Page:In the high heavens.djvu/375

 the gravitation on the large globe would be 109 times as great as that on the earth. It is, however, known that in consequence of the high temperature of the sun its materials are so much more expanded than are those of the earth, that the sun's mean density is only about one-quarter of that of the earth. In consequence of this we see that the gravitation of a body on the sun's surface must be one-fourth of what it would have been if the sun had a mean density equal to that of the earth. It thus appears that the gravitation at the surface of the sun must be about 27 times as great as the gravitation on the earth.

The effect of gravitation on our globe is well known to be able to impart to each body in the course of one second a velocity equal to 82 feet per second. It therefore follows that a body falling at the sun's surface receives in each second an increment of velocity to the extent of 864 feet per second. But the visible parts of the sun are composed of gaseous or vaporous materials. From the molecular spectrum of gases we have been taught to believe that the molecules of which the sun is composed are in incessant motion. Gravitation constantly tends to impart to each molecule an increase of velocity downwards. It is quite true that we cannot expect each molecule should actually acquire an additional velocity of 864 feet each second. Indeed, in our own atmosphere we have an illustration of the absurdity of such a notion.

The gravitation on the earth imparts to every falling body a speed of 32 feet per second. Of course if there were only a single molecule coming in from outside space it would doubtless hurry in towards the earth