tonyj18

normally in most fields of science to calculate the specific density you would use: ρ = m / V = 1 / vg (1) where ρ = density (kg/m3) m = mass (kg,) V = volume (m3) vg = specific volume (m3/kg,) and I believe that as we still do not know exactly what the inner layers are made of and therefore we don't know their m in kg's then an approximation has been assumed What is the best estimate of the densities of the various layers of the Earth?Estimates vary, but some approximate values should be as follows (in grams per cubic centimeter): Continental Crust: 2.7 to 3.0Oceanic Crust: 3.0 to 3.3Mantle (silicates): 3.3 to 5.7 (increasing with depth?)Outer Core (liquid): 9.9 to 12.2Inner Core (solid): 12.6 to 13.0

As yet no one has been able to explain what gravity is, so any theory on what could cause gravity, can't be deemed to be wrong. My comment on density of the earth being an estimation is because it is an average of all of the material on the planet. But as yet we still do not know for sure what the deeper layers of the earth consist of. The density of Earth is calculated by dividing the planet’s mass by its volume, then simplifying from The average density of Earth is 5,515 kg/m3. Since the average density of surface material is only around 3,000 kg/m3, we must conclude that denser materials exist within Earth's core. Seismic measurements show that the core is divided into two parts, a "solid" inner core with a radius of ~1,220 km[3] and a liquid outer core extending beyond it to a radius of ~3,400 km. The densities are between 9,900 and 12,200 kg/m3 in the outer core and 12,600–13,000 kg/m3 in the inner core.[4] The inner core is generally believed to be composed primarily of iron and some nickel. It is not necessarily a solid, but, because it is able to deflect seismic waves, it must behave as a solid in some fashion. Experimental evidence has at times been critical of crystal models of the core. Other experimental studies show a discrepancy under high pressure: diamond anvil (static) studies at core pressures yield melting temperatures that are approximately 2000K below those from shock laser (dynamic) studies. The laser studies create plasma and the results are suggestive that constraining inner core conditions will depend on whether the inner core is a solid or is a plasma with the density of a solid. This is an area of active research.

I have never questioned the calculations or equations we currently have to mathematically access Gravitational forces, and I not sure why you keep questioning this, my post was specifically asking, " What causes gravity" , we can all see the effect gravity has and we can all use the equations we currently have ,so I have no idea what this contradicting evidence is.

Hi Strange this forum is not compulsory ,it is only for people to discuss this topic in a grown up manner, if you aren't happy then don't join in the forum

You must also remember that the density of earth is only an approximation based on what we believe the earth is composed of ,at this point in time

I believe Saturn's radius is approx 58,232 km and it's gravity 10.44 m/s2 earths radius is approx 6,371 km and its gravity 9.78 m/s2 ,do you see the problem with gravity being dependant on mass alone?

Yes point taken swansont , what if we were to look at the mass of two objects and give then a volume of 100 kilograms and 100 m3 each ,and for argument sake say that this would equate to 980newton's . And if we were to take one of the objects and compress it into an area of 10 m3 ,their gravity would be the same, but if I was to add another 90 m3 of similar compressed particles to achieve the same 100 m3 of space, then this object should produce a superior gravitational force to the first object . What if at the centre of the earth or near to it we have matter that has been compressed by 1,000,000 into a much more compressed/denser object that is able to emit an overriding gravitation force that predominates over other objects, this doesn't exclude other objects on earth each having their own gravitation attraction to each other, but the overriding influence is pulling objects down the this central object. This object doesn't need to be a perfect ball, it could resemble the gravitational maps we see showing a distorted earth surface and variations in gravity depending on where you are standing on the earth's surface

The inner core I suspect is extremely compact due to the weight of everything above it, so I imagine this would have evolved slowly over time, initially the gravitation pull would have be less towards the centre, but as the earth formed and the layers of earth grew and developed it would have become more and more compact and gravitation would have increased, perhaps........... I am quite convinced the mass is not as important and the density ,I guess one extreme example is a black hole, not really a good example.

Thanks Mike, nice to finally see someone who has been developing their own theory ,most of the other postings are just quotes from historical theories from Newton and Einstein and the more recent non-relativistic gravitational calculations ,which still doesn't explain the nature of gravity specifically here on earth and what is actually is and where it emulates from. I was hoping this forum you encourage people like your self to put forward you theories, and we seem to be getting somewhere and maybe collectively we can discover or deduce how it occurs. I would like to know your thoughts of what I can understand so far. Gravity appears to be strong enough to attract all objects downwards towards the centre of the planet ,regardless of my position above or below sea level the overwhelming attraction is downwards. It also appears as though gravity does not depend on mass ,if I was to place a small object on the ground beside Mt Everest, I would not observe the object been drawn sideways to the mountain, it would continue to be drawn down towards the centre of the earth. There may be a infinitely small attraction sideways but for this discussion lets ignore this. Someone also suggested how can you be certain its the centre of the earth, but it you were to examine core samples taken from the earth ,you can see the upper most layers are less compacted than the deepest layers because gravity is pulling continually pulling downwards compacting the deepest layers as the weight of the upper layers pushes down on them. So I am suggesting if Gravity does not really depend on the mass or size of the object then it must be dependant on the density of the object, the density of the inner core must be incredibly superior to anything we have seen to date. Their must be some many atoms compacted into a tiny space, that is producing a superior gravitation attraction that all objects above it ,are drawn down to it regardless of their mass. I don't believe that this gravitational matter needs to be of the same composition for every planet ,moon ,star ,because it would be silly to think every other planet etc. share the same composition as the earth, but it is probable that they formed in a similar manner and have at their centre a hugely dense mass producing a similar gravitational attraction and this would be proportional to the size of the object, so Isaac's mathematically equations still apply.

point taken, but I am not sure this explains what gravity is, but would I be correct is saying, it explains one theory as to how gravity could work .

I accept Albert's explanation that gravity its not directly affecting light, but that light is following the curvature in space time, so light be the one exception to the rule.

I think we are getting slightly off topic, light is affected by gravity but in a slightly different way " Albert Einstein. In 1915 he proposed the theory of general relativity. General relativity explained, in a consistent way, how gravity affects light. We now knew that while photons have no mass, they do possess momentum . We also knew that photons are affected by gravitational fields not because photons have mass, but because gravitational fields (in particular, strong gravitational fields) change the shape of space-time. The photons are responding to the curvature in space-time, not directly to the gravitational field. Space-time is the four-dimensional "space" we live in -- there are 3 spatial dimensions (think of X,Y, and Z) and one time dimension. I was more interested at the nature of gravity.

Yes I agreed, I was not commenting on the specific gravitational force that earth creates, it is easily overcome, as you say ,and earth gravity has a limited range, this is more about what specifically is gravity or what causes gravity

What do we know about gravity; we know that on earth gravity acts on every object known to us here on earth, nothing escapes the gravitational attraction from Earth's inner core. And if we consider that everything on Earth share the same building blocks (atoms),then the attraction must relate to a part of the atom ; either the proton, electron or neutron. Protons carry a positive electrical charge, electrons carry a negative electrical charge and neutrons carry no electrical charge at all. The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons 'orbit' the nucleus. A particular atom will have the same number of protons and electrons and most atoms have at least as many neutrons as protons. Protons and neutrons are both composed of other particles called quarks and gluons. Protons contain two 'up' quarks and one 'down' quark while neutrons contain one 'up' quark and two 'down' quarks. The gluons are responsible for binding the quarks to one another. It is possible that every atom on earth also produces Gravity and is attracted to other atoms is the same way ,such as us, are we producing gravity but only on a small scale, not enough to be affected by the greater gravitational force produced at the earths inner core. So what could this inner core consist of ,to produce a superior gravitational force, I would suggest that it could consist of anything, but the only overriding requirement is that it is immensely dense, i.e. well compacted almost like a small 'black hole" but visible. So you would in effect have a huge amount of Atoms compressed into a small space, but producing a superior gravitation force that is attracting every other atom on the earth surface. This would explain why other objects in space produce gravity, but they don't necessarily have to share the same material make up, in essence they could be made of any type of material ,but it needs to be very dense. And this may be directly related to the spherical shape of the planets, stars etc , their inner cores are immensely dense and radiating out a combine gravitational force that would supersede any object of a lesser density on the surface. I would be interested to know your thoughts mainly on the nature of gravity ,specifically on what you think it actually is.