12 Issues for the Future
257
Of course, Wheeler’s Experiment can be applied to material particles, as
well as photons; QM is quite explicit on this point. In 2015, A.G. Manning
and co-workers at the Australian National University carried out the experiment with an ultra-cold Helium atom [27], and observed the same quantum
effects that had been observed with photons and smaller particles.
We may ask ourselves just how large can an object be before QM gives
way to classical Newtonian physics. A recent experiment has extended this
boundary even further with the report of a two-slit interference experiment
showing the wave-like quantum behaviour of molecules comprising up to
2000 atoms [28]. The results cannot be explained classically, and are in
excellent agreement with the predictions of Quantum Mechanics.
12.9 Are Space and Time chunky?
In Chap. 5 we saw that, from as early as the 5th Century BCE, Philosophers
such as Leucippus and Democritus, queried whether matter, which superficially appears continuous, is actually constituted from small, indivisible
particles, which they called atoms. This idea lay dormant for two millennia,
until revived and confirmed by scientists such as John Dalton, Robert Brown
and Albert Einstein. Every student of chemistry today knows that if you
divide a drop of water into smaller and smaller droplets, you finally arrive at
a single molecule of water, which, when further divided, is no longer water,
but atoms of hydrogen and oxygen. This reawakening to atomic theory led
to the rich field of Fundamental Particle Physics, which is one of the exciting
frontiers of modern physics, and is described in Chaps. 8 and 9.
Quantum Mechanics carries the process of discretisation much further. In
fact any electric charge must be a multiple of the charge of an electron (with
the exception of quarks, whose charge, as we saw in Chap. 9, is a multiple of
one third the electronic charge). The development of Quantum Mechanics in
the 1920s was based on the realisation that not just matter, but also energy,
and other quantities such as angular momenta, come in discrete packets, or
quanta. Indeed, Einstein showed that matter and energy were different forms
of the same thing, and could be transformed back and forwards from one to
the other.
Around this time much debate was also taking place in mathematics on
the nature of the continuum of real numbers. During the period 1918–1921,
Hermann Weyl, a renowned mathematician and physicist, was tackling the
problem of providing the mathematical continuum—the real number line—
with a logically sound formulation. He came to accept that this aim was
257
Of course, Wheeler’s Experiment can be applied to material particles, as
well as photons; QM is quite explicit on this point. In 2015, A.G. Manning
and co-workers at the Australian National University carried out the experiment with an ultra-cold Helium atom [27], and observed the same quantum
effects that had been observed with photons and smaller particles.
We may ask ourselves just how large can an object be before QM gives
way to classical Newtonian physics. A recent experiment has extended this
boundary even further with the report of a two-slit interference experiment
showing the wave-like quantum behaviour of molecules comprising up to
2000 atoms [28]. The results cannot be explained classically, and are in
excellent agreement with the predictions of Quantum Mechanics.
12.9 Are Space and Time chunky?
In Chap. 5 we saw that, from as early as the 5th Century BCE, Philosophers
such as Leucippus and Democritus, queried whether matter, which superficially appears continuous, is actually constituted from small, indivisible
particles, which they called atoms. This idea lay dormant for two millennia,
until revived and confirmed by scientists such as John Dalton, Robert Brown
and Albert Einstein. Every student of chemistry today knows that if you
divide a drop of water into smaller and smaller droplets, you finally arrive at
a single molecule of water, which, when further divided, is no longer water,
but atoms of hydrogen and oxygen. This reawakening to atomic theory led
to the rich field of Fundamental Particle Physics, which is one of the exciting
frontiers of modern physics, and is described in Chaps. 8 and 9.
Quantum Mechanics carries the process of discretisation much further. In
fact any electric charge must be a multiple of the charge of an electron (with
the exception of quarks, whose charge, as we saw in Chap. 9, is a multiple of
one third the electronic charge). The development of Quantum Mechanics in
the 1920s was based on the realisation that not just matter, but also energy,
and other quantities such as angular momenta, come in discrete packets, or
quanta. Indeed, Einstein showed that matter and energy were different forms
of the same thing, and could be transformed back and forwards from one to
the other.
Around this time much debate was also taking place in mathematics on
the nature of the continuum of real numbers. During the period 1918–1921,
Hermann Weyl, a renowned mathematician and physicist, was tackling the
problem of providing the mathematical continuum—the real number line—
with a logically sound formulation. He came to accept that this aim was