APS News


Lubell Too Ready to Compromise

Michael Lubell in his January 2005 Inside the Beltway column would have us get over the results of the last election. He says we need to build bridges to the White House and to Middle America.

Oh really? We have a my-way-or-the-highway White House that is interested only if scientists support its ideological positions. Such bridges will be built on ethical quicksand. And, just how do we build bridges to a Middle America captured by the Administration's polarizing talk of "moral values"? I guess we can start by saying: Hey, intentional creationism may have some merit after all. Lubell seems to say: To get along, you gotta go along.

What is needed from the scientific community is not capitulation but more people to speak up and fight against the control and censoring of information flow from scientists to the public. We need more people like James E. Hansen, head of the NASA Goddard Institute for Space Studies in New York, who has denounced the Bush administration's policy on climate change (see p. A17 of the Washington Post, 1/19/05). We need to give ourselves a better chance to inform the public and government officials about the results and implications of our work and have that discussed in open debate.

Free and open channels of communication are fundamental to a democracy; they are vital in making decisions for effective funding and evaluations of scientific efforts.

Harry A. Schafft
Silver Spring, MD

Cardboard Cutout Misrepresents Relativity

Ed Note: The "error" referred to in this letter is contained in the caption to a photo, where we explained the thinness of a cardboard cutout of Einstein as being "Lorentz contracted." We believe most readers took this with the intended grain of salt.

There is a physics error on page 1 of the January 2005 issue of APS News. It is an especially interesting error, since we now celebrate the 100th anniversary of Einstein's development of the special theory of relativity.

The notion that one sees an object severely contracted, if that object travels at velocity near that of light is not correct. The trap lies in the method of measurement used when "one sees." Einstein's prescription for the measurement of a rapidly moving body of unknown length l is a defining "thought" experiement Observers at rest in our system observe the ends of the moving object at points x1 and x2, simultaneously. The length of the object, as measured in our system, is then x2 - x1. In this prescription for measurement, the Lorentz contraction results.

Hovever, the experiment is difficult. Since the length is not known at the outset, one does not know where to position the two observers. Of course a continuum of observers or some other trick could be used, but an infinite number of observers is hard to come by.

When one observer looks at a rapidly moving object, the result for the length is quite different. The problem stems from the fact that the light signal from the front end of the object reaches the single observer after having traveled a different distance than the light signal from the rear. Stated another way, the light seem by the observer at any one time left the front and rear of the object at two different times.

For the case of a nearby rapidly moving object, as shown in your page 1 article, the object appears greatly elongated as it approaches, and is seen foreshortened by a much greater factor than the Lorentz factor, as it retreats. Most writers, prior to the late 1950s, made the same error as is made in your article, i.e., they assumed that one would see the Lorentz contraction. Circa 1959, two cases were treated correctly. One dealt with very close distances of approach, as in your article, and reached the conclusions described above. The other dealt with very large distances of closest approach. In that case also, one does not see the Lorentz contraction. Instead one sees the object as undistorted except for a rotation.

These conclusions do not reflect on the brilliance nor on the correctness of special relativity. Rather they indicate a certain experimental naivety of many who apply relativity to laboratory situtations.

Roy Weinstein
Houston, TX

Article Misstates Order

The December APS News article on the 2004 Nobel Prize states that the discovery of asymptotic freedom by Gross et al. led to QCD, the theory of the strong interaction. This is definitely wrong.

The theory was discussed about one year before that by Gell-Mann and myself. Gross, Wilczek and Politzer agree with us about this, as does the Nobel Foundation, which declared that the prize was solely given to asymptotic freedom, and another prize might be given to the proponents of the theory in the future.

H. Fritzsch
Munich, Germany

APS encourages the redistribution of the materials included in this newspaper provided that attribution to the source is noted and the materials are not truncated or changed.

Editor: Alan Chodos
Associate Editor: Jennifer Ouellette