I’ve been thinking a great deal about asteroid impact.
The probability of an earth-destroying impact is very tiny…and there is nothing that can be done about them anyway -beyond having a global lottery for places on the last Virgin Galactic flight.
The most significant opportunity to outlive an asteroid impact is surely to deal with the problem of medium-sized bodies hammering into a major city.
Today’s invention is therefore an asteroid-proof metropolis.
Build a city on a wheeled platform which is free to move on a special set of orthogonal railway lines, as shown (we already create whole airports on roller bearings, in areas of earthquake activity).
A few hours before being struck, a city of this type could be powered out of the predicted line of fire. There would be significant damage to the surrounding landscape, but the city itself would avoid catastrophe.