The Washington herald., 1910-03-20
WHAT IS A coMErY
Eminent. Astronomer Answers PERTH
nent Questions on Live Topic.

Eminent. Astronomer Answers PERTH
nent Questions on Live Topic.
Garrett p sersiss, in New Tork American.
A reader OF the American asks the fol-
lowing questions. confessIng that the re-
cent influx OF remarkable comets, and
the prediction that ono of them is going
to give us q taste Of its real quality next
May, have given him comets on the
brain
First Do you think they are projee-
tiles shot from the sun?
Second. Is there any solid nucleus?
Third. How DO you account for the
fact that the gaseous portion does not
condense and solidify into crystalline par
ticles IN space which registers go de-
grees below zero centigrade?
Fourth. II you take a magnifying
glass. either a spectacle lens or read
ing glass, and focus the light from an
ordinary incandescent lamp and manip-
ulate the glass at different angles you
can produce a comet In miniature, and
you can turn IT'S tail either from the
light or toward the light at viii Do
you think that would explain the Illusion
Of a comets tail?
Answer J. It is probable that comets
have originated from the sun. but not in
the form OF projectiles shot out of It.
The trend OF recent investigation is TO
show that comets. like the planets. were
originally formed from the primeval mass
OF matter that gave birth to the sun and
his system of attendant bodies
Comets. according TO this view. are not
simple interlopers from outer space, as
was formerly supposed, but they have as
much right TO claim nationality In the
soler system as nave the planets They
differ from the planets in being less
massive and in having orbits much more
eccentric They are the suns scouts,
and their excursions carry them to enor-
nous distances into the wastes of ex-
tra-planetary space, but sooner or later
they come back to report at headquar-
tiers.
Answer >. The nucleus of comet is
probably solid. but not a single solid
body. II is likely that the head Of a
comet consists Of a multitude OF solid
particles. like a close packed mass Of
meteors. The fact that many comets are
known TO have turned into meteor
swarms strengthens this probability.
Answer 3. The gaseous portion OF
comet does not condense into crystals
because there IS practically no pressure
exerted upon it in open space. The cold
there would no doubt be sufficient to
liquefy or solidify any gas. but expert
ment shows that cold alone cannot pro-
duce this transformation; there must be
great pressure also.
Answer 4, II the tail OF a comet were
nothing but an Illusion. produced by the
sunlight thrown into the form of & beam.
like the rays caused by open pigeon
holes in hay NOV, there would have
70 be all about the sun and throughout
the solar system some kind of dusty me-
dunn or atmosphere 10 reflect the light.
There is no evidence Of the existence OF
anything Of the kind. and II it did exist
IL would produce a general misty illu-
mination I'm the sky.
In order that the head OF q comet
should act Ike lens Il would have TO
be transparent TO the ordinary rays OF
light. which is contrary TO all that we
know OF the nature Of such bodies.
Then, too, the shapes and the changes
undergone by the tails of comets are in
consistent with the hypothesis that they
are simply condensed beams of sunlight.
The spectroscope also gives positive ev-
idence that the eminations from comets
consist OF gases. mingled perhaps with
minute solid particles. They always con-
tain hydrocarbon gases. The wonderful
tail Of the recent comet a showed the
presence Of sodium, the basic element Of
common salt
In short there is no getting away
from the fact that comets are very real
things, and it viii be no Illusion that we
shall have to deal with next May If Hal,
ley's comet stretches its tail over the
earth, however innocuous the reality may
be.