Synopsis:
If the study of falling bodies and celestial orbits pioneered
by Galileo,
Descartes,
and Newton
provided the right frame of mind in the human quest into the
secrets of Nature, the past century has witnessed the real
power of scientific reasoning. Re-living through that legacy
offers tremendous satisfaction for every student of physics.
The following dialogue between students at HKBU and their
teacher during the Physics Academic Week 2000, conveys some
of the excitement, and perhaps also a glimpse of what is to
come...
(Picture of Galileo - This photo was
downloaded from American Institute of Physics website http://www.aip.org/)
(Picture of Descartes - This photo was
downloaded from American Institute of Physics website http://www.aip.org/)
(Picture of Newton - This photo was downloaded
from American Institute of Physics website http://www.aip.org/)
Dialogue
 Professor,
can you name three discoveries in physics in the 20th century
that had the most impact on the mankind?
A: Atomic energy, semiconductors, laser and applications...
 What
was the most important theoretical development in physics
in the 20th century?
A: Actually two, relativity theory and quantum mechanics.
Revolutionised our views on space, time, and matter large
and small.
 What
was the state of physics at the end of the 19th century?
A: The 19th century physics is the story of ELECTRICITY.
Tremendous impact on mankind. With lights in households, life
was never the same again. Travelling made much easier... But
there were a few unsettling things, like the nature of E&M
waves --- something is waving, but can the vacuum really wave?
The Michelson-Morley
experiment... And the unexplained spectrum of
the sunlight... But by and large, people were content with
the existing theory, particularly after Maxwell's
grand unification of E and M.
(Picture of Maxwell - This photo was
downloaded from American Institute of Physics website http://www.aip.org/)
 So
who threw the stone into the tranquil water?
A: Things started to happen right around 1900
with Planck's
ingenious introduction of light quanta to explain the radiation
spectrum, but the New Physics really started to gather pace
after the seminal work of Albert Einstein in 1905, and the
exciting experimental studies on atoms...
(Picture of Planck - This photo was downloaded
from American Institute of Physics website http://www.aip.org/)
 Did
you say Einstein?
I heard that the Time magazine made him the Man
of the Century. Of course everyone knows his famous theory
on relativity... Was he really talking about the difference
between spending the evening with a beautiful girl or to sit
in a geometry class, or was there something else to it? What
made him so famous?
A: To understand Einstein you need to imagine
yourself being a young student studying physics in Europe
(more precisely a young man of Jewish tradition attending
math and physics lectures in the German-speaking part of Switzerland)
exactly 100 years ago. He had many strange ideas, but above
all he was in thorough command of the scientific knowledge
at the time and never settles for half-answers...
(Picture of Einstein - This photo was
downloaded from American Institute of Physics website http://www.aip.org/)
 The
Atom theory was the next thing to come, right?
A: You are right. Several models were postulated about the
atom at the time and it was difficult to find out which one
had the most truth in it, because each had its own difficulties
with either the experiment or the classical E&M theory
or both. But very soon, Bohr
put forward a model
that explains an unbelievably simple mathematical pattern
in the absorption spectrum of the hydrogen atom. The impact
of this discovery can be compared with that of Galileo on
the ratio of distances travelled by a ball rolling down an
inclined surface in regular time intervals... The pattern
was striking in simplicity but inconceivable for any kind
of particle motion. Eventually physicists had to invent an
excuse to explain it, i.e., that there is nothing as a particle
and nothing as a wave in this world, or put it in other words,
particle is a wave and wave is a particle... The statement
is so confusing that people are struggling with it up to this
day! Nevertheless, a beautiful mathematical theory grew out
of these shaky conceptions, i.e., the Quantum
Mechanics. So after 250 years, physicists finally
managed to surpass Newton... The theory formed the basis of
today's Physics, Chemistry and Biology, and is responsible
for all the new inventions such as the semiconductors, lasers,
computer displays... You name it.
(Picture of Bohr - This photo was downloaded
from American Institute of Physics website http://www.aip.org/)
 I
can see that you have pretty much covered my 2nd year physics
in 5 min, although it took 20 years of research if I remember
correctly. But what did physicists do after the invention
of QM?
A: Most of them were busy learning the new tool and applying
it to everything one can touch and feel. This led to the development
of solid state physics. But a few were after something deeper,
and this something is the nucleus of an atom. The nucleus
became a big, expensive, and dangerous toy for physicists.
Soon they discovered that, like everything else, the nucleus
can be broken apart and a bunch of smaller particles, sometimes
the nucleus of a lighter element, sometimes an entirely new
type of monster never seen before by humans, come out. Ever
since, physicists started to shoot or smash these particles
against anything they can get hold of or against each other
and managed to find more and more interesting properties about
them, each led to a Nobel Prize in physics! So you see one
can go pretty far with a rusty idea and big money!
 I
see¡K But was there anything that did not need so much
money and big accelerators that use up all the electricity
of a medium-sized city?
A: Of course. After the World War II, the solid state physics
undergone tremendous expansion. The invention
of transistors, although a technical development,
led to a whole new industry and generated a lot of research
money. Now we can understand and calculate almost every property
of a simple material like copper, aluminium, iron, etc., and
some alloys. We also have good theories for more complex systems
like polymers (plastic bags) and soap bubbles, and to some
extent the breathing motion of blood cells. A lot of new materials
were designed, sometimes with atomic precision because we
have mastered the principles of atomic bonding, electric conduction,
light absorption and emission, etc. There are a few loose
ends still, such as superconductivity and aspects of magnetism,
but by and large, things are under control. This was a big
progress compared to 100 years ago.
(Transistor)
 Any
thoughts about physics in the next hundred years?
A: Throughout the 20th century, physics and physicists were
in the driving seat for developments in science and technology,
in the human endeavour into the mysteries of Nature. Prominent
physicists were called in to command on the atomic bomb projects
during the World War II. Another dramatic moment in history
was when Richard
Feynman explained the cause for the explosion
of the US space shuttle Challenger by simply dipping a rubber
ring into a glass of ice water and showed how it lost its
entropic
elasticity! Just in the last decade or so, however,
physics seems to be loosing that grip. The emerging horses
that are pulling the world around in a strong way and attracting
the fascination of the public are the software
industry and biomedics. So, at least for the
moment, physics is taking a back seat. May be this is just
a period of regrouping our strength. Many of us are thinking
hard and trying to identify the hydrogen atom of biology!
One thing for sure is that biology is about something ALIVE
and REPRODUCES. These words simply do not exist in the physics
dictionary. And we know life is much less predictable than
the mechanical motion of a pendulum, although only a mad person
would characterise it as a completely random sequence of events...
There is an emerging concept called emergent properties of
a complex dynamical system. Something new emerges in a logical
yet unexpected way from the old... Life has a chance in physics,
and physics needs a new life!
(Picture of Richard Feynman - This photo
was downloaded from American Institute of Physics website
http://www.aip.org/)
10. Thank you, Professor! What you said today made me feel
proud as a student of physics. I did not know that physics
changes with time and time is relative in physics... It sounds
like physics can be interesting as well as useful. Wish you
success in your new expedition of life and, if you ever need
an assistant...
- End -
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