Sunday, May 29, 2005

Einstein on Space

In 2001 I read Max Jammer's book on Einstein and religion [1] and liked it very much (see my review [2] of this book). So I bought Jammer's another book on space [3]. The book contains a foreword written by Albert Einstein in 1953, less than two years before his death. The foreword gives me a good understanding of the history of the concept of space, so that I almost feel it unnecessary to read Jammer's book except chapter 6, which was added in the third edition and entitled "Recent Developments."

Einstein writes as follows: There are the two concepts of space: (a) space as positional quality of the world of material objects; (b) space as container of all material objects. In case (a), space without a material object is inconceivable. In case (b), a material object can only be conceived as existing in space.

Einstein further explains like this: Newton's concept of absolute space as the independent cause of the inertial behavior of material bodies corresponds to (b). Leibniz and Huygens resisted to this concept, and the subsequent development supported their resistance, because the concept of the material object as the fundamental concept of physics was gradually replaced by that of the field. If the laws of this field are not dependent on a particular choice of coordinate system, then the introduction of an independent (absolute) space is no longer necessary. -- Einstein adds the words, "There is no space without a field." --

However, Jammer argues in chapter 6 of his book that the Leibniz-Huygens concept of space, called the theory of relational space, is no longer universally accepted, referring to the new version of relationism proposed by Reichenbach and Grünbaum. I would like to write about space again after reading Jammer's new chapter.
  1. M. Jammer, Einstein and Religion: Physics and Theology (Princeton University Press, 1999).
  2. A Scholarly Description of Einstein's Religious Philosophy (2001).
  3. M. Jammer, Concepts of Space: The History of Theories of Space in Physics 3rd enlarged edition (Dover, New York, 1993; 1st edition 1954, 2nd edition 1969, both by Harvard University Press, Cambridge, Massachusetts, 1954).

Sunday, May 22, 2005

Einstein on Atomic Bombs

I have found the following words of Albert Einstein in the May issue of the APS News published by the American Physical Society [1]:
To have security against atomic bombs and against the other biological weapons, we have to prevent war, for if we cannot prevent war every nation will use every means that is at their disposal; and in spite of all promises they make, they will do it. At the same time, so long as war is not prevented, all the governments of the nations have to prepare for war, and if you have to prepare for war, then you are in a state where you cannot abolish war. (Spoken at a one-day conference at the Institute for Advanced Study on November 17, 1946.)
These words are cited in an article by Patricia Rife of the Graduate school of Technology and Management at the University of Maryland's University College. She begins the article by writing, "Albert Einstein was morally opposed to war throughout his life, and this ethical stance had deep roots in his childhood education."

After citing the above words of Einstein near the end of the article, Rife concludes her article as follows: "These words still ring true today, 59 years later. Will a new generation hear them and rise to our own social responsibilities? ... like Einstein ...I continue to work for this ethical stance."

It is wonderful that Einstein contributed to the mankind not only by his incomparable scientific accomplishments but also by these and other heavy words on war and atomic bombs. What would Einstein say if he were alive and heard about the movement of changing the Article 9 (the renunciation of war) of the Constitution of Japan?
  1. P. Rife, "Einstein, Ethics and the Atomic Bomb" APS News, Vol. 14, No. 5, p. 8 (2005). (Article based on a talk given at the 2005 APS March Meeting in Los Angeles.)
Related Sites

Friday, May 06, 2005

Classification Schemes of Memory

As I wrote in a previous blog [1], I learned about a classification scheme of memory from the review [2] of a book [3]. I wanted to learn more about it. At a Web site [4] I have learned the following: There are three schemes of classification of memory, i.e., classification by duration, classification by information type and classification by temporal direction. The scheme I learned before is the first one, and it classifies long-term memory, the largest part of any model about memory, into declarative (explicit) and procedural (or non-declarative; implicit) memories.

The classification by information type deals only with the long-term memory. Then it is not a scheme independent of the classification by duration but the one that subdivides the latter. The explanation of the latter at the above Web site [4] is as follows:
Classification by Duration

A basic and generally accepted classification of memory is based on the duration of memory retention, and identifies three distinct types of memory: sensory memory, short-term memory, and long-term memory.
The classification by temporal direction is explained as follows:
Classification by Temporal Direction

A further major way to distinguish different memory functions is whether the content to be remembered is in the past, retrospective memory, or whether the content is to be remembered in the future, prospective memory. Thus, retrospective memory as a category includes semantic memory and episodic/autobiographical memory. In contrast, prospective memory is memory for future intentions, or 'remembering to remember' (Winograd, 1988). Prospective memory can be further broken down into event- and time-based prospective remembering. Time-based prospective memories are triggered by a time-cue, such as going to the doctor (action) at 4 pm (cue). Event-based prospective memories are intentions triggered by cues, such as remembering to post a letter (action) after seeing a mailbox (cue). Cues do not need to be related to the action (as the mailbox example is), and lists, sticky-notes, knotted handkerchiefs, or string around the finger are all examples of cues that are produced by people as a strategy to enhance prospective memory.
Can this classification be said to be the one at the same level with the classification by duration from a different viewpoint? Anyway I doubt that prospective memory is essentially different from retrospective memory. The former seems only to be the special case of the latter in which the retrospective content is a decision already made in the form of a schedule related to the future.

I also cite the description about declarative memory [4] below.
Declarative memory requires conscious recall, in that some conscious process must call back the information. It is sometimes called explicit memory, since it consists of information that is explicitly stored and retrieved.

Declarative memory can be further sub-divided into semantic memory, which concerns facts taken independent of context; and episodic memory, which concerns information specific to a particular context, such as a time and place. Semantic memory allows the encoding of abstract knowledge about the world, such as "Paris is the capital of France". Episodic memory, on the other hand, is used for more personal memories, such as the sensations, emotions, and personal associations of a particular place or time. Autobiographical memory - memory for particular events within one's own life - is generally viewed as either equivalent to, or a subset of, episodic memory. Visual memory is part of memory preserving some characteristics of our senses pertaining to visual experience. We are able to place in memory information that resembles objects, places, animals or people in sort of a mental image.
At first I thought that the word "information" used in the review [2] to explain the semantic memory seemed a little odd in the context. Considering the fact that classification of memory can be made by information type, however, the use of the word "information" is quite natural.

  1. Speeding Up of Life at Higher Ages (May 4, 2005).
  2. Y. Dudai, Nature Vol. 434, p. 823 (2005).
  3. D. Draaisma, Why Life speeds Up As You Get Older: How Memory Shapes Our Past translated by A. & E. Pomerans (Cambridge University Press, 2004).
  4. Memory - Learn all about Memory (

Wednesday, May 04, 2005

Speeding Up of Life at Higher Ages

We sometimes say, "Time passes faster as we get older." But this is a strange expression, because we cannot define the speed of time. In physics speed is defined as the distance traversed by something within a unit time, and time is not the thing that travels through space. In everyday language the concept of speed is also used to refer to the frequency of some event happening within a unit time. For example, we say about a woman who utters many words within a given duration of time, "She speaks quite quickly." However, time is not an event happening along time either.

In the latest issue of Nature I found a review [1] on the book entitled "Why Life Speeds Up As You Get Older" [2]. "Life speeds up." -- This seems to be an appropriate expression. The appropriateness comes quite naturally; the author of the book, Douwe Draaisma, is a historian of psychology at the University of Groningen in the Netherlands. I wanted to know what was the author's answer to the question "Why does life speed up as you get older?" and read the review.

The reviewer, Yadin Dudai of the Department of Neurobiology, Weizmann Institute of Science in Israel, writes a brief introduction to the science of memory in the first half of his review. Note that the subtitle of the book reviewed is "How Memory Shapes Our Past." So, I noticed that the central theme of the book is not human perception of time but memory.

From the review we learn the followings: Memory can be classified into "declarative memory" and "non-declarative memory." The latter refers to bodily memory such as habits and modified reflexes. The former refers to conscious memory, and includes "episodic memory" and "semantic memory." "Episodic memory" is mental travel to the personal past, usually involving some re-experienced emotion. "Semantic memory" is acquired information transparent to conscious awareness and not always related to unique personal experience.

Dudai then tells us these: Draaisma's book reminds us that an interest in memory is primarily synonymous with a wish to understand the joy and sorrow of personal memory, i.e., "episodic memory." The book is a fine collection for memory lovers who will appreciate the facts it contains as well as rich metaphors. The title of the book comes from one of touching essays included in it. -- Oh, I could not learn the answer to the question "Why does life speed up as you get older?" --

Then I sought other reviews on Draaisma's book at Web site. There was just one good review written by a customer. The writer, Rob Hardy, is a psychiatrist and is ranked at the 50th among customers who send reviews (by the way, I am the 3537th). He kindly writes what I wanted to know as follows: There is not a fully accepted reason for that question. William James explained in 1890 that in youth, there were novel experiences, something new every day, but that every passing year brought routine that smoothed the days, weeks, and years into a collapse of time. A period full of memories, viewed in retrospect, seems to expand and be fuller and longer. [William James (1842 - 1912) was an American philosopher and psychologist, and was the novelist Henry James's brother.]
  1. Y. Dudai, Nature Vol. 434, p. 823 (2005).
  2. D. Draaisma, Why Life speeds Up As You Get Older: How Memory Shapes Our Past translated by A. & E. Pomerans (Cambridge University Press, 2004).
  3. R. Hardy, Evaluation of Our Real Memories ( Web site, 2005).