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We could have already passed the great filter. Maybe going from single celled life to multicellular life is extremely rare. It did not appear on earth for 2-3 b

We could have already passed the great filter. Maybe going from single celled life to multicellular life is extremely rare. It did not appear on earth for 2-3 billion years after the appearance of single celled life. The creation of single celled life could also be great filter. Good evidence of that comes about a billion years after the formation of the Earth. And then there is a species that can escape its home planet. Apart from some single celled life on rocks ejected by impacts (not going to colonize the galaxy with those rare events), that took another billion years after multicellular life evolved. But, as Elon Musk emphasizes, we should get life into the solar system now. We don't know how rare life getting to this stage is and how likely it is to regress and never recover the capability. And in any case, current theory suggests that the sun will expand in the next few hundreds of millions of years making Earth uninhabitable to current life on Earth. Not very long compared to the 4.5 billion years Earth has existed.

brimble 5y ago
> And in any case, current theory suggests that the sun will expand in the next few hundreds of millions of years making Earth uninhabitable to current life on Earth. It's the brightening, more than the expansion, that'll do it. It'll ruin the carbonate/silicate cycle in a few hundred million years, progressively forcing plants into worse and worse metabolic pathways, so reducing the total energy available to the biosphere, until finally plant life is basically wiped out. IOW, 700-900MY from now, is the end of large fauna on planet Earth, followed soon after by the end of nearly all smaller fauna, too, and all or nearly all plants. Back to single-celled and very simple multi-cellular life, until most of that's killed a few hundred million years later, too, by the loss of all surface water. There will be little or no life left on Earth way before the sun significantly expands. Barring significant geo-engineering efforts.

brimble 5y ago

> And in any case, current theory suggests that the sun will expand in the next few hundreds of millions of years making Earth uninhabitable to current life on Earth. It's the brightening, more than the expansion, that'll do it. It'll ruin the carbonate/silicate cycle in a few hundred million years, progressively forcing plants into worse and worse metabolic pathways, so reducing the total energy available to the biosphere, until finally plant life is basically wiped out. IOW, 700-900MY from now, is the end of large fauna on planet Earth, followed soon after by the end of nearly all smaller fauna, too, and all or nearly all plants. Back to single-celled and very simple multi-cellular life, until most of that's killed a few hundred million years later, too, by the loss of all surface water. There will be little or no life left on Earth way before the sun significantly expands. Barring significant geo-engineering efforts.