Observations placeholder

Lyall Watson – Heaven’s Breath

In 1953, two meteorologists finally proved that warm air lifts from Earth’s surface in great buoyant bubbles, exactly like the vapour that rises from the bottom of a kettle of gently boiling water.  These bubbles or ‘thermal shells’ are self contained meteorological systems with their own internal turbulence.  If they were visible, they would look like giant rotating smoke rings.  And it is inside these that the larger birds with broad wings come to soar so effortlessly over land, that they seem, in the words of Keats.

‘to sleep wing wide upon the air’

They are carried aloft as passengers inside parcels of air that rise faster than the birds’ gliding flight causes them to fall, and never reach the bottom of such a bubble, because the air inside it is spinning fast enough to keep them flying horizontally.

This bubble stream system of convection is clearly the most effective way of transporting heat upwards without too great a loss.  Once they reach a certain height and size, the bubbles drift with the wind, redistributing warmth and with it the creatures held captive inside the temperature shell.  Swallows have been seen soaring and feeding inside such bubbles at heights of up to 2000 metres and can, in an average high altitude wind of around 50 kilometres an hour, be carried 1000 kilometres away in a single day.

Without wind shear over the ocean or thermal bubbles over the land, soaring is impossible and gliding becomes a problem.  The main difficulty with them as ways of getting about is that there is always some drag.  Gliding flight can never be horizontal without drastic loss of speed.  To fly on the level successfully there has to be thrust, there has to be power behind the flight.  It is not enough just to have aerodynamic wings.  You also have to flap them.