The Science of Battlestar Galactica

by Di Justo, Patrick

  Wait, it gets better.

  The executive producer Ron Moore wanted to set the action of this episode in the cloud layers of a Jovian planet because he envisioned Vipers and Cylon Raiders playing their game of cat and mouse, ducking in and out of different cloud layers—re-creating the feel of classic submarine movies like Run Silent, Run Deep. He couldn’t have picked a better spot. Within Jupiter’s atmosphere, like Earth’s, there are clouds at different levels. Unlike Earth, where all the clouds are water vapor or ice crystals, having the same composition whether solid or liquid, Jupiter’s cloud layers have different compositions and different colors. The outermost clouds are composed of white ammonia crystals. Impurities within the ammonia give these clouds a yellowish or beige tinge. Deeper is a layer of rust-colored clouds of ammonium hydrosulfide. Deeper still is a cloud deck composed primarily of water.

  Wait, it gets even better.

  The primary point of the episode “Maelstrom” is that this planet is where Kara Thrace finally meets her destiny—a destiny that, according to the Cylon Leoben, has “already been written.” Again, a more perfect setting could not have been chosen.

  If the planet is rotating, and Jovian planets tend to rotate very rapidly, the planet’s clouds will separate themselves into bands called belts and zones; these counterrotating wind patterns run parallel to a planet’s equator, and are not unlike the trade winds and westerlies on Earth. These belts and zones also segregate into clouds at different elevations. Zones have the higher clouds, and they are composed mostly of those white ammonia crystals; belts are deeper and are composed of rusty ammonium hydrosulfide clouds (we see this with Jupiter and with the gas giant planet in Kara’s vision in “He That Believeth in Me”).

  Also, as on Earth, storms occasionally spiral through the tropics: the Great Red Spot on Jupiter—also known as the Eye of Jupiter—is a huge anticyclone, at least four hundred years old, and large enough to hold the four inner planets of our solar system! When the Voyager 2 spacecraft passed Neptune in 1989, it saw a similar storm that was “only” the size of Earth that scientists called “The Great Dark Spot.”

  If Kara’s storm on Maelstrom were anything like hurricanes on Earth, then peering into the eye of the storm, we could glimpse successively deeper layers of clouds. Framed within the nearly circular shape of the eye, the beige/yellowish white ammonia clouds would blend into the reddish ammonium hydrosulfide clouds. Looking deeper still, by the time we could see down to the clouds of water vapor, the light levels would be very low, nearly extinguished. The clouds would tend to look bluish. In summary, we would see a storm with concentric rings of blue, then red, then yellow. Does this sound even remotely familiar?

  Starbuck’s apartment on Caprica, the Mandala painted on her wall.

  Leoben was right. Kara’s destiny had, in fact already been written. The painting on the wall in her apartment on Caprica—which we first saw in “Valley of Darkness”—turns out, entirely by coincidence, to be a painting of a cyclonic storm on a Jovian planet. Over her entire life Kara foresaw the place where she would meet her destiny. Serendipity.‹

  One possibility is that Titan has an active geology, complete with a warm interior that gives rise to volcanoes. Not the volcanoes we have here on Earth, but another type of volcanoes altogether. Titan has cryovolcanoes.

  Here on Earth, a volcano is where incredibly hot liquid lava spews out of an opening in the planet’s crust and eventually solidifies into rock. Titan is so cold that liquid water just a few degrees above freezing is equivalent to an exotic hot material like lava. Titan’s cryovolcanoes spew a liquid mix (water, methane, and ammonia) out of openings in the moon’s crust. These form clouds, which eventually rain (or drizzle) their hydrocarbons into the lakes of Titan. The rest eventually freezes into a solid material (ice).

  On Earth a magma chamber is a subsurface cavity filled with molten rock under tremendous pressure. A volcanic eruption occurs when the molten rock is able to force its way to the surface. Consider a magma chamber on Titan. If ice is a rock in the outer solar system, then water can be considered magma. If cryovolcanoes on Titan spew water, ammonia, and hydrocarbons, and we recall that NASA’s search for life in the universe begins with a search for liquid water, then a magma chamber on a moon like Titan would be a possible abode for life.

  CHAPTER 18

  Black Holes

  In the episode “Daybreak, Part I,” Raptor pilots Racetrack and Skulls, both participants in Felix Gaeta’s mutiny, are paroled to undertake the dangerous mission of locating the Cylon Colony. On one sortie, they jump into what they initially think is an asteroid field. A sudden jolt and SINGULARITY DETECTED flashing on their DRADIS screen tells them that they’re actually in an accretion disk of . . . something. Skulls calls it a singularity; Racetrack calls it a black hole. During a later briefing, the terms are used interchangeably: Starbuck calls the object a naked singularity, while Apollo says that the colony is “bound within the gravity well of a black hole.” What is the difference? Is there a difference?

  Black holes have been called many things: “a hole in space,” “a monster that eats everything,” “a sphere of no return.”1 They are almost always places where the collapsing core of a star that has gone supernova has attained nearly infinite density, creating a place where the mathematics of modern physics breaks down—a singularity. The Cylon Colony was in a stable orbit around a singularity. How is such a thing possible? Why wouldn’t the Colony get sucked instantly into the black hole?

  Admiral William Adama.

  XO Saul Tigh.

  Contrary to popular belief, a black hole is not an insatiable vacuum cleaner, sucking in everything in the universe. If our Sun were magically replaced by a black hole of the same mass, Earth and other planets would continue in their orbits like before. ce So the Cylon Colony and its Raiders, Galactica and her Raptors, could all fly around the accretion disk as long as they didn’t get too close to the black hole. But how close is too close?

  In the Eastern Front trenches of World War I, Karl Schwarzschild, a German astrophysicist serving as an artillery lieutenant, wrote a paper in which he calculated exactly what “too close to a black hole” means.cf Black holes are called black because their gravitational fields are so powerful that near the singularity nothing, not even light, is able to escape. How close can an object get before it is forever trapped within the clutches of a black hole’s gravity?

  To be forever trapped by a black hole, an object would have to be unable to reach escape velocity. The escape velocity for a black hole—or any body like a planet or a star that has gravity—is simply a measure of the velocity cg an object, like a spacecraft, must attain to break free of its gravitational hold, and is given by

  Where ve is the escape velocity, G is the universal gravitational constant, M is the mass of the body, and r is the radial distance from body center. Any NASA spacecraft bound for another planet must first escape Earth’s gravity by reaching escape velocity, which is 11.2 km/s. For a black hole, this is obviously much higher.

  The escape velocity for a black hole depends solely on the mass of the black hole, not upon the mass of the object trying to escape; therefore, a black hole’s escape velocity is the same for a spacecraft, an atom, or even photons. The speed of light is a universal speed limit. If we determine the proximity to a black hole where the escape speed is equal to the speed of light, we have determined “the point of no return” or the point where nothing can escape.ch

  An examination of Schwarzschild event horizons for black holes of varying masses leads to a startling observation: Look at how small these event horizon radii are! Think about this for a moment. If our Sun were to become a black hole, you would have to be slightly less than 3 km away to get close to the event horizon.

  Mass of Black Hole Schwarzschild Radius/ Event Horizon

  1 Earth 8.75 mm

  1 Sun 2.95 km

  4 Suns 11.8 km

  10 Suns 29.5 km

  100 Suns 295 km

>   1000 Suns 2950 km

  But what if . . . ?

  Recall that in “Daybreak, Part I” Starbuck said that Galactica would face a different jeopardy from the singularity the Cylon Colony orbited: “The tidal stresses are too strong, tear the ship apart before we got within 10 SU.” A spacecraft near a strong source of gravity like a black hole that also has a large gravity gradient will experience a tidal force—when the gravitational force on the part of the spacecraft nearest the black hole is significantly greater than on the trailing edge. When you stand outside at noon, with the sun directly overhead, the sun’s gravity is pulling on your head ever so slightly more than it is pulling on your feet. The difference is unnoticeable for something as small as a person, but over the length of something the size of Galactica, the tidal effect of a black hole makes the ship even more fragile than you are!

  What would happen as Galactica approached the event horizon of a 10-solar-mass black hole? Assume that the hull of the ship can withstand a force of 6,000 kilograms per square meter per second before it breaks apart. How close can Galactica approach before being torn apart? A Raptor? You?

  How close to a black hole is too close?

  When approaching a black hole, remember this simple rule: a small object like a person can get much closer to a black hole before getting torn to shreds. In our 10-solar-mass black hole example, when comparing any two objects, the smaller object gets closer to the event horizon every time, yet all three objects undergo “spaghettifaction”—they are pulled apart lengthwise—long before reaching that point. Comparing the graph on this page to the Schwartzschild Radii in the table on page 179, we see that for a 10-solar-mass black hole, even something as small as a Raptor is torn apart by tidal stresses before reaching the event horizon. From this table we also see that Starbuck’s comment about the ship being torn apart before getting within 10 SU was clearly hyperbole, even given Galactica’s compromised structural integrity.

  As we saw in “Daybreak,” that intense gravitational field of a singularity also creates an infalling spiral of matter and energy—an accretion disk. Recall that the Cylon Colony was in a stable orbit within the accretion disk surrounding a singularity. That orbit might best be described as “stable, with a lot of work.” Gas drag, as well as the action of all those particles in the accretion disk impacting the Colony, would change its momentum and perturb its orbit in short order. Only by constantly compensating for that change in momentum could the Colony be said to have a stable orbit.

  NAKED SINGULARITIES

  We’ve discussed singularities, but Starbuck said that the object Racetrack and Skulls found was a naked singularity. What makes it different from other singularities?

  Stars spin. Their cores spin. When a star explodes, the remnants of the star retain their spin, and so the resulting singularity also spins. It turns out that if a singularity is spinning fast enough, a relativistic effect called frame-dragging can leave it without an event horizon, exposed to the universe. This may not sound like a big deal until you realize that although the event horizon normally shields the universe from a singularity, it also shields the universe from the effects of a singularity. Within a singularity, matter becomes so dense, and the gravitational field so powerful, that the laws of the Standard Model of Physics, and the graceful equations that go with them, all break down. As the physicist Pankaj S. Joshi of the Tata Institute in India puts it, singularities ci “are places of magic, where science fails.”

  Places of magic??? Where science fails?!?! Yes. At a singularity, the density of matter and the strength of gravity are immeasurable. Literally anything could happen. New universes could be created. Giant gravity waves could come crashing out. Trillions and trillions of bunny rabbits could appear. Protons and neutrons could simply cease to exist. Literally anything.

  For the most part this is not a problem, since most singularities are surrounded by an event horizon. Anything on the other side of the event horizon effectively disappears from our universe forever, erased from our space-time as if it had never existed in the first place. The singularity’s new universes, gravitational waves, and bunnies can never have any effect on our universe.

  However, a naked singularity does not have an event horizon. You could fly right up to the edge of the singularity and fly back out again. Gravitational tidal forces permitting, of course. While you were there, you would be subject more to the laws of magic than of physics.

  You might even come back with a new body in a brand-new Viper.

  In the case of black holes, the accretion disk is formed by whatever gas and dust are available in the nearby stellar neighborhood, cj pulled in to the black hole not only by its gravity, but by its magnetic field as well. These particles slam into each other as they spiral into the black hole, and the resulting friction makes them glow. As they spiral in toward the black hole, the particles of gas and dust get hotter and hotter until they begin to emit X-raysck just before they reach the event horizon.

  Raptors are FTL-capable and, as such, could theoretically enter the event horizon of a black hole, and exit again. If somehow you could make it all the way through the event horizon and withstand the tidal stresses, what would you see?

  Nothing. That is, nothing unusual.

  You wouldn’t necessarily know you had even crossed the event horizon. Light from the outside universe would still continue to reach you. It would be Doppler-shifted away from you, and it would seem to be less intense than it was, but it would be there until you reached the singularity, the place at the center of a black hole where the original matter of the star now has infinite density and zero volume. What happens when you reach that point? No one knows. However you managed to survive the tidal forces, you’d never survive the singularity. Is the singularity the end of your existence, or is it a portal to another universe? If it is a portal, and if you somehow could traverse it, would you remain who you are?

  CHAPTER 19

  There’s No Sound in Space, and No Color, Either

  It was one of the most thrilling moments of the show: Apollo is flying through the Ionian Nebula, ready to do battle with the Cylons, when suddenly Starbuck’s Viper—which he had seen destroyed a few months before—appears next to his. Shaking off his shock and relief, Apollo manages to banter (and, predictably, argue) with Kara as they fly through the tendrils of colored gas in the nebula.

  Scenes like this are ruining the field of amateur astronomy.

  Amateur astronomers are people who study the night sky because they want to. They load up their cars and travel dozens or even hundreds of miles away from the light pollution of the cities and suburbs to a place out in the country with dark skies. There they unpack their telescopes—which they know how to dismantle and reassemble in the dark—and hold observing sessions, known as star parties, for the general public.

  Amateur astronomers bring their telescopes wherever people have shown the slightest interest at looking at the night sky: after-school events, overnight Scouting campsites, even daytime street fairs, where they swaddle their telescopes in insulation and filters to show off the Sun. At these star parties, children eager to learn about the wonders of the universe—and parents eager to recapture their own lost wonder—patiently wait in line for a chance to peer through the eyepiece. And after a few seconds of gazing at the glory of the heavens, they look up and utter the same three words: “Is that it?”

  Sharon and Karl Agathon.

  Karl "Helo" Agathon.

  Their disappointment is the fault of one of the most successful satellites ever placed in orbit: the Hubble Space Telescope (HST). Launched in 1990 and put into working order in 1993, the Hubble can show us stars being born and stars dying; can show us planets around the Sun and planets around other stars; and can show us millions of galaxies shining like jewels in a patch of sky no bigger than your fingertip. The Hubble Space Telescope’s beautiful images, swirling and burning with vibrant colors, have revolutionized the public’s appreciation of astronomy. Mostly for the be
tter, but sometimes very much for the worse.

  To begin with, as this is being written HST’s cameras are more than 20 years old, and thus are much more primitive than the one in your cell phone. That’s worth repeating: the cameras in the Hubble Space Telescope are more primitive, and probably less powerful, than the simple camera in your cell phone. They don’t even see in color. Instead, the image in the telescope is held very still while multiple black-and-white images are taken through different-colored filters. By taking a black-and-white picture through the red filter, the camera highlights the red objects in its field of view. Follow this with pictures taken through the green filter and the blue filter, and Hubble’s cameras can capture all the necessary color information in a particular image. It is a simple matter to then combine the three filtered black-and-white images in a computer to make a full-color image. There are forty-eight filters in Hubble’s eye, each tuned to a particular wavelength or band of light.

  These filters are very important, because they can help astronomers figure out what is happening inside a nebula. A hydrogen alpha (Hα) filter, for example, shows scientists which areas of space contain ionized hydrogen gas. Ionized hydrogen gives off light in one wavelength: the rose-red hue of 656.281 nanometers, and the Hα filter is designed to block out other light and let only that wavelength through. That filter probably gets used a lot—since the material universe is mostly made of hydrogen, most nebulae, when seen in color, are overwhelmingly rose red.