THE CHINA MAIL, MARCH 1, 1937.
Page
The Graphic Laboratory Of
0
UR
universe:
Popular
probably
Science
space. Ід
is bulæ. It fails for distances greater verse has been enthusiastically em- expand into infinite too fantastically big to be un- than about a dozen light years, which braced by certain prominent astron- other words, our universe is only derstood by the simple minds of men, falls short even of the limits of our omers such as Sir Arthur Edding- an isolated event in an infinite ocean but this never has and never will own galaxy.
ton and the Abbe Georges Lemaitre, of time. Most scientists instine- prevent us from trying to picture it Fortunately, it is possible to ex- but by comparatively few others. tively shun this attitude. They in terms of symbols we car com- tend this limit by an indirect meth- In spite of the fact that the uni- prefer to regard the cosmos as a prehend. At various times in the od bassed upon certain convenient verse gives every appearance of ex- continuons show and not a one- past it has been likened by philoso- characteristics of three different panding, the majority of the as- night stand.
phers with more imagination than types of stars. Cepheid variables tronomers do not believe that it is. A more specific objection along accurate data to a hollow hemisphere, are stars that repeatedly flare into It is significant that Hubble and the same line is that the time of or a series of concentric spheres, or extreme brilliance and then fade Humason themselves are not inclin- expansion, and therefore the age of an egg, or a turtle.
back to their former states; it has ed to accept this conclusion from the universe, can be calculated as But it has been only during the been found that the actual maximum their data.
somewhere in the neighbourhood of last decade that astronomers have brilliance of such stars can be cal- The objections to the theory are ten billion years, which is much dared to paint the strangest picture culated from the time interval be many, and some of them difficult to less than the apparent ages of some of all. This time the universe has tween successive peaks.
answer. The most obvious one, and of the individual stars. It is diffi been likened to an explosion. The The giant class B stars, which the easiest one to refute, is the cult to conceive how a tree can be idea would be wholly preposterous can be detected by peculiarities in question of why our particular gal- younger than its leaves. The sup- were it not for the fact that it is their spectra, have been found to axy should happen to be the center porters of the expanding universe the most obvious conclusion from a series of highly accurate observa- tions.
But before explaining this it will be necessary to describe the back
By Dr. Thomas M. Beck
counter with the suggestion that perhaps the universe alternately expands and contracts like an ac- cordion, and also remind their op- ponents that the ages of stars are not measured by stop watch, but
ground. The universe is made up of be of practically the same size and of the repulsion. Actually there is are little better than shrewd gues- stars, along with some planets, me- actual brilliance. The nove, which no need of considering it the cen- ses and that they could easily be teors, and unassociated clouds of gas unpredictably fare up and then ter. Motion is relative anyway, far-wrong.-
not
or galaxies.
~as.
*
are also similarly ignorant of al of the
of light. It would legital to assume that we are not moving at all,
and dust. However, the stars are slowly fade away, are almost all and if the nebule were all moving It would seem that we do not scattered evenly throughout equally bright at their peaks of apart at speeds proportional to their have enough knowledge at present" space, but swarm together in a great luminescence. number of groups known as nebule
separations, as they appear to be to settle the matter definitely. It Thus we have available three types doing, then, no matter where the is true that we do not know enough A typical neblua is distinctly flat-of stars whose actual brightness we
observation was made, the observer about matter to say for certain tened, like a discus or a watch, and always know. By comparing this would appear to himself to be in what it can or cannot do, but wa
the motionless centre. rotates around its center at speeds with the apparent brightness which are appalling when expressed seen from the earth we can readily in figures but are relatively too calculate the distance of such a star: the fact that if the universe is now the The most powerful objection see small to be observed directly. The A painstaking search of nearby expanding, then there must have but that light itself is gradually average nebula contains billions of nebula has revealed a sufficient been a time when it was packed shifted to the red in passing over stars and is about 100,000 light number of these stars to enable us closely together. This means that vast spaces We have not been able years in diameter and 10,000 light to determine the distances of the there was a time when it was a to prove. rears in thickness (a light year is stars and therefore the nebule. The relatively compact lump, but that becaus the distance travelled by a beam of method extends the measurements to it is now bursting apart and will over light in one year).
about ten million light years, be-
If our own nebula is pictured as yond which individual stars can no a watch, then we are located be longer be seen, although the nebulz neath the upper part of the second themselves are still visible through dial, about a third of the way in the telescope as faintly luminous side. From this point we may gaze
clouds.
in the direction of the circumfer A fortunate circumstance enables ence, where the stars naturally ap- astronomers to plunge still farther pear to lie most thickly. Most of into space. Nebule are not points of these stars are so far away from light, but form an image of meas- us that our unaided eyes cannot re- urable dimensions from which the cognize them as individuals, but there actual size of the nebula can be cal- are so many of them that they culated if its distance be known. Now, appear in the aggregate as the enough nebular distances have been faintly luminous band we call the determined by the method described Milky Way, or galaxy.
in the preceding paragraph to in- Since a considerable part of our dicate that all nebulæ are of about own nebula is too far away to be the same size.
seen by the naked eye, we hardly. That is, they are of about the same. could expect to see any other one size in the same sense that all dogs without the aid of a telescope. As are of about the same size. Such a matter of fact, one of our closest a generalization is not very pre- nebular neighbours, the great nebula eise, but it is by no means useless: of Andromeda, can be seen as a tiny When we say that some creature is cloud of haze under favourable con- is big as a dog we do not give a ditions, but it is an exception to the very clear idea of its size, but we rule. Most of them can be detected indicate that it is smaller than only with the help of the most po elephant and larger than a mouse." werful telescopes and cameras.
Yet thousands of them already
If nebula were exactly equal in have been discovered, and it is esti size their distances could be easily mated that there are 100 million calculated from the size of their more of them within range of the
images
Actually they vary
telescopes of the present. Still they to make this method highly
can hardly be said to be crowded together. The average nebula is about a million light years from its nearest neighbour.
Inasmuch as the validity concept of the exploding depends on the accurac fantastically large figures, be well to outline the me
they are
direct method.
distances, by nothin displacement
observed from diametr poin
on the earth's orb used to find the distanc
an
when applied to individual But fortunately, nebule travel alone, Usually they assembled in swarms of several hundred, known The average size
Close
aver
in our laboratories, we do not have the space
to pass the light.
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