sun contributes to the common object, Jupiter will contribute at least
a thousand parts; and this inequality appears all the more striking,
not to say unjust, when it is remembered that the sun is more
abundantly provided with moment of momentum than is Jupiter--the sun
has, in fact, about twenty thousand times as much.

The case may be illustrated by supposing that a rich man and a poor
man combine together to achieve some common purpose to which both are
to contribute. The ethical notion that Dives shall contribute
largely, according to his large means, and Lazarus according to his
slender means, is quite antagonistic to the scale which dynamics has
imposed. Dynamics declares that the rich man need only give a penny to
every pound that has to be extorted from the poor man. Now this is
precisely the case with regard to the sun and Jupiter, and it involves
a somewhat curious consequence. As long as Jupiter possesses available
moment of momentum, we may be certain that no large contribution of
moment of momentum has been obtained from the sun. For, returning to
our illustration, if we find that Lazarus still has something left in
his pocket, we are of course assured that Dives cannot have expended
much, because, as Lazarus had but little to begin with, and as Dives
only puts in a penny for every pound that Lazarus spends, it is
obvious that no large amount can have been devoted to the common
object. Hence it follows that whatever transfer of moment of momentum
has taken place in the sun-Jupiter system has been almost entirely
obtained at the expense of Jupiter. Now in the solar system at
present, the orbital moment of momentum of Jupiter is nearly fifty
thousand times as great as his present store of rotational moment of
momentum. If, therefore, the departure of Jupiter from the sun had
been the consequence of tidal evolution, it would follow that Jupiter
must once have contained many thousands of times the moment of
momentum that he has at present. This seems utterly incredible, for
even were Jupiter dilated into an enormously large mass of vaporous
matter, spinning round with the utmost conceivable speed, it is
impossible that he should ever have possessed enough moment of
momentum. We are therefore forced to the conclusion that the tides
alone do not provide sufficient explanation for the retreat of Jupiter
from the sun.

There is rather a subtle point in the considerations now brought
forward, on which it will be