Six Not-So-Easy Pieces: Einsteins
Relativity, Symmetry, And Space-
Time by Richard P. Feynman
Pedagogical Gem
No twentieth-century American scientist is better known to a wider
spectrum of people than Richard P. Feynman (1918–1988)—physicist,
teacher, author, and cultural icon. His autobiographies and biographies
have been read and enjoyed by millions of readers around the world, while
his wit and eccentricities have made him the subject of TV specials and
even a theatrical film. The spectacular reception of the book and audio
versions of Feynman’s Six Easy Pieces (published in 1995) resulted in a
worldwide clamor for “More Feynman! More Feynman!” The outcome is
these six additional lectures, drawn from the celebrated three-volume
Lectures on Physics. Though slightly more challenging than the first six,
these lectures are more focused, delving into the most revolutionary
discovery in twentieth-century physics: Einstein’s Theory of Relativity. No
single breakthrough in twentieth-century physics (with the possible

exception of quantum mechanics) changed our view of the world more
than that of Einstein’s discovery of relativity. The notions that the flow of
time is not a constant, that the mass of an object depends on its velocity,
and that the speed of light is a constant no matter what the motion of the
observer, at first seemed shocking to scientists and laymen alike. But, as
Feynman shows so clearly and so entertainingly in the lectures chosen for
this volume, these crazy notions are no mere dry principles of physics, but
are things of beauty and elegance. No one—not even Einstein himself—
explained these difficult, anti-intuitive concepts more clearly, or with more
verve and gusto, than Richard Feynman.
Personal Review: Six Not-So-Easy Pieces: Einsteins Relativity,
Symmetry, And Space-Time by Richard P. Feynman
In the introduction to this book, Roger Penrose, another great theoretical
physicist of our times, states that "Relativity is not airy-fairy philosophy, nor
is space-time mere mathematical formalism. It is a foundational ingredient
of the very universe in which we live." On that note, it is encouraging for
many readers that this book offers a great opportunity to take that extra
step to learn the mathematical constructions for the effects of Lorentz
transformations, Einstein's equations, relativistic dynamics; equivalence of
mass and energy, Lorentz contraction and transformation of time. It
requires undergraduate level physics, but comes with easy to follow
instructions from the great maestro himself. Frequent references to his
three volume book, Lectures in physics is valuable for readers who are
familiar with his work.
Position and time measured in one frame of reference (one observer) is
different from another frame of reference (another observer). Therefore
Lorentz transformation must be examined to understand physical reality.
When we look at an object, we find that it has an apparent width and
depth, but they are not fundamental properties of the object, because if we
look at it from a different frame of reference it would look different. In
Lorentz transformations we see is a mixture of space and time. An event
(physical reality) is defined by both space and time because the position of
an object is characterized by the time. The description of the object also
depends upon the frame of reference (observer). If the observer is
travelling at the speed of light, his perception of the object would be
different from someone in a stationary state. The difference between
spacetime, and space and the interval provides interesting sense of reality.
For example, anything happening to Sun "now" will affect earth only after 8
minutes (that is how long light takes to reach us.) Thus an event "right
now" can not be defined, it is a mystery, because we are not affected by it
right now, but can be affected later after eight minutes. The "now" is an
idea or a concept of our mind, it is not physically definable at the moment,
and we have to wait to observe it separated by distance in (light) time. The
example of page 64 establishes that simultaneity is not a unique thing in
the universe, because it means different things to different observers.

Relativistic dynamics; objects moving at high speeds (during forward
motion) comparable to the speed of light shortens its physical length, and
also time slows down (time-dilation) for the stationary observer, but the
time remains the same for the moving astronaut. Thus for an observer
moving under uniform velocity will not know he is in motion. The uniform
velocity can not be detected without looking from outside, but the uniform
rotation about a fixed axis can be detected without looking from outside. As
noted earlier, the moving objects become heavier proportional to the speed
given by the famous Einstein's equation, and at close to the speed of light
the mass becomes enormous, and hence sufficient energy is not available
to move anything beyond the speed o light.
There are many websites that explains the transition from Newtonian
mechanics to the theory of relativity to explain physical reality. Some of
them are referenced below, but is great to read Richard Feynamn,
because he did not like scientific ideas without a good physical foundation,
and his approach is strikingly original. His efforts are strenuous in teaching
and making the reader understand the basic concepts. I especially
recommend chapters 3 and 4 for a quick appreciation of the subject: Highly
recommended to all readers interested in physics of reality.
[...]
3. The Pleasure of Finding Things Out: The Best Short Works of Richard
P. Feynman (Helix Books)
4. The Feynman Lectures on Physics including Feynman's Tips on
Physics: The Definitive and Extended Edition
5. The Feynman Lectures on Physics
6. Einstein's Theory of Relativity
7. Special Theory of Relativity (Routledge Classics)
8. Space and Time in Special Relativity
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