by Neil Fraser, November 2000
Were they hostile, asleep, or dead? For eight years the great radio telescopes at Arecibo and Green Bank had been tracking the approaching ships. That they were ships was no longer in doubt; comets and asteroids are not usually in the habit of performing braking maneuvers. Their current approach pattern would insert them into a solar orbit in fourteen months. Other than the staggering size of the ships and their current trajectories, little else was known about the aliens. Repeated messages on frequencies ranging from radio up through X-rays had been ignored.
Nature abhors a vacuum, and the vacuum of information concerning the aliens was quickly filled with dozens of conflicting theories. Maybe they simply weren't listening to the electromagnetic spectrum, having long ago found better ways to communicate. Maybe they were traveling in suspended animation and hadn't woken up yet. Maybe they had all died on their long voyage, leaving the ships on autopilot. Maybe they were hostile, and weren't going to waste time chatting with the current tenants of Earth.
Naturally it was this last theory which worried people the most and received the most attention from the media and politicians alike. Both the USA and Russia had adapted their nuclear missiles for space-based operations. However nobody seriously believed that a few thousand warheads left over from the cold war would be of much concern to a civilisation that could cross interstellar space. So the decision was made to take out the ultimate insurance policy.
The prototype for this insurance policy was currently sitting in Discovery's payload bay. Dr. Hewitt looked dubiously at the pile of girders through the cabin window. It looked more like a jumble of Meccano than a bomb that could destroy a planet. "Houston: Discovery. We're ready to deploy the porcupine." she stated.
"Discovery: Houston. That's great. You're doing fantastic work up there. We're all proud of you." came the reply. Hewitt mentally recoiled at the sickly sugary tone that Mission Control invariably used when talking to astronauts.
Slowly, the spring-loaded equipment pallet was ejected out of the shuttle. When it was one hundred meters away Hewitt radioed a series of commands to the porcupine's onboard computers, and the device started to unfold itself. One by one, four trusses extended outwards and locked themselves at the vertices of an imaginary tetrahedron. Each truss was a particle accelerator aimed inward at a common focus. To Hewitt, it looked like a giant version of a child's jumping jack, or of a medieval caltrop.
The concept of a chain reaction had been known to physics for more than a century. One atom that transmutes to a different type of atom can emit neutrons that can cause nearby atoms to transmute, and so on. Such a reaction will grow exponentially until the supporting material is completely consumed. Until recently it was assumed that such a reaction could only happen in extremely rare radioactive materials such as some isotopes of uranium or plutonium. However, researchers at the National Ignition Facility had discovered a new form of chain reaction that could be supported by nitrogen. To be more precise, the researchers had merely computed the possibility of this chain reaction; no direct experimentation was possible. Seventy-eight percent of Earth's atmosphere is composed of nitrogen, and a nitrogen reaction experiment that got loose would sweep around the planet in less than a day. The entire line of research was immediately discontinued and classified. Nobody wanted a so-called 'rogue state' developing the trigger for a nitrogen reaction, then holding the entire world hostage.
Dr. Hewitt had therefore been shocked when she'd been ordered to reassemble her team and instructed to turn theories into hardware with all due haste. She was also shocked to discover that she didn't have a budget. Four of the NSA's best super computers were placed at her disposal, complete with the stable of programmers required to craft the simulations that her team needed. Hewitt was beginning to dread the time when the project was complete and these resources were just as quickly withdrawn. But for now the overriding priority was to construct a device that could destroy the planet, thereby potentially saving the planet. If the aliens were intent on claiming Earth as their own (and there was absolutely no way of knowing), then our last act would be to detonate a nitrogen bomb. This intent would be transmitted to the approaching ships as graphically as possible so that they would know that no matter what they did, they couldn't have our planet. It was indeed the ultimate insurance policy; one that hopefully would never be used.
The federal benefaction had the desired effect. Like the Apollo program, the Manhattan project and the Panama excavations, seemingly insurmountable obstacles were overwhelmed or circumvented. All problems but one. Hewitt's entire work was dependent on computer simulations. Simulations that were based on physical benchmarks far removed from the area they were operating in now. The computers predicted that the bomb would work, but the computers were basing this prediction on an uncomfortably long chain of extrapolations. It quickly became obvious that a real-world test needed to be conducted. It didn't even matter if the test was a failure, since it would still provide a fixed data point from which to fine-tune further simulations. However, there was nowhere on Earth that such a test could be safely performed.
Discovery had completed a half-dozen orbits before the porcupine had fully deployed itself and been given a clean bill of health. When it was certain that no EVAs would be required to repair some aspect of the porcupine's hardware, the space shuttle made a brief burn and reduced its orbital velocity by a few meters per second. Hewitt watched the porcupine drift astern. Eventually it was no more than a bright star. So tiny compared to the huge blue globe of Earth hanging over her head. Yet powerful enough to destroy that globe if it were detonated inside the atmosphere.
"Discovery: Houston. One minute till ignition. Confirm the data integrity of the downlink."
Hewitt glanced at both of the redundant computers that were recording the porcupine's telemetry.
"Houston: Discovery. Checksums valid. We're getting good data."
"Thirty seconds. Good luck up there."
To the rest of the crew, ignition was a considerable anti-climax. The briefest flash of light from a point source behind the Shuttle was all there was to show for the estimated two billion dollars poured into this project. But to Hewitt, it was everything she had been waiting for. The computers on the porcupine had performed their job well. They had transmitted temperature, pressure, radiation and a dozen other parameters right up to the moment the shock wave reduced them to their component atoms. All that invaluable information was now safely stored onboard Discovery. Hewitt immediately started to download this hard-won data to her colleges anxiously waiting back on Earth. Although the detailed analysis would take months, one thing was clear as she scrolled through the columns of numbers: a nitrogen reaction had been successfully triggered.
For the first time Hewitt was able to completely relax. The mission was a success, and there was virtually nothing for her to do for the remaining three days that Discovery was due to remain in orbit. Like the countless astronauts before her, she gravitated towards those irresistible windows and gazed out at the one sight that the Human mind could never tire of: Earth. The Mediterranean Sea was passing by underneath. Greece was visible to the north, partially obscured by clouds. Hewitt imagined all the people below her and wondered if a single one of them realised that someone was watching them. She toyed with this idea with some amusement; it gave a strange feeling of power. Then she suddenly thought of the approaching alien ships, and wondered if they were watching her primitive space vehicle with equal detachment.
In a deliberate effort to rid her mind of this idea, Hewitt looked back at Earth. Night was falling quickly as the Shuttle swept around the curve of the Earth. Soon all that was left was a thin crescent of blue and white retreating behind her. As the sun disappeared, the stars flooded out to fill the void. A luminous haze ahead caught her attention. It was hanging just a few degrees above the eastern limb. Hewitt studied it for some moments and concluded that it must be a nebula of some kind. Then with a realisation that made her skin crawl, she noticed that it was growing. She checked her watch; it had been an hour and a half since the porcupine had been tested. That was exactly the time it would take for the Shuttle to make one orbit. The faintly glowing cloud must in some way be related to the test, but she couldn't see how. It must be a hundred kilometers across, which ruled out the possibility that it was a debris field of the porcupine itself. There hadn't enough material on the porcupine to form such a large structure. Besides, any debris would have continued to travel in orbit at Mach 25, whereas this cloud appeared to be stationary. It was defying gravity as it floated in the vacuum of space.
The vacuum of space. There was no such thing. With a sinking feeling, Hewitt remembered that even at this altitude there were still 10,000 atoms of air per cubic meter. The calculations had shown that this wasn't nearly enough to sustain a nitrogen reaction. Whether it was a rounding error or a shifted decimal point made no difference anymore. The reaction she had triggered was spreading. In another hour it would reach ground level. By the next day Earth's atmosphere would be completely burned. The shuttle would be unaffected as it orbited the dying world below. She and the rest of the crew would have a week to watch the final outcome of the experiment before their supplies ran out.
Robert Oppenheimer had been premature when he stated "I am become Death, Destroyer of Worlds."
It should be noted that before the Trinity explosion in New Mexico, there were a number of Manhattan project scientists who were genuinely concerned that their bomb might trigger a nitrogen-oxygen reaction that would sweep around the world and end all life. Their calculations (in a report codenamed LA-602) indicated that although the bomb would trigger this reaction, it would not be self-sustaining and thus wouldn't spread. Fortunately they were right.