The Science of Interstellar

In March 2014, while I was writing this book, the CMB imprint was discovered by a team assembled by Jamie Bock (Figure 16.10),[30] a cosmologist down the hall from me at Caltech.

^{Fig. 16.10. The Bicep2 instrument, built by Jamie Bock’s team, that discovered the imprint of primordial gravitational waves. Bicep2, at the South Pole, is here shown at twilight, which occurs only twice a year at the South Pole. It is surrounded by a shield to protect it from radiation from the surrounding ice sheet. The upper right inset shows the measured imprint on the CMB: a polarization pattern. The CMB’s electric field points along the short dashed directions.}

It was a fantastic discovery, but with a cautionary note: the imprint that Jamie and his team found might possibly be due to something else and not gravitational waves. As this book goes to press, intense efforts are underway to find out for sure.

If the imprint is really due to gravitational waves from the big bang, then this is the type of cosmological discovery that comes along perhaps once every fifty years. It brings us a glimpse of the universe a trillionth of a trillionth of a trillionth of a second after the universe’s birth. It confirms theorists’ prediction that the expansion of the universe at that early moment was exceedingly fast, “inflationarily fast” in cosmologists’ jargon. It ushers in a whole new era for cosmology.

Having indulged my passion for gravitational waves, having seen how they could be used to discover Interstellar’s wormhole—and having explored the properties of wormholes, especially Interstellar’s—I now take you on a tour of the other side of the Interstellar wormhole. A tour of Miller’s planet, Mann’s planet, and the Endurance, which carries Cooper there.

V EXPLORING GARGANTUA’S ENVIRONS

17 Miller’s Planet

The first planet that Cooper and his crew visit is Miller’s. The most impressive things about this planet are the extreme slowing of time there, gigantic water waves, and huge tidal gravity. All three are related, and arise from the planet’s closeness to Gargantua.

The Planet’s Orbit

In my interpretation of Interstellar’s science, Miller’s planet is at the blue location in Figure 17.1, very close to Gargantua’s horizon. (See Chapters 6 and 7.)

^{Fig. 17.1. The warped space around Gargantua as seen from the bulk, with one space dimension omitted. Also, the orbits of Miller’s planet and the Endurance, parked and waiting for the crew to return.}

Space there is warped like the surface of a cylinder. In the figure, the cylinder’s cross sections are circles whose circumferences don’t change as we move nearer to or farther from Gargantua. In reality, when we restore the missing dimension, the cross sections are spheroids, whose circumferences don’t change as we move nearer or farther.

So why is this location different from any other on the cylinder? What makes this location special?

The key to the answer is the warping of time, which does not show up in Figure 17.1. Time slows near Gargantua, and the slowing becomes more extreme as we get closer and closer to Gargantua’s event horizon. Therefore, according to Einstein’s law of time warps (Chapter 4), gravity becomes ultrastrong as we near the horizon. The red curve in Figure 17.2, which depicts the strength of the gravitational force, turns sharply upward. By contrast, the centrifugal force that the planet feels (the blue curve) has a more gradually changing slope. As a result, the two curves cross at two locations. There the planet can travel around Gargantua with the outward centrifugal force balancing the inward gravitational force.

^{Fig. 17.2. The gravitational and centrifugal forces on Miller’s planet.}

At the inner balance point, the planet’s orbit is unstable: If the planet gets pushed outward a tiny bit (for example, by the gravity of some passing comet), the centrifugal force wins the competition and pushes the planet further outward. If the planet is pushed inward, the gravitational force wins and the planet is pulled into Gargantua. This means Miller’s planet can’t live for long at the inner balance point.