Wood ignites at temperatures in the hundreds of degrees. How are some wildfires supposedly started by sunlight without human action or lightning?

Question

Wood ignites at temperatures in the hundreds of degrees. How are some wildfires supposedly started by sunlight without human action or lightning?

In: 1508

Answer 1

All by itself, sunlight isn’t hot enough. But if it’s magnified by some kind of reflective or refractive human object, like glass from windows or bottles, or shiny metal or something, it can, in very rare circumstances, be hot enough to create a tiny little spot of fairly intense heat, like when you burn ants with a magnifying glass. Researchers still aren’t sure if this has ever happened and sparked a wildfire, but it is theoretically possible.

The majority of wildfires are ignited by human carelessness (discarded cigarettes, sparks from a car dragging something on the road, abandoned campfires, bad electrical lines, etc.) or outright arson. And it’s assumed the remainder are from lightning.