Alternative views on gravity?

[happy snapper]

wow.. I love your answer to number 4..A perfect reply allmost. i also think there is a link between dark matter and GRAVITY

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dark matter and gravity...Can anyone explain there ideas on the link

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I believe that so called dark matter doesnt react with gravity but actually causes it and can explain how

Edited November 26, 2009 by happy snapper
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[ajb]

no 1...Is it possible for a particle to be smaller than an atom?

 

Yes.

 

The problem comes when you try to play "atomic billiards". Quantum mechanics spoils this picture.

 

no 2 ...Is it possible for a particle to travel towards an atom enter it and leave unhindered?

 

Yes, we discussed this in terms of scattering.

 

It is possible to fire particles through objects and see them pass right through. Generically some will be scattered.

 

Insane_Alien's example is good. Neutrinos interact via the weak force. The probability of interacting (scattering) with an atom is small, but non-zero.

 

no0 3 ...Is it possible that a particle can be affected on its journey by an electron or the necleus.?

 

If they interact yes.

 

Given what we know right now the interaction will be via the electoweak, strong or gravitational forces. Stated "semi-classically" the "micro particle" that comes close to an electron exchanges momentum via a field.

 

The closes thing I can think of to your idea is that of a gravition. That is the quanta associated with the gravitational field. In a quantum picture, particles interact gravitationally via exchange of gravitons.

 

Or are you proposing some other field? That is allowed. There may be other forces we have yet to encounter.

 

no 4... Is it possible that dark matter may be all around us but the only reason we cant see it is that it is small ?

 

Depends what you mean here. It is all around us in the sense that our Galaxy is full of the stuff.

 

But if you mean are we in a homogeneous and isotropic "bath" of dark matter then I would say no.

 

Any small fluctuations in the density are unstable and would grow. We will see "lumps" of the stuff all over the place. This may be related to galaxy seeding.

 

If you get a no to all from everyone then forget it.

If not then you should get back to me and listen.

 

Not quite as simple as yes or no.

 

My idea doesnt go against any rules of PHYSICS.

 

I did not say that it did. However, unless you state things carefully and formulate them with equal care it is difficult to say if it is in-line with basic physics or not.

 

Of course, any new work should go a step beyond current understanding but not at the cost of completely destroying what is well established.

 

You might try and say how Einstein's relativity "destroyed" the old physics. This is just not true. Einstein's relativity contains Galilean relativity ("classical Newtonian mechanics") and Newton's law of gravity in certain limits.

 

 

Have you ever had any of your friends ever have an original idea of how GRAVITY actually works..Id say never.

 

This is besides the point really. However, I do know people personally and professionally that do work on gravity in various context.

 

I myself do not, at least not directly. But I think I am qualified to tackle most of the questions that are likely to arise via this forum. At the least I am usually able to give some direction in the literature.

 

Classical relativity is a very interesting subject in its own right. Something I should read up on more.

 

Just because we cant see something or measure it does not mean it is not there.

 

This is starting to get meta-physical.

 

The view point I take (feel free to disagree) is that the only real things are what we can measure. One may add the proviso of at least in principle, if you expect current technology to miss them.

 

I feel we need to think like this otherwise we get in to a whole mess trying to dissect and interpret physical theories.

 

If a particle is so small it can travel within an atom then we can not measure it because we are made of atoms and all our instruments are made of atoms.Put a receptor deep in a mountain and it can never capture a particle if the said particle has the abilility to travel within the atoms of the receptor.Thes particles enter the receptor and exit unhindered in ther journey.Because these instruments can not capture them does not mean they do not exist..I believe that we do measure them every day but because it is such a common measurment we dont even notice it.

 

Do we or do we not measure them?

 

If they interact not at all with anything that we can measure then how can they exist?

 

It is of course possible that they interact so weakly that we do not notice them in the energy range that we are currently probing.

 

But could something that interacts vastly weaker than gravity is known to explain gravity?

[insane_alien]

i didn't say it reacted with gravity, i said it interacted with gravity. there is a difference.

 

we know it interacts with gravity because we can see the effects on stars and galaxies. infact, if we use computer modelling and observations of the motions of stars we can map out where there should be mass for the stars to be moving the way they do.

 

we did this and it detected a fair bit of mass where there was no visible matter. only trace quantities of gas and dust and cetainly no starsor gravitationally significant bodies. this is the closest we can get to a direct observation of darkmatter.

 

the map and more about it can be seen here http://www.space.com/scienceastronomy/070108_mm_darkmatter_map.html

 

and here http://news.bbc.co.uk/1/hi/6235751.stm

 

it is important to note that while dark matter interacts via gravity it is not the only thing that interactscia gravity. anything with mass interacts with gravity that includesthe quarks electrons gluons etc. etc. that make up you.

[ajb]

anything with mass interacts with gravity that includesthe quarks electrons gluons etc. etc. that make up you.

 

Not quite right. Anything with energy-momentum can be a source of gravity.

 

Often one may consider "test particles" that effectively have no gravitational field themselves (not sources) but still couple to the gravitational field.

 

This is exactly the same as test particles in electromagnetic theory, which you are probably familiar with. Charged, so they interact but do not create their own field.

[insane_alien]

ah right. forgot about that bit of it.

[happy snapper]

We measure dark matter as we do gravity.The observation of gravitys affect is its measurment also.

I say that the so called grafitons and dark matter are one and the same thing.

Measure gravity and you are measuring dark matter.We measure it every day in our everyday life but dont see it that way as it is so familiar to us.

Dark matter doesnt react with gravity.It causes gravity.Its force is applied to every atom it encounters equal to the gravitational force...If many particles of dark matter hits an atom the atom will move .Every atom is hit and every atom moves.That is how we measure dark matter. Just as we measure gravity.Dark matter moves in every direction across space.As it has mass it must react with every atom it encounters.I believe that the density of dark matter is not uniform .A single atom may not encounter a unform amount of dark matter that hits it.And in this instance the atom must move.Dark matter is on a small scale but prolific in its distribution.Every atom in the universe is controled and moulded by this invisible force.Amagine a single atom in deep space being hit from all sides by this dark matter.If equal force from all sides then the atom can not move.Most of the dark matter passes through an atom and carries on with its journey but a small amout does not exit.It has reacted with the parts that make up the atom. So less dark matter exits the atom than entered it. Now instead of one atom we have two atoms in close proximitary to each other.Both being hit by the same dark matter but it can not be equal force from all sides as the two faces of the atom that look at each other have less dark matter hitting them, as the ajacent atom has captured a small amount before it has reaches the second atom.So both atoms have less force aplied to them from this facing side..So they must move towards each other.If an atom moves then so must a grain of sand a planet or star.If dark matter has mass and is in motion this must be.It can not be otherwise.Does this sound like GRAVITY?

Edited November 27, 2009 by happy snapper

[ajb]

Does this sound like GRAVITY?

 

It sounds like "dark matter micro particles" are gravitons, in a rough sort of way.

 

But what your idea reminds me of the most is the Casimir effect.

 

There is a net difference in the energy density between the atoms as compared to outside. This effect is due to quantisation of the forces. It is really a second quantisation phenomena.

 

In the Casimir effect between plates the force can be attractive or repulsive, depending on the exact set up. The force also falls off very rapidly with the distance between the plates.

 

Now, as your theory is classical interpreting it as a Casimir effect may be difficult. What you would have to show is

 

1) The force is always attractive

2) The dominance of a [math]1/r^{2}[/math] term in the force.

 

I would expect there to be a "gravitational Casimir" effect in quantum gravity, but I imagine this is very difficult to calculate. One maybe able to use general relativity as an effective theory and do this up to one loop. But for sure, the force will tiny and be dominated by classical gravity in most circumstances. Maybe one could cook up something on atomic scales.

[insane_alien]

The thing is, dark matter is different from gravity itself.

 

A graviton is a particle hypothesised to travel at the speed of light, and transmit the force of gravity.

 

a particle of dark matter is a particle that has significant mass and does not travel at the speed of light(otherwise the mapped darkmatter shouldn't appear like it does). it only interacts by the exchange of gravitons(assuming gravitons exist in the first place, we have more evidence for dark matter than gravitons).

 

dark matter and gravitons are different there is no escaping this.

 

also, on reading your post, you are proposing that dark matter 'hits' atoms. how does this occur? they only interact via gravity. gravity would not cause a dark matter particle to bounce off say a quark. or anything.

 

it seems that you are assuming that they are little tiny balls of 'stuff' that behave a lot like bouncy balls. this is very very wrong. you only get this sort of behaviour when you have fairly large objects like a virus.

[happy snapper]

Im saying that an atom being equally bombarded from all sides by dark matter will not move . but another atom that obstructs the path of said dark matter will change the amount of dark matter that reaches the 1st atom.So it will not now be equally hit from all directions. The atom must move towards the direction of least force.As both atoms shield each other then there facing sides have less force aplied to them and must move towards each other. If this worked for a single atom it would also work for a group of atoms.If a particle can travel though an atom and also be stopped by an atom this has to work.The more atoms in a group that the dark matter travels though the less that exit that group.Amagine a man stading on earth.The amount of dark matter that hits his atoms is allways the same from above..The dark matter that hits him from bellow is less because the atoms of earth itself have have stopped some on there jouney through the mass of the earth..On the moon the amount that hit him from above are the same as on earth but because the moon has less mass it stops less dark matter reaching the man from bellow.so he has less weight.All the bodies in the solar sytem shield each other from this force causing them to have less overall force aplied to them from the facing sides.This is what binds them. If particles can travel through an atom then this must happen.

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I never said gravitons exist..And I cant see why dark matter cant travel at these speeds. They are not atoms.And im not even saying that what im talking about is your so called dark matter..Im saying that for my idea to work these particles are spread thoughout the universe.And even though there small thats a lot of matter, That may just add up to what is missing.Call them dark matter or call them SMP..There name doesnt matter..

Edited November 27, 2009 by happy snapper
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[insane_alien]

but atoms can only interact with dark matter via gravity. they cannot be 'bombarded' with it. the dark matter will just pass by and have a small gravitational effec on it.very very tiny.

 

also, there are a multitude of dark matter particles passing through you right now yet you can move fine. and they're going through you in all directions, some are going into the earth, some are going away from the earth and i wouldn't be surprised if there were a whole bunch orbiting the earth.

 

you still assume that dark matter paricles and all other particles are some little solid lumps that will bounce off each other when hit. this isn't the case at all or we'd have observed dark matter directly by now. this would mean it interacted via another force such as the weak nuclear force. we KNOW that it doesn't.

[ajb]

(assuming gravitons exist in the first place, we have more evidence for dark matter than gravitons).

 

To date there is no compelling evidence of gravitons being realised in nature.

 

How can we understand this?

 

Well, particles in the context of quantum field theory are associated with perturbation theory. In essence you expand your theory to look like harmonic oscillators + corrections. The particle are associated with these harmonic oscillators.

 

You get a problem in doing this. The corrections blow up to infinity and it is not clear what you have done makes any sense. To remedy this you need renormalisation theory. There are different ways to view this, but by adding infinite terms you can cancel the infinite correction terms and end up with everything finite.

 

That is perturbative quantum field theory in two paragraphs, done very badly!

 

The problem is if we try to the same with general relativity (plus possible extra terms) the procedure of making everything finite does not work. This is even worse than the classical infinities of singularities. We get an infinite number of infinities in general!

 

However, this does not mean that general relativity cannot be made into a quantum theory. It means that perturbation theory, that has worked well for other theories does not work for gravity.

 

It is believed, and there is some evidence for this that gravity is asymptotically safe and renormalisation can remove the infinities, but not as a pertubative theory. Thus, we may have a well defined quantum gravity theory but no gravitons!

 

From a quantum field theory point of view this seems disturbing.

 

However, string theory seems to remedy most of this. String theory does offer a perturbative theory of quantum gravity.

 

...it seems that you are assuming that they are little tiny balls of 'stuff' that behave a lot like bouncy balls. this is very very wrong. you only get this sort of behaviour when you have fairly large objects like a virus.

 

"Atomic billiards" went out with the discovery of quantum mechanics.

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I never said gravitons exist..And I cant see why dark matter cant travel at these speeds.

 

In order to gravitationally "clump" they require mass. They can still interact with gravity if they were massless.

 

Otherwise they will never be slowed down from the speed of light.

 

Have a look at special relativity.

[happy snapper]

Whe I said bombarded I never sad anything about the atoms being hit.And as ive said most do travel though both you and me and the earth on there journey. but not all.And not once did I say anything about bouncing particles or lums of dark matter.I havent a clue what dark matter is made of just like everyone else doesnt.All im saying that if it is matter it has mass and if it comes into contact with something that is also made of mass then a reaction will occur.That doesnt mean that it will react with every atom it meets.I believe it has the ability to travel within the confines of an atom with no reaction.But if it comes into contact with a part that makes up the atom a reaction will occur.Most of this matter travels though the atom with no affect on itself or the atom

Edited November 27, 2009 by happy snapper

[ajb]

All im saying that if it is matter it has mass and if it comes into contact with something that is also made of mass then a reaction will occur.

 

Ok, so your micro particles have mass (I assume non-tachyonic ) and thus you acknowledge that they must travel at a speed less that the speed of light?

 

Do you mean interaction rather than reaction? You should think of interaction simply as exchange of momentum at this level.

 

The notion of "contact" used here seems far to much classical billiards to be very instructive. But ok, most go through with little or no effect.

[happy snapper]

you may be able to help me on something..energy=mass in motion..am I right..If so surely then is energy and mass interchangable? or are they just the same thing but in different states?

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A bat hits a ball..The ball moves.At an atomic level is this reaction or interaction

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When I say contact I mean that they have an effect on each other.I dont mean that they shake hands

[ajb]

you may be able to help me on something..energy=mass in motion..am I right..If so surely then is energy and mass interchangable? or are they just the same thing but in different states?

 

Mass in motion has kinetic energy.

 

Energy is a property of stuff.

 

This notion of interchangeable depends on exactly what you mean.

 

What [math]E=mc^{2}[/math] tells us is that in the rest frame of a massive particle it has energy equal to it's mass times the speed of light squared.

 

A bat hits a ball..The ball moves.At an atomic level is this reaction or interaction

 

The interaction refers how the bat and ball "talk to each other", it is (dominantly) electromagnetic in origin.

 

Reaction really refers to the forces involved. Forces come in pairs, action and reaction which are totally arbitrary assignments. The bat exerts a force on the ball and the ball exerts a force on the bat.

 

When I say contact I mean that they have an effect on each other.I dont mean that they shake hands

 

They "shake hands" via a field. They do not come into contact as such.

[happy snapper]

One thing im not happy about is if these MFs do interact with the parts of the atom where do they go after this interation.Does an atom require energy to survive? It seem that atoms have internal motion.Can this happen without an energy sorce.Can they have a free ride?

[ajb]

One thing im not happy about is if these MFs do interact with the parts of the atom where do they go after this interation.

 

In principle they could be absorbed by the electrons to produce an excited atom. Just like photons do. I am unsure if having massive particles makes this difficult. We would also have to think about what quantum numbers we expect to be preserved.

 

The atom would then decay to a lower energy state kicking out a photon or similar.

 

 

Does an atom require energy to survive? It seem that atoms have internal motion.Can this happen without an energy sorce.Can they have a free ride?

 

An atom does not require an outside power source to be stable, if that is what you mean.

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Your thoughts "smell like" a massive graviton theory. You should note that massive gravitons have been proposed as a candidate for cold dark matter.

Edited November 27, 2009 by ajb
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[happy snapper]

So why does an electron not just exit the atom.How can it be held there without an energy sorce.It moves and is in contant exceleration without energy.How can that be?

[ajb]

So why does an electron not just exit the atom.How can it be held there without an energy sorce.It moves and is in contant exceleration without energy.How can that be?

 

It is attracted to the nucleus via electromagnetism.

 

The energy of the electron does not change so their is no need for a power source.

 

An electron gain enough energy from a photon and leave the atom leaving behind an ion.

[happy snapper]

Seems real wierd to me .This attraction can move the electron from a straight line corse without any energy being needed.Sound like perpectual motion.Do they really know that or is it an idea

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Mybee my MP are giving them a little push

[ajb]

You should think of the electrons as sitting in an electrostatic well created by the nucleus. An external source of energy is only needed for the electron to escape. No power source is needed to keep the electrons in their orbits.

 

Nothing to do with perpetual motion.

[Sisyphus]

So why does an electron not just exit the atom.How can it be held there without an energy sorce.It moves and is in contant exceleration without energy.How can that be?

 

Two things:

 

1) Electrons are not in "orbit" in the same sense planets are in orbit around the sun. An electron is not like a ball whizzing around in a circle. Its location is described by a wave function. Its "orbit" is more like a "cloud of probability" than a circular path. (That's still an oversimplification, though.)

 

2) Constant acceleration does not mean a change in energy. A satellite circling the Earth has a constant gravitational potential energy with respect to it, and no external energy source is needed. Yet it's constantly being accelerated the rate of freefall.

[walkntune]

I never said gravitons exist..And I cant see why dark matter cant travel at these speeds. They are not atoms.And im not even saying that what im talking about is your so called dark matter..Im saying that for my idea to work these particles are spread thoughout the universe.And even though there small thats a lot of matter, That may just add up to what is missing.Call them dark matter or call them SMP..There name doesnt matter..

 

Are you talking about tachyon energy particles that are faster than the speed of light?

[happy snapper]

The Moon can constantly change its direction without a force being applied to it? That just seems imposible to me.An object will move in a straight line unless a force is applied to it.That makes more sence to me.I say that gravity is the force that is applied to the moon that moves it from a straight line.I say that gravity is an exterior force that pushes the moon and earth towards each other and not an attration between the 2 bodies.

[DJBruce]

The Moon can constantly change its direction without a force being applied to it? That just seems imposible to me.An object will move in a straight line unless a force is applied to it.That makes more sence to me.I say that gravity is the force that is applied to the moon that moves it from a straight line.I say that gravity is an exterior force that pushes the moon and earth towards each other and not an attration between the 2 bodies.

 

To your first question I would remind you of Newton's First Law: "An object in motion will continue in motion in a straight line unless acted upon by an unbalanced force." Yes, you are correct gravity is the force that cause the moon to travel in a curved path. Your latter description of gravity seems similar to general relativity, so you might want to investigate that.