The Science of Interstellar

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

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.

Chapter 14. Wormholes

For greater detail on wormholes, I especially recommend Lorentzian Wormholes: From Einstein to Hawking (Visser 1995), despite its being nearly twenty years old. I also recommend the last chapter of Black Holes & Time Warps

(Thorne 1994), Chapter 9 of Time Travel and Warp Drives (Everett and Roman 2012), and Chapter 8 of Black Holes, Wormholes, and Time Machines (Al-Khalili 2012). For an up-to-date discussion of the exotic matter required to hold a wormhole open, see Chapter 11 of Time Travel and Warp Drives (Everett and Roman 2012).

Chapter 15. Visualizing Interstellar’s Wormhole

Paul Franklin’s team and I give much greater detail about our work on wormhole visualization in one or more articles that we plan to make available on the web at http://arxiv.org/find/gr-qc.

Chapter 16. Discovering the Wormhole: Gravitational Waves

For up-to-date information about LIGO and the search for gravitational waves, see the website of the LIGO Scientific Collaboration, http://www.ligo.org, especially the “News” and “Magazine” sections; also the LIGO Laboratory’s website http://www.ligo.caltech.edu, and also Kai Staats’s 2014 movie at http://www.space.com/25489-ligo-a-passion-for-understanding-complete-film.html. On the web you can also find a number of pedagogical lectures by me about gravitational waves and the warped side of the universe, for example my three “Pauli Lectures” at http://www.multimedia.ethz.ch/speakers/pauli/2011, which should be watched in the opposite order to their listing (that is, from the bottom, upward); and at a moderately technical level, http://www.youtube.com/watch?v=Lzrlr3b5aO8. For movies of black-hole collisions and the gravitational waves they emit, based on the SXS team’s simulations, see http://www.blackholes.org/explore2.html.