Interstellar: Wormholes and Intergalactic Travel – A: Background

Interstellar: Wormholes and Intergalactic Travel – A: Background


Howard Adelman

WARNING: This blog may make you dizzy and may be a hazard o your sense of balance, especially if you are resting on a Sunday morning.

Interstellar began with the postulate that drought, alternating with severe windstorms and then a blight infection, had ended the possibility of life on Earth. When we were in Marin County, it was pouring after years of drought. This was the case in Israel. In many situations, we have been torn between the optimism of nature’s eternal return and the pessimism that the end is near. This was especially true of agricultural societies, like the various ethnic groups that had settled in pre-conquest Mexico and that we learned about when we visited the second floor of the Museum of Anthropology in Mexico City on Friday. We are always condemned to fight our way past these two extreme possibilities or opt for flight as a third option. This very highly improbable conjunction of events provides the backstory for the movie.

If the relatively high altitude of Mexico City affects cardiovascular functions and the production of red blood cells in the body, think what long term space flight would induce – not only these results, but muscle and skeletal deterioration. After just flying from Oakland to Mexico City, my nails seemed to grow longer, but also more brittle; usually one nail fractures after a long flight, and one did. In space, a traveler is faced with not just reduced air pressure, but with no air pressure – a vacuum – not to count extreme cold (and sometimes extreme heat) and greatly increased radiation. The perils make Odysseus passing between the six-headed monster, Scylla, and the whirlpool of Charybdis seem like child’s play. Except, of course, if the whirlpool, like a wormhole, is seen as an opportunity rather than a terrible danger. I thought about this all week and the fact that I never finished my review of Interstellar by writing on the science in the film. Since our personal odyssey in Mexico City ended with a full day at the artisans market on Saturday, and we did not even make it to the Frida Kahlo Museum, I will finish my commentary on Interstellar, specifically on the science in that fictional odyssey, first by first providing some background and then, subsequently, commenting more directly on the science in the movie.

I have never seen a movie so packed with basic physics and biology as Interstellar. No wonder Kip Thorne wrote a whole book, The Science of Interstellar, discussing that science. (For a more professional perspective on that science, read Neil deGrasse Tyson’s commentary: I have relied on Thorne’s book a great deal in my comments, but since I am not a physicist I am bound to have made mistakes in my interpretation and welcome corrections.) As discussed in the last blog on the movie, given our present knowledge, the only possible way to reach another planet outside our solar system would take generations and require “generational” spacecraft. Alternatively, suspended animation could be employed. Frozen embryos could as well. Interstellar employs the last two techniques along with a third one. The major innovation utilized is not to travel to a planet in one of the nearby stars in our galaxy, but extend the human lifespan based on a warp in space-time by traveling to another galaxy through a wormhole.

Rather than traveling to another star in The Milky Way, it may be easier to travel to a planet in another galaxy millions or even billions of light years away taking advantage of space-time curvature. (Remember, a light year is the distance traveled in one year moving at the speed of light.) The latter is the proposition, and a valid, though almost impossible and unlikely, scientific premise of the movie, Interstellar. Further, understanding the science is important, otherwise you will be prone to make mistakes. Though as you shall see, I think the movie strays too often from science fiction into science fantasy, I disagree with David Denby’s review in The New Yorker. He wrote without elaboration: “the final third goes into pure science fantasy – and changing what we know about black holes.” It does not.

Interestingly, though the production of the movie induced Kip Thorne to make some scientific discoveries on how black holes work, which he will write up as technical papers for publication, the movie claims to stay within what is known, what is a possible expectation (an educated guess) and what is, at least, not impossible according to today’s scientific understanding. With respect to the latter, the film, in spite of its heavy science overload, does not, like the TV series Star Trek, introduce new scientific concepts that Star Trek did, such as a “warp drive” that would allow a space ship to move faster than light, a concept that previously was widely considered a scientific impossibility. In the development of cosmic theories, the imaginative leap of conceiving of a “warp drive”, however, influenced the development of Alcubierre’s theory.

The latter theory, and the concept of what became known as an Alcubierre drive, is named after the physicist, Miguel Alcubierre, who proposed a theoretical model of how a spaceship might be able to travel faster than light, in fact, considerably faster. It became the main competitor to the traversable wormhole as the mode by which intergalactic flight could proceed by taking advantage of the space-time warp. This movie roots its science in the concept of a wormhole. It helps to understand that choice if it is to be considered an alternative.

The choice might be seen analogous to an eighteenth century scientist wondering whether, in order to get to China from North America, it would be faster to fly into space and land on the other side of the earth in twelve hours or, alternatively, drill a hole through the centre of the earth to lessen the distance considerably. The first depends on increasing speed. The second depends on reducing distance. The traversable wormhole is analogous to reducing distance. Using a thruster that can propel an object much faster than the speed of light increases speed. Without a radical solution to either problem, space travel outside our solar system is, de facto, impossible. Look at how long it took Voyager I to travel from Earth to slip around Jupiter within just one solar system in just one galaxy. A laser-powered spaceship with sails traveling at one-tenth the speed of light would take almost half a century just to reach the nearest galaxy.

On the other hand, note that wormholes are theoretical only. None have been found. It is difficult to understand how one could be created naturally. Nor can one easily imagine creating one since we live in four dimensions and would have to enter into at least a fifth dimension first to create the wormhole. Finally, even in theory, a traversable wormhole is only a Planck length, that is 0.000000000000000000000000000000001 centimetres, a hundredth of a billionth of a billionth the size of the nucleus of an atom. So we would have to have a means of enlarging it to human dimensions, an enormous scale of enlargement akin to stretching a nylon stocking from New York to Jupiter AND back. Assuming it did not fracture or split or explode, once enlarged, there has to be a system of holding the mouth of the hole open. How could this be done? By threading the opening with exotic matter, if that could be found, and then only by getting outside our dimension in the first place to carry out the action, theoretically in an area where exotic matter was to be found. According to what we know now, this is impossible. Once again, we are in the realm of science fantasy rather than science fiction, especially since Professor Brand in the movie envisions that “They” hold the wormhole open.

Given the virtual impossibility of any one of these steps, let alone the combination, Interstellar opted out of the problems altogether and simply stated that a wormhole had been found within our solar system of suitable size and with its mouth wide open. Now this is fiction based on no known reality or even reasonable scientific possibility. But it is not absolutely scientifically impossible.

Since the astronomer, Edwin Hubble, just under a century ago, established that all stars were not part of the same galaxy, we have learned that there are about a trillion galaxies. Our sun resides in one of those trillion galaxies. Our sun is a relatively medium sized star among up to 400 billion stars in the Milky Way galaxy alone. Our galaxy is 100,000-120,000 light years in diameter. That is, it takes over a hundred thousand years for light to travel across our galaxy from one side through the centre to the other side. Our solar system is located about half way between the circumference and the centre in the Milky Way galaxy. The universe is simply humungous. Just to travel outside our solar system requires either increasing speed enormously or reducing distance. Further, the little we know about the universe relates to matter that makes up only 5% of the universe. The rest is either dark matter – 27% – or dark energy – 68% – of which we know almost nothing. So science fiction relies on our tremendous ignorance about the universe much more than on what is known.

Galaxies are found in clusters. Our galaxy is part of the Virgo Supercluster that, in turn, is but a small part of a much larger Laniakea Supercluster. So how can one possibly travel from one galaxy to another? It is theoretically possible because of the relatively recently discovered space-time warp. (Cf. Stephen Hawking, Thorpe went further and relied on gravitational waves or ripples in the space-time continuum resulting from a collision of two black holes in outer space that tore a neutron star apart and, thereby, allowed Dr. Brand, when he was a young scientist using a Laser Interferometer Gravitational Observatory, to detect that a wormhole had been created within our galaxy near Saturn by a burst of very high energy gravitational waves that were detected when a small proportion of those waves were captured by the wormhole. Except that whole rationale was excised from the movie in the fear that too much science would deaden the impact. Hence the discovery of the wormhole was really left unexplained.

But black holes and their singularities, wormholes and gravitational anomalies were all envisioned as possible by Stephen Hawking’s concept of the space-time warp. To take one example of a gravitational anomaly within our solar system, the precession of Mercury, that is, its shift in orientation of its rotational axis, does not follow Newton’s Law of gravity precisely, even though the deviation is extremely miniscule, This year, actual gravitational waves related to gravitational anomalies were probably detected indirectly (still to be confirmed), though the imprint takes place on electromagnetic waves. However, the anomalies presumed in Interstellar are totally fictitious, such as the way the tractors and harvesters converge on Cooper’s farmhouse because of a distortion in the GPS system. (I wanted to say that it was just me doing the navigation.) Another takes place when the dust settles in Murph’s library to form a bar code. None of these are scientifically plausible. Unless, of course, Professor Brand’s theory of “They” in the fourth dimension of space produce a gravitational anomaly that reads like the effects of an electromagnetic field and establishes that Einstein’s theory of gravity as a constant (G) is incorrect.

(No, I have not yet seen The Theory of Everything, the recent non-science fiction movie about Hawking’s twenty-five year marriage. Hopefully, it is as good as Ron Howard’s Academy Award-winning 2001 movie, A Beautiful Mind, that starred Russell Crowe as the brilliant mathematician at Princeton, John Nash, who won the Nobel Prize for economics, of all things, for his contributions to game theory. I also expect A Theory of Everything will be more accurate in reflecting the main protagonist’s life and in expressing the science.)

Albert Einstein in his General Theory of Relativity discovered that space (and time) were curved. Einstein did not, nor, I believe, do the majority of theoretical and astro-physicists, believe that time travel to the past is possible, as Stephen Spielberg’s science fantasy comedy, Back to the Future, envisioned. There are many reasons, even though, according to the General Theory of Relativity, it is possible to envision a space-time bubble in which travel could take place even faster than the speed of light. There are at least three reasons why such a project would be impossible. First, the energy produced would burn up the spaceship. Secondly, the spaceship would be subject to the enormous forces of Hawking radiation. Third, it would be impossible to guide the spaceship as the signal ahead of the spaceship would have to travel faster than the spaceship itself and then it would be impossible for the astronaut to guide the ship. Relativity, though envisioning time as a fourth dimension, presumes that time only travels forward even though we look backward in time when we see light arrive from faraway stars.

(For a much more extensive examination of this question, see the special issue of Scientific American on A Question of Time: The Ultimate Paradox. See also Roberto Mangabeira Unger and Lee Smolin (2014) The Singular Universe and the Reality of Time: A Proposal in Natural Philosophy. These writers argue that there is only one universe at a time since Time is real. As Heraclitus argued, all is change. Mathematical theory is subordinate to this reality. Time travel to the past is theoretically possible in theoretical physics rooted in mathematics; it is impossible in nature, not just technically impossible, but conceptually impossible.)

The movie does not envision time travel, though time is slowed down for the astronauts. Time travel is science fantasy. The changing speed of time is another matter. This movie is supposedly science fiction. Traveling through a wormhole is the enormous conceit of the movie. For, until now, no one has ever seen a wormhole. However, if the theoretical postulate of a wormhole could be discovered, and discovered within our galaxy, for the travel envisioned in Interstellar, the energy requirement of a macroscopic spaceship would be reduced enormously, analogous to reducing the energy requirements from the mass-energy of Jupiter to the energy that was needed by Voyager I.

So should or could spaceships rely on spatial distortion to achieve the goal of intergalactic travel or on much more powerful thrusters, such as an envisioned quantum vacuum plasma thruster? The movie does not explore options, but elects a theoretically feasible route permitted by mathematical equations. Of course, if the alternative of enormously more powerful thrusters were feasible, such as the use of quantum vacuum fluctuations or through a pre-selected shaping of the electric field (a Serrano Field Effect Thruster) to develop enough thrust to propel the spacecraft, then the spacecraft would not be required to carry any propellant, almost a prerequisite to envisioning the kind of space travel envisioned in Interstellar.

So which direction do we take – search for a feasible faster-than-light (FTL) or superluminal thrust for both movement and communications, or a mode of travel that takes advantage of folds in the space-time continuum using the energy produced within the hole to get through it? That is, if an unusually distorted region of space-time of a wormhole could be located – the movie presumes one was found near Saturn – then a spacecraft, while traveling to the rim of the wormhole, would have to use normal subluminal rocket thrust to reach the edge of the wormhole, and could do so in far less time than light takes to travel to reach a very distant location. In other words, do not try to travel much faster than light; try to envision a way of making the distance very much shorter.

But why a wormhole? Why not a black hole? Why could this method not also be used in traveling into a dark hole? After all, wormholes are only theoretical. Black holes have been proven to exist. Theoretically, a black hole could be used, as the physicist Harold White showed a decade ago. For the spacecraft would develop energy akin to dark energy characteristic of black holes without requiring NASA or another space agency to harness exotic matter to produce the enormous amounts of energy required for a superthruster. Many black holes have been located, unlike any wormhole.

Ironically, I just read a report that, for the first time, astronomers are on the verge of getting their first image of the supermassive black hole at the centre of our galaxy, the Milky Way. Black holes are billions of times more massive than our sun with so much energy that they effect and distort the host galaxy within which they are found. With energy so powerful, a black hole occupies very little space. Since it does not emit light but sucks in light and even whole stars, no one has previously been able to actually observe a black hole.

However, using massive computer power and a world-wide cooperative effort and multiple telescopes coordinated by MIT’s Haystack Observatory using the Event Horizon Telescope, it seems like the first picture of a black hole, or, at least, the event horizon of a black hole, the one in the region of our galaxy known as Sagittarius A that emits a complex radio source, will soon be available for viewing. We will have another important proof of Einstein’s Theory of General Relativity.