Page:Popular Science Monthly Volume 38.djvu/77

Rh and to say that not only have we the same matter everywhere, but all celestial bodies, including the earth, are due to an exquisitely simple evolution of matter in the form of meteoritic dust. We have no longer to rest content with the fact that all nature is one chemically: we have the cause.

Secondly, I propose to make as short and simple a statement as I can of the general idea of the new cosmogony suggested by the spectroscopic survey to which I have referred.

I must, in the first place, ask my readers to grant me the scientific use of their imagination; and in order that it may not be called upon to cope with questions as to whether space is infinite or not, or whether space and time ever had a beginning, we will not consider the possibility of the beginning of things or attempt to define the totality of space, but we will in imagination clear a certain part of space and then set certain possibilities at work.

How much space shall we clear? A very good idea of one of the units of space which is very convenient for me to employ here—mean the distance of the nearest star or one of the nearest stars—can be obtained by stating the time taken by light in performing the journey between the earth and the stars, knowing as we do that light travels one hundred and eighty-six thousand miles in a second, In the case of the nearest stars the time thus required is about three and a half years. With regard to the twelfth-magnitude stars, we find that in all probability the distance in their case is so great that light, instead of taking three and a half years, takes three thousand five hundred years to reach us.

The space included in a sphere with this radius will be sufficient for our purpose. The stars that we shall have to abolish for the purpose of this preliminary inquiry number something like six millions; the probability being that, if we consider the stars visible, not in the largest telescopes, but in those which are now considered of moderate dimensions, their numbers may be reckoned at something between thirty and fifty millions.

Imagine, then, this part of space cleared of all matter. We shall have a dark void, and the probability is that all that dark void will sooner or later, in consequence of conditions existing in other parts of space into which we have not inquired, be filled with some form of matter so fine that it is impossible to give it a chemical name.

Next we may imagine that this something without a chemical name may curdle into something which is more allied with our terrestrial chemistry, and the chances are, so far as we know, that that first substance will be either hydrogen itself or some substance seen in the spectrum of hydrogen or closely associated spectra.

It is just possible that at this point we enter the region of