While this rule in nature is more often associated with the study of chemistry, we mention it here for the sake of completeness. One of the great conclusions rendered by science in the eighteenth century was the notion that in any chemical reaction mass is conserved; that is to say, there exists after a reaction just as much mass before the reaction. This is not immediately obvious to anyone who has hauled into the house several cords of wood and have subsequently carried out a few pails of ashes. The person most responsible for suggesting that matter is neither created nor destroyed in a chemical reaction is the French chemist Antoine Lavoisier.
Mass-Energy
The nineteenth century ended with many
of the fundamental ideas in physics and chemistry in serious peril.
J.J.Thomson showed that atoms have constituent parts and were
therefore not indivisible. Becquerel, the discoverer of radioactivity,
was on his way to showing that some atoms were changeable. Max
Planck was suggesting that light, which had been declared a wave
phenomenon by Thomas Young in 1801, now had particle properties
under the right conditions.
Despite all of this upheaval in physics, it is unlikely that anyone
anticipated the spate of change unleashed by Albert Einstein
in 1905. In other parts of this web site, the reader will see
the consequences of Einstein's work with the photoelectric effect,
for which he was awarded the Nobel prize in physics in 1921. Later
in this unit we will take a first look at special relativity and
the odd effects on space and time that follow when objects travel
close to the speed of light.
However, his most famous work in 1905 was the synthesis of that
which is lumpy and tangible (mass) together with that which is
wavy and intangible (energy). He did this ever so succinctly with
the relationship E = mc*2, perhaps the most famous equation for
anyone who has not studied physics. The rule suggests that there
is but one kind of stuff, mass-energy. Under the proper circumstances,
a small amount of mass can be annihilated to produce an enormous
quantity of energy. Or a high-energy gamma ray, upon colliding
with some target, can be converted into matter. It is this famous
equation that stands center-stage in nuclear fission and fusion.