The Science of Interstellar

by Thorne, Kip

  How, in this interpretation, do I explain Amelia Brand’s description of time as seen by beings in the bulk? “To Them time may be just another physical dimension. To Them the past might be a canyon They can climb into and the future a mountain They can climb up.”

  Einstein’s laws, extended into the bulk, tell us that local bulk time can’t behave this way. Nothing in the bulk can go backward in local bulk time. However, when looking into our brane from the bulk, Cooper and bulk beings can and do see our brane’s time (bedroom time) behave like Brand says. As seen from the bulk, “our brane’s time can look like just another physical dimension,” to paraphrase Brand. “Our brane’s past looks like a canyon that Cooper can climb into [by traveling down the tesseract’s diagonal channel], and our brane’s future looks like a mountain that Cooper can climb up [by traveling up the tesseract’s diagonal channel; Figure 29.14].”

  This is my physicist’s interpretation of Brand’s words. And Chris interprets them similarly.

  Touching Brand Across the Fifth Dimension

  In Interstellar, with the quantum data safely in Murph’s hands, Cooper’s mission is finished. The tesseract, carrying him through the bulk, begins to close.

  As it is closing, he sees the wormhole. And within the wormhole, he sees the Endurance on its maiden voyage to Gargantua. As he sweeps past the Endurance, he reaches out and gravitationally touches Brand across the fifth dimension. She thinks she has been touched by a bulk being. She has . . . by a being riding through the bulk in a rapidly closing tesseract. By an exhausted, older Cooper.

  * * *

  56 Why leftward? So the tube is always at the same transverse position at any specific moment of bedroom time. Think about it.

  57 I can easily write down a mathematical description of spacetime warping that achieves this—a warping that bulk engineers could try to build to facilitate gravitational signals going forward in local bulk time, but backward relative to bedroom time; see the technical notes for this chapter, at the end of the book, especially Figure TN.1. Whether the bulk engineers could actually build this warping in practice depends on the laws of quantum gravity—laws that I don’t know, but TARS discovers in Gargantua’s singularity.

  58 Via an optical illusion.

  31

  Lifting Colonies off Earth

  Early in Interstellar, when Cooper first visits the NASA facility, he is shown a giant, cylindrical enclosure being constructed to carry thousands of humans into space and house them for many generations: a space colony. And he’s told there are others being constructed elsewhere.

  “How does it get off Earth?” Cooper asks the Professor. “Those first gravitational anomalies changed everything,” the Professor replies. “Suddenly we knew that harnessing gravity was real. So I started working on the theory—and we started building this station.”

  At the end of Interstellar we see everyday life back on even keel, inside the colony, floating in space (Figure 31.1).

  Fig. 31.1. Kids playing baseball inside the space colony, as seen by Cooper looking through a window. [From Interstellar, used courtesy of Warner Bros. Entertainment Inc.]

  How did it get lifted into space? The key, of course, was the quantum data (in my scientist’s interpretation, the quantum gravity laws) that TARS extracted from Gargantua’s singularity (Chapters 26 and 28) and Cooper transmitted to Murph (Chapter 30).

  In my interpretation, by discarding quantum fluctuations from those laws (Chapter 26), Murph learned the nonquantum laws that govern gravitational anomalies. And from those laws, she figured out how to control the anomalies.

  As a physicist, I’m eager to know the details. Was Professor Brand on the right track in the equations that covered his blackboards? (Chapter 25 and this book’s page at Interstellar.withgoogle.com.) Did he really have half the answer, as Murph asserted before getting the quantum data? Or was he way off? Is the secret to anomalies and controlling gravity something completely different?

  Perhaps a sequel to Interstellar will tell us. Christopher Nolan is a master of sequels; just watch his Batman trilogy.

  But one thing seems clear. Murph must have figured out how to reduce Newton’s gravitational constant G inside the Earth. Recall (Chapter 25) that the Earth’s gravitational pull is given by Newton’s inverse square law: g = Gm/r2, where r2 is the squared distance from the Earth’s center, m is the mass of the Earth, and G is Newton’s gravitational constant. Cut Newton’s G in half and you reduce the Earth’s gravity by two. Cut G by a thousand and you reduce the Earth’s gravity by a thousand.

  In my interpretation, with Newton’s G reduced inside the Earth to, say, a thousandth its normal value for, say, an hour, rocket engines could lift the enormous colonies into space.

  As a byproduct, in my interpretation the Earth’s core—no longer compressed by the enormous weight of the planet above—must have sprung outward, pushing the Earth’s surface upward. Gigantic earthquakes and tsunamis must have followed, wreaking havoc on Earth as the colonies soared into space, a terrible price for the Earth to pay on top of its blight-driven catastrophe. When Newton’s G was restored to normal strength, the Earth must have shrunk back to its normal size, wreaking more earthquake and tsunami havoc.

  But humanity was saved. And Cooper and ninety-four-year-old Murph were reunited. Then Cooper set out in search of Amelia Brand in the far reaches of the universe.

  Some Parting Thoughts

  Every time I watch Interstellar and browse back through this book, I’m amazed at the enormous variety of science they contain. And the richness and beauty of that science.

  More than anything, I’m moved by Interstellar’s underlying, optimistic message: We live in a universe governed by physical laws. By laws that we humans are capable of discovering, deciphering, mastering, and using to control our own fate. Even without bulk beings to help us, we humans are capable of dealing with most any catastrophe the universe may throw at us, and even those catastrophes we throw at ourselves—from climate change to biological and nuclear catastrophes.

  But doing so, controlling our own fate, requires that a large fraction of us understand and appreciate science: How it operates. What it teaches us about the universe, the Earth, and life. What it can achieve. What its limitations are, due to inadequate knowledge or technology. How those limitations may be overcome. How we transition from speculation to educated guess to truth. How extremely rare are revolutions in which our perceived truth changes, yet how very important.

  I hope this book contributes to that understanding.

  WHERE CAN YOU LEARN MORE?

  Chapter 1. A Scientist in Hollywood: The Genesis of Interstellar

  For readers interested in the culture of Hollywood and the shifting sands of moviemaking, I highly recommend two books by my partner, Lynda Obst: Hello, He Lied: & Other Truths from the Hollywood Trenches (Obst 1996) and Sleepless in Hollywood: Tales from the New Abnormal in the Movie Business (Obst 2013).

  Chapter 2. Our Universe in Brief

  For an overview of our entire universe with lots of great pictures, and with connections to what you can see in the night sky with your naked eye, binoculars, and telescopes, see Universe: The Definitive Visual Guide (Rees 2005). Many good books have been written about what happened in our universe’s earliest moments, its big-bang origin, and how the big bang may have gotten started. I particularly like The Inflationary Universe (Guth 1997); Big Bang: The Origin of the Universe (Singh 2004); Many Worlds in One: The Search for Other Universes (Vilenkin 2006); The Book of Universes: Exploring the Limits of the Cosmos (Barrow 2011); and Chapters 3, 14, and 16 of From Eternity to Here: The Quest for the Ultimate Theory of Time (Carroll 2011). For current research on the big bang, see the blog by Sean Carroll, Preposterous Universe (Carroll 2014) at http://www.preposterousuniverse.com/blog/.

  Chapter 3. The Laws That Control the Universe

  Richard Feyn
man, one of the great physicists of the twentieth century, gave a series of lectures for the general public in 1964 that delved deeply into the nature of the laws that control our universe. He wrote up his lectures in one of my favorite books of all time, The Character of Physical Law (Feynman 1965). For a more detailed, more up-to-date, and much longer book on the same topic, see The Fabric of the Cosmos: Space, Time, and the Texture of Reality (Greene 2004). Easier going, perhaps more fun, and equally deep is The Grand Design (Hawking and Mlodinow 2010).

  Chapter 4. Warped Time and Space, and Tidal Gravity

  For historical details on Einstein’s concepts of warped time and space, their connection to tidal gravity, and his relativistic laws built on these concepts, see Chapters 1 and 2 of Black Holes & Time Warps: Einstein’s Outrageous Legacy (Thorne 1994); and for a plethora of experiments that show Einstein was right, see Was Einstein Right? Putting General Relativity to the Test (Will 1993). “Subtle Is the Lord . . .”: The Science and the Life of Albert Einstein (Pais 1982) is a biography of Einstein that focuses in depth on all of Einstein’s contributions to science; it’s much tougher going and much more scholarly than Thorne or Will. There are other, more comprehensive biographies of Einstein—I especially like Einstein: His Life and Universe (Isaacson 2007)—but no other biography treats Einstein’s science with anything approaching the accuracy and detail of Pais.

  Gravity from the Ground Up: An Introductory Guide to Gravity and General Relativity (Schutz 2003) is an in-depth discussion of gravity and its roles in our universe (both Newtonian gravity and Einstein’s warped spacetime), written for the general reader. For the same material at the level of an advanced undergraduate physics or engineering student, I like the textbooks by James Hartle, Gravity: An Introduction to Einstein’s General Relativity (Hartle 2003), and by Bernard Schutz, A First Course in General Relativity (Schutz 2009).

  Chapter 5. Black Holes

  For greater detail on black holes and how we came to know the things we think we know about them, I suggest Gravity’s Fatal Attraction: Black Holes in the Universe (Begelman and Rees 2009), Black Holes & Time Warps (Thorne 1994), and a lecture that I gave in 2012 at Stephen Hawking’s seventieth birthday party: http://www.ctc.cam.ac.uk/hawking70/multimedia_kt.html. Andrea Ghez describes her team’s wonderful discoveries about the black hole at the center of our Milky Way Galaxy in a Ted talk at http://www.ted.com/speakers/andrea_ghez and on her team’s website, http://www.galacticcenter.astro.ucla.edu.

  Chapter 6. Gargantua’s Anatomy

  For properties of black holes that are featured in this chapter, see Chapter 7 of Black Holes & Time Warps (Thorne 1994), especially pp. 272–295; and at a more technical level, with equations, Gravity: An Introduction to Einstein’s General Relativity (Hartle 2003). Also see the appendix Some Technical Notes in this book. For the shell of fire and the orbits of photons temporarily trapped in it, see Edward Teo’s technical paper (Teo 2003).

  Chapter 7. Gravitational Slingshots

  For a discussion of gravitational slingshots at a modestly more technical level than mine, I recommend the Wikipedia article http://en.wikipedia.org/wiki/Gravity_assist. But don’t believe what it says about slingshots around black holes. Its statement (as of July 4, 2014) that “if a spacecraft gets close to the Schwarzschild radius [horizon] of a black hole, space becomes so curved that slingshot orbits require more energy to escape than the energy that could be added by the black hole’s motion” is just plain wrong. Indeed, you should always read Wikipedia with some cautious skepticism. In my experience, in areas where I am an expert, roughly 10 percent of Wikipedia’s statements are wrong or misleading.

  More reliable than Wikipedia for gravitational slingshots, but less comprehensive, is http://www2.jpl.nasa.gov/basics/grav/primer.php. A gravitational-slingshot video game has been developed in connection with Interstellar; see Game.InterstellarMovie.com.

  For a somewhat technical discussion of the intermediate-mass black holes that I invoke for gravitational slingshots, see Chapter 4 of Black Hole Astrophysics: The Engine Paradigm (Meier 2012).

  You can generate and explore complicated orbits around fast-spinning black holes, such as that in Figure 7.6, using a tool written by David Saroff and available at http://demonstrations.wolfram.com/3DKerrBlackHoleOrbits.

  Chapter 8. Imaging Gargantua

  Simulations of the gravitational lensing of star fields by black holes, similar to those that underlie Interstellar, have been carried out previously by a number of physicists and can be found on the web. Especially impressive are those by Alain Riazuelo; see www2.iap.fr/users/riazuelo/interstellar. See also the section on Chapter 28, below.

  Paul Franklin’s team and I plan to write several somewhat technical articles about the simulations that they carried out using the equations I gave them: the simulations underlying Interstellar’s images of Gargantua and its disk and the wormhole, and additional simulations that have revealed surprising things. You can access these articles on the web at http://arxiv.org/find/gr-qc.

  Chapter 9. Disks and Jets

  For in-depth discussions of quasars, accretion disks, and jets, see Gravity’s Fatal Attraction (Begelman and Rees 2009), Chapter 9 of Black Holes & Time Warps (Thorne 1994), and at a more technical and more detailed level, Black Hole Astrophysics (Meier 2012). For the tidal disruption of stars by black holes and the resulting accretion disks, see the website of James Guillochon (who, with colleagues, was responsible for the simulations that underlie Figures 9.5 and 9.6): http://astrocrash.net/projects/tidal-disruption-of-stars/. For astrophysically realistic film clips of accretion disks and their jets, I recommend some by Ralf Kaehler (Stanford University) at http://www.slac.stanford.edu/~kaehler/homepage/visual izations/black-holes.html, based on simulations by Jonathan C. McKinney, Alexander Tchekhovskoy, and Roger D. Blandford (McKinney, Tchekhovskoy, and Blandford 2012). For some images of accretion disks with Doppler shifts included as well as gravitational lensing, see the website of the astrophysicist Avery Broderick, http://www.science.uwaterloo.ca/~abroderi/Press/. The simulations that underlie Gargantua’s accretion disk in Interstellar (for example, Figure 9.9) will be described in one or more articles to appear at http://arxiv.org/find/gr-qc.

  Chapter 10. Accident Is the First Building Block of Evolution

  I don’t know any nontechnical discussions of the simulations that show the star density near a massive black hole growing, rather than decreasing. For a technical discussion and analysis, see Chapter 7 of Dynamics and Evolution of Galactic Nuclei (Merritt 2013), particularly Figure 7.4.

  Chapter 11. Blight

  If you watch the daily science news, or just observe the world around you, you’ll see examples of the kinds of scenarios that my biologist colleagues describe in this chapter—mild examples, thus far, fortunately; not catastrophic examples. A recent one is the amazing jump of a lethal virus from plants to honeybees, http://blogs.scientificamerican.com/artful-amoeba/2014/01/31/suspicious-virus-makes-rare-cross-kingdom-leap-from-plants-to-honeybees; this was a far bigger jump than that from okra to corn in Interstellar, but a far less lethal pathogen. Another example is the rapid demise of tree species once dominant on the American scene: not only the American chestnut tree mentioned by Meyerowitz in Chapter 11, but the American elm tree, http://landscaping.about.com/cs/treesshrubs/a/american_elms.htm, and the giant pine trees around my cabin on Palomar Mountain, near the 200-inch telescope.

  Chapter 12. Gasping for Oxygen

  The cycling of oxygen between the breathable oxygen molecule O2, and carbon dioxide CO2, and also (more slowly) other forms, is called the Earth’s “oxygen cycle.” Google it. The cycling of carbon between CO2 in the atmosphere, plants (dead and alive), and also (much more slowly) other forms such as coal, oil, and kerogen, is called the “carbon cycle.” Google it, too. Obviously these cycles are coupled; they influence each other. They are the foundation for Chapter 13.

  Chapter 13. Interstellar Travel

&n
bsp; Exoplanets (planets beyond our solar system) are being discovered at a furious pace. Nearly complete catalogs, updated daily, are at http://exoplanet.eu and http://exoplanets.org. A catalog of exoplanets that could be habitable is at http://phl.upr.edu/hec. For the human side and history of the search for exoplanets and life beyond the solar system, see Mirror Earth: The Search for Our Planet’s Twin (Lemonick 2012) and Five Billion Years of Solitude: The Search for Life Among the Stars (Billings 2013); for technical and scientific details, see The Exoplanet Handbook (Perryman 2011). Confessions of an Alien Hunter: A Scientist’s Search for Extraterrestrial Intelligence (Shostak 2009) is an excellent description of the search for extraterrestrial intelligence (SETI) via radio signals from beyond Earth and by other methods.

  For information about technologies that we humans could pursue in our quest for interstellar travel, I suggest http://en.wikipedia.org/wiki/Interstellar_travel and http://fourthmillenniumfoundation.org. The astronaut Mae Jemmison is spearheading a quest to send humans beyond the solar system in the next century; see http://100yss.org. A lot of nonsense is written about interstellar travel via warp drives and wormholes. The technology of this century and likely the next few is incapable of any realistic effort in this direction, unless some far more advanced civilization provides us with the necessary spacetime warps, as in Interstellar. So don’t waste your time reading articles and claims about us humans producing strong enough warps for interstellar travel in your lifetime or that of your great-grandchildren.