1
New Theories / mechanism of gravity
« on: 19/02/2009 08:51:22 »
GRAVITY
ANOTHER POINT OF VIEW
INTRODUCTION
Gravity, among all the forces and laws of nature, stands out as one that most affects daily living. In moving from place to place, we know that we must use energy to keep going against the combined effects of gravity and friction rather than being able to float gracefully about in any desired direction. We avoid high exposed places without thinking about it too much, because we know that falling can be very bad for us, and we take care not to stand beneath large unstable heavy things.
With all our familiarity with the effects of gravity, and unlike most other forces and phenomena, we still don’t know how gravity works. For the moment, let’s not try to think at Albert Einstein’s level, where there is an explanation in the ‘curvature’ of space-time, except to note that space or time would have to be very obviously curved to account for the pain that can be felt when one falls over onto concrete.
Since Einstein, no one has been able to establish any other plausible physical mechanism to account for gravity. That may be because gravity and other forces of attraction, such as magnetism between opposite poles, are harder to imagine than forces that work through repulsion, such as simply to push something away with a hand or a foot, or to propel a vehicle with a rocket motor or a jet engine.
The force of gravity has, from long ago, been defined and measured. The scientist Galileo used the leaning tower of Pisa to demonstrate that objects of different mass would fall to earth from the same height in the same time, making allowance for the way passage through the air would slow some things down more than others. The great scientist and mathematician, Sir Isaac Newton, legendary for his detailed analysis of planetary motion, determined that gravitational force between any two physical objects would be proportional to the product of their masses, and inversely proportional to the square of the distance between them.
Newton also determined that when a force is applied to an object, it will accelerate in proportion to that force and inversely proportional to its mass. The force of gravity was thus explained as an acceleration affecting all objects that have mass. This model for gravity has with a very high level of accuracy – but not 100% as has more recently been observed in the case of the orbit of the planet Mercury – accounted for the motions of all the stars, planets, moons and galaxies in the universe.
Gravity obeys the principle of superposition. That is, if there are not just two objects, but many more (to help illustrate, we can assume that some are in direct line astern), each object will affect each further object as if the intervening ones did not exist. For example, the tides on the Earth are driven by both the Moon and the Sun. When in line with each other such as at new Moon or full Moon, there is an especially high tide on the seas of the Earth.
There are huge numbers of objects in the universe and billions of atomic particles in every physical object that we can see or hold. Every atom in the universe gravitationally affects every other atom in the universe, all according to Newton’s laws and the principle of superposition.
This gives rise to a puzzle in two parts. The first part of the puzzle is that we know force is needed to accelerate a mass and that every thing, right down to atomic level and beyond, provides such a force through gravity and therefore a corresponding amount of energy. Considering any small particle ‘M’. Gravity is exerted between M and every other small particle in the universe in proportion to the product of each pairing of M with all the other masses and, of course, reduced by the square of their respective distances. This endows each particle with colossal potential energy due only to the presence of other particles. A collapsed universe may one day prove this energy to exist but there is a nagging thought that the gravitational force a particle can generate should perhaps be a property of the particle and not a property of its surroundings.
The second part of the puzzle has to do with the inverse square law. This says that if there is a gravitational force of 1 Newton between two masses M1 and M2 one metre apart, that force will be 0.25 N if the distance were increased to two metres, and be about 0,11 N at three metres, dividing 1 Newton by the square of 1, 2 and 3 respectively for these distances.
When a balloon is inflated, the area of its surface increases in proportion to the square of its diameter. The volume of air needed inside increases in proportion to the cube of the diameter. But we have seen that gravity does not behave as an expanding surface. It affects everything within a volume and is unaffected by obstacles in its path. Therefore one would expect gravitational effects to diminish according to an inverse cube law, not an inverse square law.
Thus, in this introduction, the notions are advanced that the behaviour of gravity contradicts what intuitively we would have expected of it in terms of its physical properties, and that it has been incredibly elusive to scientific efforts for its detection.
Perhaps we have been looking for it in the wrong places,
A SCENARIO
1 Matter does not need to generate gravitational energy and attract other matter, but it can act as an obstacle to the passage of gravitational force.
2 There is omni-directional gravity permeating the universe. This is commonly understood, but in this scenario it acts in the opposite direction to that currently perceived.
Consider any two particles in this universe. They would be forced towards each other due only to the shielding effect that each one has for the other. The net force on each would be inversely proportional to the square of their separation, and proportional to the product of their masses.
It is not supposed that all the gravitational forces flowing omni-directionally through the boundaries of matter will interact with all the particles within. Indeed, most will pass through, others, perhaps being either deflected, reflected or absorbed and will not continue further along their original lines. If a single object is considered, it should remain in equilibrium as a result. But place another object nearby, and then the flow of gravitational force from the direction of the original object will be reduced somewhat, and vice versa.
The resulting motion of each individual interaction would probably follow the laws of conservation of momentum and energy.
Introduce more particles, and they will add to the shielding effect, maintaining the same Inverse Square and Product of Masses relationships that are observed today. Superposition of the gravitational effect is achieved simply as a result that once a gravitational flow has been deflected, the effect is felt everywhere downstream of the deflecting object. In omni-directional flow, that means everywhere.
This scenario invites many questions. For example, what would be the source of the gravitational force? Why deny the possibility that gravity attracts when there are strong attractive forces within the atomic nucleus and in magnets? And many more.
The following sections attempt to deal with some of these; others are questions that are not comfortably explained even with gravity being seen as an attractive force.
Pertinent to this scenario, however, is the principle of William of Occam’s ‘razor’. Is it simpler to explain gravity as an intelligent force that has infinite reach to all particles in the known and unknown universe, and then somehow to provide a towing service in the correct direction at the correct rate? All this while assuming each particle to be capable of contributing its share of the needed energy – each particle matching the sum of gravitational energy shared with every other particle in the universe. It is this assumption that leads to the expectation that the universe might at some time reverse its expansion, overcoming immense outward kinetic energy.
Curvature of space-time caused by the presence of mass is a very short but definitely not simple explanation, and it does not help much in identifying a physical mechanism – a project that occupies many learned minds in searches for gravity particles and waves even now.
SOME DIFFICULT QUESTIONS
1 Where would this omni directional gravitational force have come from?
If it is generated from within matter itself as a repelling force, we might have to accept that matter is expanding at the same time as being accreted together. Edwin Hubble measured cosmic expansion to be a fact and some studies have indicated some acceleration.
If all matter were expanding it would be interesting to see if that made any difference because the only measures we have of size are all relative and sourced in matter. We could not tell the difference between expansion of matter into empty space, and the contraction of space in and around matter.
If it is not generated by matter itself, then we might have to look at the example of background radiation, and wonder whether gravity could have a similar source. Background radiation is believed to be from the ‘big bang’ of creation and was detected initially by accident by Edwin Hubble and his team. It took a year of adjustment, cleaning and analysis before it was found to be a universal radiation. It exists as a low frequency signal from all directions with very little variation in wavelength or strength. It is an omni directional radiation.
For gravitational radiation to behave as it does, it would need to have a very small particle size or very short wavelength to account for the stability of small particles, and very high flux density to account for black holes. If true, then it does raise the possibility that there may be an upper limit to the compression that gravity can achieve within a black hole.
2 If magnets can attract, then why can’t gravity do the same?
Magnets exhibit an approximately inverse cube distance-force relationship with each other, and this removes one of the issues about gravity.
Magnets work because of alignments of positively and negatively charged particles within their structures called dipoles. Strong magnets have well aligned dipoles and weak magnets have greater randomness in dipole orientation. If we choose within a magnet an orientation for one dipole, then there should be a greater chance that it will be affected by gravitational radiation or collision from an arrival at right angles to the major axis of a dipole than an arrival parallel to that axis.
For strong magnets with a high degree of dipole alignment, it may be possible for gravitational shielding to produce what would look like strong magnetic effects, and in materials with completely random alignments, to produce none at all.
3 If there is a gravitational field out there, how is it possible for moving objects in free space not to be slowed down because of differences in collision velocity along the line of travel?
This is a difficult question. I think we have exactly the same problem with our present conception of gravitation - if everything is pulled towards each other, should there not be a difference in gravitational attraction along the line of travel? An orbiting satellite should rapidly lose altitude because of it.
But we know that gravity does not impose a lesser force from behind the direction of travel (except due to the inverse square law) and this may be due to the way that waves such as shock waves change their rate of forward propagation as a function of the material through which they pass. It is calculated as function of the material’s Young’s modulus and its density.
Thus, a shock wave travelling through touching layers of glass, wood and metal would travel with three different velocities, which are additional to any motion this composite might have. If a wave can “catch up” or slow down with a moving body, then the speed of collision with internal particles might be a constant.
The speed of light will be measured the same in a laboratory on the ground as aboard an orbiting space station, a difference of some tens of thousands of kilometres an hour. If gravitational arrivals behave like light, then the speed of a collision with internal particles might be a constant.
If the collision speeds are constant regardless of the trajectory of the body concerned, then it should not be impeded along its line of travel.
4 Black holes are thought to be almost infinitely dense and very small inside their event horizons as they accrete more and more mass and seem to be without limit in their power. Would this not exceed the plausible gravitational flux density postulated for any field acting on an inert mass?
Gravitational flux density certainly seems to be enough to trap light. And there also seems to be no limit to the capacity of empty space to accept such high concentrations of force and radiation. Every part of the universe not occupied by matter continuously allows free passage to billions of photons and other stellar emissions, gravitational forces, and whatever else is out there. The emptiness of atoms is an indication that if there a gravitational flux, most of it would pass through without interacting. Compression would cause more flux to interact, progressively.
CONCLUSION
There is no general theory to explain all physical phenomena. Either this will come with time and perseverance, or there is none to be had, or something that has been accepted as true is, in some part, false.
The history of scientific research has been one of hypothesis, debate, measurement, modelling and formulation, and testing. It is the great strength of the scientific community and the reason why people have progressed so far.
If there is a sense of hiatus in this forward progress, maybe it is because one of out fundamental concepts has not been debated enough – that of the mechanism of gravity.
ANOTHER POINT OF VIEW
INTRODUCTION
Gravity, among all the forces and laws of nature, stands out as one that most affects daily living. In moving from place to place, we know that we must use energy to keep going against the combined effects of gravity and friction rather than being able to float gracefully about in any desired direction. We avoid high exposed places without thinking about it too much, because we know that falling can be very bad for us, and we take care not to stand beneath large unstable heavy things.
With all our familiarity with the effects of gravity, and unlike most other forces and phenomena, we still don’t know how gravity works. For the moment, let’s not try to think at Albert Einstein’s level, where there is an explanation in the ‘curvature’ of space-time, except to note that space or time would have to be very obviously curved to account for the pain that can be felt when one falls over onto concrete.
Since Einstein, no one has been able to establish any other plausible physical mechanism to account for gravity. That may be because gravity and other forces of attraction, such as magnetism between opposite poles, are harder to imagine than forces that work through repulsion, such as simply to push something away with a hand or a foot, or to propel a vehicle with a rocket motor or a jet engine.
The force of gravity has, from long ago, been defined and measured. The scientist Galileo used the leaning tower of Pisa to demonstrate that objects of different mass would fall to earth from the same height in the same time, making allowance for the way passage through the air would slow some things down more than others. The great scientist and mathematician, Sir Isaac Newton, legendary for his detailed analysis of planetary motion, determined that gravitational force between any two physical objects would be proportional to the product of their masses, and inversely proportional to the square of the distance between them.
Newton also determined that when a force is applied to an object, it will accelerate in proportion to that force and inversely proportional to its mass. The force of gravity was thus explained as an acceleration affecting all objects that have mass. This model for gravity has with a very high level of accuracy – but not 100% as has more recently been observed in the case of the orbit of the planet Mercury – accounted for the motions of all the stars, planets, moons and galaxies in the universe.
Gravity obeys the principle of superposition. That is, if there are not just two objects, but many more (to help illustrate, we can assume that some are in direct line astern), each object will affect each further object as if the intervening ones did not exist. For example, the tides on the Earth are driven by both the Moon and the Sun. When in line with each other such as at new Moon or full Moon, there is an especially high tide on the seas of the Earth.
There are huge numbers of objects in the universe and billions of atomic particles in every physical object that we can see or hold. Every atom in the universe gravitationally affects every other atom in the universe, all according to Newton’s laws and the principle of superposition.
This gives rise to a puzzle in two parts. The first part of the puzzle is that we know force is needed to accelerate a mass and that every thing, right down to atomic level and beyond, provides such a force through gravity and therefore a corresponding amount of energy. Considering any small particle ‘M’. Gravity is exerted between M and every other small particle in the universe in proportion to the product of each pairing of M with all the other masses and, of course, reduced by the square of their respective distances. This endows each particle with colossal potential energy due only to the presence of other particles. A collapsed universe may one day prove this energy to exist but there is a nagging thought that the gravitational force a particle can generate should perhaps be a property of the particle and not a property of its surroundings.
The second part of the puzzle has to do with the inverse square law. This says that if there is a gravitational force of 1 Newton between two masses M1 and M2 one metre apart, that force will be 0.25 N if the distance were increased to two metres, and be about 0,11 N at three metres, dividing 1 Newton by the square of 1, 2 and 3 respectively for these distances.
When a balloon is inflated, the area of its surface increases in proportion to the square of its diameter. The volume of air needed inside increases in proportion to the cube of the diameter. But we have seen that gravity does not behave as an expanding surface. It affects everything within a volume and is unaffected by obstacles in its path. Therefore one would expect gravitational effects to diminish according to an inverse cube law, not an inverse square law.
Thus, in this introduction, the notions are advanced that the behaviour of gravity contradicts what intuitively we would have expected of it in terms of its physical properties, and that it has been incredibly elusive to scientific efforts for its detection.
Perhaps we have been looking for it in the wrong places,
A SCENARIO
1 Matter does not need to generate gravitational energy and attract other matter, but it can act as an obstacle to the passage of gravitational force.
2 There is omni-directional gravity permeating the universe. This is commonly understood, but in this scenario it acts in the opposite direction to that currently perceived.
Consider any two particles in this universe. They would be forced towards each other due only to the shielding effect that each one has for the other. The net force on each would be inversely proportional to the square of their separation, and proportional to the product of their masses.
It is not supposed that all the gravitational forces flowing omni-directionally through the boundaries of matter will interact with all the particles within. Indeed, most will pass through, others, perhaps being either deflected, reflected or absorbed and will not continue further along their original lines. If a single object is considered, it should remain in equilibrium as a result. But place another object nearby, and then the flow of gravitational force from the direction of the original object will be reduced somewhat, and vice versa.
The resulting motion of each individual interaction would probably follow the laws of conservation of momentum and energy.
Introduce more particles, and they will add to the shielding effect, maintaining the same Inverse Square and Product of Masses relationships that are observed today. Superposition of the gravitational effect is achieved simply as a result that once a gravitational flow has been deflected, the effect is felt everywhere downstream of the deflecting object. In omni-directional flow, that means everywhere.
This scenario invites many questions. For example, what would be the source of the gravitational force? Why deny the possibility that gravity attracts when there are strong attractive forces within the atomic nucleus and in magnets? And many more.
The following sections attempt to deal with some of these; others are questions that are not comfortably explained even with gravity being seen as an attractive force.
Pertinent to this scenario, however, is the principle of William of Occam’s ‘razor’. Is it simpler to explain gravity as an intelligent force that has infinite reach to all particles in the known and unknown universe, and then somehow to provide a towing service in the correct direction at the correct rate? All this while assuming each particle to be capable of contributing its share of the needed energy – each particle matching the sum of gravitational energy shared with every other particle in the universe. It is this assumption that leads to the expectation that the universe might at some time reverse its expansion, overcoming immense outward kinetic energy.
Curvature of space-time caused by the presence of mass is a very short but definitely not simple explanation, and it does not help much in identifying a physical mechanism – a project that occupies many learned minds in searches for gravity particles and waves even now.
SOME DIFFICULT QUESTIONS
1 Where would this omni directional gravitational force have come from?
If it is generated from within matter itself as a repelling force, we might have to accept that matter is expanding at the same time as being accreted together. Edwin Hubble measured cosmic expansion to be a fact and some studies have indicated some acceleration.
If all matter were expanding it would be interesting to see if that made any difference because the only measures we have of size are all relative and sourced in matter. We could not tell the difference between expansion of matter into empty space, and the contraction of space in and around matter.
If it is not generated by matter itself, then we might have to look at the example of background radiation, and wonder whether gravity could have a similar source. Background radiation is believed to be from the ‘big bang’ of creation and was detected initially by accident by Edwin Hubble and his team. It took a year of adjustment, cleaning and analysis before it was found to be a universal radiation. It exists as a low frequency signal from all directions with very little variation in wavelength or strength. It is an omni directional radiation.
For gravitational radiation to behave as it does, it would need to have a very small particle size or very short wavelength to account for the stability of small particles, and very high flux density to account for black holes. If true, then it does raise the possibility that there may be an upper limit to the compression that gravity can achieve within a black hole.
2 If magnets can attract, then why can’t gravity do the same?
Magnets exhibit an approximately inverse cube distance-force relationship with each other, and this removes one of the issues about gravity.
Magnets work because of alignments of positively and negatively charged particles within their structures called dipoles. Strong magnets have well aligned dipoles and weak magnets have greater randomness in dipole orientation. If we choose within a magnet an orientation for one dipole, then there should be a greater chance that it will be affected by gravitational radiation or collision from an arrival at right angles to the major axis of a dipole than an arrival parallel to that axis.
For strong magnets with a high degree of dipole alignment, it may be possible for gravitational shielding to produce what would look like strong magnetic effects, and in materials with completely random alignments, to produce none at all.
3 If there is a gravitational field out there, how is it possible for moving objects in free space not to be slowed down because of differences in collision velocity along the line of travel?
This is a difficult question. I think we have exactly the same problem with our present conception of gravitation - if everything is pulled towards each other, should there not be a difference in gravitational attraction along the line of travel? An orbiting satellite should rapidly lose altitude because of it.
But we know that gravity does not impose a lesser force from behind the direction of travel (except due to the inverse square law) and this may be due to the way that waves such as shock waves change their rate of forward propagation as a function of the material through which they pass. It is calculated as function of the material’s Young’s modulus and its density.
Thus, a shock wave travelling through touching layers of glass, wood and metal would travel with three different velocities, which are additional to any motion this composite might have. If a wave can “catch up” or slow down with a moving body, then the speed of collision with internal particles might be a constant.
The speed of light will be measured the same in a laboratory on the ground as aboard an orbiting space station, a difference of some tens of thousands of kilometres an hour. If gravitational arrivals behave like light, then the speed of a collision with internal particles might be a constant.
If the collision speeds are constant regardless of the trajectory of the body concerned, then it should not be impeded along its line of travel.
4 Black holes are thought to be almost infinitely dense and very small inside their event horizons as they accrete more and more mass and seem to be without limit in their power. Would this not exceed the plausible gravitational flux density postulated for any field acting on an inert mass?
Gravitational flux density certainly seems to be enough to trap light. And there also seems to be no limit to the capacity of empty space to accept such high concentrations of force and radiation. Every part of the universe not occupied by matter continuously allows free passage to billions of photons and other stellar emissions, gravitational forces, and whatever else is out there. The emptiness of atoms is an indication that if there a gravitational flux, most of it would pass through without interacting. Compression would cause more flux to interact, progressively.
CONCLUSION
There is no general theory to explain all physical phenomena. Either this will come with time and perseverance, or there is none to be had, or something that has been accepted as true is, in some part, false.
The history of scientific research has been one of hypothesis, debate, measurement, modelling and formulation, and testing. It is the great strength of the scientific community and the reason why people have progressed so far.
If there is a sense of hiatus in this forward progress, maybe it is because one of out fundamental concepts has not been debated enough – that of the mechanism of gravity.