Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1918-05-05
SCIENTIFIC WRITING
ON TAILS OF COMETS.
Writer Relates How Scattered Par
ticlcs Might BE Condensed
Into Cubic Foot.
EYE 1NsENsIBLE TO DISTANCE
Possible to Make Stupcndous Dis.
play, Although Millions Of Miles
From the Earth - Something
about Stars OF the Milky Way.
ny GAnnEr-r p. sEnvIss.

sri,sr SAYS the suSstamee 81 ths eo,re en-
tall could he contained in an ordnar,
rare all that what renders the tai
j.. Jr.
To clear up the paradox Imagine the
particles, or molecules, OF tho comets
:ail to be so widely distributed that
each Is in the midst OF free space
Of ono cubic mile. Then, considering
only the surface. a thin plane
parallel to the surface, there would
be 10000 particles in an area measur-
ina 100 miles on a side; or 10000. 000,-
u00 in an area OF 100000 miles on
side.
This last named area, II situated at
distance of about 10000 900 miles,
would cover 4 space on the sky rough
IT, equal to that occupied By the full
moon Now. 10000. 00O,0O0 particles
distributed over the apparent area OF
Tho fun moon would be so crowded
hat the eye would not be sensible of
tho angular distance between them,
which would be only about onc-flftieth
Of u second OF arc.
separately they would be invisible
because OF their minuteness. but when
seen in apparent contact they would
rcilict the sunlight like a body OF mist.
Tho principle Is the same as that which
renders 4 slight fog or smoke invisible
70 those who are in the midst OF II,
although when viewed from a consider
able distance (Which has the effect OF
mnssing the particles together) 1t may
appear very distinct.
But upon the supposition that we
have made OF the average distance be-
tween the PARTICLES in the comets tail,
tho amount OF light reflected by the
agsregation. when 50 distant that they
seem to blcad together. would really bu
TO- t,at, t1,n Nos, Ia, la to-, IL.
d!catcs. for the particles are not dis
;rbuted in single plane: on the con-
tTary, there Is depth as well as length
and breadth to be considered. If we
TAX" n section of the tail 100000 NJ lea
each way. measured in three dimen-
IONS. then the total number OF par
ilcics. each surrounded by q space OF
one cubic mile. would be no less than
= thousand millions OF millions.
Many OF these would be concealed be-
hind others, but many would also lie
in line with the interstices in the fore
ranks. and thus the apparent density
would be increased, and With 1t the
brightness.
ASSIGNING ONE PARTICLE
TO EACH CUBIC MILE
Let US suppose the tail OF Halley's
Comet TO have been 25.00o.00O miles
long, and. allowing for the narrow
ness near inc ncaQ ana the
spreading out in the moro distant
parts. to have had an average diameter
OF 10000 miles. Then, assigning one
! particle to each cubic mile. there
would he n total OF more than eight
| quadrillion particles in the whole tail.
Now. condense the tall down to tho
dimensions of single cubic mile.
The eight quadrllion particles crowd
ed into cubic mile Will be at an
average distance apart OF about ono
third OF an inch. Finally compress
the cubic mile Into tho spCce of n cub bic
foot. The eight quadrillion particles
! in Il cubic foot will still be about
-16,00oth OF an inch apart At first
! sight this looks like a great density.
! but that IL is not so becomes evident
/ when we remember that there are prob
J ably as many as forty Quadrillion mole
/ culcs in large pinhead. and the par.
! ,icles OF II comets tail may DO no
! larger than molecules.
/ So you see that IL the tail Of Hallcy's
! Comet were condensed into suit
/ case 1t would not be burdensome to
/ carry, Notwithstanding the fact that
/ all these molecules when nunl, out In
! sunlit space. and removed SO far from
! the eye that their tiny recections join
! hands. are able to impress our Won
| GcrinS little brains with a sense OF
/ ilimitable awe.
sr.AHS OF MILKY WAY
ARE MOSTLY INVISIBLE
I Something of tho same effect is seen
I al the case OF the Milky Way. Tho
Dtars composing tho Milky Way nre
! so remote that separately the eye can
| not see them, because the light OF ono
| alone Is insufficient in quantity TO i'm
| press the sense Of vision: but at their
| practically Unreasonable distance
| from us they seem to be masscd to-
/ scthcr like sands on the seashore, and
/ ;hus the whole body OF them furnishes
| quantity of light which Is able to
| impress the eye, SO that we perceive
/ ShcIn in the form of family luminous
/ oand spanning the heavens.
] The Xodiacal Light furnishes another
| instance. and SO. too. does the corona
! OF the sun. which is too faint to be
/ seen ut all except during a total eclipse
! Ike that which will occur In this
! country on the Sth of next June.
But because the tails OF comets are
( SO tenuous. II should not be assumed
! that there is nothing dense or solid
! about them. Nearly all the mass OF
| the comet is condensed in its nucleus,
or head. While II is probable that the
mead is rot single solid body yet 1t
may consist of an aggregation OF solid
bodies. which may be either small
m:tcors or masses OF considerable size.
| The head Of comet must be in state
/ OF violent commotion when 1t nears
tie sun, and collisions occurring among
! its parts may be ono cause OF the
formation of the tall consisting Of
electrified dust.