The Study of Astronomy, adapted to the capacities of youth / In twelve familiar dialogues, between a tutor and his pupil: explaining the general phænomena of the heavenly bodies, the theory of the tides, &c.

by teacher of astronomy John Stedman

Pupil. A conjunction, I suppose, when the sun is between the earth and the planet, and an opposition when the earth is between the sun and the planet; that is, when the planet is nearest to us, and appears to be opposite to the sun?

Tutor. You are right.—Therefore, when in conjunction it rises and sets, nearly with the sun; but in opposition, it rises nearly when the sun sets, and sets when he rises.

Pupil. Why do you say nearly, Sir?

Tutor. Because it cannot be exactly, but when the sun, earth, and planet are in a right line, which seldom happens.

Pupil. How do you account for this, Sir?

Tutor. At present I fear you will not be able to comprehend what I wish to explain, as I must use a term you are unacquainted with. The reason is, that the planets are very seldom in or near their nodes at their conjunctions or oppositions.

Pupil. I do not indeed understand what you mean by the word nodes.

Tutor. It will be explained to you in due time, and I shall conclude this evening with a few more remarks relative to the appearance of the planets.

Pupil. Any thing you please, Sir.

Tutor. You know that the planets, being opaque bodies, receive their light from the sun; and that only that part which is turned to the sun can be enlightened by him, whilst the opposite side must remain in darkness.