Life on Other Planets: Crash Course Kids #45.1


earth by now you guys really know your way around this place I mean I get that you knew a lot about Earth before we started all this but now you know how things really work around here and how things work on our planet has a lot to do with why earth is so special what makes it special you well not just you I mean I’m sure you’re special and everything but what I mean is us likes giraffes and sea slugs and banana trees things with the ability to grow reproduce react and change as far as we know earth is the only planet that has life but that’s only as far as we know what about all the stuff that we don’t know remember when we talked about the vast mind-boggling headache-inducing size of the universe yeah it’s big there’s a lot we don’t know and at the top of the list of things we don’t know is the question are we alone is Earth really so special in the universe or in a galaxy far far away could there be life forms looking up into the sky wondering the exact same thing that’s a big question before we try to tackle it we should lay out what life needs here by examining the recipe for life on Earth we’ll be better able to look for life among the stars so what does life need first of all a star if we weren’t circling the Sun you and I wouldn’t be here for a couple of reasons the Sun provides energy it’s the basis of all the world’s food chains it’s the fuel that drives almost all living things the Sun also provides warmth which allows water to exist in liquid form Earth’s orbit around the Sun is in kind of a sweet spot it’s not so cold that all the water is frozen and it’s not so hot that all the water turns to vapor hmm what’s the other thing that life needs ah food living things need food for the energy that we get from it and again it all starts with the Sun plants take energy from the Sun and turn it into chemical energy which can then be transferred to all of the animals that eat those plants or other animals so if life on Earth needs food water and warmth to survive then what might alien life be like well it depends just like life on earth it would depend on the circumstances of the planet and the resources available to the living things they’re no water maybe animals instead rely on liquid methane instead of liquid water too far from a star maybe they get their energy and warmth from heat vents in the crust of the planet like the heat vents at the bottom of our oceans perhaps there’s a planet that’s always covered in thick clouds close to the ground creatures that would have a hard time seeing one another so they need another way to communicate perhaps these aliens use smells and sounds to recognize each other and perhaps they have hard outer shells to keep them protected in case other bigger aliens come around looking for a snack no matter what these aliens look like one thing’s for certain their food chains would seem very familiar how so well the planet would still need producers to turn energy from starlight into chemical energy say some kind of alien plant like things and an alien planet would also have consumers things that eat the producers and probably secondary consumers to the things that eat those first level consumers and of course this planet would need decomposers without this part of the food chain waste would build up on the planet making it totally unlivable not to mention really gross all of these organisms would all be on the planet together helping each other survive by creating complex ecosystems entangled interlocking food webs now I know this all sounds like science fiction but as we’ve talked about the universe is a crazy big place astronomers think that every star in the Milky Way galaxy has at least one planet and there are billions of stars in our galaxy alone that doesn’t include the whole rest of the mega huge universe so astronomers think that life on other planets isn’t just possible it’s likely maybe life on other planets look like dinosaurs or jellyfish maybe it’s just tiny bacteria too small to see without a microscope or maybe it’s all these things and more just like on earth a big wild party of diverse beautiful life I for one can’t wait to find out

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