1920 Cambridge U
[Quotes from Meta Research]
Eddington (1920, p. 109) was already aware of the mostly equivalent "refracting medium" explanation for GR features, which retains Euclidean space and time in the same mathematical formalism. In essence, the bending of light, gravitational redshift, Mercury perihelion advance, and radar time delay can all be consequences of electromagnetic wave motion through an underlying refracting medium that is made denser in proportion to the nearness of a source of gravity.
Sir Arthur Eddington (1926), "The temperature of space", Internal constitution of the stars, Cambridge University Press, reprinted 1988, chapter 13.
[Actual text from pages 105 and 106 of Eddington's book that I got on line via a Google search string Arthur Eddington 1920. The interesting part is that he seems to be describing gravity as a process of refraction.]
Note: On previous pages Eddington sets up a thought experiment that describes a circular field of hurdles with more hurdles toward the center and less toward the outside.
Sir Arthur Eddington (1920)
Now suppose a heavy particle
wishes to cross this field,
passing near but not
through the centre. In Euclidean space,
with the hurdles uniformly distributed, it travels in a straight
line, i.e. it
goes between any two points by a path giving
fewest hurdle jumps. We may assume that in the non-Euclidean
field with rearranged hurdles, the
still goes by the path
of least effort. In fact, in any small
portion we cannot distinguish
between the rearrangement and a distortion ; so we may imagine
that the particle
takes each portion
as it comes according to the
rule, and is not troubled by the rearrangement which is only
visible to a general survey of the whole field *.
it will pay not to go straight through the dense
but to keep a little to the outside where the hurdles
not too much, or the path will be unduly lengthened.
track will thus be a little concave to the centre,
and an onlooker will say that it has been attracted to the centre.
It is rather curious that we should call it attraction, when the
track has rather been avoiding the central region; but it is clear
that the direction of motion has been bent round in the way
attributable to an attractive force.
This bending of the path is additional to that due to the
Newtonian force of
gravitation which depends on the second
in the formula. As already explained
it is in
general a far smaller effect and will appear only as a minute
correction to Newton's law. The only case where the two rise
to equal importance is when the track is that of a light-wave,
or of a
particle moving with a speed approaching
for then dr2
rises to the same order of magnitude as dt2.
To sum up, a ray of light passing near a heavy particle
be bent, firstly, owing to the non-Euclidean character of the
combination of time with space. This bending is equivalent
that due to Newtonian gravitation, and may be calculated in
Note: by Vernon Brown
It seems to me that Eddington is suggesting that the path of light will be bent by Neutonian gravity and in addition will be refracted an additional approximately equal amount.