Geometry as a Branch of Physics (1949)
“The solution of (1), which represents a homogeneous manifold, may be written in the form:ds^2 = \frac{d\rho^2}{1 - \kappa^2\rho^2} - \rho^2 (d\theta^2 + sin^2 \theta \; d\phi^2) + (1 - \kappa^2 \rho^2)\; c^2 d\tau^2, \qquad (2)where \kappa = \sqrt \frac{\lambda}{3}. If we consider \rho as determining distance from the origin… and \tau as measuring the proper-time of a clock at the origin, we are led to the de Sitter spherical world…”
"On Relativistic Cosmology" (1928)
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Howard P. Robertson 28
American mathematician and physicist 1903–1961Related quotes

Source: History of Mathematics (1925) Vol.2, p.449
1 - \frac{Kr^2}{12} + …
Geometry as a Branch of Physics (1949)
Geometry as a Branch of Physics (1949)

p, 125
The Structure of the Universe: An Introduction to Cosmology (1949)

Source: History of Mathematics (1925) Vol.2, p.461

The point P where the two parabolas intersect is given by<center><math>\begin{cases}y^2 = bx\\x^2 = ay\end{cases}</math></center>whence, as before,<center><math>\frac{a}{x} = \frac{x}{y} = \frac{y}{b}.</math></center>
Apollonius of Perga (1896)

1745
Source: History of Mathematics (1925) Vol.2, p.469

The Foundations of Mathematics (1925)

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Song lyrics, Parade Under the Cherry Moon (1986)