Humans are very bad at understanding exponential growth (eg: virus spread in populations). So here's an illustration I use in talks.

Here's Wembley Stadium. The watering system develops a fault: in minute 1 one drop of water is released; minute 2, two drops, min 3 eight drops 1/

Now, a drop of water has a volume of 0.07 cc, or 0.000007 cubic metres. Wembley Stadium has a volume of 1.1 MILLION cubic metres. The watering system doubles the number of drops output every minute.

How many hours before Wembley overflows? Or is it minutes? Have a guess. 2/

So here's what happens. After 16 minutes, the watering system - where the output is doubling every minute, remember - is outputting the equivalent of a bathtub every minute: 0.27 cubic metres.

After 26 minutes: pitch area of 12,500 sq m is 3cm deep in water. 3/

After 28 minutes the total water in the stadium is not quite enough to fill an Olympic swimming pool (2,500 cubic metres).

After 31 minutes, the per-minute output = 3 Olympic pools. The pitch is covered in 1.2m of water: waist-deep. 4/