Six alternative relationships between the gravitational field and the matter field are presented:

Alternative 1: That the matter field represents the transmitting medium for light in vacuo and that the gravitational field exhibits Newtonian gravitational forces¹ upon such transmitted light.

Alternative 2: That the matter field represents the transmitting medium for light in vacuo and that the gravitational field exhibits no Newtonian gravitational forces upon such transmitted light. 

Alternative 3: That the matter field and the gravitational field are the same entity and that gravity has no effect upon light transmission other than providing the medium for such transmission in vacuo.

Alternative 4: That the matter field and the gravitational field are the same entity and that the gravitational field provides the medium for light transmission in vacuo.while exhibiting Newtonian gravitational forces upon such transmitted light. 

Alternative 5: That the gravitational field and the matter field interact to comprise the conducting medium for light in vacuo and that the gravitational field component does not exhibit Newtonian gravitational forces upon such transmitted light. 

Alternative 6: That the gravitational field and the matter field interact to comprise the conducting medium for light in vacuo and that the gravitational field component exhibits Newtonian gravitational forces upon such transmitted light.

Alternatives 1 and 3 represent the most probable field models for light transmission in vacuo whereas Alternatives 4 and 6 represent the least probable models. The improbability of the latter two alternatives stems from the unlikely condition that the gravitational field would exhibit Newtonian gravitational forces upon light in vacuo while simultaneously acting as the conducting medium for such light.

Certain experimental and observational data are examined with reference to Alternatives 1 and 3 as set out immediately above:

The Pound-Rebka-Snider and J.W. Brault Redshift Experiments. 

The redshift measurements of gamma rays traveling vertically from the surface of the earth by Pound et al. [4] as well as the redshift measurements of the solar spectrum by Brault [5] are analyzed in accordance with Alternatives 1 and 3 as set out immediately above:

Alternative 1 treats the redshift observations as resulting from the gravitational falling of light in conjunction with the transmission of such light through an area of higher matter field intensity (density) near the earth (or sun), to an area of lower matter field intensity farther from the earth (or sun). ²

Alternative 3 treats the redshift observations as resulting exclusively from the transmission of light through the decreasing intensity of the gravitational field medium as the distance from the earth (or sun) increases, and makes no allowance for Newtonian gravitational effects in the redshift measurements.

The time delay of radio waves near the sun as predicted by I. Shapiro [6] and supported by experiment, is consistent with both Alternatives 1 and 3 since the matter field or gravitational field medium intensity near the sun would result in a reduced radio wave transmission speed. Alternative 1 treats such delay as resulting from the effects predicted by Newtonian gravitational theory combined with the increased matter field intensity near the sun, whereas Alternative 3 treats the delay as resulting solely from the slower wave transmission speed through the increased intensity of the gravitational field medium near the sun.

Observations of the deflection of light and radio waves near the sun as well as observations of gravitational lensing [7] are consistent with the general angles of deflection that would be produced by refraction in a matter or gravitational field medium surrounding massive bodies. 

Alternative 1 attributes the observed deflection to the result of the combination of the falling of light in a gravitational field and the refraction of light produced by the increased intensity of the matter field near such bodied. It should be noted that a refractive component in such deflection may be difficult to detect since the deflection produced by gravity may mask any refractive effects produced by the matter field medium. 

Alternative 3 treats the deflection of light as a purely refractive effect of electromagnetic energy transmission through the increased gravitational field intensity surrounding massive bodies. It is important to note that, although the matter field or the gravitational field medium may constitute an ideal transmitting medium for electromagnetic energy in vacuo and may be essentially non-dispersive, the possibility of dispersion of the deflected light should not be disregarded.

2Note: From a waveform view, an electromagnetic wave transmitted through a matter field or gravitational field medium of decreasing field intensity is "stretched" since the leading wavepeak always enters the area of reduced field intensity in advance of the trailing wavepeak. Since the wavespeed is higher in this less "dense" medium, the leading wavepeak has a higher transmission speed than the trailing wavepeak, thus producing an increased wavepeak separation or "redshift."