.

I would say my decisions are made. Not sure that you have actually made decisions about Newton's work.

You're babbling at random. Try to make sense, please.

On your inquiry as to my position, some right, some absurd, and some not what they purport to be. (Newton’s third law should read to every force there is a like and opposite force, law of gravity absurd, first law of motion Newton’s second law under the condition of zero unbalanced force.)

What on earth does this mean? It reads like nonsense.

You are saying if one element of Newton’s laws are right, all elements are. Doesn’t necessarily follow.

Er... no, I'm not saying that. Conceivably, Newton's law of gravity could be wrong, while his laws of motion are correct. As for the laws of motion themselves, the third law is automatically correct, seeing as it is tied up to how the term "force" is defined. For Newton III to be wrong, we'd need a new definition of "force". As for Newton I and II, both are well established and supported by literally millions of experiments and observations.

You haven't been able to answer how an the lesser mass of an apple applies the same force to the earth as what the earth does to the apple. The truth is you don't know and we both know that you don't, so why bother replying?

I've explained it to you at least 3 times now. Gravitational attraction between two objects is an interaction. Take another look at the equation above. The force magnitude depends on the masses of both objects taking part in the interaction, not on the mass of just one of them.

You have no alternative to offer, or any coherent objection.

The apple accelerates towards the earth. The earth does not accelerate towards the apple.

But it is an observed fact that both masses accelerate in a gravitational interaction, not just one, contrary to your claim.

If Newton said gravity is proportional to mass and also that unlike masses apply an equal force to each other, he contradicted himself. No big deal, I guess, but he did.

Your imprecision with language makes it not worth replying to this, since I'd have to guess what your meaning is here. Want to try again?

Isaac Newton said that gravity is proportional to mass,

"gravity" is an effect. It is not proportional to anything. Are you referring to gravitational force, gravitational acceleration, or what? Be specific, and try to be clear.

 

[Vkothii]

What is a "force"? I bet that plane dude doesn't really know; although it looks a lot like he said he does back there, the definition has yet to appear.

Then there's the question of what a force does, distinct from what it is. No answer yet.

Why not just tell us, since no-one else appears to have worked it out?
(And Newton thought he knew, obviously that guy was nowhere near as intelligent).

Can plane describe why I feel both hands being pulled together, if I hold either end of an elastic string and stretch it outwards?

Why doesn't just one hand feel a pull?
Or if I tie one end to a nail in a wall, and pull the elastic with both hands. Does the wall feel a pull, or just my hands? Or should I only use one hand, to be consistent?

 

[plane]

How do you explain, planetary wobble then? Or binary star systems etc.



Where is the contradiction?

If the concept of a small mass pulling a large mass is flawed, the explanation to phenomea believed to be explained by it will lie else where.

The contradiction.

1/ The greater the mass, the greater the rate of acceleration towards mass.

2/ Newton's gravity says the product of unlike masses produce a like force.

In 1/ a falling object is subject to a force proportional to the mass that is falling towards.

In 2/ A falling object is subject to a force that is proportional to the product of its mass and the mass it is falling towards.

Think I have some diagrams a few posts back explaining how Newton went wrong.

What is it about Newton's law of gravity that you can't grasp? It involves two masses. Look:



In other words, the gravitational force acting on mass 1 is equal to the gravitational force acting on mass 2, and the magnitude of the force depends on the magnitudes of both masses.

You seem to think that gravitational force depends only on the mass of the larger object. But Newton's law of gravity plainly contradicts you, and you are offering no alternative formula.

Why would I offer an alternative formula? Would I not just point out the problems with the errant formula. As I have done.

James R I have reached the stage in life where I recognize that you can’t reason with people who believe that a small mass pulls a large mass as much as a large mass pulls a small mass. So my heart isn't really in this.

But do you understand you explain nothing?

On what you post here, 1/ How is the gravitational force acting on mass 1 equal to the gravitational force acting on mass 2?

Stating it doesn’t explain it.

Then 2/ How do mass 1 and 2 physically link up to produce these two forces? If that is what you believe happens.

Your prerogative but you never even begin to answer these questions

You're babbling at random. Try to make sense, please.

Bit subtle for you. I was implying that you have learnt by rote without understanding what you are learning. Went over your somewhat brainwashed head I guess.

What on earth does this mean? It reads like nonsense.

It means Newton’s first law of motion is not a law of motion, Newton’s third law is not presented correctly and Newton’s law of gravity is absurd. I mean, a particle in your near vicinity pulling the whole universe towards it. If someone came on a science forum with that theory, the pseudo science section is where it would belong for a very long time.

Er... no, I'm not saying that. Conceivably, Newton's law of gravity could be wrong, while his laws of motion are correct. As for the laws of motion themselves, the third law is automatically correct, seeing as it is tied up to how the term "force" is defined. For Newton III to be wrong, we'd need a new definition of "force". As for Newton I and II, both are well established and supported by literally millions of experiments and observations.

Newton’s second law passes muster.

I've explained it to you at least 3 times now. Gravitational attraction between two objects is an interaction. Take another look at the equation above. The force magnitude depends on the masses of both objects taking part in the interaction, not on the mass of just one of them.

Pardon me but would you not need to elaborate on what you physically mean be interaction to have credibility in your explanation. Honestly, if you know what you are on about, you should be able to do better than italics to explain things.

You have no alternative to offer, or any coherent objection.

I do have a perfect alternative explanation about the tides to offer. And my objections seem more than coherent to me. Be specific about which one you find incoherent.

But it is an observed fact that both masses accelerate in a gravitational interaction, not just one, contrary to your claim.

What observation are you referring to? We will go through it if you want.

Your imprecision with language makes it not worth replying to this, since I'd have to guess what your meaning is here. Want to try again?

Language precise actually. Read again. Newton said 1/ gravity is proportional to mass and 2/ unlike masses (your m1 and m2) apply equal forces to each other. I have done a bit in this thread to explain it, if you can’t get it, not sure what else I can do. If you have a closed mind, you have a closed mind.

If you only want to pay lip service (or typing service if that is the equivalent on the internet), why bother replying?

"gravity" is an effect. It is not proportional to anything. Are you referring to gravitational force, gravitational acceleration, or what? Be specific, and try to be clear.

Referring to the link provided (underlined if you go back to the post in question). James R, you aren’t really up to serious debate. Three or more questions here you are shy on answering. You can either answer them or you can't.

 

[Steve100]

The contradiction.

1/ The greater the mass, the greater the rate of acceleration towards mass.

2/ Newton's gravity says the product of unlike masses produce a like force.

In 1/ a falling object is subject to a force proportional to the mass that is falling towards.

In 2/ A falling object is subject to a force that is proportional to the product of its mass and the mass it is falling towards.

Think I have some diagrams a few posts back explaining how Newton went wrong.

Stick F=Ma into Newton's law of gravitation and you will see there is no contradiction.

 

[Reiku]

I have watched this for a very long time. I wish the 'so-called' professionals of physics would explain this properly.

The $$M$$ and $$m$$, hold the same value, but not intensity of the gravitational force. But, there is an equal force, but not intensity, acting on both objects. So if there is a magnitude of 10,000 units, whereas, an apple may have 0.003 % of that value, that value according to relativity is reduced from 10,000, so that the value spoken of in the latter, has a value of intensity stronger than that of the apple, so that the apple does not alter the earth in any dramatic way.

It's the same as the train phenom in relativity. Suppose a train was moving 5 miles per hour, and aboard the train where Jack and James, and they wanted to play a game of catch with a ball. Imagine Jack stood at one end of the cart and James stood at the other end.

Now, Jack throws the ball to James at six miles per hour, and James throws it back, at the same speed. Aboard the train nothing looks wrong. The ball is thrown back and forth at the same speed. For those stationed on the platform watching the game, it is a little different. When Jack throws the ball to James, the ball is observed to move faster with a speed of eleven miles per hour. When James throws the ball it moves considerably slower, only one mile per hour.

Why does the ball move at different speeds? - Well, one needs to take into consideration the velocity of the train, including the direction the ball is thrown. If Jack throws the ball, the speed of the ball works with the train, so the speed of the train must be added with the speed of the ball. If James throws it, The speed of the train must be deducted from the speed of the ball, because the throw is going against the momentum of the train. If the ball was a photon (fastest particle of light), things change. The photon will be seen to be traveling at the same speed according to the observers on the platform and the observers aboard the train, no matter how fast it was moving!

 

[James R]

plane:

The contradiction.

1/ The greater the mass, the greater the rate of acceleration towards mass.

Maybe this is part of your problem, since it is wrong. The acceleration of object A falling towards object B is NOT determined by the mass of object B. Acceleration of object A depends on the force on object A and the mass of object A.

To summarise for you: the acceleration of object A depends on the mass of object A, not object B.

Why would I offer an alternative formula?

You should offer some evidence against Newton's law, if that is what you're disputing. So far, you haven't provided anything that backs up your claims. Physics is a quantitative science. It makes numerical predictions of things like accelerations, not just qualitative hand-waving nonsense.

James R I have reached the stage in life where I recognize that you can’t reason with people who believe that a small mass pulls a large mass as much as a large mass pulls a small mass. So my heart isn't really in this.

Ok. You can leave sciforums now, then. Bye.

On what you post here, 1/ How is the gravitational force acting on mass 1 equal to the gravitational force acting on mass 2?

Stating it doesn’t explain it.

I think it would be a complete waste of my time to attempt to explain the concept of a field to you, or virtual particle exchange, or any other conceptualisation of how gravitation works. You haven't even managed to learn Newton's laws of motion yet, so how can you hope to understand anything more complicated, without any kind of grounding in the basics?

Bit subtle for you. I was implying that you have learnt by rote without understanding what you are learning. Went over your somewhat brainwashed head I guess.

Meh. Whatever. You're hardly in a position to judge my learning.

It means Newton’s first law of motion is not a law of motion, Newton’s third law is not presented correctly and Newton’s law of gravity is absurd.

Explain yourself - if you can - or this is just another collection of empty nonsense.

Why is Newton's 1st law not a law of motion? What is it, then?
How should Newton's 3rd law be presented "correctly"? (You haven't given any sign of understanding it, based on your posts above, so you're not in a position to judge whether it is presented correctly or not, as far as I can tell.)
And what would be a correct numerical law of gravity, if Newton's law is wrong?

Put up or shut up.

Newton’s second law passes muster.

Well then. You should be aware that the m in Newton's second law refers to the mass of the accelerating object, and not the mass of the object it is accelerating towards. Agreed?

Pardon me but would you not need to elaborate on what you physically mean be interaction to have credibility in your explanation. Honestly, if you know what you are on about, you should be able to do better than italics to explain things.

All forces are interactions. By "interaction", I mean that one object causes another object to do something. I push you - you move backwards. My push was a force acting on you, and what occurred was an interaction between the two of us. As I push you, I also feel some resistance to my push - that's the equal force pushing back on me, in accordance with Newton's 3rd law of motion (which you believe is somehow "incorrectly presented", though you can't explain how or why).

I do have a perfect alternative explanation about the tides to offer.

I believe I debunked that earlier in the thread. Please review my previous posts.

But it is an observed fact that both masses accelerate in a gravitational interaction, not just one, contrary to your claim.

What observation are you referring to? We will go through it if you want.

Take, for example, any binary star system with two stars of approximately equal mass. They are observed to orbit around their common centre-of-mass position. What is NOT observed is one star (the slightly more massive one) sitting still in space while the other one (the less massive one) orbits around the centre of the first star.

We can go through it if you want.

Language precise actually. Read again. Newton said 1/ gravity is proportional to mass

What do you mean when you write "1/gravity"? Is this an obscure reference to force, or what?

 

[Vkothii]

What's so hard about understanding that two bodies accelerating toward each other's centre, each see an equivalent FORCE, because it's one interaction - the force is distributed by the masses of each body?

So they accelerate accordingly - their acceleration is distributed as the mass (of each body)?

A spring has a constant, gravitation has a constant; the analogy fits. One spring or constant pull on two objects connected to the ends.
Why is this such a problem?

Why does Newton use the same formula, essentially for both mechanics/dynamics fields, which is how he understood them?

 

[plane]

Stick F=Ma into Newton's law of gravitation and you will see there is no contradiction.

Rubbish.

mg = kM/d x d

Means the mass of the body causing the falling is proportional to the rate of acceleration of the body doing the falling.

Maybe this is part of your problem, since it is wrong. The acceleration of object A falling towards object B is NOT determined by the mass of object B. Acceleration of object A depends on the force on object A and the mass of object A.

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.

 

[AlphaNumeric]

mg = kM/d x d

Means the mass of the body causing the falling is proportional to the rate of acceleration of the body doing the falling.

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?