The Lorentz-Fitzgerald Diet

In this poem, the speaker, who considers himself vastly overweight, is trying

Illustration from the excellent book, Relativity for the Million, by Martin Gardner, and illustrated by Anthony Ravielli, Macmillan, New York, 1962.

to find a shortcut for losing that excess weight. He remembers back to his school days, in which he took a physics course that discussed relativity. In that discussion, he remembers the drawing of two spaceships passing one another at relativistic speeds (speeds that are significant fractions of the speed of light). Each of the spaceships' pilots would see the other as "compressed" in the direction of motion; hence, "instant skinniness," at least in our hero's mind. Things go downhill from there. . .

In Relativity Theory, there are three effects that become evident at relativistic speeds:

Compression in the direction of motion (which can't be measured directly, since any "ruler" you use would be shortened by the same amount);
An increase in mass (not just weight, which is dependent upon the local gravitational field); and
The slowing of time itself (hence, the "twin paradox," where one of a pair of twins goes off in a fast spaceship and, aging more slowly than his stay-at-home twin, returns to find his twin much older than himself).

The length and time-speed of an object moving at relativistic speeds are directly proportional, and mass is inversely proportional, to:

where c is the speed of light: 186,282.3960 miles per second or 299,792.4562 kilometers per second. Thus, a spaceship moving at 161,325 miles/sec would be half its normal length, time would elapse half as fast as normal, and its mass while moving would be twice its rest mass.

This poem was first published in the January/February 1999 issue of Quantum Magazine, and then in the May 1999 issue of The New Zealand Science Monthly.

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The Lorentz-Fitzgerald Diet
Copyright 1998 David Arns

When looking in the mirror one day, dismayed by what I'd seen,
"Svelte" was not the word that leapt to mind;
I seemed distinctly--thicker--than I think I'd ever been,
As I scanned both sides, the front, and the behind.

As I stood, annoyed at just how far I'd let it go,
I recalled an image seen some years before:
Something in an illustration drawn to let us know
That folks get thin as through deep space they soar!

"Yes!" I cried, "that's it! The little man inside the rocket
Got wondrous thin as past his friend he flew!"
With breakneck speed, my stopwatch in my hand, wherewith to clock it;
I'd drop off fifty pounds or more, I knew.

I hurried to my bookshelf, quickly found the physics section,
And felt the thrill that great discovery warrants;
The index had "FitzGerald" and, additional reflection
Brought associated names like "Hendrik Lorentz."

In the early days of physics, back when "ether" was a fad,
Both Lorentz and FitzGerald did some math
To show why Michelson and Morley's famed experiment went bad,
And where they had departed from the path.

I read in fascination how FitzGerald's new equation
Would show how thin a person could become.
Then, my size would be no longer just a topic for evasion,
For I'd be thin! (At least, as seen by some.)

His equation's easy: just divide velocity by c
(Where c's the speed of light, I'm sure you know)
Then square it, and subtract from 1, and finally--here's the key--
Square root the difference and, well, there you go.

Let's see, now: if I wanted to arrive at half my size,
And revel in the thinness I'd attain,
To five hundred eighty million MPH, my speed would rise,
Or else from social gatherings I'd abstain.

You can bet I was excited, one hair's breadth from going out
To buy an ion-powered ship to fly,
When a paragraph whose subject matter also talked about
The Lorentz/FitzGerald contraction caught my eye.

Oh, why I read that paragraph, I'll never, ever know!
My plans were dashed in shards upon the floor!
The next thing that I learned is time itself begins to slow,
As velocity increases more and more.

This means, of course, my normal, laid-back, easy-going style
Would slow yet more, and I could ill afford
To talk much slower still, or 'twould be such a numbing trial
That folks would doze right off, completely bored!

And that was not the worst of it! That selfsame paragraph
Described how high-speed things tend to get heavy!
So even though I'd look like I was thin (don't make me laugh),
My mass would tend toward that of a Chevy!

Well, I came to the conclusion that a "diet" such as this
Is impractical, and thus, with grim defiance,
I admit that if I just eat less, my weight won't be amiss--
For, after all, this isn't rocket science!

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