Cloud Weight, the Daily Storm Cloud Hector and a Record-Long Lightning Bolt

Latvian news portal Delfi has published a collection of educational facts about human history and atmospheric phenomena. It looks at how heavy clouds are, which storm cloud appears daily over islands in northern Australia, and how long the longest observed lightning bolt was.

How many generations humanity has had

Scientists estimate that since the first Homo sapiens appeared on Earth, between 10,000 and 12,195 generations have lived.

A cloud can weigh a million tonnes

Cumulus clouds look light, but they stay aloft because moist air is lighter than dry air. Counting only the water droplets, one cubic metre of cloud holds about half a gram of water. For a cloud of one cubic kilometre, or a billion cubic metres, that comes to roughly 500 tonnes of water. Taking into account all the moist air, one cubic metre weighs about 1.003 kilograms, and the whole cloud about a million tonnes. That is still less than the mass of one cubic kilometre of dry air.

Hector, a storm on schedule

The Tiwi Islands off Australia's northern coast are home to about two thousand people. The islands' microclimate regularly produces a storm cloud known as Hector. From September to March it appears every day at around 3 p.m. and often reaches a height of 20 kilometres. Before modern satellite navigation, sailors and pilots used Hector to find their bearings.

The longest lightning bolt

The longest lightning discharge observed so far came from a storm in 2017. The World Meteorological Organization only recently confirmed it as an official record, using data from both satellites and ground-based sensors. The bolt flashed across 829 kilometres, from eastern Texas through Oklahoma, Arkansas and Kansas to Missouri.