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3847 - MAX
PLANCK - introduces the quantum world? The quantum world is one in which rules that
are completely foreign to our everyday experience dictate bizarre behavior. 100 or so physicists at the dawn of the 20th
century, were trying to figure out how atoms worked. Little did they know what
their courageous, creative thinking would become a few decades later a quantum
revolution.
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------------- 3847 - MAX PLANCK - introduces the quantum world?
- The quantum revolution was a very hard
process of letting go of thinking ways that had framed science since Galileo
and Newton. These habits were firmly rooted in the notion of
“determinism“. Scientists held that
physical causes have predictable effects, or that nature follows a simple
order.
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- The idea behind this worldview was that
nature made sense, that it obeyed rational rules, like clocks do. Letting go of
this way of thinking took tremendous intellectual courage and imagination. It
is a story that needs to be told many times over.
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- The quantum era was the result of a series of
laboratory discoveries during the second half of the 19th century that refused
to be explained by the prevalent classical worldview, a view based on Newtonian
mechanics, electromagnetism, and thermodynamics, the physics of heat.
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The first problem
seems easy enough: Heated objects emit radiation of a certain kind. For
example, you emit radiation in the infrared spectrum, because your body
temperature hovers around 98° F. A candle glows in the visible spectrum because
it is hotter.
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- The question then is to figure out the
relation between the temperature of an object and its glow. To do this in a
simplified way, physicists studied not hot objects in general, but what happens
to a cavity when it is heated up. And that’s when things got weird.
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- The problem they described came to be known
as “black-body radiation“, the electromagnetic radiation trapped inside a
closed cavity. Black-body here simply means an object that produces radiation
on its own, without anything coming in.
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- Studying the properties of this radiation by
poking a hole in the cavity and studying the radiation that leaked out, it
became clear that the shape and material of the cavity do not matter. All that
matters is the temperature inside the cavity. Since the cavity is hot, atoms
from its walls will produce radiation that will fill the space.
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- The physics of the time predicted that the
cavity would be filled mostly with highly energetic, or high-frequency,
radiation. But that was not what the experiments revealed. Instead, they showed
that there is a distribution of electromagnetic waves inside the cavity with
different frequencies. Some waves dominate the spectrum, but not the ones with
the highest or lowest frequencies. How could this be?
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- The problem inspired the German physicist Max
Planck, who wrote in his Scientific Autobiography that, “This experimental
result represents something absolute, and since I had always regarded the
search for the absolute as the loftiest goal of all scientific activity, I
eagerly set to work.”
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- Max Planck was German theoretical
physicist (April, 23, 1858 –-- 4
October 1947) whose discovery of energy quanta won him the Nobel Prize in
Physics in 1918.
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- Planck made many substantial contributions to
theoretical physics, but his fame as a physicist rests primarily on his role as
the originator of quantum theory, which revolutionized human understanding of
atomic and subatomic processes.
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- Planck announced on October 19, 1900, to the Berlin Physical Society that he had
obtained a formula that nicely fitted the results of the experiments. But
finding the fit was not enough. As he wrote later, “On the very day when I
formulated this law, I began to devote myself to the task of investing it with
a true physical meaning.” Why this fit and not another one?
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- In working to explain the physics behind his
formula, Planck was led to the radical assumption that atoms do not give
radiation away continuously, but in discrete multiples of a fundamental amount.
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- Atoms deal with energy as we deal with
money, always in multiples of a smallest quantity. One dollar equals 100 cents,
and ten dollars equals 1,000 cents. All financial transactions in the U.S. are
in multiples of a cent. For the black-body radiation with its many waves of
different frequencies, each frequency released relates to a minimum
proportional “cent” of energy. The higher the frequency of the radiation, the
larger its “cent.”
-
The mathematical formula for this “minimum
cent” of energy reads E = hf, where E is the energy, f is the frequency of the
radiation, and h is Planck’s constant.
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------------------ “h” is 6.625 *10^-34 kilogram meters^2 /
second.
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- Planck found its value by fitting his formula
to the experimental black-body curve. Radiation of a particular frequency can
only appear as multiples of its fundamental “cent,” which he later called
“quantum“, a word that in late Latin meant a portion of something.
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- Planck was far from happy with the
consequences of his quantum hypothesis. In fact, he spent years trying to
explain the existence of a quantum of energy using classical physics. He was a
reluctant revolutionary, forcefully led by a deep sense of scientific honesty
to propose an idea he was not comfortable with. As he wrote in his
autobiography:
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- “My futile attempts to fit the… quantum…
somehow into the classical theory continued for a number of years, and they
cost me a great deal of effort. Many of my colleagues saw in this something
bordering on a tragedy. But I feel differently about it… I now knew that the…
quantum… played a far more significant part in physics than I had originally
been inclined to suspect, and this recognition made me see clearly the need for
the introduction of totally new methods of analysis and reasoning in the
treatment of atomic problems.”
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- Planck was right. The quantum theory he
helped propose evolved into an even deeper departure from the old physics than
Einstein’s theory of relativity. Classical physics is based on continuous
processes, such as planets orbiting the Sun or waves propagating on water. Our
whole perception of the world is based on phenomena that continuously evolve in
space and time.
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- The world of the very small works in a
completely different way. It is a world of “discontinuous processes“, a world
where rules alien to our everyday experience dictate bizarre behavior.
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- We are effectively blind to the radical
nature of the quantum world. The energies we commonly deal with contain such an
enormous number of energy quanta, that its “graininess” obscures our ability to
see it. It is as if we lived in a world of billionaires, where a cent is a
perfectly negligible amount of money. But in the world of the very small, the
cent, or the quantum, rules.
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- Planck’s hypothesis changed physics, and
eventually the world. He could not have predicted this. Neither could Einstein,
Bohr, Schrodinger, Heisenberg, and the other quantum pioneers. They knew they had
hit on something different. But no one could have anticipated how far the
quantum would change the world.
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January 26, 2022 MAX PLANCK
- introduces the quantum world?
3847
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--------------------- --- Friday, January 27, 2023 ---------------------------
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