Boston, June 24, 1833.
POPULAR LESSONS IN ASTRONOMY.
LESSON I.
THE EARTH IN ITS RELATION TO THE SUN, MOON AND STARS.
§ 1. The Earth on which we live, and on which plants, trees and animals successively live and die, is only a small part of the world; it is but one of the smallest bodies in the Universe. To the world belong yet the Sun from which we receive warmth and light, the Moon, and an innumerable class of bodies, which, at night, appear to us as so many points of light. These are called Stars.
The reason why the Stars appear to us so small, is because they are so far from us; and things appear smaller in proportion as they are farther removed from us. This you will have noticed, when looking from a high steeple on the people below, or on a vessel far out in the harbour, or on a chain of mountains at a great distance.
§ 2. Most all Stars appear to us, every night in the same position; they seem actually to be fixed in the heavens; and for this reason they are called fixed Stars. There are however Ten others, of which it has been ascertained that they move regularly round the Sun in large circles. These are called Planets or wandering Stars.—The fixed Stars are supposed to be similar to the Sun, in as much as they are bodies which have their own light. The Planets, on the contrary, are of themselves dark bodies, and receive, like our Earth, light and warmth from the Sun. We see them only in consequence of the solar light which they reflect from their surfaces, and this is the reason why they appear to us as bright as the other Stars.
§ 3. The discoveries of Philosophers have proved beyond a doubt, that our Earth itself is one of those Planets, which move round the Sun in stupendous large circles, whose grandeur is hardly conceived by the most powerful imagination. Our Earth, therefore, is, itself, a Wandering Star, and the line in which it moves round the Sun is called its Way or Orbit.
§ 4. The Planets, together with our Earth keep each a certain fixed distance from the Sun. On this account they do not disturb each other in their orbits. But they vary from each other in magnitude; although all of them (consequently also our Earth) have a round shape, similar to a ball.