Small Relationship between the Late Physicist Tonomura and Me

On Wednesday, May 2, mass media reported the following news:

Physicist Tonomura dies at 70
A fellow at electronics giant Hitachi Ltd. tipped as a future Nobel Prize winner for years, Akira Tonomura died of pancreatic cancer early on May 2, 2012, at a hospital in Saitama Prefecture. He was 70. Tonomura was known for developing electron holography for observing microscopic structures in matter using the wave nature of electrons and confirming the so-called Aharonov-Bohm effect, the existence of which had long been disputed among physicists. (Kyodo)

An obituary of Tonomura also appeared at the Web site of European Superconductivity News Forum. Besides his achievements described in the above report, the experiment in which Tonomura and his coworkers showed the quantum interference of single electrons is famous because Robert Crease mentioned it in his book "The Prism and the Pendulum: The Ten Most Beautiful Experiments in Science" (Random House, 2003; paperback, 2004). We can see the movie of this experiment in the video of Tonomura's lecture delivered at the Royal Institution in 1994. It is quite a pity that the possibility of Tonomura's receiving Nobel Prize was lost by his passing.

I exchanged email messages with him once. Within one and a half hours, he replied to my pointing out of a minor error in his review paper written in Japanese, showing his sincere personality. In order to make him learn, if he wanted to do so, what a person I am, I appended the URL of my homepage at the end of my message. So, he browsed the homepage and, unexpectedly, wrote words to praise it (regrettably, I am not updating the homepage these years). I would like to express my condolence by quoting our email messages below:

From: Tatsuo Tabata
To: Akira Tonomura
Date: Date: Thu, 6 Jan 2005 08:01
Subject: Some words about "Quantum mechanics: Japanese contributions to its fundamentals"

Dear Dr. Tonomura,

I read your article published in Butsuri Vol. 60, No. 1, p. 3 and learned much from it. I am only afraid that the expression, "S. Weinberg who made the final theory and got Nobel Prize," in line 8 of the second paragraph, Chapter 1, is not correct. Surely, Weinberg published a book entitled, "Dreams of a Final Theory" (1992; paperback 1994). However, such a theory is yet dreams of physicists, just as the whole title of his book indicates. What is made by Weinberg and Abdus Salam independently and extended by Sheldon Glashow is the unification of electromagnetism and the weak interaction, and it is part of what is called the Standard Model.

We hear that the purpose of the series of papers "Physics in Japan: The Past 100 Years and the Prospect," of which yours is one, is "to tell the public about the deep interest and charm of physics." Then, it would extremely be important to describe correctly even about minute points. I would like to recommend you to publish a correction in the next issue.

Sincerely,
Tatsuo Tabata
Home page, http://www3.ocn.ne.jp/~tttabata/

(Originally written in Japanese)

From: Akira Tonomura
To: Tatsuo Tabata
Date: Thu, 6 Jan 2005 09:28
Subject: Re: Some words about "Quantum mechanics: Japanese contributions to its fundamentals"

Dear Professor Tabata,

Thank you for your email message in which you pointed out an error in my paper. Surely, the expression, 'S. Weinberg who "made" the final theory and got Nobel Prize,' is incorrect. Passages of the paper have been much modified by the instruction of the editorial committee that senior high school students should be able to understand them. Therefore, I would like to consult a member of the committee to publish a correction.

I have browsed your home page and been much impressed to learn that it contains newest information not only about science but also other wide fields. I hope that your activity proceeds further.

Thanking you again for your message,

Sincerely,
Akira Tonomura

(Translated from Japanese by T. T.)

Boy of Age 16 Asks Me about Relativity, etc. 12. If Dark Energy Is Real, What Will Happen to the Relativity Theory?

Estimated distribution of dark matter making up 22% of the mass of the universe and dark energy making up 74%, with 'normal' matter making up only 0.4% of the mass of the universe. By PeteSF at en.wikipedia [Public domain], via Wikimedia Commons.

A friend of mine on Twitter, Aaron (a pseudonym), is an overseas, 16-year old boy, who seriously admires Albert Einstein and wants to become a physicist. He continually writes me (Ted, also a pseudonym) questions about the theory of relativity and related topics, and I am sending answers. In this series of blog posts, those questions and answers are reproduced with modifications. I am not an expert in the fields of physics related to relativity. So, my answers might contain errors. If you find any error, please do not hesitate to write a comment for the benefit, not only of the boy and me, but also of other readers.

Aaron: If dark energy* is true, what will happen to the relativity theory?

* In 1998, observations of Type Ia supernovae by the High-z Supernova Search Team followed in 1999 by the Supernova Cosmology Project suggested that the expansion of the universe is accelerating. (This work was awarded by the Nobel Prize in Physics in 2011.) Dark energy is a hypothetical form of energy that permeates all of space and causes this accelerating expansion of the universe. The exact physics behind dark energy is yet unknown. (Adapted from Ref. 1.)

Ted: It is a difficult question for me, so that I have consulted Ref. 1. We see the following explanation there:

"Some theorists think that dark energy and cosmic acceleration are a failure of general relativity on very large scales, larger than superclusters. However, most attempts at modifying general relativity have turned out to be either equivalent to theories of quintessence, or inconsistent with observations."

Thus, we can assume that, at the worst, general relativity might be necessary to be supplemented by a new theory for extremely large distances beyond the size of superclusters. Even in that case, however, it would not mean that general relativity was wrong but that it was a highly accurate approximation to the true theory of gravitational phenomena.

References

1. "Dark energy," Wikipedia: The Free Encyclopedia (11 February 2012 at 02:02).

(Originally written on June 9, 2011)

Boy of Age 16 Asks Me about Relativity, etc. 11. How Do We Prove a=F/m?

Newton's first and second laws, in Latin, from the original 1687 Principia Mathematica. Source: http://www.loc.gov/exhibits/world/images/s123.jpg
[Public domain], via Wikimedia Commons.

A friend of mine on Twitter, Aaron (a pseudonym), is an overseas, 16-year old boy, who seriously admires Albert Einstein and wants to become a physicist. He continually writes me (Ted, also a pseudonym) questions about the theory of relativity and related topics, and I am sending answers. In this series of blog posts, those questions and answers are reproduced with modifications. I am not an expert in the fields of physics related to relativity. So, my answers might contain errors. If you find any error, please do not hesitate to write a comment for the benefit, not only of the boy and me, but also of other readers.

Aaron: How do we prove a=F/m?

Ted: Your question is considered to be equivalent to this: Can we derive Newton's second law of motion F=ma from a more fundamental principle? (Here, F is the net external force acting on a body, m is the mass of the body and a is the acceleration the body obtains.) We cannot derive this equation from any other principle. Newton assumed it and presented it as a law. The validity of the equation can experimentally be confirmed. For example, we measure accelerations of the bodies of different masses by applying the same force to find that the result is inversely proportional to the known masses. Another confirmation comes from the application of the law to planetary motion. The law combined with Newton's law of universal gravitation neatly explains Kepler's laws of planetary motion empirically found. Thus, the equation is certainly a law. This law can be considered equivalently as a fundamental postulate in the (classical) mechanics of a particle* or as a definition of force and mass [1].

* The mechanics of a particle treats the motion of bodies (objects) which are considered or idealized as a particle, in the sense that the extent of the body is neglected in the evaluation of its motion, i.e., the object is small compared to the distances involved in the analysis, or the deformation and rotation of the body is of no importance in the analysis [2].

By the way, April 18 was the anniversary of Albert Einstein's death, so that I made a short blog post about it. Please enjoy the article here.

References

1. H. Goldstein, Classical Mechanics (Addison-Wesley,1950) p. 1.
2. "Newton's laws of motion," Wikipedia: The Free Encyclopedia (19 February 2012 at 09:36).

(Originally written on April 20 and 22, 2011)

Boy of Age 16 Asks Me about Relativity, etc.10. Body's Mass Increases with Increasing Speed. Then, Why Is Light Mass Zero?

The diagram of Ole Roemer's method, used in 1676, to determine the speed of light by observing the eclipse (D) and reappearance (C) of (B) Jupiter's moon Io from different locations (E, F, G, H, L, K) in Earth orbit around the Sun (A). By Roemer.jpg: Ole Roemer derivative work: Gregors (Roemer.jpg) [Public domain], via Wikimedia Commons. (This diagram is not directly related to the present question, but is put here by the reminiscence from the speed of light.")

A friend of mine on Twitter, Aaron (a pseudonym), is an overseas, 16-year old boy, who seriously admires Albert Einstein and wants to become a physicist. He continually writes me (Ted, also a pseudonym) questions about the theory of relativity and related topics, and I am sending answers. In this series of blog posts, those questions and answers are reproduced with modifications. I am not an expert in the fields of physics related to relativity. So, my answers might contain errors. If you find any error, please do not hesitate to write a comment for the benefit, not only of the boy and me, but also of other readers.

Aaron's question of this time is closely related to the question made in the fifth story of this series, "The object's mass is zero when it is traveling at the speed of light, right? Where does its mass go?" Ted's answer to that question seems to have been insufficient for his understanding.

Aaron: According to Einstein's relativity, the mass of a body will increase when its speed approaches the speed of light, right? Then, how does it come that light has zero mass?

Ted: The relativistic increase of mass is caused, so to speak, as a result of "prohibiting" the acceleration of a body with a finite rest mass to a speed equal to or larger than the speed of light in vacuum. The light quantum, or the photon, has zero mass and always has the maximum constant speed without getting acceleration, so that no "prohibition" works on light. Light is a distinct entity in the Universe.

The above explanation is quite metaphorical. Physicists' understanding is just that the photon always has zero mass and light speed without suffering any change, even independently of relative velocity of the observer to the photon, because this hypothesis proposed by Einstein is consistent with every observation.

(Originally written on April 8 and 9, 2011)

Hans Svensson (1935–2011)

On January 23, 2012, I received an email message with an attachment from my former coworker Pedro Andreo in Stockholm. The attachment was a PDF file of the latest issue of European Medical Physics News [1], in which the report of interview with him [2] and a page in memory of Hans Svensson [3] were contained. Pedro is one of two authors who wrote about memories of the Swedish radiation physicist Svensson on that page.

Searching on the Internet, I found the report "Hans Svensson — In memoriam" [4] written in Swedish. According to the report, Svensson died on December 7, 2011, after a short illness. He was born on March 18, 1935, and began his academic career as a student in Lund in 1956. In 1963, he came to Umeå as a medical physicist and received his doctorate there in 1970 in the subject of radiation physics. In 1982, he became full-time professor of radiation physics associated with the mission of an operation manager, a position he held until his retirement in 2000. During his career, he had significant international commitments and received a number of prestigious awards. He has been active professor emeritus at Umeå University since 2000.

Pedro praises Svensson's work done as the Chairman of Report Committee for ICRU Report 35 [5] by the words "probably his greatest single achievement" [3]. I learned Svenssons's name well before the publication of this report, probably by ICRU Report 21 [6], which was the earlier version of ICRU Report 35 with an essentially same title as that and contained seven papers of Svensson's group in its list of references.* I talked with Svensson twice, once on a day of the International Conference on Radiation Research held in Tokyo in 1979 and next in his office at IAEA in May 1989 (the above photo was taken on the latter occasion). Both our meetings were of a short time, but I vividly remember his kindness. Indeed, it was he who gave me helpful advice to cooperate with Pedro.** I sincerely pray for Hans Svensson to sleep peacefully in heaven.

References

1. European Medical Physics News, Winter 2011/12 (2012).
2. "Pedro Andreo — the road to and through Medical Physics," ibid. p. 6.
3. "Hans Svensson — one of the Pioneers in our field," ibid. p. 23.
4. M. Karlsson, "Hans Svensson — In memoriam," Web page of Radiofysik.org (2012).
5. Radiation Dosimetry: Electrons with Initial Energies Between 1 and 50 MeV, ICRU Report 21 (International Commission on Radiation Units and Measurements, 1972).
6. Radiation Dosimetry: Electron Beams with Energies Between 1 and 50 MeV, ICRU Report 35 (International Commission on Radiation Units and Measurements, 1984).

Notes

* By the way, the list of references in ICRU Report 21 also contained six of our papers on the work done at Radiation Center of Osaka Prefecture; and a similar list in ICRU Report 35, five later papers on our work.
** The collaboration produced 11 papers published in refereed journals in the period 1991–1998.