There is a widespread idea that these
difficulties have proved fatal to the old nebular hypothesis, and
there are distinguished astronomers who think so. But Sir R. Ball
(see note), Professor Lowell (see note), Professor Pickering
(Annals of Harvard College Observatory, 53, III), and other high
authorities deny this, and work out the newly discovered
movements on the lines of the old theory. They hold that all the
bodies in the solar system once turned in the same direction as
Uranus and Neptune, and the tidal influence of the sun has
changed the rotation of most of them. The planets farthest from
the sun would naturally not be so much affected by it. The same
principle would explain the retrograde movement of the outer
satellites of Saturn and Jupiter. Sir R. Ball further works out
the principles on which the particles of the condensing nebula
would tend to form a disk rotating on its central axis. The
ring-theory of Laplace is practically abandoned. The spiral
nebula is evidently the standard type, and the condensing nebula
must conform to it. In this we are greatly helped by the current
theory of the origin of spiral nebulae.
We saw previously that new stars sometimes appear in the sky, and
the recent closer scrutiny of the heavens shows this occurrence
to be fairly frequent.
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