And why are they throwing them at Russia?

Sooner or later, it was bound to happen. On 30 June 1908, Moscow escaped destruction by three hours and four thousand kilometres - a margin invisibly small by the standards of the universe. Again, on 12 February 1947, yet another Russian city had a still narrower escape, when the second great meteorite of the twentieth century detonated less than four hundred kilometres from Vladivostok, with an explosion rivalling that of the newly invented uranium bomb.

In those days, there was nothing that men could do to protect themselves against the last random shots in the cosmic bombardment that had once scarred the face of the Moon. The meteorites of 1908 and 1947 had struck uninhabited wilderness; but by the end of the twenty-​first century, there was no region left on Earth that could be safely used for celestial target practice. The human race had spread from pole to pole. And so, inevitably...

At 09.46 GMT on the morning of 11 September, in the exceptionally beautiful summer of the year 2077, most of the inhabitants of Europe saw a dazzling fireball appear in the eastern sky. Within seconds it was brighter than the sun, and as it moved across the heavens - at first in utter silence - it left behind it a churning column of dust and smoke.

Somewhere above Austria it began to disintegrate, producing a series of concussions so violent that more than a million people had their hearing permanently damaged. They were the lucky ones.

Moving at fifty kilometres a second, a thousand tons of rock and metal impacted on the plains of northern Italy, destroying in a few flaming moments the labour of centuries. The cities of Padua and Verona were wiped from the face of the earth; and the last glories of Venice sank for ever beneath the sea as the waters of the Adriatic came thundering landwards after the hammer-​blow from space.

Six hundred thousand people died, and the total damage was more than a trillion dollars. But the loss to art, to history, to science - to the whole human race, for the rest of time - was beyond all computation. It was as if a great war had been fought and lost in a single morning; and few could draw much pleasure from the fact that, as the dust of destruction slowly settled, for months the whole world witnessed the most splendid dawns and sunsets since Krakatoa.

After the initial shock, mankind reacted with a determination and a unity that no earlier age could have shown. Such a disaster, it was realized, might not occur again for a thousand years - but it might occur tomorrow. And the next time, the consequences could be even worse.

Very well; there would be no next time.

A hundred years earlier a much poorer world, with far feebler resources, had squandered its wealth attempting to destroy weapons launched, suicidally, by mankind against itself. The effort had never been successful, but the skills acquired then had not been forgotten. Now they could be used for a far nobler purpose, and on an infinitely vaster stage. No meteorite large enough to cause catastrophe would ever again be allowed to breach the defences of Earth.

So began Project SPACEGUARD. Fifty years later - and in a way that none of its designers could ever have anticipated - it justified its existence.

Rendezvous with Rama, Arthur C. Clarke

At approximately 9:20 on Friday, a meteoroid exploded over the Russian city of Chelyabinsk.  Estimates as to the object's exact size and weight vary - NASA's estimate is 17 meters in diameter and a weight of about ten metric tonnes.  Windows shattered,  buildings were damaged, and over a thousand people were injured, over one hundred of whom required hospitalization.

Coincidentally, the Chelyabinsk explosion took place sixteen hours before asteroid DA2012, 50 meters in diameter and 190,000 metric tonnes in weight, came within 27,000 kilometers of Earth, the closest recorded passage of an object of that size.  

I don't know who's tossing these things at us, but I have to think that eventually they're going to throw a strike.

- Sid