What If the Earth Had Two Moons?: And Nine Other Thought-Provoking Speculations on the Solar System - Hardcover

Comins, Neil F.

Hardcover

ISBN 10: 0312598920 ISBN 13: 9780312598921

Publisher: St. Martin's Press, 2010

Synopsis

“What if?” questions stimulate people to think in new ways, to refresh old ideas, and to make new discoveries. In What If the Earth Had Two Moons, Neil Comins leads us on a fascinating ten-world journey as we explore what our planet would be like under alternative astronomical conditions. In each case, the Earth would be different, often in surprising ways.

The title chapter, for example, gives us a second moon orbiting closer to Earth than the one we have now. The night sky is a lot brighter, but that won’t last forever. Eventually the moons collide, with one extra-massive moon emerging after a period during which Earth sports a Saturn-like ring.

This and nine and other speculative essays provide us with insights into the Earth as it exists today, while shedding new light on the burgeoning search for life on planets orbiting other stars. 

Appealing to adult and young adult readers alike, this book follows on the author’s previous bestseller, What If the Moon Didn’t Exist?, with completely new scenarios backed by the latest astronomical research.

About this title

About the Author

Neil F. Comins is a professor of physics and astronomy at the University of Maine and author of popular scientific books, articles, and textbooks. He earned a Bachelor of Science degree from Cornell and a Ph.D. in astrophysics from University College, Cardiff, Wales.  

Excerpt. © Reprinted by permission. All rights reserved.

WHAT IF THE EARTH HAD TWO MOONS?
1What If the Earth Had Two Moons?DIMAAN, LLUNA, AND KUUThey came in the dead of night. One moment the bedroom was filled with the sounds of forest animals behind the village, the next with the deep shouts of men, rattling of heavily armored horses, and the ominous creaking of a carriage. A whip snapped; dogs began yelping; the leader of the group issued orders. They stopped right in front of his cottage. Lying in bed he heard his neighbors shuttering their windows and barring their doors. He knew that such actions would not protect them. The intruders would get in anywhere they wanted. As he finished this thought, his front door flew off its hinges, landing on the floor with a brittle crash.He was up now, but as he moved to get out of bed, his mistress grabbed his arm. She was trembling, her eyes wide with the same terror he felt, but which he hid so she would not fear the worst. "Why?" she asked, hoarsely, softly."I don't know. Maybe," he smiled wanly, "I forgot to pay our taxes.""They wouldn't be here for that.""It was ajoke," he said, lightly. She gave him the "not now" look, but he missed it as the stairs were filled with the clattering of hobnailed boots. Doors opened and slammed shut. The children began crying.Then their bedroom door opened and an officer, followed by four soldiers, strode in."Galileo Galilei?" the officer demanded.Galileo nodded. Without taking his eyes off Galileo, the man issued an order. "Take him.""You will leave her and the children?" Galileo inquired, meekly."We only have orders to arrest you," the officer said, adding, "in the name of the Holy Inquisition."If there is any justice in the world it occurred then, as a cluster of meteorites burst through the roof. A pair of them plunged into two of the soldiers, who fell dead.Galileo laughed. The officer cursed and said, "Damned nuisance." Then he turned to the remaining soldiers and ordered them to take Galileo. Marina screamed as they dragged him out of bed. Galileo watched her, and their arms reached out to each other and then separated in slow motion.The prison carriage, merely a cage on wheels drawn by a sickly horse, clattered and clanged as it carried the nightshirt-clad Galileo through the town and up to the castle. His body glowed red in the light of the moon Lluna shining and spurting molten rock overhead. He saw the eyes of hundreds of people watching him through slits in their shuttered windows. For perhaps the first time in his unruly life he wondered what they were thinking.Over the next two weeks Marina, disguised as a scullery maid, brought Galileo his food, passing it through a small opening in the locked door, talking to him in whispers. She told him about the children and how the inquisitors had taken all his papers. He asked if "they" had asked her about anything in particular that he was working on. She shook her head.For six weeks, Galileo sat in his prison room on a bed of straw and rough burlap, wearing the same nightshirt, which literally rotted on his body. During the first week, his arrogance kept him aloof, as he waited for inquisitors to question him. They never came. During the second week, his reserve turned to anger. The people taking turns monitoring him through a series of hidden mirrors saw him circlingaround the room, rubbing against the wall opposite his bed, then against the wall with the door, then against his bed, and finally against the outer wall, with the commode and window. As he circled, he rubbed the walls with his hand until it was raw. After the second week, Marina stopped coming. She could not stand the smells.During the third week, as his anger dissipated, he found solace in continuing his studies. The day before his imprisonment, he had received a letter full of technical details of the observations made by Martinelli on the island of San Salvador in the New World. He had spent that day memorizing the results in it. Now he compared those observations, meticulously recorded by his friend, with the ones he had made at the same time and the ones that they both had made twenty years before. Sifting through all this data chiseled in stone in his eidetic memory, and scribbling calculations in the dust on the floor, he completed the work that had obsessed him for years. And he was right! The angles between the telescopes observing the same place on the moon Lluna had changed over the decades. Lluna was moving away from his world, Dimaan. Despite the squalor, the arrogance returned.During the fourth week he started pounding on the door, demanding to be released. No one came to tell him to stop, and the door never opened. During the fifth week, confusion surrounding his arrest, imprisonment, and this interminable isolation broke through his defenses. The original question returned. Why had they arrested him? It must be something to do with his observations of the heavens, he reasoned, but what? His renowned ability to focus and concentrate evaporated.During the sixth week, he started thinking about errors he had made: errors of commission and errors of omission. Maybe, just maybe, he should have married Marina. Perhaps he shouldn't have fired Sestilia. Vincenzo really deserved the raise he had requested all those years ago. And what about his girls ... .The day after the tears appeared, an orderly opened the door, gagged, and vomited. Then he ordered Galileo out. Nearly naked, Galileo stumbled into the hallway. The gaggle of guards all backed away. With spears, they prodded him down the corridor and into a room through the middle of which ran a stream of water. He was tossed apiece of soap, a towel, and a robe, and ordered to bathe, which he did with as much zest as he could muster.The courtroom was a study in contrasts. On the side where the three judges sat, the walls were covered with dark wood panels and an immense tapestry. Glasses and pitchers filled with crystal-clear water sat in front of each of them, along with baskets of fruits and nuts. On the other side, Galileo stood on a bare wooden platform in an alcove surrounded by gray, rough-hewn walls."How do you plead and do you agree to recant what you have said?" the central judge, tall, with a goatee beard, demanded."Are you out of your tiny mind?" Galileo demanded. "That is, if you have one at all. I have done nothing wrong. Nothing," he hissed at them.The three judges and the guards against the side walls all gaped.The judge on Galileo's right regained his composure first. Scribbling something on the sheet in front of him, he half turned his head toward the astronomer. "Do you really believe that? Do you think you would be here if we didn't have proof positive of your transgression?"Galileo glared at him. The silence filling the room became so thick that several guards shook their heads to clear their minds."Do you deny ...""I have done nothing wrong and made no mistakes," Galileo interrupted, through clenched teeth.The third judge sat back, smiled briefly, and began speaking, putting his index finger to his lips as Galileo opened his mouth."We think that you misunderstand us." He motioned for the guards to leave. When they were gone, he rounded on Galileo. "We know that our planet, Dimaan, and the heavens have been here forever. They are immutable. Unchanging in Essential Essence.""Earthquakes, volcanoes, sunspots," Galileo interjected, unsure where this was going."Mere challenges to humans," the judge said, smiling. "Our Creator does not want us to think we live in paradise here. You, however, claim that you can prove that there are irreversible changes in the universe. These, in turn, lead to the conclusion that our planet, and by extension, the universe, has not been here, fundamentally unchanged, forever.""I ... I don't follow," Galileo murmured, the bravado draining."Then I will explain ... if you have a brain to understand," the judge sneered. "Dimaan has two moons, Lluna and Kuu. Lluna is ninesixteenths the distance of Kuu, a relationship of perfect squares that the Church finds consistent with its teachings. You," he stabbed a finger at Galileo, "have secretly proposed that Lluna is moving away from Dimaan, toward Kuu. You have a co-conspirator, Luigi Martinelli, in San Salvador. He is there to provide you with data that will allegedly prove your hypothesis. And he has sent you that information."The judge waved papers at Galileo, who squinted, unable to make out what was on them. The judge rose regally and, walking around the desk, handed them to Galileo. They were a copy of the letter he had received before his arrest."I don't unders--," he began, but suddenly he did. "This data, with my own, proves that Lluna is moving away. Hence it was closer yesterday and closer still each previous day. Once upon a time it must have been captured or it was part of Dimaan, flung off," he did a quick calculation in his head, "nearly a billion years ago.""So if what you propose is true, Dimaan and Lluna were not the same in Essential Essence a billion years ago as they are today.""Doesn't it give you a headache to think that everything has been as it is forever? What happened before forever?""Your caustic blasphemy will gain you nothing," the central judge said, his voice icy."If I can prove Lluna's recession, then science can rethink the evolution of our world. Otherwise, we are stuck with a universe that has lasted forever, a Lord who has also existed forever, and life that has only recently been put here. But why now? Why were we not created a trillion years ago? Or a billion years from now? It makes no sense to me."Silence hung in the air like molten lead. "Our Lord works in mysterious ways. She has given us Her teachings and we are here to make sure that no one ... I mean no one ... goes astray. You, sir, are going astray and you are beginning to take others with you. This is absolutely unacceptable. You will ... you must recant these heretical beliefs here and now and vow to never mention them again, except as errors.""And if I refuse?""The past six weeks of confinement will only be the beginning. We will tortu ... teach ... you using every tool at our disposal. They are many tools, each more--instructive--than the previous one. Halfway through your instruction, you will plead for death--but it will be denied. Eventually we will rip your arms ...""And what if ... what if I am right and you are wrong? What if I can prove what I claim is true?"The three judges looked at each other and the one on Galileo's right nodded slowly. "I think it would be a mistake to start with your 'education.' We will begin by educating your mistress and children."Earth is unique in the solar system1 for many reasons. Some distinctive properties are entirely obvious (complex surface life comes to mind), whereas others are more subtle, such as Earth having one Moon. In comparison, Mars has two moons, Jupiter has at least sixty-three, and the other planets have numbers between these two. (Venus and Mercury have none.) Furthermore, our Moon2 has the mass of the Earth, whereas all the other moons in the solar system have masses less than the masses of their planets.The Moon's existence, combined with its large mass compared to the Earth and the fact that it is the only natural body orbiting our planet, has led to many changes from what the Earth would have been like without it. Because of the Moon's existence life formed relatively rapidly; the day is twenty-four hours long rather than being roughly eight hours long; tides are three times higher than they would be otherwise; many species of animals that are active at night could not exist without moonlight to aid their hunting, navigating, and mating activities; our planet's rotation axis does not randomly change direction as it would otherwise do; and we have an essentially constant cycle of seasons, which we wouldn't otherwise have, among many other things. Each of these results of our having a Moon, in turn, has affected myriad other aspects of the Earth and life on it. Any modification to the Earth or its astronomical environment leads to fascinating changes inour world, as well as providing new perspectives and insights into our planet as it is now. In this first of ten alternate worlds we explore what Earth would be like if we had two massive moons today instead of just one.The Earthlike planet in this chapter, called Dimaan, begins its life identical to the early Earth in size, composition, and distance from the Sun. Based on geological and fossil evidence, the Earth was initially spinning much faster than it is today. Although that rate is not yet known, I give Dimaan a plausible eight-hour day when it first formed. Neither Earth nor Dimaan had a moon at first. Ours came into existence within about 200 million years of the Earth's forming.Moons can form in four ways: from impacts, in which the planet is struck and thereby ejects debris that becomes one or more moons; simultaneously with a planet, in which the moons and planet condense together (Appendix); by fission, wherein the moons are literally thrown off a rapidly rotating planet (Appendix); and by capture of the moons after the planet has formed.Most astronomers believe that our Moon formed as the result of a collision between Earth and a Mars-sized body. The intruder hit Earth at an angle that ejected debris into orbit in the same general direction in which our planet was spinning. This rubble formed a short-lived ring that was much smaller but, interestingly, much more massive than all of Saturn's rings combined. As this material orbited, it began colliding with itself and bunching together under the influence of its own gravitational attraction until it coalesced into the Moon. This is how I posit Dimaan's first moon, Kuu, formed.Although it is entirely possible for an impact of a small planet onto a larger one to splash enough debris into orbit to form two moons similar to ours, such moons would drift together and collide billions of years before advanced life evolved on Dimaan (Appendix). Because I want that second moon around for people to enjoy, I posit that Dimaan captures its second moon long after the first one formed.CAPTURE OF THE SECOND MOONThe process of forming a star and its host of orbiting objects is a very, very messy affair involving countless collisions. The star system begins as aslowly swirling eddy of gas and dust in a giant interstellar cloud that begins to contract under the influence of its own gravitational attraction. In the case of our solar system or that of Dimaan, the central region of this eddy condenses to become the Sun. The material in its outer reaches becomes a disk of gas and dust, parts of which condense to form the planets, moons, and smaller orbiting pieces of debris such as asteroids and comets.Most moons are potato-shaped bodies typically a few miles across that were originally not bound to planets. As these small bodies drifted past them, the planets captured them with relative ease. In our solar system, the tiny moons include Phobos and Deimos orbiting Mars, and at least 150 moons orbiting the giant planets Jupiter, Saturn, Uranus, and Neptune. For each piece of space debris that was captured, millions of similar objects struck planets or sped past too rapidly to go into orbit.Even though our solar ...

Edition details

• Publisher: St. Martin's Press
• Publication date: 2010
• ISBN 10: 0312598920
• ISBN 13: 9780312598921
• Binding: Hardcover
• Language: English
• Edition number: 1
• Number of pages: 304