Something that I usually took for granted but now that I think about it I never truly knew. How do we define life? Is it through growth and reproduction? But if that were the case then wouldn’t fire technically be alive by those standards? What about viruses? I heard that they fall into some sort of weird category due to their behavior.
Living things take stuff and turn it into other stuff. Fire does that as well, but living things turn some of that stuff into their own persistent structure, and can persist for some varying amount of time in the absence of some of the stuff they need: when fire runs out of stuff to burn, it stops existing and leaves nothing structural of itself behind.
I had a biology teacher that summed it up by saying that “life is an anti-entropy phenomenon.”
I like the Carl Sagan definition a “self-sustaining chemical system capable of Darwinian evolution.” More ideas found here.
Homeostasis. There are other factors, but that’s the big one. It’s fuzzy, with viruses and prions on the boundary.
Didn’t Picard say a wrist-watch was alive?
Life constantly uses energy to keep itself from diffusing into the environment.
In a college biology course they discussed a half dozen or so traits of life. I don’t know if those traits are universal, but looking online I found this which sound similar.
That seems to be the general definition. Even though fire grows and reproduces I wouldn’t exactly call it alive.
Fire doesn’t have offspring, doesn’t have complex chemistry, isn’t made of cells, doesn’t respond to the environment, etc.
It spreads, but it doesn’t reproduce.
Either way, they did (from what I remember) discuss how viruses were in this middle ground of life and not life.
I don’t think I have a very strong investment in the use of the term. In practice, I kind of go with “the organisms that everyone else tends to think are alive, that’s life”, but if the situation became more complicated, (most likely for-example being the emergence of sentient or apparently-sentient computers and robots and whatnot), I would pretty quickly admit I don’t have much of a working definition.
If I were in charge of marking down which of the planets we’ve studied seem to have extant life on them, I’d look towards self-sustaining processes. As with the sentient-robot thingie, I don’t feel like we’ve as of yet been confronted with serious candidates, but I can easily imagine that we could encounter some processes where some folks would say “hey that’s life” while others were saying “no it isn’t because reasons”, and I’d again be left shrugging my shoulders and admitting I don’t have much invested in the definition to begin with.
Fire does not have substance. It is the effect of a rapid chemical reaction, which produces a great deal of EM (light and heat).
Life, by contrast, is what happens while you are making plans.
Its that part that sucks before an organism ceases to exist.
I’ve read that there is not a complete consensus on how to define “life”. In particular, I’ve also seen it said that, because viruses don’t really qualify for being alive, it makes more sense to say that instead of “killing” them, a more accurate statement would be that they can be “deactivated”.
And how do seeds fit into this? They can be completely dormant for decades and then spring to life if watered?
Dennis
First, I use this simple test. There may be some nuance, but those are the basics.