Photo of mountain tops with fresh snow
Why do puffy clouds have flat bottoms? This was just one of the many questions Rob posed as we explored different aspects of earth’s atmosphere. Earth’s breathable atmosphere is the only habitat we really, truly live in, but owing to the normal invisibility of air, we forget about it.

So why are clouds flat on the bottom? Rob characterized clouds as forming when bubbles of warm air break loose from the ground and rise up. We know higher places, like mountains, are colder. If there’s enough water vapour in that air, as it rises past a critical altitude the vapour condenses on microscopic particles, producing visible water droplets. The visible cloud may be flat bottomed, but below that straight-line, level zone where condensation begins, the lower part of the bubble of warm, rising air may be as round as the top.

Rob presented his own photos of a variety of other phenomena, such as violent downdrafts tumbling out the bottom of a cloud, the natural blue haze of clean desert air in the Grand Canyon, and mirages of both the Mojave Desert and the Canadian Arctic.