"But he travels around the sun in the same direction the Earth does," I objected. "I should think we ought to aim a little ahead of him, or to the left, to allow for his motion forward in his orbit." "That looks reasonable at first sight, doesn't it?" said the doctor. "But a little learning is a dangerous thing. I will explain to you why we must steer a little behind him after I have had my nap. I am too sleepy now;" and he finished with a yawn. He soon fell asleep, and I was left alone to think over the events of the day and the still more strange happenings of the night. It hurt my eyes to look long through the telescope, so I closed them and gave free rein to my thoughts. How soon will it be morning? How shall I know when it _is_ morning? That term "morning" applies only to the surface of revolving planets. I had just seen the morning come at midnight, and then the darkness of night fall again directly after morning. After all, what are night and morning? The one is a passing into the shadow of the Earth, and the other is simply the emerging into the light. They depend on a rotation, and we shall know no more of them until we land on a revolving planet again. But which shall we have on the trip, night or daylight? Naturally we would very soon emerge from the little shadow cast by the Earth. It had taken us but an hour or two to travel out of it into the daylight and then back into the darkness again. Even if we did not leave it, the Earth would move on and leave us. And what then? Nothing but uninterrupted, untempered, unhindered daylight! Eternal, dazzling, direct sunlight, unrelieved by any night, unstrained through any clouds! This deep blue of the starry night would be succeeded by the hot, white light of a scorching, gleaming Sun. And then (the thought chilled my bones as it fell upon me!), then how would we see Mars? How would we see any star, or perchance the Moon? Even the Earth might be drowned in that sea of everlasting, all-engulfing brilliancy! Nothing in all the Universe would be visible but the beaming Sun, and he too blindingly bright to look upon. As the truth of all this took hold of me, it filled me with a growing terror. At any moment we might emerge from this grateful shadow of the Earth, and then we would be lost, drowned, engulfed in a blinding, sight-suffocating light! In desperate terror I looked around toward the doctor, as if for assistance. He was sleeping peacefully. He had never thought of it! _This_ was the great thing he had overlooked! Even at starting he had a dreadful presentiment of it.