Relativity and Common Sense: A New Approach to Einstein

by Herman Bondi

This radically reoriented and popular presentation of Einstein's Special Theory of Relativity derives its concepts from Newtonian ideas rather than by opposing them. Sir Hermann Bondi explains the concepts of force, momentum, rotation, sound, and light and their relation to velocity. He then demonstrates that time is relative rather than absolute, that high speeds affect the nature of time, and that acceleration affects speed, time, and mass. Very little mathematics is required, and 60 illustrations augment the text.

Genres: Physics, Nonfiction, Science

192 pages, Paperback

First published January 1, 1980

Reviews

[J.D. Steens · Rating 3 out of 5]

Bondi writes that Einstein builds on and extends Newton rather than replaces him. Newton’s theories of motion work well for everyday life, but not for the velocities that approach the speed of light. That’s where Einstein comes in and this is where I ran into a wall. Even so, the book is a keeper. The key concepts and background – velocity, momentum, mass, energy, light, time, Lorentz transformation, acceleration – are all there, waiting for an eureka moment.

Addition/revision August 27, 2022:

A eureka moment occurred of sorts after a second reading. Bondi relates right up front that Newton removed velocity from the study of motion. Specifically, Bondi writes of the natural motion of celestial bodies: “Before Newton the permanence of their motion was thought to require explanation – an explanation that might be thought of as force. It was only Newton who saw that the question was wrongly put. There was nothing to be explained about velocity; what did require explanation were the changes of velocity accelerations.” Stated this way, Newton takes velocity, natural motion, right off the table for the following centuries. But, it seems to me, this skews – and confuses – the cosmic forces that are at play. Specifically, it puts inertial, straight-line, motion into an intellectual backwater, relative to gravity and its accelerating power (deviation from straight-line motion).

Did Einstein rehab inertia by pointing out that it was the flip side of gravity (they were the same thing). Whereas large gravitational masses pull smaller masses toward themselves, smaller masses resist such pulling to the degree that they can because of their own inertial mass, which “wants” to go in a straight line. (1) Counter power is a pushing away (a push of the smaller mass away from its larger mass). (2) For Einstein, then, the source of cosmic movement was both internal (straight-line movement and resistance to the deviating, acceleration forces) and external (the “pull” of larger gravitational masses).

Then it gets more complicated with Einstein’s theory on space-time curvature as it is this, the curvature by the presence of a larger gravitational mass, that creates pathways toward the gravitational center, and it is this “warpage” that curves straight-line motion toward a larger gravitational body. There’s no pulling as such; there is, rather, the following of spacetime pathways. Seen this way, isn’t gravity, as an attractive force in Newton’s sense, a now archaic term in the way that gravity is characterized?

Or, alternatively, and maybe more in line with Einstein, a large gravitational mass depresses spacetime (3) and thus it has an accelerating force on other energy and matter in its vicinity (local effect). But such a force, albeit indirect, is always, and equally, countered by an inertial force, the power of this “pulled” body to stay in a state of rest or straight-line motion. While gravity pulls, inertia resists (or pushes itself away from the pulling force).

Are there not philosophical ways to describe these physical phenomena? Isn’t inertia an equilibrium state that, yang-and yin-like (4) has an active and passive mode. In its active, thesis mode, inertia is an internal force within a body to persist in its straight-line motion or in its state of rest. In its passive, antithesis mode, inertia is an internal force to maintain its state of motion or rest via resistance to external accelerating forces.

The reason for the counter, antithesis mode is because of the active mode of inertia coming from another body that has accelerating effects, creating either by its movement or its sheer presence (large gravitational mass), deviation for another’s body’s inertial, equilibrium state (and its straight-line motion or its state of rest).

The dynamic interaction is governed by power differentials whereby (a) one prevails over another (a large body incorporates the smaller body), (b) both bodies find a balance point (gravitational center) that lies between the two, or (c) one “successfully” escapes the gravitational pull of the other (via velocity and distance).

Characterized this way, these yang-yin dynamics have philosophical implications as, off-hand, they apply to life, per Schopenhauer’s Will. Life (energy-mass) moves as thesis. It encounters resistance (from non-life, and other life). The power differential between life as a force and its encountered resistance is resolved in the form of a new equilibrium state, pretty much along the lines stated in the prior paragraph.

(1) “Attraction” is the conceptual hurdle. Bodies-mass come together, but via inertia, they resist being diverted from their straight-line motion.

(2) The phrasing of this dynamic in terms of a larger body’s effect on a smaller body is for illustrative purposes only. As I understand it, both “pull” and resist each other because of their own inertial properties.

(3). “Depresses” is not the best term as it suggests a that the spacetime is a flat fabric, much like the surface of water. Rather, spacetime becomes concentrated into a spherical, gravitational center , from all directions.

(4). I lead with “yang” because it is inertial movement (the active thesis) that drives this dialectical process.

[Daniel Reis · Rating 4 out of 5]

Excellent. Even if one doesn't fully comprehend all the intricacies of each equation presented (though they are relatively easy to follow, for some, I'd imagine, as they are presented in a sequential and straightforward manner), or is able to visualize, fully, the ramifications of temporal manipulation, this was a very sincerely helpful book. It gets deep into Lorentz Transformations and other such relative oddities that crop up if one were able to jump through time, even explaining in painstaking detail how relativity works and is defined for a layman's mind such as my own.

[Rama Rao · Rating 4 out of 5]

An illustration of Special Theory of Relativity

This is one of the first books which use common sense approach to the understanding of special theory of relativity using illustrations, drawings and diagrams. At one time this theory was considered mysterious, which is in fact obvious and clear-cut extension of ordinary ideas to the realm of high velocities. The author first presents Newtonian ideas followed by the concept and characteristic effects of special relativity in a non mathematical language. Then he introduces Lorentz Transformation (LT) in chapter 10, which involves systems of coordinates moving relative to each other and then uses LT to establish the basics of the theory. Readers with very limited mathematical background should have no trouble in understanding the elementary aspects of the relativity. This is a cute little book (177 pages, size 7.92'' x 5.36"), which is classified into three parts. The first part introduces the classical mechanics; concepts of force, momentum, angular momentum, velocity of light and uniqueness of light. The second part deals with the peculiarities of high speeds, relationship of inertial (uniformly moving, constant velocity) and moving observers and the need for theory of relativity to understand high speed situation and a brief introduction to Lorentz Transformation. The final part discusses the consequences of traveling faster than light, acceleration (non-inertial motion) and high velocities on mass. Chapters 8 and 9 are crucial to the common sense approach to the understanding of relativity. The reader may need time and patience to read these two chapters to understand relativity. Chapter 11 discusses some interesting consequences of special relativity; for travels faster than light there is no link between cause and effect, in other words that effect could precede cause. This book is very affordable and useful; I encourage the reader to consider adding this book to his/her personal library.

[Ken McGuire · Rating 5 out of 5]

Back in High School I found this in a local bookstore for $3.95. It looked interesting, and it let me see a bit of the logic of how Relativity works. And I remembered all these years later that it was a decent introduction.

Now, many years later, including after many university physics classes, including TAing one, I figured I would read it again. Looking at it with my new "glasses", I am amazed at how much solid physics is in this small little book. I would not hesitate to give this to anyone with any interest in the subject.

There are a few British expressions that may jar the reader. Some examples are a bit out of date (but not really many). Many more examples could be added.

But if you want to see the Physics of Relativity without being buried in Math, this is the place. Amazingly, while the math is hidden, this is still real Physics, and his derivation allows the reader to actually figure things out and solve real problems. In fact, I would encourage you to do so!

[Robert Lomas · Rating 5 out of 5]

This is a well written account of the limitations of Newtonian Mechanics as means of understanding the need for a relativistic approach to the unification of space-time. It builds from simple "common sense" observations into the implications of a geometry limited by the time of travel of information. It is not "maths-free" but does not require much more than an understanding of co-ordinate geometry to follow the argument. Bondi is a clear and well organised writer. If you want to understand how the stranger aspects of relativistic space time then try to get hold of a copy of this sadly out-of-print book. It would make a great Kindle read.

[Paul Bond · Rating 3 out of 5]

Out of several "Einstein for Everyone" books I tried in high school, this came the closest to sinking in. Newton's description of the physical universe has some deep appeal, an iron grip on our collective imagination. Explaining relativity in essentially Newtonian terms does pedagogical wonders -- even though I suspect it somehow represents a serious intellectual compromise, and may not provide an ideal basis for those who want to explore the theory in more detail.

[keith koenigsberg · Rating 5 out of 5]

This may be the best book about relativity I have ever read, and I have read many. The ideas are presented very clearly, with great diagrams and relatively little math. Indispensable book.