The Unseen World and Other Essays | Page 9

nebulous stage, but are still at a whiter heat than our sun; and we also
find many stars which yield the same sort of spectrum as our sun. The
inference seems forced upon us that the same process of concentration
which has gone on in the case of our solar nebula has been going on in
the case of other nebulae. The history of the sun is but a type of the
history of stars in general. And when we consider that all other visible
stars and nebulae are cooling and contracting bodies, like our sun, to
what other conclusion could we very well come? When we look at
Sirius, for instance, we do not see him surrounded by planets, for at
such a distance no planet could be visible, even Sirius himself, though
fourteen times larger than our sun, appearing only as a "twinkling little
star." But a comparative survey of the heavens assures us that Sirius
can hardly have arrived at his present stage of concentration without
detaching, planet-forming rings, for there is no reason for supposing
that mechanical laws out there are at all different from what they are in
our own system. And the same kind of inference must apply to all the
matured stars which we see in the heavens.
When we duly take all these things into the account, the case of our
solar system will appear as only one of a thousand cases of evolution
and dissolution with which the heavens furnish us. Other stars, like our
sun, have undoubtedly started as vaporous masses, and have thrown off
planets in contracting. The inference may seem a bold one, but it after
all involves no other assumption than that of the continuity of natural
phenomena. It is not likely, therefore, that the solar system will forever
be left to itself. Stars which strongly gravitate toward each other, while
moving through a perennially resisting medium, must in time be drawn
together. The collision of our extinct sun with one of the Pleiades, after
this manner, would very likely suffice to generate even a grander
nebula than the one with which we started. Possibly the entire galactic

system may, in an inconceivably remote future, remodel itself in this
way; and possibly the nebula from which our own group of planets has
been formed may have owed its origin to the disintegration of systems
which had accomplished their career in the depths of the bygone
eternity.
When the problem is extended to these huge dimensions, the prospect
of an ultimate cessation of cosmical work is indefinitely postponed, but
at the same time it becomes impossible for us to deal very securely
with the questions we have raised. The magnitudes and periods we
have introduced are so nearly infinite as to baffle speculation itself:
One point, however, we seem dimly to discern. Supposing the stellar
universe not to be absolutely infinite in extent, we may hold that the
day of doom, so often postponed, must come at last. The concentration
of matter and dissipation of energy, so often checked, must in the end
prevail, so that, as the final outcome of things, the entire universe will
be reduced to a single enormous ball, dead and frozen, solid and black,
its potential energy of motion having been all transformed into heat and
radiated away. Such a conclusion has been suggested by Sir William
Thomson, and it is quite forcibly stated by the authors of "The Unseen
Universe." They remind us that "if there be any one form of energy less
readily or less completely transformable than the others, and if
transformations constantly go on, more and more of the whole energy
of the universe will inevitably sink into this lower grade as time
advances." Now radiant heat, as we have seen, is such a lower grade of
energy. "At each transformation of heat-energy into work, a large
portion is degraded, while only a small portion is transformed into
work. So that while it is very easy to change all of our mechanical or
useful energy into heat, it is only possible to transform a portion of this
heat-energy back again into work. After each change, too, the heat
becomes more and more dissipated or degraded, and less and less
available for any future transformation. In other words," our authors
continue, "the tendency of heat is towards equalization; heat is par
excellence the communist of our universe, and it will no doubt
ultimately bring the system to an end. .... It is absolutely certain that life,
so far as it is physical, depends essentially upon transformations of
energy; it is also absolutely certain that age after age the possibility of

such transformations is becoming less and less; and, so far as we yet
know, the final state of the present universe must