All the light which is radiated... will, after it has traveled a distance <math>r</math>, lie on the surface of a sphere whose area <math>S</math> is… - Howard P. Robertson
" "All the light which is radiated... will, after it has traveled a distance <math>r</math>, lie on the surface of a sphere whose area <math>S</math> is given by the first of the formulae (3). And since the practical procedure... in determining <math>d</math> is equivalent to assuming that all this light lies on the surface of a Euclidean sphere of radius <math>d</math>, it follows...<math>4 \pi d^2 = S = 4 \pi r^2 (1 - \frac{K r^2}{3} + ...);</math>whence, to our approximation 4)<math>d = r (1- \frac{K r^2}{6} + ...),</math> or
<math>r = d (1 + \frac{K d^2}{6} + ...).</math>
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About Howard P. Robertson
Howard Percy Robertson (January 27, 1903 – August 26, 1961) was an American mathematician and physicist known for contributions related to physical cosmology and the uncertainty principle. He was Professor of Mathematical Physics at the California Institute of Technology and Princeton University.
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Howard Percy Robertson
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H. P. Robertson
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Additional quotes by Howard P. Robertson
The value of the intrinsic approach is especially apparent in considering 3-dimensional congruence spaces... The intrinsic geometry of such a space of curvature <math>K</math> provides formulae for the surface area <math>S</math> and the volume <math>V</math> of a "small sphere" of radius <math>r</math>, whose leading terms are 3)<math>S = 4 \pi r^2 (1 - \frac{Kr^2}{3} + ...)</math>,
<math>V = \frac{4}{3} \pi r^3 (1 - \frac{Kr^2}{5} + ...)</math>.
[T]he astronomical data give the number N of nebulae counted out to a given inferred "distance" <math>d</math>, and in order to determine the curvature... we must express N, or equivalently <math>V</math>, to which it is assumed proportional, in terms of <math>d</math>. ...from the second of formulae (3) and... (4)... to the approximation here adopted, 5)<math>V = \frac{4}{3} \pi d^2 (1 + \frac{3}{10} K d^2 + ...);</math>...plotting N against... <math>d</math> and comparing... with the formula (5), it should be possible operationally to determine the "curvature" <math>K</math>.
What is the true geometry of the plate? ...Anyone examining the situation will prefer Poincaré's common-sense solution... to attribute it Euclidean geometry, and to consider the measured deviations... as due to the actions of a force (thermal stresses in the rule). ...On employing a brass rule in place of one of steel we would find that the local curvature is trebled—and an ideal rule (c = 0) would... lead to Euclidean geometry.
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