Evening star., 1948-11-26
Stars, Men and Atoms
Sun, Moon Tides Found
In Eurth's Atmosphere
Effect of 2 Bodies Is Reverse of That
Manifest on the Sea
Rv Thny11e p Honru

Bv lHOmdS N. Henfp
There is a sun tide and a moon tide in the
earth's atmosphere.
1t is high sun tide at about 10 am. and 10
pm. every day and 1t is about 10 times the
size of the biggest moon tide.
This has just been reported to the National
Academy of Sciences by DR.. J. Bjerknes Of
the Geofysiske Institute Of Norway after
long series of precise measurements Of chang.
ing atmosphere pressure.
Sun Tide Greater.
The major sun tide, he explains, is pro.
gressive wave which follows the sun from east
to west with rising and decreasing pressures
along it's path Theoretically the great blanket
of air which covers the earth should be rising
and falling due to the gravitational pull OF
the sun at almost perfect 12-hour intervals.
This never can occur exactly. however, be-
cause Of the .nnumerable complicating factors
which have made 1t difficult in the past even to
detect the sun tides existence.
The most surprising finding, DR.. Bjerknes
said, is that the sun tide is so much greater
than the moon tide, whereas the pull OF the
two bodies on the sea is exactly the reverse.
The suns pull is a relatively minor factor in
calculating ocean tides, whereas the moons pull
is hardly discernible in the atmosphere. Yet
in theory the gravitational attraction Of the
earths satellite should be much greater than
that of the far distant sun under any cir.
cumstances.
Believed to Affect Weather.
DR.. Bjerknes, who has been one of the chief
developers of the newer techniques of weather
forecssting, says the contradiction can be ex.
planned by a tuning fork effect for which he
has developed a complicated mathematical
theory. Once started, the wave motion has
tended to build up to its present magnitude
The sun tide, he explains reaches its great.
est magnitude at the equator and vaniShes
completely at the poles where the pull of the
sun would be expected to be almost nom
existent.
The existence Of these major air tides, az
well as some smaller ones, long has been as
sumed in theory but observations to demon-
strate them have been extremely difficult.
They are believed to have some effect on
weather.
The whirling galaxies of space-each made
up of billions of stars-slow down as they
grow old.
Measurement OF the speed of rotation Of
these monster aggregations-the Milky Way
galaxy which includes all the visible stars is
typical example-has just been reported to
| the National Academy Of Sciences by DR.. N. U.
| MayaN of the Lick Observatory.
| Some are nearly formless patches in the far
heavens. They are supposed to be quite young
galaxies Their periods Of rotation about
| their centers of gravity are estimated to be
from 100000 to 100000 years. The next
oldest type have taken on a definite form.
and look something like july pinwheel. They
| have slowed down so that their periods Of rota.
ton range from 100000 to 100000 years.
The vast Milky Way system may fall into
this category.
Speed Is Calculable.
Then come the very clearly defined spirals.
supposedly the Oldest OF all. They have rota-
ton periods, Dr. Mayall finds, ranging from
1900, 900 to 25o000,000 years and have become
sedate citizens Of the coSmic family.
The approximate speed Of rotation can be
calculated, DR.. Mayall says, by displacements
of the lines in the spectra of these great con.
centrations of stars, so distant that light from
| the nearest of them, moving at $4,000 miles
| second, requires a million years to reach the
| earth. Much depends, however on the distance
and this is very difficult to determine at pres
ent. One of the major uses which will be made
Of the California Institute Of Technolosy's new
20O-inch telescope will be to set up an accurate
| yardstick of cosmic distances.
Some of the galaxies appear to be much
brighter than others but Dr. Mayall's investi.
cations indicate that this has little relation to
rotational speed The finding that there is
such an enormous range in speeds between
galaxies of the same category. it is admitted.
may be due to the difficulty of measurement
which depends on almost undesirable diff
ferences in the spectra. On the other hand, it
may indicate that galaxies are like men-some
slowing down rapidly while others continue
| fast pace I'D to old age