Secret Murder

In the 1995 novel The Killing Star by Charles Pellegrino and George Zebroswski, paranoid aliens attack Earth with a projectile that they have accelerated to more than 90 percent of the speed of light. This so called 'relativistic bomb' (a device that uses no explosive but depends for its lethal violence on kinetic energy) wipes out al life on Earth. All that is left of humanity is a pungent smell and the remains of the Pyramids.  In the novel there existed in the Galaxy a paranoid civilisation that was jealous of any others that might arise and threaten its supremacy. Therefore, no sooner had it learned of the existence of its neighbours than it would seek to annihilate them.

It was an ingenious idea. The existence of these evil beings would explain the failure of our search for life in space. Instead, we find a great silence, an absence of any alien radio signals. Either no civilisations exist, or else they keep quiet because they are terrified of revealing their existence and becoming victims of genocidal attack.  The only flaw in this idea is that the perpetrators may themselves face retaliation. Unlike a successful murderer, they would have failed to make their crime look like an accident. Another novelist has solved this difficulty. Paul K. McAuley, in his novel Eternal Light, suggests that aliens who possessed huge amount of wealth and technological power and who wanted to commit genocide would hurl, not a small projectile at the planet of their intended victims, but a star! The result would be less dramatic than the projectile but just as sure. Suppose our own Solar System was a victim. The incoming star would not even need to collide with the sun to have a devastating effect on the biosphere. On passing through the Oort Cloud of comets, it would disrupt them, sending many of them falling inwards towards the Sun. Since the cloud contains tens of billions of comets, a huge number could be expected to collide with the Earth.  Even if these collisions did not render our planet uninhabitable, the gravity of the incoming start would distort Earth's orbit, making it highly eccentric. Our oceans would evaporate as it came too close to the Sun, and our atmosphere would freeze as it alternately went too far in the opposite direction.  And yet those who survived the tragedy could be deceived into thinking that it was an accident and not a murderous attack. According to a recent report in the New Scientist, st6ars have been discovered that fly out of the Galaxy at speeds of more than 800 kilometers per second.  This happens because they narrowly escape being captured by the black hole that lied in the centre of the Galaxy. Instead of being sucked into it (is is the fate of many stars), they are hurled out, as if by a slingshot, and hurtle off into intergalactic space.  And so, if the far future brings interstellar wars, it may become commonplace to use the stars themselves as missiles. Then, when an inhabited world is obliterated, no one can be sure that it was not an accident.