by Michio Kaku
This de Sitter expansion may have given rise to the original inflation that initiated the Big Bang. But it is also causing the universe to expand exponentially once again. Unfortunately, physicists are at a loss to explain any of this from first principles. String theory comes closest to explaining dark energy, but the problem is that it cannot predict the precise amount of dark energy in the universe. String theory says that, depending on how you curl up ten-dimensional hyperspace, one can obtain different values for dark energy, but it does not predict precisely how much dark energy there is.
The final possibility is to create a wormhole: Assuming that wormholes are possible, there is still another hurdle to negotiate. One must be sure that matter is stable on the other side of the wormhole. For example, the reason why our universe is possible is because the proton is stable, or at least so stable that our universe has not collapsed down to a lower state in the 13.8 billion years of its existence. It is possible that the other universes in the multiverse may have a ground state in which, for example, the proton can decay to an even lower-mass particle, such as a positron. In this case, all the familiar chemical elements of the periodic table will decay, and this universe will consist of a mist of elections and neutrinos, unsuitable for stable atomic matter. So one must take care to enter a parallel universe in which matter is similar to ours and is stable.
All these speculations at first seem preposterous: A. Guth, “Eternal Inflation and Its Implications,” Journal of Physics A 40, no. 25 (2007): 6811.
Also, when we look in one direction: Inflationary theory answers several puzzling aspects of the Big Bang. First, our universe seems to be extremely flat, much flatter than usually proposed in the standard Big Bang theory. This can be explained by postulating that our universe had an expansion much faster than previously thought. A tiny portion of the original universe then inflated enormously and was flattened out in the process. Second, the theory explains why the universe is much more uniform than it should be. By looking in all directions in space, we see that the universe is quite uniform. But (because the speed of light is the ultimate velocity) there was not enough time for the original universe to mix thoroughly. This can be explained by assuming that a tiny piece of the original Big Bang was in fact uniform, but that uniform piece was inflated to give the uniform universe of today.
Beyond these two achievements, the inflationary universe theory so far agrees with all the data coming in from the cosmic microwave background. This does not mean that the theory is correct, only that it agrees with all the cosmological data so far. Time will tell if the theory is correct. One glaring problem with inflation is that no one knows what caused it. The theory works fine after the instant of inflation but says absolutely nothing about what caused the original universe to inflate.
SUGGESTED READING
Arny, Thomas, and Stephen Schneider. Explorations: An Introduction to Astronomy. New York: McGraw-Hill, 2016.
Asimov, Isaac. Foundation. New York: Random House, 2004.
Barrat, James. Our Final Invention: Artificial Intelligence and the End of the Human Era. New York: Thomas Dunn Books, 2013.
Benford, James, and Gregory Benford. Starship Century: Toward the Grandest Horizon. Middletown, DE: Microwave Sciences, 2013.
Bostrom, Nick. Superintelligence: Paths, Dangers, Strategies. Oxford: Oxford University Press, 2014.
Brockman, John, ed. What to Think About Machines That Think. New York: Harper Perennial, 2015.
Clancy, Paul, Andre Brack, and Gerda Horneck. Looking for Life, Searching the Solar System. Cambridge: Cambridge University Press, 2005.
Comins, Neil, and William Kaufmann III. Discovering the Universe. New York: W. H. Freeman, 2008.
Davies, Paul. The Eerie Silence. New York: Houghton Mifflin Harcourt, 2010.
Freedman, Roger, Robert M. Geller, and William Kaufmann III. Universe. New York: W. H. Freeman, 2011.
Georges, Thomas M. Digital Soul: Intelligent Machines and Human Values. New York: Perseus Books, 2003.
Gilster, Paul. Centauri Dreams. New York: Springer Books, 2004.
Golub, Leon, and Jay Pasachoff. The Nearest Star. Cambridge: Harvard University Press, 2001.
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———. The Living Cosmos: Our Search for Life in the Universe. New York: Random House, 2007.
Kaku, Michio. The Future of the Mind. New York: Anchor Books, 2014.
———. The Physics of the Future. New York: Anchor Books, 2011.
———. Visions: How Science Will Revolutionize the 21st Century. New York: Anchor Books, 1999.
Kasting, James. How to Find a Habitable Planet. Princeton: Princeton University Press, 2010.
Lemonick, Michael D. Mirror Earth: The Search for Our Planet’s Twin. New York: Walker and Co., 2012.
———. Other Worlds: The Search for Life in the Universe. New York: Simon and Schuster, 1998.
Lewis, John S. Asteroid Mining 101: Wealth for the New Space Economy. Mountain View, CA: Deep Space Industries, 2014.
Neufeld, Michael. Von Braun: Dreamer of Space, Engineer of War. New York: Vintage Books, 2008.
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Summers, Michael, and James Trefil. Exoplanets: Diamond Worlds, Super Earths, Pulsar Planets, and the New Search for Life Beyond Our Solar System. Washington, D.C.: Smithsonian Books, 2017.
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Vance, Ashlee, and Fred Sanders. Elon Musk: Tesla, SpaceX, and the Quest for a Fantastic Future. New York: HarperCollins, 2015.
Wachhorst, Wyn. The Dream of Spaceflight. New York: Perseus Books, 2000.
Wohlforth, Charles, and Amanda R. Hendrix. Beyond Earth: Our Path to a New Home in the Planets. New York: Pantheon Books, 2017.
Woodward, James F. Making Starships and Stargates: The Science of Interstellar Transport and Absurdly Benign Wormholes. New York: Springer, 2012.
Zubrin, Robert. The Case for Mars. New York: Free Press, 2011.
ILLUSTRATION CREDITS
1 Mapping Specialists, Ltd.
2 NASA
3 NASA
4 Adrian Mann
5 Adrian Mann
6 Mapping Specialists, Ltd.
7 Mark Rademaker
8 The Habitable Exoplanets Catalog, PHL @ UPR Arecibo (phl.upr.edu)
9 NASA
ABOUT THE AUTHOR
Michio Kaku is a professor of theoretical physics at the City University of New York, cofounder of string field theory, and the author of several widely acclaimed science books, including Beyond Einstein, The Future of the Mind, Hyperspace, Physics of the Future, and Physics of the Impossible. He is the science correspondent for CBS This Morning, and host of numerous TV science specials and of the radio programs Science Fantastic and Exploration.
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Table of Contents
Also by Michio Kaku
Title Page
Copyright
Dedication
Contents
Acknowledgments
Prologue
Introduction: Toward a Multiplanet Species
Part I: Leaving the Earth
1. Preparing for Liftoff
2. New Golden Age of Space Travel
3. Mining the Heavens
4. Mars or Bust
5. Mars: The Garden Planet
6. Gas Giants, Comets, and Beyond
Part II: Voyage to the Stars
7. Robots in Space
8. Building a Starship
9. Kepler and a Universe of Planets
Part III: Life in the Universe
10. Immortality
11. Transhumanism and Technology
12. Search for Extraterrestrial Life
13. Advanced Civilizations
14. Leaving the Universe
Notes
Suggested Reading
Illustration Credits
About the Author