Let There Be Light | National Geographic

the other factor in creating a
long-lasting light that doesn’t burn up
is the glass bulb and Paul Doherty of
the exploratorium can proven this is a
replica of a bulb from 1900 and it uses
a carbon filament now when you put
electricity through the carbon it glows
incandescent makes light but it doesn’t
melt and that’s the key incandescence is
the emission of light from something hot
carbon and tungsten have the strongest
heat resistance of all elements most
modern bulbs use tungsten filaments
because it temperatures over 1800
degrees they are much more durable
what’s the role of the bulb these lights
all have this case around them and that
case the bulb protects the hot filament
from the oxygen in the air creating an
oxygen free zone within the bulb is the
key to incandescent light this is what’s
inside it’s the filament we saw in the
clear glass bulb earlier and when I put
electric current through it and it heats
up the oxygen in the air will burn it so
here it goes so I’m going to heat up the
filament and as it gets hot enough it
will begin to burn in the air
to make bulbs glass has to be extracted
from Sam here in the sim plots and pits
of Southern Nevada they mine over 1
million tons a year sand is the
technical term used to describe rock
which has been pulverized by the ocean
or other types of erosion this cocktail
of tiny grains is around seventy six
percent silica four percent clay and
twenty percent other impurities it’s the
silica that’s needed to make clear glass
for flashlight bulbs in nature
translucent silica is seen in quartz
crystals but turning pulverized quartz
back into something you can see through
is an epic journey
around twenty six percent of this sand
will become glass
each of these trucks has enough sand to
make 560,000 flash light bulbs
to make glass sand is mixed with a few
other key ingredients