Dr.Leonisa O. Bernardo

A Question About Space and Time

Dr. LEONISA O. BERNARDO is the current Dean of the College of Arts and Sciences, Southern Luzon State University. She obtained her Doctor of Philosophy degree from the University of the Philippines Open University as a DOST-SEI scholar. Dr. Bernardo has a Master of Science Degree from the De La Salle University. A licenced chemical engineer, she has made intensive researches on the formulation of herbal bath soap from kamias fruit (K-GANDA), and thorough studies on Chemistry Education.

Vignettes are “little vines” or stories from the lives of scientists. They are historically correct but the details are fictional. Vignette is one means of integrating the history of science in science courses so that students could view science as a dynamic human process rather than a stagnant body of facts. Information is presented here in an entertaining and interesting manner to cultivate positive attitudes toward science. This vignette entitled “A Question About Space and Time” may be used as an introduction to the topic “Special Theory of Relativity.” It will help the students understand the connection between classical mechanics and the revolutionary concept of relativity and see how these concepts were discovered and developed. It also shows the making of a scientist and addresses the scientific attributes of one. Teachers are encouraged to write their own vignette that is relevant to their chosen topic and use it as a supplemental material in teaching. Vignette construction may be assigned as a project to make students appreciate the nature of science and develop their craft in writing.

Hi! You may call me Albert. I once dreamed of taking an engineering course, maybe because I grew at the sight of electrical apparatuses. Manufacturing them was my family business when we were still in Munich. Unfortunately I failed the examination I took in Zurich Polytechnic. I wonder if I will be able to pursue a career that will suit my interests. I continued my secondary education and luckily, I had excellent teachers and I enjoyed first-rate facilities in physics. This experience changed my plan and brought me to something else when I returned and studied in Zurich Polytechnic. In 1990 I graduated as a secondary school teacher of mathematics and physics.

STOP the story for discussion. Possible questions for discussion: What influences Albert in the choice of career in line with science? Do you consider Albert successful after all? Why? What characteristics make him such? At this point, does your description of Albert probably make one a scientist in the future?

Instead of practicing a teaching profession I obtained a post at the Swiss patent office in Bern. The work required careful attention while examining patent applications. It sharpened my analytical mind and my constant exposure to various inventions and discoveries enriched me with ideas. Although I had no chance of close contact with theoretician colleagues and of knowledge in scientific literature my thoughts about early scientists’ findings sustained my quest for knowledge.

Again, STOP the story for discussion. Possible questions for discussion: Do you think Albert made the right decision of working in a patent office instead of teaching in a secondary school? If you were Albert would you be able to sustain your interest in science?

I greatly admired Galileo for his bold support of the Copernican view of the moving Earth. I was fascinated by his work on mechanics of motion wherein he used pendulum and inclined planes to prove that motion did not require a force. His findings exactly opposed that of Aristotle’s beliefs that the Earth was the center of the universe and that motion required a force to initiate it.

Newton who was born several months after the death of Galileo started from what the latter has proven and the former developed his famous laws of motion. This completed the overthrow of the Aristotelian ideas that had dominated the thinking of the best minds for 2000 years.

It seems that science at the end of the nineteenth century looked back on a period of great progress. The theories developed had been very successful in explaining a wide range of natural phenomena.

Again, STOP the story for discussion. Possible questions for discussion: Could you cite some specific accomplishments of the three scientists mentioned here? How did the early scientists influence Albert as a promising scientist?

The ideas in my mind blossomed into three short papers which I wrote during my spare time. One of these papers explained a revolutionary theory that changed the whole conception of nature at the turn of the 20^th century. Let me tell you how I thought about it.

Once more I pondered on Newtonian mechanics describing how bodies change their position in space with time. I must admit that the concept of “position” and “space” confused me. While I was standing at the window of a railway carriage, which was traveling uniformly, I dropped a stone on the embankment. I saw the stone descents in a straight line. A pedestrian who was standing at the footpath said that he saw the stone fall in a parabolic curve.

So I asked, “Do the ‘positions’ traversed by the stone ‘lie in reality’ on a straight line or on a parabola?”

Again, STOP the story for discussion. Possible questions for discussion: What basic quantities are involved in describing the motion of an object? Are these quantities absolute? Answer the question asked by Albert at the last line?

What is meant here by motion “in space?” I proposed that the phrase “motion in space” be replaced by “motion relative to a practically rigid body of reference”. Instead of “body reference” let me use the term “system of coordinates”. Therefore, we say that the stone traverses a straight line relative to a system of co-ordinates rigidly attached to the carriage, but relative to a system of co-ordinates rigidly attached to the ground (embankment) the stone traverses a parabola. With this example it is clearly seen that there is no such thing as an independently existing trajectory, but only trajectory relative to a particular body of reference. This was the take off point of the more interesting concepts I have written about.

Again, STOP the story for discussion. Possible questions for discussion: Now, can you differentiate the classical mechanics of Newton from Albert’s new concept of mechanics in describing motion?

Let me take your imagination further through a “gedanken” experiment (which means thought experiment). I suggest that to understand the theory behind this, you must not rely on the intuitive concepts of time and space.

Suppose there are two identical clocks. One of the clocks is on a spaceship while the other remains on Earth. The man on the spaceship flashes a light and measures the time it takes the light to travel across and return after reflecting from a mirror. The observer on Earth observes the same process. But to this observer, the spaceship is moving. So the light travels the diagonal path in going across the spaceship, reflecting off the mirror, and returning to the sender. (See Figure 2.) Although the light travels at the same speed to this observer, it travels a greater distance. The two observers measure the time intervals required by light to travel across the spaceship.

Again, STOP the story for discussion. Possible questions for discussion: Will the two observers measure the same time intervals? Is time an absolute quantity?

Since light travels a greater distance as observed by the man on Earth, the time interval between the two events (the sending of the light, and its reception on the spaceship) is greater for the observer on Earth than for the observer on the spaceship. Let me simply state that: A moving clock run more slowly than a clock at rest. Time is actually measured to pass more slowly in any moving reference frame as compared to a clock at rest. So, I must say that time is not absolute. This is just one of the results of my special theory of relativity, and is known as time dilation. And I was known to all as EINSTEIN, the initiator of modern physics.

END OF THE STORY. Possible questions for discussion: Do you think the clocks are somehow at fault? Does the concept of time dilation violate our commonsense understanding of time? Is it hard for you to accept the concept of time dilation?

REFERENCES

Beiser, A. (1987). Concepts of Modern Physics. 4^th ed. New York: McGraw-Hill
Book company. 1-10.

Giancoli, D. (2007). Physics: Principles with Applications. 6^th ed. Singapore:
Prentice Hall International. 792-808.

Hewitt, P. (1993). Conceptual Physics. 7^th ed. New York: Harper Collins College
Publishers. 20-23.

1997 Grolier, Inc.

AUTHOR’S NOTES: Albert Einstein lived from 1879-1955. The three papers he wrote are the special theory of relativity, photoelectric effect, and statistical mechanics in Brownian motion. He continued the initial concept of the special theory of relativity into the general theory of relativity. His conclusions signal the birth of modern physics.

Scientific attitudes addressed by the vignette:

• Curiosity
• Empiricism
• Determinism
• Scientific manipulation
• Precision
• Respect for theory
• Thirst for knowledge
• Willingness to change one’s mind in response to evidence
• Suspension judgment
• Thrill of discovery
• Communication
• Accuracy
• Perseverance