WHAT do the space shuttle and a giant explosion in 1908 have in common? Both have been followed by strange, glowing clouds, and these may point to what caused the Tunguska blast a century ago.
The blast destroyed a swathe of Siberian forest near the Tunguska river, and a day later people across Europe saw strange clouds that lit up the night sky. These were probably noctilucent clouds: rare clouds of ice crystals high enough to reflect sunlight long after sunset (see image).
The fact that the clouds were seen just a day later suggests the explosion somehow…
