"Here on Earth, life began very early on after our planet's formation: at least 3.8 billion years ago and possibly even earlier. By 2.7 billion years ago, it had developed photosynthesis. A little later, aerobic respiration developed, followed by eukaryotic cells, multicellularity, and sexual reproduction. More than half a million years ago, the first fungi, plants, and animals appeared, leading to a planet whose continents and oceans were overrun with large, complex, differentiated organisms."
"With so many other planets out there in the Universe, it seems like an inevitability that there would be other worlds where similar successes have occurred. However, our Sun is relatively uncommon among stars, as lower-mass red dwarf stars vastly outnumber stars like our own. Although nearly all of the Earth-sized worlds we've found so far orbit these small low-mass, low-luminosity red dwarf stars, none of them show evidence of having life on them, or even the potential for housing life on them"
Life on Earth began at least 3.8 billion years ago and developed photosynthesis by 2.7 billion years ago. Aerobic respiration, eukaryotic cells, multicellularity, and sexual reproduction followed, then fungi, plants, and animals transformed the planet. Human beings produced an intelligent, technologically advanced species on the cusp of becoming spacefaring. Red dwarf stars vastly outnumber Sun-like stars, and most known Earth-sized exoplanets orbit these low-mass, low-luminosity stars. None of those worlds show detectable signs of life or habitability with current measurements. Star formation arises from contraction and fragmentation of massive cold gas clouds that seed protostellar collapse and fusion.
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