The Science of Interstellar

This is rather like one of my favorite Escher drawings, Waterfall (Figure 30.6). Downward in the drawing is analogous to the forward flow of bedroom time, and the flowing water is analogous to the forward flow of local time. A leaf on the water is carried forward with the water just like signals in the bulk are carried forward in local time.

^{Fig. 30.6. Waterfall. [Drawing by M. C. Escher.]}

When carried by water down the waterfall, the leaf is like the light ray from the book to Cooper: It travels not only forward in local time but also downward (forward in bedroom time). When carried along the aqueduct, the leaf is like the gravitational signal from Cooper to the book: it travels forward in local time but upward[58] (so backward in bedroom time).

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.

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.