Update

The Guardian's Warren Murray picks up on the questions we raised earlier about the minutes-long time lapse between when the meteor was first sighted and when the first of a series of booms was heard.

It simply took the sound waves that long to travel the distance to the observer, he writes. And the series of booms is attributable to multiple shock waves created by the meteor(s):

In our coverage we've remarked on the fact that the sonic boom in some videos happens a couple of minutes after the meteor passes.

This isn't surprising, it just means the camera was at sufficient distance that the sound took a while to reach it. Sound travels at 330km/h, so a three-second delay would mean you're a kilometre away roughly. A 30-second delay, roughly 10km etc. And the thing would have been visible to people and cameras from a long, long way away, even though the size and brightness would have made it seem quite close for many people who were in fact a long way off.

Also, a sonic boom doesn't happen at any particular instant or point in time, i.e. when the object first entered the atmosphere or first broke the sound barrier. The shockwave and the boom follows the object along its entire path as long as it's supersonic, so anyone it goes past will hear a boom. That's one reason why international agreement was never reached for the Concorde to fly supersonic across whole continents or populated areas - it would have created huge noise pollution all the way along its supersonic path.

Then there's the multiple sonic booms issue. Put simply, a body going supersonic creates multiple shock waves and therefore can make multiple booms: one in front, one behind, plus others potentially. This partly depends on its shape, changes in trajectory etc. The space shuttle was always known for two booms. Also, consider how very loud those booms in Russia would have been, and the fact that echoes off the sides of mountains etc would have in turn travelled a very long way and been heard some time afterwards.