Page:Popular Science Monthly Volume 67.djvu/245

Rh thousands of the heavenly bodies, and in all stages from thin gaseous masses to cold non-luminous solid bodies.

Now that we know so much of the past history of the solar system, and in addition that our nearest neighbor is more than 200,000 times the distance to the sun, also that the whole system is itself moving in space at the rate of about 400 millions of miles a year in the direction of the star Vega, we yet need to know whether this motion is a drift or part of an orbit. At present no one knows. The directions and rates of motion of a number of stars have been very well determined, but such measures are not numerous enough to enable us to say whether there is more order in the movements of stars than there is among the molecules of a gas, where molecular collisions are constantly taking place. Such phenomena as that of the new star which suddenly blazed out in Perseus are now explained only by assuming stellar collisions wherein the masses are so large and have such velocity that impact at once reduces them to incandescent gas. This means the possibility of such disaster to the solar system, but it is a present comfort to know that if we were to collide with our nearest neighbor at present rate, 12 miles a second, it will take nearly 50,000 years to reach it.

We have now about a hundred million stars in sight, and astronomers have been surprised that a greater number of the more remote ones are not to be seen. The actual number of stars in our universe is much smaller than had been supposed, and instead of there being an infinite number in an infinite space the present outlook is that there is a boundary to the visible universe; but this remains to be determined, and this problem is engaging attention in several of the great observatories. We all want to know what kind of a universe we live in and the series of events that take place in it. In older times there were supposed to be but seven members of the solar system. The nineteenth century discovered more than five hundred. Eros was discovered only six or eight years ago, while additional moons to both Jupiter and Saturn were seen for the first time within ten years. It is not probable that all have been discovered. Search is yet being made for other planets.

Though limited, one can get some idea of the magnitude of the universe when it appears that some of the remote stars are so far away as to require something like a million years for their light to reach us, though light travels at the rate of 186,000 miles a second—a distance so great that it would take trillions of years to reach them at the rate that we now are moving in space, namely about 400 millions of miles a year. Space seems illimitable, time is long, and if matter be indestructible, yet the solar system as we know it will have gone through all its phases of growth, maturity, old age and death, long enough before the general aspect of the heavens will have been greatly changed