What standard will we use to judge whether it is life or not?
Surely we must realize that life on other planets can be so vastly different than life on Earth that applying an Earthly standard to classify alien lifeforms could be foolish.
Surely we must realize that life on other planets can be so vastly different than life on Earth that applying an Earthly standard to classify alien lifeforms could be foolish.
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Sure, you can fantasize about any weird life that can live anywhere that we wouldn't even recognize as life.
BUT, there is one tell-tale sign of discovery of life on an exoplanet, that can be done in a practical sense. If we indeed discover high concentrations of the diatomic form of oxygen gas (that we have in our own atmosphere) in the atmosphere of an exoplanet, then we can very likely conclude that there is life there to make it.
So far, only photosynthesis is known to be able to render elemental oxygen, and photosynthesis isn't known to occur without life. Sure some may be randomly created in the planetary formation process, but it usually ends up all burning with flammable gasses once the planet finally stabilizes. On all oxygen-free planets, all the fires that could ever happen have already happened, using up all O2. But, if there is life regenerating it, then it can remain long-term.
GRANTED, this is only a discovery of the same kind of life we have on Earth, and I admit it. However, you didn't ask "how we will know when we have exhausted all possibilities of discovery of life?". You asked "how we will know when we HAVE discovered life?".
Overlooking a planet as an option for life, and considering it uninhabitable, is NOT a discovery of life.
BUT, there is one tell-tale sign of discovery of life on an exoplanet, that can be done in a practical sense. If we indeed discover high concentrations of the diatomic form of oxygen gas (that we have in our own atmosphere) in the atmosphere of an exoplanet, then we can very likely conclude that there is life there to make it.
So far, only photosynthesis is known to be able to render elemental oxygen, and photosynthesis isn't known to occur without life. Sure some may be randomly created in the planetary formation process, but it usually ends up all burning with flammable gasses once the planet finally stabilizes. On all oxygen-free planets, all the fires that could ever happen have already happened, using up all O2. But, if there is life regenerating it, then it can remain long-term.
GRANTED, this is only a discovery of the same kind of life we have on Earth, and I admit it. However, you didn't ask "how we will know when we have exhausted all possibilities of discovery of life?". You asked "how we will know when we HAVE discovered life?".
Overlooking a planet as an option for life, and considering it uninhabitable, is NOT a discovery of life.
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Here on Earth, something is considered living when it exhibits all of the following characteristics: homeostasis, organization, metabolism, growth, adaptation, response to stimuli, and reproduction.
I can understand that alien life may be fundamentally different or may be missing a critical component that defines life on Earth. But there's no point in pondering what a redefinition might be like until we come to that point. There are not many flaws in the current definition. Alien life should be very similar, fundamentally, to Earth life. But in the case it's not, then life shall be redefined only at that point. We take everything into consideration. Would you consider a rock living? Of course you wouldn't! Would you consider an artificial intelligence robot living? Well, that's definitely up for debate. But we haven't even come across something so bizarre yet! We can't contemplate when there's no need to.
I can understand that alien life may be fundamentally different or may be missing a critical component that defines life on Earth. But there's no point in pondering what a redefinition might be like until we come to that point. There are not many flaws in the current definition. Alien life should be very similar, fundamentally, to Earth life. But in the case it's not, then life shall be redefined only at that point. We take everything into consideration. Would you consider a rock living? Of course you wouldn't! Would you consider an artificial intelligence robot living? Well, that's definitely up for debate. But we haven't even come across something so bizarre yet! We can't contemplate when there's no need to.