The Case for a Galactic Defense System

George Michael. Skeptic. Volume 21, Issue 4. 2016.

Last June, the long awaited sequel Independence Day: Resurgence opened in theaters around the world. Although not as commercially successful as its blockbuster predecessor, the film at least elaborated in greater detail on alien motivations for conquering Earth. As explained in the story, the alien mothership sought to harvest the heat of the Earth’s core, which in the process would destroy the planet’s magnetic field, thus obliterating all of its inhabitants. Such a scenario is highly improbable because there would be more feasible methods for alien civilizations to extract comparatively greater amounts of energy, including harnessing the heat of stars, which are estimated to number 400 billion in the Milky Way Galaxy alone. Moreover, it does not seem plausible that an advanced alien civilization capable of traversing interstellar distances would be interested in extracting the relatively crude energy sources or harvesting resources to be found on Earth when such commodities could be obtained in much greater quantities closer to the home planet. From the perspective of an advanced alien civilization, plundering the Earth for its resources would be neither practical nor desirable. Be that as it may, there would be good reasons for interstellar colonization, primarily for defensive, rather than offensive purposes. To ensure its longterm survival, a civilization would need to keep apprised of what is happening outside of its star system, for there are a number of perils that lurk in the Galaxy. Thus, the construction of a Galactic Defense System is advisable.

Perils In the Galaxy

The most serious threats that we face in the Galaxy are not hostile aliens as depicted in science fiction films, but naturally occurring astronomical phenomena. Concomitant with the discovery of new celestial bodies, astronomers have come to understand the perilous nature of the cosmos. These discoveries correlate with recent findings in the field of geology. Periodic mass extinctions as indicated in the Earth’s fossil record suggest a galactic culprit may be responsible. The physicists Richard Muller and Robert Rohde, for example, found a distinct 62 million-year cycle in the pattern of marine extinctions. Perhaps as our solar system passes through the Milky Way’s spiral arm, the Earth is subjected to a number of exogenous forces stemming from that part of the Galaxy.

Astronomical events have the potential to wipe out life over broad swaths of space. To give one example, when a large star explodes in a supernova the radiation produced within 30 light years of a habitable planet would probably destroy all of its surface life. In July of 2016 it was reported that an exploding star might have triggered a minor mass extinction 2.59 million years ago, around the start of the Pleistocene, when hominins began to flourish in Africa. Thankfully, our Sun is located in the suburbs, far from the galactic center where most supernovae occur. Astronomers have not detected any large stars with the potential to become supernovae in the vicinity of our solar system. But other habitable planets may host advanced alien civilizations that are not so fortunate, in which case they would have a great incentive to monitor potential supernovae.

The most powerful known explosions in the universe-gamma ray bursts-emit more energy in a few seconds than the Sun will emit in its lifetime. Although their cause is not yet certain, these massive explosions might be produced when neutron stars merge with each other. Such events occur about every hundred million years in the Milky Way Galaxy. Awesomely bright, they can be seen far away across the universe. Even if one occurred in a distant region in the Galaxy, it could possibly destroy our protective ozone layer and by doing so, sterilize all life on the planet. Far more powerful than a supernova, some astronomers believe that a gamma ray burst from up to 10,000 light years away could affect the Earth.

Finally, there are the perils related to comets and asteroids. Although less immediate and devastating in their initial impact, they occur with much greater frequency than supernovae and gamma ray bursts. In fact, in some instances comet and asteroid impacts can wipe out complex life forms on a planet at a stroke. The roughly 200 known asteroids whose paths take them near Earth pose a real threat to life on this planet. About 20 percent of them, sooner or later, are bound to strike Earth, with possibly devastating consequences. Every few hundred years on average, the Earth is struck by an object about 70 meters in diameter. The resulting energy is roughly 50 megatons-equal to the largest nuclear weapon ever detonated. Even worse, approximately every 10,000 years, a 200-meter object that could precipitate serious climatic changes collides with Earth. And every million years, an impact by an object over 2 kilometers occurs, the impact of which produces an explosion equivalent to nearly a million megatons. Such an impact would provoke a global catastrophe, wiping out a significant fraction of the human race-perhaps up to a billion people on the planet. Geological evidence suggests that asteroids have been implicated in mass extinctions in Earth’s past, as indicated by the massive Chicxulub crater buried beneath the Yucatán Peninsula in Mexico. The asteroid that struck the Earth 66 million years ago likely engendered the demise of the dinosaurs.

Astronomical disasters can come without much warning. At present, Earth’s civilization is left to the mercy of the vicissitudes of the Galaxy. But with exciting scientific and technological developments on the horizon, we may someday realistically plan a defense system to guard against these galactic perils.

Prototypical Earth-based Defense Systems

Throughout Earth’s history, a number of defense systems have been produced to protect nations against international threats. Under the leadership of Emperor Quin Shi Huang, construction commenced on the Great Wall of China in 220 BCE to guard against the various nomadic tribes of the Eurasian Steppe. During the Cold War, the joint U.S.-Canadian command-NORAD-was established to provide an aerospace warning and defense system for North America, primarily against the threat of the Soviet Union. Even more ambitious, in 1983 President Ronald Reagan proposed the Strategic Defense Initiative (popularly called Star Wars) as a missile defense system intended to protect the United States and its allies from attack by ballistic nuclear missiles. Although an operational system has yet to be deployed, technological advances could one day make such a system feasible.

The good news is that since the end of the Cold War, both the United States and Russia have drastically reduced their nuclear arsenals. According to many indices-as Steven Pinker noted in The Better Angels of Our Nature-the world is actually becoming a safer place. More and more, governments reject the appropriateness of waging war. As a consequence, if the nations of the world can get past their differences, military systems-such as ballistic missile defense-might be redesigned for protection from threats outside of our planet.

Someday the human race might develop the capacity to obliterate dangerous asteroids or deflect them away from the Earth. It has been suggested that a nuclear weapon could be used to destroy an incoming asteroid exploding it into enough small pieces so that it would produce a harmless, though spectacular, meteor shower. Another method would be to nudge an asteroid out of harm’s way with slow but steady rockets that could be attached to one side. Even more exotic, lasers could be used to vaporize or deflect potentially hazardous objects en route to Earth. Working in collaboration with the European Space Agency and Johns Hopkins University’s Applied Physics Laboratory, NASA is examining ways to redirect near-Earth objects away from our planet using a variety of techniques. Of course, deflection technology would have a great potential for misuse. Its dual-use nature means that it could be utilized for offensive military operations, which would make arms control efforts problematical.

A Galactic Defense System

To date, nations have built defense systems to protect themselves against their terrestrial rivals. If governments around the world could someday set aside their differences, however, they could embark on a truly planetary defense network to protect the Earth from exogenous forces in space. What form would a Galactic Defense System take? Technology permitting, a network of sensors deployed throughout the Galaxy could be used to detect astronomical events and alert the Earth to potential perils related thereto. A number of formidable challenges would have to be surmounted in creating this network, but the fledging field of robotics holds much promise on the construction end of the project. John von Neumann and Ronald Bracewell once conjectured that extraterrestrial civilizations might send selfreplicating robotic probes to explore other solar systems. These probes would be programmed to extract raw materials and construct additional new machines that would spread throughout the universe. Inasmuch as these machines would be selfreplicating, they would require no additional effort or expenditure from the civilization that created the original prototype. New breakthroughs in nanotechnology and computers could someday enable the development of long-range space missions capable of establishing a galactic network of sensors.

With a monitoring system functional in the galaxy, an advanced civilization on Earth could take measures to protect itself against dangerous eventualities emanating from deep space. One obvious method would be to construct a protective bubble around the planet. Freeman Dyson theorized that a hypothetical megastructure could be utilized to encompass a star as a system of orbiting solar power satellites to capture most of the energy output. To be sure, constructing a Dyson sphere, as it has come to be called, would be a gargantuan engineering undertaking, but a theoretically possible one. To complete the project, Dyson suggested it might be possible to use solar energy to dismantle planets and rearrange their pieces as parts of a massive solar collection sphere. The proposed biosphere would not be a solid shell, but rather, a “loose collection or swarm of objects” independently orbiting the star. Although Dyson had energy extraction in mind when theorizing on his megastructure, the basic design could certainly be modified for protective purposes as well. This part of a Galactic Defense System could be constructed in such a way as to totally envelop the home planet, which would provide a protective shield from harmful cosmic rays.

Of course, it is quite possible that an advanced civilization might someday transition to a form of post-biological life. In that vein, in 2005 the noted inventor Ray Kurzweil predicted that by the year 2045 we will reach the Singularity, that is, an epoch in which humans will transcend their biological bodies and meld with computers. According to Kurzweil, this transition will be the natural next evolutionary step. But even if intelligent sentient beings have evolved to a form of post-biological life, they would still most likely be concerned with developments in their galaxy. After all, an electromagnetic pulse (EMP) on Earth can disrupt and damage electronic equipment. Likewise, solar activities-including flares and coronal mass ejections-could destroy power grids on Earth. It would seem to follow that the cosmic rays emanating from supernovae and gamma ray bursts could be harmful to computer-based life as well. Consequently, even sentient machines would have an interest in developing some sort of Galactic Defense System.

Perhaps even more challenging than the engineering projects discussed above would be to develop a message system that could relay superluminal messages to the home planet or space colony. Inasmuch as the lethal X-rays and gamma rays emitted by supernovae travel as electromagnetic waves, they would reach the Earth at the speed of light and their lethal effects would be sudden. Therefore, even if probes were deployed in distant regions of the cosmos and their messages were relayed back to the home civilization by way of standard electromagnetic transmissions, it would be too late by the time they arrived. Not long after we saw the stellar explosion, or received the warning message, we would soon be dead. To be effective, this early warning system would have to somehow relay information back to the mother planet at a rate faster than the speed of light.

According to Albert Einstein’s 1905 Special Theory of Relativity nothing can travel faster than light, which would seem to rule out the prospect of a superluminal communication network as envisaged for the Galactic Defense System. However, Einstein later amended his own theory in 1915 with the General Theory of Relativity in which he conceded that under certain conditions, the superluminal transmission of information is theoretically possible. For instance, one could use large amounts of energy to continuously stretch space and time. The fabric of space could be compressed so that a radio message or even a spacecraft could travel though the medium at a sub-luminal speed yet arrive at a point in time and space comparable to having traveled at a superluminal speed. Another way to avoid the cosmic speed limit would be to use a wormhole as a shortcut across space and time. Einstein and Nathan Rosen once speculated that a so-called “Einstein-Rosen bridge” could connect two universes creating a shortcut through time and space. Theoretically, one could create a wormhole by compressing an object so that it becomes smaller than its “event horizon.” The energy requirements for such a system, though, would be extraordinary and well beyond the scope of our current capabilities.

More promising would be the use of quantum entanglement to transmit information. This concept grew out of a paper written in 1935 by Einstein, Boris Podolsky, and Nathan Rosen. Their thought experiment-which came to be known as the EPR paradox-maintains that when two particles, such as photons or electrons interact with one another, the observation of one particle will produce instantaneous effects for the observer of the twin particle, even when vast distances separate the particles. In the parlance of theoretical physics, such particles are said to be “entangled.”

In the EPR paper, Einstein sought to demonstrate that the Copenhagen interpretation of quantum mechanics was incomplete. Largely devised by Niels Bohr and Werner Heisenberg, it posits that physical systems do not have definite properties prior to being measured as had been assumed in classical physics. Instead, at the quantum level, we can only predict the probabilities that measurements will produce certain results. The very act of measurement affects the system causing the set of probabilities-or “superposition”-to collapse to only one possible value immediately after the measurement. A central tenet of the Copenhagen interpretation is the Heisenberg Uncertainty Principle, which posits that one cannot simultaneously know the exact momentum and position of a particle. Consistent with the EPR paradox, however, the state of particle B would depend on which measurement an observer chose to make of particle A. Thus, how could particle B possibly “know” whether it should have a precisely defined momentum or a precisely defined position? This proposition would seem to violate Einstein’s dictum of locality, which postulates that what happens in one place cannot affect something in a faraway location unless a signal is sent to the other location at a speed equal to or less than the speed of light. Einstein concluded that no reasonable definition of reality could permit this phenomenon, which he derided as “spooky action at a distance.”

Nevertheless, entanglement has been demonstrated on numerous occasions in experiments conducted by noted theoretical physicists, including Nicholas Gisin, John Bell, Anton Zeilinger, and Alain Aspect. When two particles are entangled with each other, they exhibit a peculiar bond that seems to transcend space.

Could quantum entanglement ever be used for practical purposes? Donald E. Tarter speculates that some day we might be able to use quantum entanglement to communicate instantaneously across vast interstellar distances. For his plan, Tarter calls for sophisticated “photon traps” that would grab and store the photons for polarization measurement. The information transmitted would be carried in the changing polarization of the photon stream. Once two space stations have entangled photons in the position, instant communication would then be possible. However, the initial contact could not exceed the classical limit of the speed of light. Tarter imagines that advanced civilizations might use massive and distant cosmic phenomena such as gamma ray bursts to carry their quantum keys throughout the universe.

Alas-at least at present-it does not appear possible to send readable messages faster than the speed of light. According to our current understanding of quantum mechanics, entanglement cannot be used to send superluminal messages because the act of measuring the spin of one pair of entangled particles always gives a random result, even if the results of the two measurements are correlated. Any attempt to pre-set the spin of a particle would break the entanglement. The “quantum message” cannot be read until one pole in the system sends a code key to the other pole in the system. As George Musser explained in his 2015 book Spooky Action at a Distance the only known way to send the code key would be to use “some run-of-the-mill communications system such as e-mail, phone, or marathon runner. The extra requirement of performing a comparison makes entangled particles useless for transmitting a signal.”

Still, exciting new research holds out promise in the area of quantum communications. For example, in September of 2015, a research team led by Hiroki Takesue succeeded in teleporting information over 62 miles using quantum entanglement. But to date, no experiment has demonstrated a way to use teleportation to send information at superluminal speeds. Despite the failure to achieve faster-than-light transmissions in a laboratory, it might someday be possible as an advanced civilization unlocks more mysteries of physics.


This proposed Galactic Defense System could serve as an early warning system alerting advanced civilizations to the astronomical perils in the Galaxy. Admittedly, the successful construction of this network presupposes yetto-be-discovered speculative laws of physics that might not exist. Further, Herculean scientific, technological, and engineering accomplishments would be necessary for its completion. But based on the history of science, it behooves us to consider the possibility that new and revolutionary discoveries could be on the horizon.

In the year 1900, the eminent British scientist and one of the founders of thermodynamics, William Thompson (Lord Kelvin), proclaimed to the British Association for the Advancement of Science that there was nothing new to be discovered in physics. All that remained was for scientists to make more and precise measurements. Then in less than two decades, relativity and quantum mechanics emerged to shake the foundations of classical physics. In the near future, a concatenation of new technologies and scientific discoveries-nanotechnology, quantum computing, fusion, and string theory-implies that progress will proceed very rapidly, exponentially, rather than linearly. With these capabilities, we may someday be ready to journey outside of our solar system and construct ambitious engineering projects, including a Galactic Defense System.