Worlds in the making: The evolution of the universe

by Svante Arrhenius

[15] A. Ritter has calculated that when two suns of equal size collide with one another from an infinite distance, the energy of the collision is not more than sufficient to enlarge the volume of the suns to four times the previous amount. The largest portion of the mass will therefore probably remain in the centre, and it will only be masses of light gases which will be ejected.

[16] This figure, -1.7, signifies that the brightness of Sirius is 2.52^2.7 = 12 times greater than that of a star of magnitude 1. Next to Sirius comes Canopus, with magnitude -1.0, being 6.3 times brighter than a star of magnitude 1.

[17] This circumstance indicates that the red color of these stars, as we have already remarked with regard to Mira Ceti, is not to be traced back to a low temperature, but rather to the dust surrounding them. The most extraordinary brightness of some stars, like Arcturus and Betelgeuse, which are redder than the sun, and whose spectra, according to Hale, resemble those of the sun-spots, presuppose a very high temperature. The characteristic lines of their spectra are produced by the relatively cool vapors of their outer portions.

[18] The presence of carbon bands in the spectrum need not be taken as a mark of low temperature. Crew and Hale have observed that these bands gradually vanished from an arc spectrum as the temperature was lowered by decreasing the current intensity.

[19] The kinetic theory of gases imagines all the molecules of a gas to be in constant motion. The internal pressure of the gas depends upon the mean velocity of the particles; but some particles will move at a greater, and some at a smaller velocity than the average.—H.B.

[20] Meanwhile a large number of organisms which are invisible under the ordinary microscope have been rendered visible by the aid of the ultra-microscope, among others the presumable microbe of the foot-and-mouth disease.

[21] The radiation pressure has here been assumed to be somewhat greater than on page 103, because the spores are here regarded as opaque, while the drops of hydrocarbons have been regarded as partially translucid to luminous rays.