Knowledge without frontiers Knowledge Without Frontiers | Page 63

Molten iron in an iron works.
TEMPERATURE OF THE SUN
Stefan is best known for the theory of black
body radiation, which states that the total
density of the energy flow from a black body
is proportional to the fourth power of its ther-
modynamic temperature. He put his equation
to practical use in order to estimate the tem-
perature of the Sun’s surface. By analysing
experimental data, in 1879 he determined the
best approximation thereof until then, 5,500
degrees Celsius (5,780 K). Interestingly, he was
one of the first to use the Kelvin scale, which
does not have negative values and starts at
Prominences on southwest limb of the sun 1900. Creative commons.
-273 degrees Celsius, absolute zero, at which all
movement of the fundamental building blocks
of matter ceases. The mathematical validation
of the equation was provided by his student
Ludwig Boltzmann five years later. The Stefan-
-Boltzmann law is the only law in physics disco-
vered by and named after a Slovenian.
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