by Michio Kaku
The only way known to go faster than light is to invoke Einstein’s general theory of relativity, where space-time becomes a fabric that can stretch, bend, and even tear. The first way is via “multiply connected spaces” (wormholes), in which two universes are joined together like Siamese twins. If we take two parallel sheets of paper and then punch a hole that connects them, then this gives us a wormhole. Or, you could somehow compress space in front of you, so that you can hop over the compressed space and travel faster than light.
Although physicists have seen no evidence of negative matter: Stephen Hawking proved a powerful theorem, which states that negative energy is essential to any solution of Einstein’s equations that allows for time travel or wormhole starships.
Negative energy is not allowed under ordinary Newtonian mechanics. However, negative energy is allowed by the quantum theory via the Casimir effect. It has been measured in the laboratory and found to be extremely tiny. If we have two large parallel metal plates, then the Casimir energy is proportional to the inverse distance of separation of the plates raised to the third power. In other words, negative energy rapidly increases in energy as the two plates are brought together.
The problem is that these plates have to be brought together to within subatomic distances, which is not possible with today’s technology. We have to assume that a very advanced civilization has somehow mastered the ability to harness vast amounts of negative energy to make time machines and wormhole spaceships possible.
I once interviewed the Mexican theoretical physicist Miguel Alcubierre: See M. Alcubierre, “The Warp Drive: Hyperfast Travel Within General Relativity,” Classical and Quantum Gravity 11, no. 5 (1994): L73–L77. When I interviewed Alcubierre for the Discovery Channel, he was confident that his solution of Einstein’s equations was a significant contribution, but he was wary of the difficulties it faced if one actually tried to build a warp drive engine. First, the space-time inside the warp bubble was causally separate from the outside world. This meant that it was impossible to steer the starship or direct it from the outside. Second, and most important, it required vast amounts of negative matter (which has never been found) and negative energy (which only exists in minute quantities). So, he concluded, major hurdles have to be solved before a workable warp engine can be built.
CHAPTER 9: KEPLER AND A UNIVERSE OF PLANETS
Bruno, Galileo’s predecessor: William Boulting, Giordano Bruno: His Life, Thought, and Martyrdom (Victoria, Australia: Leopold Classic Library, 2014).
“This space we declare to be infinite”: Ibid.
A big breakthrough came with the 2009 launch of the Kepler spacecraft: For more on the Kepler spacecraft, see the NASA website: http://www.kepler.arc.nasa.gov.
The Kepler spacecraft focused on one tiny spot in the Milky Way galaxy. Even then, it has found evidence of four thousand or so planets orbiting other stars. But from that tiny spot, we can extrapolate to the entire galaxy and hence get a rough analysis of the planets in the Milky Way. Succeeding missions after the Kepler will focus on different regions of the Milky Way galaxy, hoping to find different types of extrasolar planets, and more Earth-like ones.
“There are planets out there that have no counterpart in our solar system”: Interview with Professor Sara Seager, Science Fantastic radio, June 2017.
“This is a game changer in exoplanetary science”: Christopher Crockett, “Year In Review: A Planet Lurks Around the Star Next Door,” Science News, December 14, 2016.
“It’s absolutely phenomenal”: Interview with Professor Sara Seager, Science Fantastic radio, June 2017.
“This is an amazing planetary system”: See www.pressreader.com/uk/the-herald/20170223/281556585596579.
CHAPTER 10: IMMORTALITY
Yet another proposal to colonize the galaxy is to send embryos: A. Crow, J. Hunt, and A. Hein, “Embryo Space Colonization to Overcome the Interstellar Time Distance Bottleneck,” Journal of the British Interplanetary Society 65 (2012): 283–85.
“Every sign, including genetics, says there’s some causality”: Linda Marsa, “What It Takes to Reach 100,” Discover Magazine, October 2016.
The mechanism of aging is slowly being revealed: It is sometimes said that immortality violates the second law of thermodynamics, which indicates that everything, including living organisms, will eventually decay, rot, and die. However, there is a loophole in the second law, which states that (in a closed system) entropy (disorder) will inevitably increase. The key word is closed. If you have an open system (where energy can be added from the outside), then entropy can be reversed. This is how a refrigerator works. The motor at the bottom of the refrigerator pushes gas through a pipe, which causes the gas to expand, causing the refrigerator to cool down. When applied to living things, it means that entropy can be reversed as long as energy is added from the outside (which is sunlight).
So our very existence is possible because sunlight can energize plants, and we can consume these plants and use this energy to repair the damage caused by entropy. Hence, we can reverse entropy locally. When discussing human immortality, one can therefore evade the second law by adding new energy locally from the outside (such as in the form of changes in diet, exercise, gene therapy, absorbing new types of enzymes, et cetera).
“I don’t think the time is quite right, but it’s close”: Quoted in Michio Kaku, The Physics of the Future (New York: Anchor Books, 2012), p. 118.
What happens if we solve the problem of aging?: The point here is that, in the main, all the pessimistic predictions of population collapse made back in the 1960s failed to materialize. In fact, the rate of expansion of the world population is actually slowing down. But the point is that the absolute population of the world is still increasing, especially in sub-Saharan Africa, so it is difficult to actually estimate the world population in 2050 and 2100. Some demographers, however, have claimed that, if trends continue, ultimately the world population could flatten out and become stable. If so, then the world population could reach a plateau of some sort and hence avoid a population catastrophe. But this is still conjectural.
“I’m as fond of my body as anyone”: See https://quotefancy.com/quote/1583084/Danny-Hillis-I-m-as-fond-of-my-body-as-anyone-but-if-I-can-be-200-with-a-body-of-silicon.
CHAPTER 11: TRANSHUMANISM AND TECHNOLOGY
“It just completely changes the landscape”: Andrew Pollack, “A Powerful New Way to Edit DNA,” New York Times, March 3, 2014; www.nytimes.com/2014/03/04/health/a-powerful-new-way-to-edit-dna.html.
“No one really has the guts to say it”: See Michio Kaku, Visions (New York: Anchor Books, 1998), p. 220 and Michio Kaku, The Physics of the Future, p. 118.
“My prediction is that by the year 2100”: Kaku, The Physics of the Future, p. 118.
Francis Fukuyama of Stanford has warned: F. Fukuyama, “The World’s Most Dangerous Ideas: Transhumanism,” Foreign Policy 144 (2004): 42–43.
CHAPTER 12: SEARCH FOR EXTRATERRESTRIAL LIFE
“We only have to look at ourselves”: Arthur C. Clarke once said, “Either there is intelligent life in the universe, or there is not. Either thought is frightening.”
“If you live in a jungle”: Rebecca Boyle, “Why These Scientists Fear Contact with Space Aliens,” NBC News, February 8, 2017; www.nbcnews.com/storyline/the-big-questions/why-these-scientists-fear-contact-space-aliens-n717271.
This is called SETI: At present, there is no universally accepted consensus concerning the SETI Project. Some believe that the galaxy may be teeming with intelligent life. Others believe that perhaps we are alone in the universe. With only one data point to analyze (our planet), there are very few rigorous guidelines to direct our analysis, other than the Drake equation.
For another opinion, see N. Bostrom, “Where Are They: Why I Hope the Search for Extraterrestrial Intelligence Finds Nothing,” MIT Technology Review Magazine, May/June 1998, 72–77.
But all this still leaves one persistent, nagging question: E. Jones, “Where Is Everybody? An Acco
unt of Fermi’s Question,” Los Alamos Technical Report LA 10311-MS, 1985. See also S. Webb, If the Universe Is Teeming with Aliens…Where Is Everybody? (New York: Copernicus Books, 2002).
“Some of these pre-utopian worlds”: Stapledon, Star Maker (New York: Dover, 2008), p. 118.
Another possibility is that they want to steal the heat: There are many other possibilities that cannot be easily dismissed. One is that perhaps we are alone in the universe. The argument here is that we are finding more and more Goldilocks zones, meaning that it becomes increasingly difficult to find planets that can fit within all these new Goldilocks zones. For example, there is a Goldilocks zone for the Milky Way galaxy. If a planet is too close to the center of the galaxy, there is too much radiation for life to exist. If it is too far from the center, then there are not enough heavy elements to create the molecules of life. The argument is that there might be so many Goldilocks zones, many of them not even discovered yet, that there might be only one planet in the universe with intelligent life. Each time there is another Goldilocks zone, it vastly decreases the probability of life. With so many of these zones, the collective probability of intelligent life is nearly zero.
Also, it is sometimes said that extraterrestrial life may be based on entirely new laws of chemistry and physics that are far beyond anything we can create in the laboratory. Hence, our understanding of nature is simply too narrow and simplistic to explain life in outer space. This may be true. And it is certainly true that entirely new surprises will be found once we explore the universe. However, it does not further the debate to simply state that alien chemistry and physics might exist. Science is based on theories that are testable, reproducible, and falsifiable, so simply postulating the existence of unknown laws of chemistry and physics does not help.
CHAPTER 13: ADVANCED CIVILIZATIONS
The tabloid headlines blared: See David Freeman, “Are Space Aliens Behind the ‘Most Mysterious Star in the Universe’?” Huffington Post, August 25, 2016; www.huffingtonpost.com/entry/are-space-aliens-behind-the-most-mysterious-star-in-the-universe_us_57bb5537e4b00d9c3a1942f1. See also Sarah Kaplan, “The Weirdest Star in the Sky Is Acting Up Again,” Washington Post, May 24, 2017; www.washingtonpost.com/news/speaking-of-science/wp/2017/05/24/the-weirdest-star-in-the-sky-is-acting-up-again/?utm_term=.5301cac2152a.
“We’d never seen anything like this star”: Ross Anderson, “The Most Mysterious Star in Our Galaxy,” The Atlantic, October 13, 2015; www.theatlantic.com/science/archive/2015/10/the-most-interesting-star-in-our-galaxy/41023.
This classification of advanced civilizations was first proposed: N. Kardashev, “Transmission of Information by Extraterrestrial Civilizations,” Soviet Astronomy 8, 1964: 217.
“The premise is that any highly advanced civilization”: Chris Impey, Beyond: Our Future in Space (New York: W. W. Norton, 2016), pp. 255–56.
“Logic tells me that it is reasonable to look for godlike signs”: David Grinspoon, Lonely Planets (New York: HarperCollins, 2003), p. 333.
The LHC has made many headlines: It is sometimes said that creating giant accelerators, like the LHC and beyond, will create a black hole that might destroy the entire planet. This is impossible for several reasons:
First, the LHC cannot create enough energy to create a black hole, which requires energies comparable to those of a giant star. The energy of the LHC is that of subatomic particles, much too small to open a hole in space-time. Second, Mother Nature bombards the Earth with subatomic particles more powerful than those created by the LHC, and the Earth is still here. So subatomic particles with energies greater than the LHC are harmless. And lastly, string theory predicts that there might be mini black holes that one day might be found with our accelerators, but these mini black holes are subatomic particles, not stars, and hence pose no danger at all.
Currently the only one capable of doing this: If we naïvely try to join the quantum theory with general relativity, we find mathematical inconsistencies that have stumped physicists for almost a century. For example, if we calculate the scattering of two gravitons (particles of gravity), we find that the resulting answer is infinite, which is meaningless. Hence, the fundamental problem facing theoretical physics is to unify gravity with the quantum theory in a way that gives finite answers.
At present, the only way known to eliminate these troublesome infinities is to use superstring theory. This theory has a powerful set of symmetries in which the infinities cancel each other out. This is because in string theory every particle has a partner, called a “sparticle.” The infinities coming from ordinary particles cancel precisely against the infinities coming from the sparticles, and hence the entire theory is finite. String theory is the only theory in physics that selects out its own dimensionality. This is because the theory is symmetric under supersymmetry. In general, all particles of the universe come in two types, bosons (which have integer spins) and fermions (which have half-integer spins). As the number of dimensions of space-time increases, the number of these fermions and bosons also increases. In general, the number of fermions rises much faster than the number of bosons. The two curves cross, however, at ten dimensions (for strings) and eleven dimensions (for membranes, like spheres and bubbles). Hence the only consistent supersymmetric theory is found in ten and eleven dimensions.
If we set the dimension of space-time at ten, then we have a consistent theory of strings. However, there are five different types of string theories in ten dimensions. For a physicist, searching for the ultimate theory of space and time, it is hard to believe that there should be five different self-consistent string theories. Ultimately, we want just one. (One of the guiding questions asked by Einstein was, Did God have a choice in making the universe? That is, Is the universe unique?)
Later, it was shown by Edward Witten that these five string theories can be unified into a single, unique theory if we add one more dimension, making it eleven-dimensional. This theory was called M-theory, and it contains membranes as well as strings. If we start with a membrane in eleven dimensions, and then we reduce one of these eleven dimensions (by flattening it, or slicing it), then we find that there are five ways in which a membrane can be reduced to a string, giving us the five known string theories. (For example, if we flatten a beach ball, leaving only the equator, then we have reduced an eleven-dimensional membrane down to a ten-dimensional string.) Unfortunately, the fundamental theory behind M-theory is totally unknown, even today. All we know is that M-theory reduces down to each of the five different string theories if we reduce eleven dimensions down to ten, and that, in the low-energy limit, M-theory reduces down to eleven-dimensional supergravity theory.
If you then kill your grandfather before you are born: Time travel poses yet another theoretical problem. If a photon, a particle of light, enters the wormhole and goes back in time a few years, then years later it can reach the present and reenter the wormhole once again. In fact it can reenter the wormhole an infinite number of times, and hence the time machine will explode. This is one of Stephen Hawking’s objections to time machines. However, there is a way to escape this problem. In the many-worlds theory of quantum mechanics, the universe constantly splits in half into parallel universes. Therefore, if time is constantly splitting, it means that the photon only goes back in time once. If it reenters the wormhole, it is simply entering a different parallel universe, and hence it only makes a single pass through the wormhole. In this way, the problem with infinities is solved. In fact, if we adopt the idea that the universe is constantly splitting into parallel realities, then all the paradoxes of time travel are solved. If you kill your grandfather before you are born, you have simply killed a grandfather in a parallel universe who resembles your grandfather. Your own grandfather in your universe was not killed at all.
CHAPTER 14: LEAVING THE UNIVERSE
In the fifth epoch, even black holes: Even black holes must eventually die. According to the uncertainty principle, everything is uncertain, even a black hole. A black hole is supposed t
o absorb 100 percent of all matter that falls into it, but this violates the uncertainty principle. Hence, there is actually a faint radiation that escapes from a black hole, called Hawking radiation. Hawking proved that it was actually a black body radiation (similar to the radiation emitted by a molten piece of metal) and therefore has a temperature associated with it. You can calculate that, over aeons, a black hole (which is actually gray) will emit enough radiation that it will no longer be stable. Then the black hole disappears in an explosion. So even black holes will eventually die.
If we assume that the Big Freeze takes place at some future time, we have to confront the fact that atomic matter as we know it might disintegrate trillions upon trillions of years from now. At present, the Standard Model of subatomic particles says that the proton should be stable. But if we generalize the model to try to unify the various atomic forces, we find that the proton may eventually decay into a positron and a neutrino. If this is true, then it means that matter (as we know it) is ultimately unstable and will decay into a mist of positrons, neutrinos, electrons, et cetera. Life probably cannot exist under these harsh conditions. According to the second law of thermodynamics, you can only extract usable work if there is difference in temperature. In the Big Freeze, however, temperatures drop to near absolute zero, so there is no more difference in temperature from which we can extract usable work. In other words, everything comes to a halt, even all possible life-forms.
What is causing this sudden change in our understanding: Dark energy is one of the greatest mysteries in all of physics. Einstein’s equations have two terms that are generally covariant. The first is the contracted curvature tensor, which measures the distortions in space-time caused by stars, dust, planets, et cetera. The second term is the volume of space-time. So even the vacuum has energy associated with it. The more the universe expands, the more vacuum there is and hence the more dark energy available to create even more expansion. In other words, the rate of expansion of the vacuum is proportional to the amount of vacuum there is. This, by definition, creates an exponential expansion of the universe, called de Sitter expansion (after the physicist who first identified it).
