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Re: [Phys-l] three central misconceptions about relativity



Dear Peter,

There is no agreement on the so-called misconceptions in special relativity.
For example, some physicists insist that mass dilation is out of fashion, Einstein never used it, and so on. But it is curious that there are still many others explain the concepts of mass dilation...

1. Leon Lederman (Nobel Laureate 1988) The God Particle: If the Universe Is the Answer, What Is the Question? (Houghton Mifflin, 1993) p. 205 “When the particle is accelerated its energy, E, and hence its mass increase.”

2. Robert Laughlin, (Nobel Laureate 1998) A Different Universe: Reinventing Physics from the Bottom Down (Basic Books, 2005) p. 119 “the weight gain acquired by objects moving at high speeds and the equivalence of mass and energy, are now routinely verified in laboratories all over the world”

3. Martinus J.G. Veltman (Nobel Laureate 1999) Facts and Mysteries in Elementary Particle Physics (World Scientific Publishing Company, 2003) p. 137 “Take a car, weighing, say, 1000 kg. Bring it to a speed of 100 km/h…You can see that energy weighs very little…”

4. Gerard ‘t Hooft, (Nobel Laureate 1999) In search of the ultimate building block (Cambridge University Press, 1997) p.17 “Mass and energy in this theory also depend on velocity.” "Modern physics teachers prefer to redefine mass such that it is velocity independent."

5. Julian Schwinger (Nobel Laureate 1965) Einstein's Legacy: The unity of space and time (Dover, 2002) p. 84 “But, when the speed has reached a value near c, and can no longer increase very much, the momentum still continues to grow because the mass gets larger.”

6. Richard Feynman (Nobel Laureate 1965) Perfectly Reasonable Deviations from the Beaten Track, (Basic Books, 2005) p. 283 “It was successful, the necessary consequential phenomena (like mass changing with velocity) were ultimately observed experimentally.”

7. George Smoot (Nobel Laureate 2006) Physics 139 Homework, url: http://aether.lbl.gov/www/classes/p139/homework/three.pdf

8. Stephen Hawking, A Brief History of Time (pg 20-21) “Because of the equivalence of energy and mass, the energy which an object has due to its motion will add to its mass. In other words, it will make it harder to increase its speed.”

9. Michio Kaku (2004) Einstein's Cosmos “For example, Einstein could show that the mass of an object increased the faster it moved. (Its mass would in fact become infinite if you hit the speed of light—which is impossible, which proves the unattainability of the speed of light.) This meant that the energy of motion was somehow being transformed into increasing the mass of the object. Thus, matter and energy are interchangeable!”

10. John W. Luetzelschwab (2003) "Apparatus to measure relativistic mass increase", American Journal of Physics, 71(9), 878.

11. Gerald Gabrielse (1995) "Relativistic mass increase at slow speeds", American Journal of Physics, 63(6), 568.

12. Olson, D. W. & Guarino, R. C. (1985). “Measuring the active gravitational mass of a moving object,” American Journal of Physics, 53 (7), 661


Alphonsus

Quoting "Craft, Peter" <PETER.CRAFT@det.nsw.edu.au>:

Gday All,

John Denker earlier stated <Again: Just because Einstein used contracted rulers and dilated
clocks in 1905 doesn't mean it is a good idea. In fact it is a terrible idea. It is *incompatible* with a modern (post-1908) understanding of the subject.>

In our state mandated Physics Syllabus, the document we base our teaching on and on which our state wide assessment material is based it says (in part)

1. identify that if c is constant then space and time become relative

2. discuss the concept that length standards are defined in terms of time in contrast to the original metre standard

3. explain qualitatively and quantitatively the consequence of special relativity in relation to:

- the relativity of simultaneity - the equivalence between mass and energy - length contraction - time dilation - mass dilation



Remembering that student are going to be asked question directly on this material, what is the *best* approach for giving my students a good intro level understanding of relativity while at the same time enabling them to answer questions in the state test?



They are asked questions such as



a) How has our understanding of time been influenced by the discovery of the constancy of the speed of light?

b) piece of radioactive material of mass 2.5 kilogram undergoes radioactive decay. How much energy is released if 10 grams of this mass are converted to energy during the decay process?

c) A mass is moving in an inertial frame of reference at a velocity v relative to a stationary observer. The observer measures an apparent mass increase of 0.37%.Calculate the value of v in m/s.


Regards

Peter Craft
Head Teacher Science
Corowa High School

Phone 02 6033 1889
Fax 02 6033 1889
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