82
R. Barrett and P. P. Delsanto
equally clear that light is composed of beams of particles. Such is the weird
and almost contradictory nature of Quantum Mechanics.
5.3 One, None, and a Hundred Thousand
In one of his best-known novels [2], Uno, Nessuno, Centomila, the Italian
writer Luigi Pirandello argued that, although we may believe in our own
enduring identity, we are in a constant state of change, not only because of
the unavoidable effects of ageing, but also because we are different when we
are with different people. We might change consciously: in fact, it may be
advantageous for a young person to show off in the presence of a desirable
potential partner, and then try to look miserable when asking for financial
support from parents. But we also change unconsciously, for when we are in
different company, we instinctively tend to distort our personality.
This behaviour is, of course, only human. Or is it? If we look at the nature
of light, we might get the impression that light is no less Pirandellian than
we are. In fact, one of the few details left to be clarified at the end of the
19th Century was precisely that: the nature of light. As we have seen in the
previous Section, the wave-like character of light was very well established by
Maxwell’s theory.
On the other hand, since antiquity poets and scientists alike have spoken
of solar and lunar rays. Newton’s corpuscular theory of light asserts that light
is made up of small discrete particles (corpuscles), which travel in straight
lines (rays). The idea of tiny elementary particles comes from the first Greek
philosophers who, even though fascinated by the immensity of the heavens,
also turned their attentions to the very small.
Objects around us are usually complex, being constructed from various
materials that are obviously different from each other and from the composite
that they form. However, suppose we isolate one of these constituents, for
example, a cube of sugar. What happens if we break it into two? Will these
two distinct parts have similar properties to each other, and to the original
cube? Suppose we now break these two halves further, and continue to do so,
over and over again. Will these minute specks of sugar also continue to taste
sweet and exhibit the other properties of the original cube? Can this decomposition proceed forever, or will we reach a limit that cannot be overcome?
If we reach this limit, will the final minute particles still be sugar with all its
properties, or will they be small specks of something else entirely?
What we have described above is a Gedankenexperiment , or thought
experiment. These intellectual exercises are used frequently in philosophy,
R. Barrett and P. P. Delsanto
equally clear that light is composed of beams of particles. Such is the weird
and almost contradictory nature of Quantum Mechanics.
5.3 One, None, and a Hundred Thousand
In one of his best-known novels [2], Uno, Nessuno, Centomila, the Italian
writer Luigi Pirandello argued that, although we may believe in our own
enduring identity, we are in a constant state of change, not only because of
the unavoidable effects of ageing, but also because we are different when we
are with different people. We might change consciously: in fact, it may be
advantageous for a young person to show off in the presence of a desirable
potential partner, and then try to look miserable when asking for financial
support from parents. But we also change unconsciously, for when we are in
different company, we instinctively tend to distort our personality.
This behaviour is, of course, only human. Or is it? If we look at the nature
of light, we might get the impression that light is no less Pirandellian than
we are. In fact, one of the few details left to be clarified at the end of the
19th Century was precisely that: the nature of light. As we have seen in the
previous Section, the wave-like character of light was very well established by
Maxwell’s theory.
On the other hand, since antiquity poets and scientists alike have spoken
of solar and lunar rays. Newton’s corpuscular theory of light asserts that light
is made up of small discrete particles (corpuscles), which travel in straight
lines (rays). The idea of tiny elementary particles comes from the first Greek
philosophers who, even though fascinated by the immensity of the heavens,
also turned their attentions to the very small.
Objects around us are usually complex, being constructed from various
materials that are obviously different from each other and from the composite
that they form. However, suppose we isolate one of these constituents, for
example, a cube of sugar. What happens if we break it into two? Will these
two distinct parts have similar properties to each other, and to the original
cube? Suppose we now break these two halves further, and continue to do so,
over and over again. Will these minute specks of sugar also continue to taste
sweet and exhibit the other properties of the original cube? Can this decomposition proceed forever, or will we reach a limit that cannot be overcome?
If we reach this limit, will the final minute particles still be sugar with all its
properties, or will they be small specks of something else entirely?
What we have described above is a Gedankenexperiment , or thought
experiment. These intellectual exercises are used frequently in philosophy,