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 in everything but what i
mean is us life 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
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 there 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 too 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