Iron.
Not the kind you press
clothes with, but rather the
element which we
have a lot of
here on Earth.
Iron is produced by dying stars.
How, you ask?
Young stars, burning brightly at millions
of degrees, have lots of hydrogen,
a simple and lightweight element.
A star is so hot, it doesn't just burn its hydrogen, it
creates atomic collisions which fuse hydrogen
atoms together to make totally different
elements; that's what nuclear fusion is.
These new elements are bigger and more complex,
so the star grows.
Of course, the hydrogen doesn't last forever
(although billions of years may seem like it)
and when it is used up, the star collapses.
As the star collapses it gets even hotter, which
causes more fusion, creating even heavier
elements -- and more heat. But it can't keep
going, the new elements get too complex to fuse
together. There is a firm stopping-point
at atomic-weight 56 which is... iron .
With no more fusion going on the star cannot
hold itself together, and it explodes.
When it explodes, a heavy element
like iron is not thrown as far as
a lighter element. So planets
closer to the sun, like ours,
contain more iron than
planets farther away.
Now...what does this
have to do with red barns?
Barns are made of wood, which rots if it
stays wet a lot; a painted barn keeps water
off, so it resists decay and lasts longer.
Starting in the 1700s, farmers started painting
their barns; with no paint stores around, they
made their own, using whatever they had on
hand: skimmed milk, ground-up limestone or
shells, and red dirt for color -- a rusty
color, actually, because the dirt
was full of iron oxide.
Red is a good color for a barn. It absorbs heat
from the sun which helps keep the barn warmer
for animals inside during the winter.
And that is why dying stars
have everything to
do with red barns!
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