The Science of Interstellar

His equation contains lots of guessing: guesses for the things called “U(Q), H_ij(Q²), W_ij, and M(standard model fields)” on his blackboard (Figure 25.7). In effect, these are guesses for the nature of the bulk fields’ force lines, and how they influence our brane, and how fields in our brane influence them. (For more explanation see Some Technical Notes at the end of this book.)

When the Professor and his team speak of “solving his equation,” in my extrapolation they mean two things. First, figure out the right forms for all these things they are guessing: “U(Q), H_ij(Q²), W_ij, and M(standard model fields).” Second (following the well-known procedure), deduce, from his equation, everything he wants to know about our universe, about the anomalies, and most important, about how to control the anomalies so as to lift colonies off the Earth.

When characters in the movie speak of “solving gravity,” they mean the same thing.

In the movie, when the Professor is very old, we see him and grown-up Murph trying to solve his equation by iterations. On a blackboard, they make a list of guesses for the unknown things (guesses that I wrote on the board just before the scene was filmed; Figures 25.8 and 25.9). Then, in my extrapolation, Murph inserts each guess into a huge computer program that they’ve written. The program computes the physical laws for that guess, and those laws’ predictions for how the gravitational anomalies behave.

^{Fig. 25.8. I ghost-write iterative guesses on the Professor’s blackboard.}

^{Fig. 25.9. Murph contemplates the list of iterative guesses. [From Interstellar, used courtesy of Warner Bros. Entertainment Inc.]}

In my extrapolation, none of the guesses predicts anomalies that look anything like the observations. But in the movie, the Professor and Murph keep trying. They keep iterating: making a guess, computing the consequences, abandoning the guess, and going on to the next guess, one guess after another after another after another, until exhaustion sets in. Then they begin again the next day.

A bit later in the movie, when the Professor is on his deathbed, he confesses to Murph: “I lied, Murph. I lied to you.” It is a poignant scene. Murph infers that he knew something was wrong with his equation, knew from the outset. And Dr. Mann tells the Professor’s daughter as much in an equally poignant scene on Mann’s planet.

But, in fact—Murph realizes, soon after the Professor’s death—“His solution was correct. He’d had it for years. It’s half the answer.” The other half can be found inside a black hole. In a black hole’s singularity.

26 Singularities and Quantum Gravity

In Interstellar Cooper and TARS seek quantum data inside Gargantua, data that could help the Professor solve his equation and lift humanity off Earth. The data, they believe, must reside inside a singularity that inhabits Gargantua’s core—a “gentle” singularity, Romilly predicts. What are the quantum data? How could they help the Professor? And what is a gentle singularity?

The Primacy of Quantum Laws

Our universe is fundamentally quantum. By this I mean that everything fluctuates randomly, at least a little bit. Everything!

When we use high-precision instruments to look at tiny things, we see big fluctuations. The location of an electron inside an atom fluctuates so rapidly and so randomly, that we can’t know where the electron is at any moment of time. The fluctuations are as big as the atom itself. That’s why the quantum laws of physics deal with probabilities for where the electron is and not with its actual location (Figure 26.1).

^{Fig. 26.1. Probability for electron’s location inside two different hydrogen atoms. The probability is big in the white regions, smaller in the red, and very small in the black. The numbers (3,0,0) and (3,2,0) are the names of the two atoms’ probability pictures.}