_ndt_ = _nd_τ [ 1 + ½ _m_*/_ac²_ (1 + _e_ cos E)/(1 - _e_ cos E) ]
from which, by applying (29),
(31) _nt_ + const = (1 + ½ _m_*/_ac²_) _n_τ + _m_*/_ac²_ Sin E.
the factor _m_*/_ac²_ is here the square of the ratio of a certain
average velocity of F in its orbit to the velocity of light. If now _m_*
denote the mass of the sun, _a_ the semi major axis of the earth’s
orbit, then this factor amounts to 10⁻⁸.
The law of mass attraction which has been just described and which is
formulated in accordance with the relativity postulate would signify
that gravitation is propagated with the velocity of light. In view of
the fact that the periodic terms in (31) are very small, it is not
possible to decide out of astronomical observations between such a law
(with the modified mechanics proposed above) and the Newtonian law of
attraction with Newtonian mechanics.
Footnote 29:
Sichel—a German word meaning a crescent or a scythe. The original term
is retained as there is no suitable English equivalent.