Hi all,First up, I should make the point that I am not a

[kizl]

Hi all,

First up, I should make the point that I am not a physicist. I studied physics at school, but can't say I was ever any good. As such, this question may have a very obvious answer that I have missed. That said, it has been puzzling me for a while so I thought I would ask a forum of people that I hope have a better understanding of these things than I do.

I understand the basics of Newton's law of gravity. I understand that the general consensus (from a non-scientificly worded perspective) is that objects with mass will attract one another.

My question is, what evidence do we have to say that the inverse is not the truth? I.e. rather than objects that have mass being things that attract other objects, why do we not believe that it is 'space' that repels objects, with what ever it is in 'space' (call it x) that is causing gravity becoming less and less strong at a rate directly proportional to the amount of mass involved? Maybe 'x' is some sort of repelling 'field' in space that reduces in strength as mass increases?

To put it another way, space has less mass and so more 'x'. Earth has more mass and so less 'x'. So it isn't the higher level of mass in the Earth that is pulling you towards it, but rather the higher level of 'x' in space that is pushing you towards the Earth.

I know that this flies in the face of conventional thinking. I know I don't have a neat formula to present to people. I am not trying to cause a debate, and I hope that I won't be told that I am wasting peoples time. I am just interested to know whether there is a specific reason that we chose that gravity was a force that attracts rather than repels. Maybe the scientific community simply flipped a coin, but I hope that there is more to it than that, and I'm hoping someone might be able to tell me what it is.

Thank you in advance for any light you are able to shed on my problem.

Regards,

Andy

 

[Dale]

Hi kizl, welcome to PF!

Here is a Wikipedia page which summarizes some of the most common "push gravity" theories, including a section on the experimental evidence that discredits them:

http://en.wikipedia.org/wiki/Le_Sage's_theory_of_gravitation

I don't know of any push gravity theory which is consistent with observation.

 

[kizl]

Just what I was looking for. Thank you :-)

 

[bill alsept]

Can anyone explain how some of the main push gravity theories listed in the link above from Dale have been discredited?

The following is quoted from one of the links:
Although matter is postulated to be very sparse in the Fatio-Le Sage theory, it cannot be perfectly transparent, because in that case no gravitational force would exist. However, the lack of perfect transparency leads to problems: with sufficient mass the amount of shading produced by two pieces of matter becomes less than the sum of the shading that each of them would produce separately, due to the overlap of their shadows (P10, above). This hypothetical effect, called gravitational shielding, implies that addition of matter does not result in a direct proportional increase in the gravitational mass. Therefore, in order to be viable, Fatio and Le Sage postulated that the shielding effect is so small as to be undetectable, which requires that the interaction cross-section of matter must be extremely small (P10, below). This places an extremely high lower-bound on the intensity of the flux required to produce the observed force of gravity. Any form of gravitational shielding would represent a violation of the equivalence principle, and would be inconsistent with the extremely precise null result observed in the Eötvös experiment and its successors — all of which have instead confirmed the precise equivalence of active and passive gravitational mass with inertial mass that was predicted by general relativity.[44] For more historical information on the connection between gravitational shielding and Le Sage gravity, see Martins,[45][46] and Borzeszkowski et al.[47]

Since Isenkrahe's proposal on the connection between density, temperature and weight was based purely on the anticipated effects of changes in material density, and since temperature at a given density can be increased or decreased, Isenkrahe's comments do not imply any fundamental relation between temperature and gravitation. (There actually is a relation between temperature and gravitation, as well as between binding energy and gravitation, but these actual effects have nothing to do with Isenkrahe's proposal. See the section below on "Coupling to Energy".) Regarding the prediction of a relation between gravitation and density, all experimental evidence indicates that there is no such relation.

In what way do these two paragraphs discredit push gravity? They just say its wrong and that it has been disproved but they don't say how. Does anyone know where to find real evidence against? For starters the evidence for the last sentence?