PRIMAEVAL CHAOS. These general theoretical results may now be applied to any mass of gas we please. Let us begin by applying them to Newton’s hypothetical “matter evenly disposed throughout an infinite space.” We return in imagination to a time when all the substance of the present stars and nebulae was spread uniformly throughout space; in brief, we start from the primaeval chaos from which most scientific theories of cosmogony have started. Hubble has estimated that if the whole of the matter in those parts of the universe we know were redistributed evenly throughout space, the gas so formed would have only about 1·5 × 10⁻³¹ times the density of water. This estimate is almost certainly on the low side, even as representing present conditions, and in trying to reconstruct the primaeval gas we must add something to allow for the molecules and atoms which have melted away into radiation in the intervening period. On the whole, perhaps 10⁻³⁰ is not an unreasonable density to assign to the hypothetical primaeval nebula. It is almost inconceivably low. In ordinary air, at a density of one eight-hundredth that of water, the average distance between adjoining molecules is about an eight-millionth part of an inch; in the primaeval gas we are now considering, the corresponding distance is two or three yards. The contrast again leads back to the theme of the extreme emptiness of space. What is the minimum weight of condensation that would persist in this primaeval gas? Calculation shews that if ordinary air were attenuated to this extraordinary degree, no condensation could persist and continue to grow unless it had at least 62½ million times the weight of the sun; any smaller weight of gas would exert so slight a gravitational pull on its outermost molecules, that their normal molecular speeds of 500 yards a second would lead to the prompt dissipation of the whole condensation. We can carry out similar calculations with reference to other assumed densities of gas, and other molecular velocities. The following table shews the weights of condensations which would be formed in primaeval masses of chaotic gas having the densities shewn in the first column, and the various molecular velocities mentioned at the heads of the remaining columns. In each case the weights of the condensations are given in terms of the weight of the sun: