This is a totally stupid question. It arose out of an ongoing conversation with my son about fire being a living thing because it has a life span (which is essentially true).
What I am looking for is a fire that has had the longest life span. It could be an eternal flame somewhere or it could be industrial waste gas or it could be a natural fire.
Please don’t say the Sun.
We wouldn’t; the Sun isn’t a fire, it’s a nuclear fusion reactor.
(By the way, fire a living thing because it has a lifespan? I’m not sure what you mean here - buildings and whatnot have life spans, even engineered into them, and they’re not alive.)
Here’s an example of a fire that’s been burning without human help since 1962.
ETA: Although I suppose the 19th century beats that nicely.
“Eternal Flame” displays blow out easily and often, even the famous ones. The pilot light on your gas stove is more reliable than JFK’s Eternal Flame.
The whole story is that we were talking about what makes things alive (BTW, he’s 6). Living things: 1) reproduce (yes to fires), excrete waste (yes to fires), have a lifespan (yes to fires), exchange gases (yes to fires), require a source of energy (yes to fires). I’m sure I’m missing something and I know that fires are not living but it was an interesting conversation and it did spark my question.
Well here is a neat little article about natural coal fires, which cotains the surprising fact that coal and oxygen can spontaniously combust at 104 degrees Fahrenheit.
Exactly how do you conclude that fire “reproduces?” And you might point out that fire doesn’t have cells, which kind of makes it non-living as far as our current model of living things goes.
Simple. I can make two fires from one. No one said anything about cells. True, all living things are made of cells as far as the cell theory goes but you have to admit, fire displays most (all) of the characteristics of living things.
That is true. Scientists and others have to work carefully when forming a definition of life to specifically exclude fire because most people have the opinion that it isn’t life even though it meets most common definitions. Requiring life to be composed of cells is just an ad hoc measure to get rid of fire as being alive. We may not require life to be composed of cells if we find life on other planets or even elsewhere on earth.
In The Singapore Grip, JG Farrell gives a great description of a huge conflagration that reminds one firefighter of a living entity.
It’s a discussion that happens every year in introductory Biology classes. While “made of cells” is a defining factor in identifying life, the “fire can reproduce” idea usually comes from the fact that a fire can/will throw out embers, which can start another fire. Kind of like other forms of life which release spores or seeds.
In an ep. of Startrek The Next Generation, Data also likens fire to a living thing.
There is a Zoroastrian Fire Temple in Yazd, Iran that claims to have had its flame since 470 AD. It was originally lit in Nahd-e-Pars in India and later brought to Iran. I’ve been to the temple in Yazd and it is behind glass and tended to by an elderly chap.
How do these underground coal fires breathe? I would expect that a mine fire would quickly use up its oxygen and smother itself before the gasses could be exchanged.
Here’s Cecil’s answer to the original question:
Why don’t we consider fire alive? What is life?
Nothing real specific, but the entropy angle is interesting.
Keep in mind that not all fire takes place in a steady or flaming state. While no expert on coal seam fires, I understand them to burn in a smoldering mode which will use available oxygen at a slower rate. Further, having visited Centralia, PA, one byproduct of the coal seam’s consumption, is creation of sink holes or subsidence, which provides new avenues for oxygen supply. Route 61 was detoured around Centralia because the ground beneath the highway was deemed insufficiently stable to safely support traffic.
When I was at school I was taught that anything that fulfilled the following seven conditions was alive: Movement, Excretion, Respiration, Reproduction, Irritability, Nutrition and Growth. We were even taught the acronym MERRING to remember this list (no, it doesn’t mean anything, but never mind).
You had to be imaginative in interpreting some of these. You might think, for instance, that plants don’t move, but no-one said the whole organism had to move. Flowers open and close in response to sunlight - that counted as “movement”. Likewise, it didn’t matter if a creature didn’t actually reproduce, as long as it could, in theory. So a Catholic priest counted as alive. 
There was a lot of wiggle room in the definition, now that I think about it. However, where fire seems to fail the test is Irritability - that is, response to external stimuli. Saying “boo” to a fire has zero effect on it.