Help from above? Part I
Updated: May 25, 2020
At first glance space seems like a good place to look to for existential, or at least global, catastrophe. The energies available for destructive processes are vastly greater than can be generated on Earth.
The collapse leading up to the death of a massive star as a supernova or gamma ray burst (GRB), for instance, releases at least a hundred times the amount of energy the sun will produce in ten billion years in less than a second. Even a few percent of that energy would do terrible things to normal matter. At its brightest, a GRB briefly produces about 1042 W of luminous energy, concentrated mostly into two narrow beams. The sun produces 1026 . The entirety of human civilization produces about 1013 W. You would need to multiply the full might of human civilization by ten 29 times to match the destructive potential of a GRB. (It’s actually worse because of how and where the energy comes out, but what’s a few orders of magnitude at this scale?)
The problem is, space is also very large.The nearest star likely to go supernova in the next 100,000 years is about 650 light years, or 6.5 quadrillion kilometers, away. The vast energy released will be spread over a vast amount of space. The sun, though puny, is only 150 million km away. We will be able to view that supernova in daylight for a few weeks, but it will be far outshone by the sun.
Simulations of supernova blast waves interacting with the shell around our solar system created by the solar wind predict that a supernova would need to happen within approximately 100 light years to directly affect earth. Models of the luminous energy interacting with Earth’s atmosphere predict a similar distance limit for significant effects. A GRB releases a similar amount of energy, but it is emitted in two narrow cones. This makes the intensity higher, so a GRB a few thousand light years away will affect Earth. This, however, causes its own difficulties. Earth would have to be sitting right in the path of one of those narrow beams.
To make matters worse, these events are not common. Only stars more than eight times the mass of the sun will go supernova. The rate of supernovae in our Galaxy is on average about one per century. GRBs are rarer still. The Galaxy is about 100,000 light years across, and massive stars are not evenly distributed. This is not to say such events never happen. Indeed, a supernova exploded within about a hundred light years of Earth only three million years ago.
Finally, we need to establish what we mean by “significant effects” on Earth. Depictions in popular culture might lead one to imagine a roiling explosion stripping the atmosphere off the planet or even disintegrating it entirely. A supernova situated where the sun is could accomplish that, but the effects of any nearby star exploding would be considerably subtler. Were a star to go supernova in our near galactic neighborhood, we would experience, for instance, an increase in ionizing radiation and charged particles striking our planet. The ozone layer could be destroyed and the climate affected. We could expect agricultural collapses, die-offs, and increased mutation rates in complex organisms. There is some evidence for a minor extinction event coincident with the nearby supernova three million years ago. Most, if not all, of our satellites and computer and electronic infrastructure could be wiped out by the equivalent of an electromagnetic pulse. The event would be relatively rapid, possibly with follow-up events as different parts of the explosion arrive over the course of years. Recovery could start quickly, though socio-political consequences may delay it considerably. Nearby exploding stars could effectively produce a global catastrophe, but circumstances would have to be extremely favorable to produce an existential one.
Perhaps counterintuitively, the most powerful destructive events in the universe are poor contenders for accomplishing CAE’s goals. Natural events like stars exploding are few and far between, and no stars likely to produce a supernova or GRB are within a convenient distance from Earth. Given that the engineering problems involved in producing an artificial event are insurmountable for the foreseeable future, this kind of cosmic disaster will not be affecting recognizable human civilization on Earth. In a future post, I will examine the advantages of the personalized service available in our own solar system.