Discuss Guides

Alice and Bob Meet the Wall of Fire Discussion Guide


Bringing together the best and most interesting science articles appearing in Quanta Magazine over the past five years, Alice and Bob Meet the Wall of Fire reports on some of the greatest scientific minds as they test the limits of human knowledge. Topics include black holes and other physics, genetics and other biologies, artificial intelligence, and neurology.

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Discussion Questions


  • Of the three fundamental postulates mentioned in Jennifer Ouellette’s “Alice and Bob Meet the Wall of Fire” essay, which do you think will get axed first?
  • Beside quantum gravity, do you see any other possible uses for tensor networks?
  • How do you feel about the idea that we are a 3D hologram projected from a 2D surface?
  • Natalie Wolchover says, “Every measure involves many assumptions.” What other assumptions, not discussed in the book, do you notice on any of the theories covered in the book?
  • Supersymmetry theorist Nathan Sieberg says about the competing multiverse theory, “I wish it would go away.” What is the danger in scientists rooting for certain theories? Do you think it gets in the way, or do you think all scientists “face the facts” when presented with evidence contrary to their theory of choice?
  • If a multiverse like the one described by Peiris is proven, what could be a practical upshot?



  • What do you think of the Bohmian interpretation, the theory that every particle has a definite position whether observed or not? How often do you think scientific breakthroughs are impeded by a theory’s deformation from just one paper? Is there a way to prevent this?
  • What do you think about quantum reconstruction, the attempt to figure out why quantum has the rules it does? At what point does asking why become no longer useful?



  • Carlo Rovelli writes in his book The Order of Time that the arrow of time is dictated by entropy being lower in the past. This is a widely recognized, classical view. However, Loyd and Popescu assert that the overall entropy of the universe stays at zero; while it is that entanglement and equilibrium were lower in the past that dictates the arrow of time. Which of these views do you think holds more merit, and what do you think we need to solve in order to either reconcile these theories or discover which (if either) are correct?
  • George Musser states here in his chapter on time capsules, “These correlations seriously mess with our intuitions about time and space.” Do you understand how Olson & Ralph’s quantum time capsule would work? If so, how do you explain it to your book club members who are struggling? If not, what factors are you having trouble grasping?
  • Is there room in physics for philosophy?
  • Does the future exist?



  • Is a system of particles that experiences an “urge to preserve freedom of future action” alive? Why or why not?
  • Do you think scientists will ever be able to create life from scratch? Why or why not?
  • How do you feel about having eaten CRISPR-ized cells in your cheese and yogurt?
  • What are some different ways life could evolve on other planets? Would these chemical makeups give them an advantage or disadvantage compared to humans?
  • What would a world entirely without natural selection (i.e. death) look like?
  • How should sex be defined? As a catch-all term or as something that not every species undergoes?
  • Can you think of an example of or an explanation for evolution not becoming more complex over time? Are the simplest organisms the best at surviving?
  • Can you think of a scenario where sponges would shed their neurons? Why might they not need them?



  • Analyze your own loneliness: how much the lack of social interaction affects you. Now compare that to your perceived social rank. Do you see a connection to your response to loneliness and your social rank in the same way that Tye and Matthews saw the connection in mice?
  • Do you think that babies are born with the ability to react to faces, or do they develop it?



  • Can you think of types of intuition that you believe a machine (or neural network) will never be able to do as well as a human?
  • Brenden Lake points out that the way a machine learns to recognize a new letter of the alphabet is not the same way a child learns a letter. Do you see any other differences between machine learning and the way people (or animals?) learn?
  • What potential uses for the silver wire network do you foresee?
  • How important do you think it is for artificially intelligent machines to have artificial curiosity?
  • Can you think of any ways curious machines could be dangerous, like the self-driving delivery vehicle that is curious about leaves but is unable to make predictions about them?



  • Why do you think the first gravitational wave detected by LIGO just so happened to be a rare case? Was it luck or are we making assumptions?



  • At what point is enough enough? What if the next discovery is only one more project, dollar, or day away and you stopped looking too soon? How do you know when to stop looking for results?
  • For Einstein, spacetime was fundamental, but the present view sees spacetime as emergent out of quantum information. If this is true, what is truly fundamental and how can we test this?
  • Where do you think string theory has helped? And where do you think it has made understanding the natural world more confusing?
  • Ellis and Silk wrote, “The imprimatur of science should be awarded only to a theory that is testable.” What is your opinion on this?
  • Do you think an alternative to string theory might exist despite no one being able to suggest an alternative theory that unifies quantum mechanics and gravity? Or do you predict we’ll find further evidence that string theory is the correct theory? Or do you think maybe the two can’t be unified in a single theory at all?


This discussion guide was written by Fahrenheit: a pop science book club and may be used in book clubs and discussion groups everywhere with or without permission.


Book Club Menu: Yogurt, cheese, and the Cosmic Crisp apple
Book Club Tunes: The Slingshot Effect – Sunspot

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