where did quantum theory come from it
started not as a crazy idea but with a
light bulb in the early 1890s the German
Bureau of Standards asked Max Planck how
to make light bulbs more efficient so
that they would give out the maximum
light for the least electrical power
the first task Planck faced was to
predict how much light a hot filament
gives off
he knew that light consists of
electromagnetic waves with different
colors of light carried by different
frequency waves the problem was to
ensure that as much light as possible
was given off by visible waves rather
than ultraviolet or infrared he tried to
work out how much light of each color a
hot object emits but his predictions
based on electromagnetic Theory kept
disagreeing with experiments instead in
what he later called an act of despair
he through the existing theory out the
window and worked backwards from
experimental measurements the data
pointed him to a new rule of physics
light waves carry energy only in packets
with high-frequency light consisting of
large packets of energy and low
frequency light consisting of small
packets of energy the idea that light
comes in packets or quanta may sound
crazy and it was at the time but
Einstein soon related it to a much more
familiar problem sharing if you want to
make a kid happy give them a cookie but
if there are two kids and you only have
one cookie you'll only be able to cheer
them up half as much and if there are
four or eight or sixteen hundred
thousand you're not gonna make them very
happy at all if they have to share one
cookie between them in fact if you have
a room with infinitely many kids but not
infinitely many cookies if you share the
cookies evenly each kid will only get an
infinitesimally small crumb and none of
them will be cheered up and they'll
still eat all your cookies the
difference between light waves and kids
is that you can't actually have
infinitely many kid
but because light waves come in all
sizes you can have arbitrarily small
light waves so you can fit infinitely
many into a room and then the light
waves would consume all your cookies I
mean energy in fact all these
infinitesimal waves together would have
an infinite capacity to absorb energy
and they'd suck all the heat out of
anything you put in the room instantly
freezing the tea in your cup or the Sun
or even a supernova
luckily the universe doesn't work that
way because as Planck guests the tiny
high frequency waves can only carry away
energy in huge packets they're like
fussy kids who only accept exactly 37
cookies or 160 mm cookies no more and no
less because they're so picky the high
frequency waves lose out and most of the
energy is carried away in lower
frequency packets that are willing to
take an equal share this common average
energy that the packets carry is in fact
what we mean by temperature so a higher
temperature just means higher average
energy and thus by Planck's rule a
higher frequency of light emitted that's
why as an object gets hotter it glows
first infrared then grant yellow white
hotter and hotter towards blue violet
ultraviolet and so on specifically
Planck's quantum theory of fussy light
tells us that light bulb filaments
should be heated to a temperature of
about 3200 Kelvin to ensure that most of
the energy is emitted as visible waves
much hotter and we'd start tanning from
the ultraviolet light actually quantum
physics has been staring us in the face
since long before light bulbs and
tanning beds human beings have been
gazing into fires for millennia with the
color of the flames spelling out quantum
all along