Tag Archives: Physics

July 29, 1925 (a Wednesday)

Werner Heisenberg.

On this date, Werner Heisenberg’s paper establishing the basic principles of quantum mechanics was received for publication by the scientific journal Zeitschrift für Physik. He later received the Nobel Prize in Physics for 1932 “for the creation of quantum mechanics, the application of which has, inter alia, led to the discovery of the allotropic forms of hydrogen”.

The leading theory of the atom when Heisenberg entered the University of Munich in 1920 was the quantum theory of Bohr, Sommerfeld, and their co-workers. This concept was based on the classical motion of electrons in well-defined orbits around the nucleus (the so-called planetary model of the atom) and the quantum restrictions were imposed arbitrarily so that the consequences of the atomic model fit in with the existing experimental results. Although the theory had been highly successful in certain situations, during the early 1920s three areas of research indicated that this theory was inadequate and would need to be replaced. These areas included the study of light emitted and absorbed by atoms (spectroscopy); the predicted properties of atoms and molecules; and the nature of light itself–did it act like waves or like a stream of particles?

During his work in Munich, Göttingen, and Copenhagen, Heisenberg engaged intensively in the theoretical study of all three of these areas of research. By 1924 physicists in Göttingen and Copenhagen were agreed that the old quantum theory had to be replaced by some new “quantum mechanics.”

Heisenberg set himself the task of finding the new quantum mechanics upon returning to Göttingen from Copenhagen in April 1925. Since the electron orbits in atoms could not be observed, it cannot be assumed with sufficient certainty that the planetary orbits of electrons postulated by Bohr really exist, thought Heisenberg. The orbital picture visualized for this model could never be put to the test of experiment. Heisenberg argued that it was a mistake to think of the structure of the atom in visual terms at all. What we really know of the atom is what we can really observe of it. Thus, Heisenberg proposed to construct a theory for describing the structure of the atom in terms of quantities which can be actually observed, such as frequencies and intensities of the light emitted or absorbed by atoms.

On June 7, to escape the effects of a bad attack of hay fever, Heisenberg left for the pollen free North Sea island of Helgoland. While there, in between climbing and learning by heart poems from Goethe’s West-östlicher Diwan, he continued to ponder the issue and eventually realized the possible solution, and he later wrote:

It was about three o’ clock at night when the final result of the calculation lay before me. At first I was deeply shaken. I was so excited that I could not think of sleep. So I left the house and awaited the sunrise on the top of a rock.

After Heisenberg returned to Göttingen, he mailed Wolfgang Pauli his calculations along with a cover letter in which he commented:

Everything is still vague and unclear to me, but it seems as if the electrons will no more move on orbits.

About July 15, Heisenberg gave the same paper of his calculations to Max Born, saying, “…he had written a crazy paper and did not dare to send it in for publication, and that Born should read it and advise him on it…” prior to publication. Heisenberg then departed on a month-long lecture trip to Holland and England and a camping trip to Scandinavia with his youth-movement group, leaving Born to analyze the paper.

After puzzling over the derivation, Born finally recognized that the unfamiliar mathematics was related to the mathematics of special arrays of numbers known as “matrices” (singular: matrix). The mathematical devices called matrices had been known since the 1850s but Heisenberg was the first to apply them in physics. Born sent Heisenberg’s paper off for publication. Using the mathematics of matrices, scientists had at last a new mechanics for calculating the quantum behavior of particles, a quantum mechanics that was sometimes referred to as “matrix mechanics.”

References:

  • Werner Heisenberg, “Über quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen” [Quantum theoretical re-interpretation of kinematic and mechanical relations], Zeitschrift für Physik, 33, 879-893, 1925 (received July 29, 1925).
  • Werner Heisenberg. Der Teil und das Ganze. (Munich: Piper, 1969.) [English: Physics and Beyond: Encounters and Conversations. A.J. Pomerans, trans. (New York: Harper & Row, 1971.)]
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May 25, 1769

Jan Ingen-Housz

On this date, the Dutch physician and scientist Jan Ingen-Housz was elected to the Royal Society of London. He is best known today for showing that light is essential to photosynthesis and thus having discovered photosynthesis. He also discovered that plants, like animals, have cellular respiration.

In the summer of 1771, Joseph Priestley had carried out experiments with air and jars, noting that a closed jar would eventually kill a mouse and extinguish a candle, but vegetation (he used mint) would allow the mouse to live and the candle to burn. Although he did not have the official names of the “types” of air he was observing, Priestly had discovered that mice and candles need something (oxygen), and plants are capable of using other things in the air (carbon dioxide) to produce that something. In short, plants restore to the air whatever breathing animals and burning candles remove.  However, Priestly and others were unable to reproducibly demonstrate oxygen production by plants because they were unaware of the requirement for light in photosynthesis.

Probably motivated by Priestley’s publications on the subject, Ingen-Housz obtained a short leave of absence in 1779 from his post in Vienna, Austria in order to do research in England on plants during the summer months. He performed more than 500 experiments trying to determine why plants restore bad air and described the results in his exceptional book entitled Experiments Upon Vegetables, Discovering Their Great Power of Purifying the Common Air in the Sunshine and of Injuring it in the Shade and at Night, published in October 1779.

Underwater plants producing bubbles of oxygen.

In some of his experiments, Ingen-Housz placed plants underwater in a transparent container.  He found they gave off bubbles of gas only when placed in sunlight and that the bubbles gradually ceased when the plants were placed in darkness. He determined that it is not because of the warmth of the sun, and it is not the sun acting on its own, but the light of the sun reacting with the green parts (stalks and leaves) of the plants.

Once he realized a gas was being produced in the presence of light, Ingen-Housz collected it and conducted a series of tests to determine its identity. He eventually discovered that a smoldering candle would relight when it was exposed to the unknown gas. This showed that it was oxygen (known at that time as ‘dephlogisticated’ or ‘vital’ air).

In another experiment, Ingen-Housz put a plant and a candle into a transparent closed space. He allowed the system to stand in sunlight for two or three days. This assured that the air inside was pure enough to support a candle flame. But he did not light the candle. Then, he covered the closed space with a black cloth and let it remain covered for several days. When he tried to light the candle it would not light. Ingen-Housz concluded that somehow the plant must have acted in darkness like an animal. It must have breathed, fouling the air. Ingen-Housz quickly printed his book in London, allowing him to take along copies when he returned to Vienna.

The biochemistry of photosynthesis.

So why is Priestley until today a well-known name in the history of science, while Ingen-Housz is virtually unknown , except for a few historians of chemistry and botany? Ingen-Housz was a humble person, not interested in fame, pomp, or circumstance. Low-key and introverted, enjoying friendships, shying away from stardom, he stood in contrast to some of his fellow researchers of that time. For example, Priestley admitted in private that Ingen-Housz indeed had been the first to describe the beneficial power of plants in a letter to Giovanni Fabroni from 1779:

I have just read and am much pleased with Dr. Ingenhousz’ work. The things of most value that he hit upon and I missed are that leaves without the rest of the plants will produce pure air and that the difference between day and night is so considerable.

Priestley promised Ingen-Housz that he would rectify the situation in a later publication. But the attribution never appeared in print; Ingen-Housz was not even mentioned by Priestley. In the meantime, Priestley repeatedly claimed in public to have observed and published before Ingen-Housz and kept repeating this until 1800. In fact, never did Priestley give an accurate reference to Ingen-Housz’ work, never did Ingen-Housz’ name appear in the index of Priestey’s works. On the other hand, Ingen-Housz systematically referred to Priestley, with much respect.  Ingen-Housz refrained from disputing the claims of his rival colleagues, but they continued as they did, obfuscating Ingen-Housz’ rightful place in science as the discoverer of photosynthesis in the eyes of the historians and the public.

References:

December 14, 1900 (a Friday)

Max Planck

On this date, Max Planck, today considered the inventor of quantum theory, presented his paper Zur Theorie des Gesetzes der Energieverteilung in Normalspektrum (On the Theory of the Law of Energy Distribution in Normal Spectrum) at a meeting of the German Physical Society in Berlin. He shocked the science world by showing that atoms emit or absorb energy in bundles, or quanta, not in a continuous stream. This concept of energy quanta conflicted fundamentally with Newtonian physics, and its importance was not fully appreciated at first, even by Planck himself, who was something of a reluctant revolutionary. However, the evidence for its validity gradually became overwhelming as its application accounted for many discrepancies between observed phenomena and classical theory, among them Einstein’s explanation of the photoelectric effect. In 1918 Planck’s fundamental contribution was recognized with the awarding of the Nobel Prize in Physics, “for the discovery of energy quanta.”

Happy Birthday!

As a result, in view of its significance, today is considered the birthday of quantum mechanics.

Assaulting Science

I have just discovered another incarnation of pseudo-science on the internet, this one promoted by a Libb Thims:

In short, Thims’ research efforts, beginning in 1995 as a curious hobby, and in 2001 as a more intense research project, have been to understand how the inequality ΔG < 0, where ΔG = ΔH – TΔS, applies to the governance and regulation of human existence, impersonally (in relationships) and socially (within a society), viewed purely in terms of a super-observer perspective, time-accelerated human reactions (surface-attached chemical reactions) point of view—in other words, in variational speak, how differentials (time variations) of Gibbs free energy change dG (available energy release or absorption) apply to the prediction and spontaneities of interactions and reactions between people, particularly in regards to the formation and dissolution of bonds, the intimate relationship marriage bond and reproduction in particular, over the course of decades of time (changes in states of experience). In categorization terms, this defines Thims as a human free energy theorist, a rare group of about forty thinkers. [emphasis added]

The amount of disinformation on the internet is truly horrendous.