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Offline Pincho

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What is a pull force?
« on: 26/02/2013 13:46:28 »
If you imagine Quantum Physics as a series of points then I can't imagine how a pull would ever happen. For example, if you pull open a door your hand atoms are behind the door handle, so your hand atoms are pushing the door open. The same with a chain, the atoms are always pushing.

Now the force formula uses mass to mass. In quantum physics particle to particle could never happen.

So can someone explain to me what a pull force is supposed to be?


 

Offline Pincho

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Re: What is a pull force?
« Reply #1 on: 26/02/2013 22:28:19 »
No replies so far. Ok so another question then... why didn't Isaac Newton say...

"The apple is pushed to the Earth."

Isaac Newton would have studied physics, and noticed that atoms always push one another, and no pull forces ever exist in nature. So why did he choose the word pull?

Why is gravity a pull force?

Why can't space push the apple to the Earth?

Why can't iron filings flow towards a magnet, and the flow have forces behind the iron filings?

Why can't the Big Bang have particles outside of the singularity that flow towards the singularity to build the Universe?

If you swap pull with push, and swap mass with a hole, so negative mass instead of mass  you get physics reversed, but maths that works the same. Then the Cosmological Constant is reversed, and the Universe expands instead of contracts.

What's wrong with that?

What's a pull force?
 

Offline simplified

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Re: What is a pull force?
« Reply #2 on: 27/02/2013 02:42:56 »
Force is attempt of potential energy to turn into kinetic energy. :)
 

Offline yor_on

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Re: What is a pull force?
« Reply #3 on: 27/02/2013 10:04:14 »
In GR gravity is neither pull or push, it's just a geometry. If you fall you don't feel pushed but rather 'drawn' towards the floor, so in that manner you can use a 'pull', and we do. To describe a free fall as something pushing is not what you experience, it's rather a absence of 'force'. And a magnet can pull, you just need to hold it above a nail to see it lift, getting 'pulled' towards the magnet. The 'force' stopping your geodesic (free fall) on Earth is the floor, applying a 'push' equal to the 'pull' one might define gravity as, from that perspective. And gravity always comes together with mass, which is why one can define it as a pull, as that is how we experience it, observing stuff around us. 'Mass attracts mass' as the saying goes. As for if 'pull' doesn't exist? We define it as existing, how would you explain a car towing a another car from a perspective of 'pushing' it? The forces we define all come from what we see, relative a 'inertial point of view' (being 'still'), as our Earth.

Here you lose me "If you swap pull with push, and swap mass with a hole, so negative mass instead of mass  you get physics reversed, but maths that works the same. Then the Cosmological Constant is reversed, and the Universe expands instead of contracts."

How do you get a 'hole'? And what would 'negative mass' be? It's not that you're assuming wrong as I, behind the words, can see that you're trying to apply a 'symmetry' to your description, but reading it I'm not sure what it means.
 

Offline Pincho

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Re: What is a pull force?
« Reply #4 on: 27/02/2013 12:52:04 »
In GR gravity is neither pull or push, it's just a geometry. If you fall you don't feel pushed but rather 'drawn' towards the floor, so in that manner you can use a 'pull', and we do. To describe a free fall as something pushing is not what you experience, it's rather a absence of 'force'. And a magnet can pull, you just need to hold it above a nail to see it lift, getting 'pulled' towards the magnet. The 'force' stopping your geodesic (free fall) on Earth is the floor, applying a 'push' equal to the 'pull' one might define gravity as, from that perspective. And gravity always comes together with mass, which is why one can define it as a pull, as that is how we experience it, observing stuff around us. 'Mass attracts mass' as the saying goes. As for if 'pull' doesn't exist? We define it as existing, how would you explain a car towing a another car from a perspective of 'pushing' it? The forces we define all come from what we see, relative a 'inertial point of view' (being 'still'), as our Earth.

Here you lose me "If you swap pull with push, and swap mass with a hole, so negative mass instead of mass  you get physics reversed, but maths that works the same. Then the Cosmological Constant is reversed, and the Universe expands instead of contracts."

How do you get a 'hole'? And what would 'negative mass' be? It's not that you're assuming wrong as I, behind the words, can see that you're trying to apply a 'symmetry' to your description, but reading it I'm not sure what it means.

Ok, but 'drawn towards', and 'attracted' also don't exist in nature. For example, if you suck the air out of a steel drum you could say that it draws itself in, but the truth is that it is squashed by the outside air pressure. It's the same with a Dyson Vacuum cleaner. Move the air out of the way, and the outside air pushes in. It's the same with any physic that looks like an attractive force. There always seems to be an outside force pushing in. If a car pulls another car, the atoms of the rope are still behind the atoms of the bumper, so in particle physics the pull is actually a push.

What you have with atoms is a break down of push forces, that's what I imagine. The bonding of the atoms is the final push force, and that would need to be a flow force.

Quote
How do you get a 'hole'? And what would 'negative mass' be? It's not that you're assuming wrong as I, behind the words, can see that you're trying to apply a 'symmetry' to your description, but reading it I'm not sure what it means.

Presume that space time needs to be a grain structure to change physics to a push force. So it would be a grain structure that has no friction. The example would be a super fluid. The best way to totally avoid friction is to have a super fluid of scalar particles. Then the Planck telescope would struggle focusing on the scalar particles. A hole would be a spin where angular momentum causes the scalar particles to scale down the particles trapped in the middle of the spin. Then more scalar particles move into the area of least resistance. Basically this is a tiny whirlpool of scalar particles, and it creates a hole between scalar particles. This is your singularity, but it is also a grain structure, so all atoms would have their own singularities, and that would be the electrons, and the nucleus. The energy is the flow of scalar particles, and that flow is also gravity, and the out flow is the positive polarity of scaled down particles that can escape the incoming flow. So now you have scalar physics working like a packet of Rice Crispies. The small particles separate from the large particles. You have an in flow, and an out flow, but all of the flows are push flows.

Now physicists say that the physics of time can all mathematically play out in reverse. The maths agrees. Well here is a situation where all of the maths is reversed. So Einstein wondering why the Universe doesn't contract is now thinking that the Universe should expand. And violla! you not only fix physics, but you also fix quantum physics into physics. For example 'Action At A Distance' is now local push action.

I suppose at this point I should ask again, what is a pull force in actual physical descriptions?
« Last Edit: 27/02/2013 13:38:52 by Pincho »
 

Offline JP

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Re: What is a pull force?
« Reply #5 on: 27/02/2013 17:38:48 »
Ok, but 'drawn towards', and 'attracted' also don't exist in nature.

But those do exist in nature.  Forces can act between two objects to pull them together.  Forces can also act to push them apart. 

Classically, gravity is an attractive force, meaning it acts between two masses to pull them towards each other.  An electrostatic force can also be a "pull" force, as you've no doubt experienced with static cling. 

There are more in-depth models in quantum mechanics and relativity, but they all reduce, in our everyday lives, to the simple idea of an attractive force.  In particular, in quantum mechanics, all forces (except for gravity) can be expressed as exchanges of virtual particles.  Virtual particles are somewhat funny beasts, such that if two particles are exchanging them, this exchange can actually pull the particles together.  This is, as far as I know, the deepest explanation we currently have of attractive forces.
 

Offline Pincho

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Re: What is a pull force?
« Reply #6 on: 27/02/2013 18:52:02 »
Ok, but 'drawn towards', and 'attracted' also don't exist in nature.

But those do exist in nature.  Forces can act between two objects to pull them together.  Forces can also act to push them apart. 

Classically, gravity is an attractive force, meaning it acts between two masses to pull them towards each other.  An electrostatic force can also be a "pull" force, as you've no doubt experienced with static cling. 

There are more in-depth models in quantum mechanics and relativity, but they all reduce, in our everyday lives, to the simple idea of an attractive force.  In particular, in quantum mechanics, all forces (except for gravity) can be expressed as exchanges of virtual particles.  Virtual particles are somewhat funny beasts, such that if two particles are exchanging them, this exchange can actually pull the particles together.  This is, as far as I know, the deepest explanation we currently have of attractive forces.

There are no physics however in the explanation. Using the word attraction alone gives me no insight into attraction. If you try to imagine attraction there are no physics that actually work. Einstein's bending of space time still produces a rear force, so it's a push force. Particles with hooks on them are still a push force, because the hooks have to hook behind something. There is no way to have a pull force that I can think of. So Gravity has to be a push force. Static Cling would be a flow force towards the electron hole like pulling the plug out of a sink. And besides which it is invisible so hardly counts as an example of anything.

If anybody can explain a pull force, I am still willing to listen. But I doubt if there are any pull, attractive forces.


The main point here is that Newton said pull, and so everyone says pull. Newton only had to say a word, and now it is expressed for no reason. If he said push we would not be having this conversation.
« Last Edit: 27/02/2013 18:58:55 by Pincho »
 

Offline JP

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Re: What is a pull force?
« Reply #7 on: 27/02/2013 21:03:02 »
The physics is simply that objects released from rest tend to configure themselves at the minimum potential energy due to whatever fields of force exist around them.  This means they move in directions to minimize this energy.  This can be in any direction, really, and "push" and "pull" are simply words you're using to describe them moving towards or away from each other. 

And again, check out descriptions of virtual particles and how they account for "pulling."  There's lots of physics there: http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html
It's not simple, though, so you'll probably have to put in some significant effort to understand it.
 

Offline Pincho

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Re: What is a pull force?
« Reply #8 on: 27/02/2013 21:18:30 »
The physics is simply that objects released from rest tend to configure themselves at the minimum potential energy due to whatever fields of force exist around them.  This means they move in directions to minimize this energy.  This can be in any direction, really, and "push" and "pull" are simply words you're using to describe them moving towards or away from each other. 

And again, check out descriptions of virtual particles and how they account for "pulling."  There's lots of physics there: http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html
It's not simple, though, so you'll probably have to put in some significant effort to understand it.

I understand that, but it has a virtual push along the curve of a wave. It's still a push. Why don't scientists like the word push? Are they too embarrassed to admit that gravity is a push force?

And yes it makes a huge difference. For one thing you don't need Dark Matter if gravity is a push force.
« Last Edit: 27/02/2013 21:22:08 by Pincho »
 

Offline JP

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Re: What is a pull force?
« Reply #9 on: 27/02/2013 21:35:53 »
Why do you insist on using the word push instead of just saying force has a direction?  You're bogging yourself down in a particular choice of term and losing sight of the physics here.  You can always say a force is a "push" along the direction of the force if you want, but that's not standard language and you'll end up confusing people.
 

Offline Pincho

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Re: What is a pull force?
« Reply #10 on: 27/02/2013 21:43:59 »
Why do you insist on using the word push instead of just saying force has a direction?  You're bogging yourself down in a particular choice of term and losing sight of the physics here.  You can always say a force is a "push" along the direction of the force if you want, but that's not standard language and you'll end up confusing people.

Because the Big Bang requires a force to push the particles together. So the force has to come from in front of the singularity. There is not supposed to be anything outside the singularity, so the particles have nothing to push them together. This means that the Big Bang would just be an expansion with nothing forming. Particles would have no way to change direction. If you put particles outside of the singularity you then have a push force towards the singularity before the Big Bang sends particles out of the singularity. But in this instance you still need to create singularities inside atoms, else the push force will just be a blow force. A blow force would blow us off the Earth. So basically there is only one way to use a push force with atoms, and that is to change the force formula to use holes instead of mass. Scientists do refer to electrons as holes, and they also have been linked to a pull force, and magnetism. So in the atoms there must be the singularities that are in fact allowing matter to flow through them.

All of that information is available from a push force, and none of it works with a pull force. In fact nobody still has identified a pull force. And Newton no way had ideas of virtual particles, and virtual waves.

I think that defining the force is very important. I think that a push force is far more obvious than a pull force in nature, and that Newton should have used nature as his observation.

« Last Edit: 27/02/2013 21:57:30 by Pincho »
 

Offline JP

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Re: What is a pull force?
« Reply #11 on: 27/02/2013 22:59:36 »
Pincho, if you want to understand forces, I suggest starting smaller than the big bang and trying to understand how forces work in physics. 

You keep saying how Newton or physics defines forces, but you're getting it completely wrong.  Physics says a force has a direction.  That's backed up extremely well by observations.  All this push, pull (and now blow) force is your own terminology--not that of physics.
 

Offline Pincho

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Re: What is a pull force?
« Reply #12 on: 27/02/2013 23:23:16 »
Pincho, if you want to understand forces, I suggest starting smaller than the big bang and trying to understand how forces work in physics. 

You keep saying how Newton or physics defines forces, but you're getting it completely wrong.  Physics says a force has a direction.  That's backed up extremely well by observations.  All this push, pull (and now blow) force is your own terminology--not that of physics.

No pull force is backed up by observation. No direction is backed up by observation when it comes to pull forces. The asteroid moves towards the Earth, but the force is never backed up by observation. Einstein says that space time bends towards mass, and yes we can observe that. However a flow force would also bend into the Earth, and a flow force is backed up by all observations, like whirlpools, and plug holes. It's a bit silly to make up new physics when all of the visible physics do the same thing with a push force. Einstein said that there should be a twist around the Earth. The twist was found. However a twist happens around a plug hole, and a whirlpool, and they are push, flow forces. Again, why re-invent the wheel?

I just find it odd that scientists need to make up a complicated explanation from a pull force, when a simple explanation is available from a flow force. My physics are all visible to the human eye, but science uses virtual particles to do the same thing.

And what about all of the Quantum Physics that become normal physics. The two slit experiment has a hidden wave interfering with the photon. Yes its the push force. Action at a distance.. yes its the push force. Particle wave duality, yes its the push force.

Quantum physics is just physics with a push force, because to have a push force you need a grain structure, and the grain structure interferes with the experiments.
« Last Edit: 27/02/2013 23:36:10 by Pincho »
 

Offline JP

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Re: What is a pull force?
« Reply #13 on: 28/02/2013 00:18:44 »
,My physics are all visible to the human eye, but science uses virtual particles to do the same thing.

If your goal here is to promote your own theory, then please keep discussion of it in the New Theories forum. 
 

Offline Pincho

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Re: What is a pull force?
« Reply #14 on: 28/02/2013 00:52:43 »
,My physics are all visible to the human eye, but science uses virtual particles to do the same thing.

If your goal here is to promote your own theory, then please keep discussion of it in the New Theories forum.

My example physics are taken from water, so nothing new about them. The Galaxy, a whirlpool. All I am saying is why invent new physics? Why did Newton invent new physics when a flow will move the apple towards the Earth? A flow will move the photon in the two slit experiment. A flow will create action at a distance.

Well I do have a theory, so I will just post that instead.
« Last Edit: 28/02/2013 01:16:09 by Pincho »
 

Offline Pmb

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Re: What is a pull force?
« Reply #15 on: 28/02/2013 04:50:28 »
The best way to think of the difference between pushing and pulling is the difference between positive and negative pressure/stress. When the stress is positive it means that you're compressing material and when its negative you're pulling material apart. Thus when you pull a car you're stretching it and when you're pushing a car you're compressing it. Compression requires positive pressure and pulling apart requires negagive pressure. Make sense?
 

Offline yor_on

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Re: What is a pull force?
« Reply #16 on: 28/02/2013 11:56:42 »
Nice one Pete, as well as JP.

I should have been clearer in my description Pincho, what gravity is, is nothing, but a 'nothing' with a preferred direction. And all forces we describe as pulling and pushing comes from our observations of nature, and how it acts. You have to remember that is only the last, a hundred and fifty or so? years physics taken those gigantic steps toward the very small as well as relativity. They put a lot of the nomenclature we use daily on their ears. A 'force' is something changing something else. it may, or may not, have a preferred direction. Gravity is a example of something even more weird, as I can't see how you would define a energy to it, although you can define a energy to what it can do with mass. But Pete and JP are the guys knowing that best :)
==
We can 'tap energy' from what gravity does to mass, as using a waterfall to drive a wheel. But let us discuss it from redshift. Imagine yourself far outside a gravity well measuring light falling towards a event horizon. Will it redshift to you? Where did it lose the 'energy' you measure it to have? To what?

A immense gravity right? Now assume a waterfall again and the wheel spinning just above the Event horizon, and we will ignore tidal forces. Would you expect the waterfalls water to have more energy as it hits the wheel?

Let's go back to that light quanta, and assume that you instead observe it infalling towards you at the event horizon. Do you expect it to have more energy, becoming blue shifted, as you now observe it from the even horizon.

Are we observing the same light quanta? You can assume that it is, and we don't need to define a simultaneous 'instant' for our observations.

And what would that light quanta's 'energy' be intrinsically, changing depending on observer, or of one magnitude?
==

To me it all seems relations, except the one where we discuss its 'intrinsic energy'. And that one must indeed be 'locally defined and measured' in the strictest sense of the words.
==

And yeah, gravity can indeed change relations.  The most important point maybe? Is that the energy you measure at both places are its 'real energy'. You can use it to drive some circuit, transforming it into electricity. And while it won't manage it for the 'far observer' most probably, it will do nicely for the 'near observer' at the event horizon.

So the light quanta's energy must be a relation relative gravity, but gravity itself is not there, as a 'substance'. Still, neither is 'space' it seems, at least not classically speaking. Those 'bosons' we expect are, as I understands it, just indirect evidence of something changing a relation to/in such 'stuff' we can measure on. Or can we measure them directly?
« Last Edit: 28/02/2013 13:08:13 by yor_on »
 

Offline yor_on

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Re: What is a pull force?
« Reply #17 on: 28/02/2013 12:06:09 »
And one more thing Pincho, I think I can see where you are going with your ideas on 'flows'. Take a look at chaos theory, and how they define it first, also on 'strange attractors'. Nature is hiding a lot from us, as we observe it seems :)
 

Offline Pincho

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Re: What is a pull force?
« Reply #18 on: 28/02/2013 12:53:51 »
Well, nice ideas from everyone. I'm going to stick with thinking in Quantum Physics however, and just go with bump forces. I think that negative energy still requires an opposing bump force, else particles would have to move themselves. I can't see how a particle could move itself. I will look into Chaos, and strange attractors.

I looked at strange attractors. yes that's the sort of thing. A continuous loop of flow forces like the weather system.

Anyway I posted my version of this chaotic flow force, and I use a scalar system to move particles from the front of the line to the back of the line...
http://www.thenakedscientists.com/forum/index.php?topic=47070.0
« Last Edit: 28/02/2013 13:09:00 by Pincho »
 

Offline simplified

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Re: What is a pull force?
« Reply #19 on: 28/02/2013 13:34:17 »
Why potential energy of spring has mass, but gravitational potential energy has no mass?
« Last Edit: 28/02/2013 17:06:34 by simplified »
 

Offline Pincho

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Re: What is a pull force?
« Reply #20 on: 28/02/2013 14:03:03 »
Quote
We can 'tap energy' from what gravity does to mass, as using a waterfall to drive a wheel. But let us discuss it from redshift. Imagine yourself far outside a gravity well measuring light falling towards a event horizon. Will it redshift to you? Where did it lose the 'energy' you measure it to have? To what?

A immense gravity right? Now assume a waterfall again and the wheel spinning just above the Event horizon, and we will ignore tidal forces. Would you expect the waterfalls water to have more energy as it hits the wheel?

Let's go back to that light quanta, and assume that you instead observe it infalling towards you at the event horizon. Do you expect it to have more energy, becoming blue shifted, as you now observe it from the even horizon.

Are we observing the same light quanta? You can assume that it is, and we don't need to define a simultaneous 'instant' for our observations.

And what would that light quanta's 'energy' be intrinsically, changing depending on observer, or of one magnitude?]We can 'tap energy' from what gravity does to mass, as using a waterfall to drive a wheel. But let us discuss it from redshift. Imagine yourself far outside a gravity well measuring light falling towards a event horizon. Will it redshift to you? Where did it lose the 'energy' you measure it to have? To what?

A immense gravity right? Now assume a waterfall again and the wheel spinning just above the Event horizon, and we will ignore tidal forces. Would you expect the waterfalls water to have more energy as it hits the wheel?

Let's go back to that light quanta, and assume that you instead observe it infalling towards you at the event horizon. Do you expect it to have more energy, becoming blue shifted, as you now observe it from the even horizon.

Are we observing the same light quanta? You can assume that it is, and we don't need to define a simultaneous 'instant' for our observations.

And what would that light quanta's 'energy' be intrinsically, changing depending on observer, or of one magnitude?

I just wanted to go back to this. The energy change of the photon does not need to be due to a pull force of gravity. You can do the same thing with a push force. In fact, I said earlier that flow forces bend into holes. Changing the bend into Einstein's bend of space time is a very strange thing to do, almost comical. Because Einstein said that the bend creates gravity, however gravity creates the bend. We see it every day when we wash our faces, and hands. Einstein is getting Cause, and effect backwards to account for a pull force. Like I say, why is science determined to have a pull force?
« Last Edit: 28/02/2013 14:09:02 by Pincho »
 

Offline yor_on

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Re: What is a pull force?
« Reply #21 on: 28/02/2013 14:10:58 »
Yeah, nice one Simplified. If I was to assume that gravity was 'energy'  I would also have to assume that as you tapped it of its 'energy', and we do, it should transform. Transform as, while you gain something ('energy'), its origin (the gravity itself) should lose something to keep the universe in a equilibrium. But gravity doesn't 'wear out' by use, does it? Not as I know at least. Its existence seems depending on mass, accelerations (locally perceived), and 'energy', as you heating up that spring to then weight it, finding it to have gained mass, and therefore more 'gravity'.
 

Offline yor_on

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Re: What is a pull force?
« Reply #22 on: 28/02/2013 14:17:19 »
Gravity neither pull or push. It's just a preferred direction. The proof for that is any 'free fall' and measuring the forces acting on the object locally. As Pete has explained, you can transform away all gravity there is, just by changing coordinate system. You standing on a tower will feel gravity acting on you, but falling from it there will be no gravity at all (ignoring tidal forces). Just think of yourself inside a black box free falling, how will you prove the existence of a gravity?
=

To be strict we should define it as 'geodesics' instead of 'free falls', but geodesics are much more non intuitive beings than a free fall to me. If we take a bullet shoot in deep space, then as long as it is accelerating it will not be in a geodesic as I think, but as soon as the acceleration stops the geodesic will come into existence, defining its further path. (although the barrel will constrict it, so we better consider it after leaving that:)
« Last Edit: 28/02/2013 15:09:08 by yor_on »
 

Offline Pincho

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Re: What is a pull force?
« Reply #23 on: 28/02/2013 15:14:13 »
Gravity neither pull or push. It's just a preferred direction. The proof for that is any 'free fall' and measuring the forces acting on the object locally. As Pete has explained, you can transform away all gravity there is, just by changing coordinate system. You standing on a tower will feel gravity acting on you, but falling from it there will be no gravity at all (ignoring tidal forces). Just think of yourself inside a black box free falling, how will you prove the existence of a gravity?
=

To be strict we should define it as 'geodesics' instead of 'free falls', but geodesics are much more non intuitive beings than a free fall to me. If we take a bullet shoot in deep space, then as long as it is accelerating it will not be in a geodesic as I think, but as soon as the acceleration stops the geodesic will come into existence, defining its further path. (although the barrel will constrict it, so we better consider it after leaving that:)

Well what is a free fall then. How does a particle propel itself along without propagation? What are the physics of the free fall? I don't like free fall, because it's a none physical situation like a pull is a none physical situation. I am reading Geodesics, that might take me a couple of weeks to turn into Quantum Physics. So I will leave my reply on that for awhile. It's good to think about these Geodesics. I haven't had new physics to work on for awhile.
« Last Edit: 28/02/2013 15:42:01 by Pincho »
 

Offline yor_on

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Re: What is a pull force?
« Reply #24 on: 28/02/2013 16:17:36 »
Wish I knew that one. But I think it's a very good question to wonder about. If you use planets and suns as your (inertial) coordinate systems, a 'free fall' is something 'in motion', also called 'relative motion', relative any of those, except if they are co moving in which case they are 'at rest' with each other. Uniform motion don't expend 'energy' as I know. Earth is one of those uniformly moving objects, or unmoving, depending on your choice of coordinate system. If you look at it from energy expended then no 'relatively moving' object expend any energy, which to me then becomes a definition of 'nothing happening'. That makes them unmoving :) if it wasn't for the fact that we can discern different uniform motions. So we have motion, uniform and accelerations, You can split both of those into different sets of 'motion' but it is when it comes to uniform motion it becomes really interesting, or confusing, to me. Because none velocity/speed will spend any energy in them? And that makes no sense to me? But it has to make sense, as it's experimentally true.

It would be so much simpler if there was just two things, uniform motions without speed/velocity changes measurable in it, and then accelerations. But as we have different sets of uniform motion there exist 'motion', and not only 'relative motion'. Although, if you isolate any two uniformly moving objects into a 'system', their motion versus each other indeed will be relative, you are free to define which ever as moving relative the other 'unmoving', and all degrees in between. The same goes for a whole universe as i think, but it doesn't change the fact that we can find different 'speeds/velocities' to uniform motion.
 

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Re: What is a pull force?
« Reply #24 on: 28/02/2013 16:17:36 »

 

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