5 Fascinating Facts About Fire

Fire Doesn’t Fit Into the Usual Categories of Matter

First, some basic science: Fire is the visible result of a chemical reaction called combustion, which occurs when a fuel substance, heat, and oxygen interact. Surprisingly, fire doesn’t fit neatly into the definitions of the four states of matter. Despite the gases involved, fire is not a gas, nor is it a liquid or solid. It comes pretty close to being a plasma, a state in which a substance’s molecules are greatly ionized and their nuclei break free of their electrons, but only extremely hot fires achieve that property. Fire’s true nature has yet to be defined.

Different Fuels Burn at Different Temperatures

The temperature of a fire usually depends on the type of fuel being consumed. When combined with air, burning wood usually maxes out at around 3600°F, a gasoline fire can reach about 3900°F, and anthracite coal fires can burn at 4000°F. On the cooler end of the spectrum, a cigarette burns at about 750°F to 1300°F, and a candle flame can hit 1800°F. The hottest fire ever created — according to Guinness World Records — is one produced by a compound called carbon subnitride (also known as dicyanoacetylene). It results a white-blue flame that can reach 9010°F.

Determining When Humans Mastered Fire Is a Hot Topic

Exactly when our ancestors mastered fire is an ongoing question. Some anthropologists have proposed that the first use of fire by a member of our genus (Homo) took place between 1.4 million and 1.7 million years ago, based on controversial evidence in Kenya and China. Another team found traces of wood ash in a South African cave that showed use of fire by Homo erectus about 1 million years ago. In 2022, researchers in Israel found the oldest known evidence of using fire specifically for cooking, dating some burned fish bones back 780,000 years.

An even trickier question is when humans made fire, rather than just using it opportunistically (for example, by gathering it from forest fires). Researchers examining Stone Age hearths in two French caves came to the conclusion that Neanderthals in that region lacked the ability to make fire, and that the knowledge probably came about after Homo sapiens arrived there, perhaps 45,000 years ago. The debate continues.

Indigenous Practices Are Helping To Prevent Out-of-Control Wildfires

For millennia, Indigenous peoples in North America used carefully controlled fires to shape the landscape for their needs, including agriculture, cultural practices, and even preventing larger wildfires. A 2021 study of tree ring evidence from the Pueblo of Jeméz in New Mexico suggests that the residents’ fire management “created a landscape that burned often but only rarely burned extensively.” In the early 20th century, however, the U.S. government began designating national forests and suppressing all fires as soon as they started there. Wildfires subsequently got worse by feeding on the overgrowth of dry vegetation. The Forest Service and other agencies are now collaborating with Tribal managers to adapt traditional fire practices into management policies, aiming to reduce the impact of wildfires.

Some Fires Have Been Burning for Decades — and Even Longer

Underground fossil fuel deposits occasionally catch fire, and they are almost impossible to put out. One of the most famous such fires is in Centralia, Pennsylvania; it started in May 1962 when part of an abandoned strip mine being used as a garbage dump ignited. The flames spread through extensive coal seams, and even today, wisps of smoke emanate from the ground. Another long-running underground fire, nicknamed “the Gates of Hell,” erupted in 1971 when geologists in Turkmenistan accidentally drilled into a pocket of natural gas and then set it on fire. The world’s longest-burning fire, a coal seam blaze within Mount Wingen in New South Wales, Australia, has them all beat — it’s been burning for at least 5,000 years.