Omaha daily bee. (Omaha [Neb.]) 187?-1922, 1915-08-17

NoANh WNAC AbOdN .
ss,ses times as great
as it now is.
Its present dis
lance is 100000 miles and this multi
piled by 1855 becomes 7,7s0. 9ss 900, 600 miles
At that distance the sun would simply be
a star in the night equal in brilliance to
Sirius, the Dog Star.
The calculation is based upon the OBJ
served fact that the amount Of light re-
ceived upon the earth from Sirius is one
T.OOO.0Oo,cOOth Of that received from the
sun. and the square OF 1000 900 is SO, $50.
II the sun were sse6s times its present
distance away its disk would be reduced
to an angular diameter of about one
forty-sixth of a second Of arc, and the
most powerful telescope in existence
could not make 1t visible as a disk. II
would appear. as all the fixed stars DO.
like a piercing point OF light, immeasur-
ably small, though intensely brilliant
The larger the telescope used the
brighter II would look, because the larger
glass would collect more light, but still
The disk would remain too minute to be
perceived or measured.
II is true that there would be spurious
or false disk, made up of concentric rings
of light, due to dlffraction, and, owing to
these appearances, which vary with the
brightness. the stars do seem to have
visible disks, but the fact that these are
not real becomes evident when we FIND
that they arc actually smaller In the tele-
scope than when viewed with the naked
eye. The higher the magnifying power
employed the. more minute the apparent
disks.
The practical disappearance of the disk
Of a star. while It's light continues to at
feet the eye. Is due TO the inability Of
the eye to perceive magnitude below Q
certain range OF dimension. Perhaps this
can best be illustrated in the following
way:
On sheet Of paper lying on your dest
make a minute circle one-eighth of ar
inch in diameter. This circle. viewed
from the ordinary distance for reading
about fourteen inches. Is Of nearly the
same size as the sun seen in the sky
You win hardly believe this to be pos
sible at first, but it Is easily proved to be
true. The angular diameter OF the sur
is (usIng round numbers) one-half de-
gree, and that is also the angular diam
eter of a one-eighth inch circle fourteen
inches from the eye.
This shows us graphically the interest.
Ing relation between visual magnitude and
distance A globe $4,000 miles in diam
etcr, viewed from a distance of 5000. 00
miles. appears no larger than a circle
one-eighth OF an inch in diameter viewed
from the ordinary distance for reading 8
book.
Now, let the sun be removed to eight
times its present distance. Its angular
diameter will become one-sixteenth Of q
degree and in order to represent It's size
upon your sheet of paper you will have
to decrease your little circle to diameter
Of only one-sixty-fourth OF an inch, which
Is the size of very small printers point
or period.
Next. remove the sun eight times
farther. or, in all eighty times its present
distance. It's diameter will then have
become 10th OF a degree, and your do
On the paper representing It's size 10 thu
eye will have shrunk TO a diameter oi
only one-six hundred and fortieth Of al
inch; in other words, II will have beconl'
smaller than a pins point and cease t
be visible to the naked eye. or II family
visible in a strong light it's disk will b.
far TOO minute for measurement withou
a magnifying glass.
At a distance, then, Of eighty times So,
10000. or 7.440.OOO0oc miles. the sun woul'
present disk too small to be distinctl,
seen without telescope, although /
would still shed upon the earth about
million times as much light as come
from the brightest of the stars, Sirius.
II would continue to be a sun to MS
rather than star. making dayligh
about 100 times more intense than tn
light of a full moon. Yet all that high
would come from a disk imperceptibil
small Oto the unaided eye). although tn
spurious disk formed would be very con
spicu0us.
Putting the sun at greater and create
distances. we should find its disk gettini
smaller and smaller. until even a tele
scope could not reveal IT, and It's ligh
diminishing until. at length. that too
would become too faint to be perceived
The enormous difference between tn
constituencies Of the eye to light and it
sensitiveness TO minute spatlal magnitud
may be shown by simply sGppOsing GU
vanishing dot. representing the suns siz
ON paper. to POSSESS a power OF ligh
equal. area for area. to that Of the sur
in that case we could see the shinin
dot when II had shrunk TO an angular al
ameter OF only a few thousandths Of
second Of arc. just as we could see tn
sun as faint star II II were removed I
several millions times It's present distancs
The star on the paper and the star In th
sky would be precisely alike.