July 1, 1965
Mr. Gerard Piel
Scientific American
415 Madison Avenue
New York, New York 10017
Dear Gerry:
I don't know who is in charge of the news releases that you call Scientific American Feature, so I am writing to you about one dated 17 June 1965, and entitled Experiments Suggest That Earth's Core is Made of Iron and Nickel.
The last paragraph of this release begins with the following sentences: "In general one or both of two effects are usually observed when materials are heavily compressed; the atoms are moved closer together, with the effect that the material becomes denser, and the geometrical arrangement of the atoms within the crystal is altered — an effect that may increase the density, have no effect on it, or even decrease the density. In one of our experiments, for example, we subjected an alloy of 90 per cent iron and 10 per cent nickel to a pressure of 4,350,000 pounds per square inch. It proved to be less compressible than pure iron end its density dropped!"
It is not true that increasing the pressure on a material can cause a decrease in the density. Such a behavior would be contrary to the principles of thermodynamics.
The statement that the density of the alloy dropped when it was subjected to a pressure of 4,350,000 pounds per square inch cannot be true.
I think that I can surmise what might have been written here (a correct description of the changes in density of the sample that might take place when the compression is carried out so rapidly that thermodynamic equilibrium is not achieved in the course of the compression). I am sure, however, that many readers would be misled by these statements.
These erroneous statements are not in the article itself, which is in the June 1965 issue of Scientific American. There are some errors in this article, and some examples of poor writing. Thus the figures showing three different structures of iron crystals are not in the positions described in the legend.
The statement is made that "At 230 kilobars the density of both became equal…" Here both refers to pure iron and in alloy. The word is misused since one could not state that the density of one became equal - the correct wording would be "The density of the two substances became equal."
I must say that I do not like the omission of the word that in the sentence "Could the discrepancy be explained by supposing lighter elements, such as silicon, are alloyed with iron in the core?" The sentence "Could the discrepancy be explained by supposing that lighter elements, such as silicon, are alloyed with iron in the core?" is much easier to understand.
This time I am not making any complaint about the scientific content of the article. The last letter of complaint that I sent to Dennis, about a serious error in an article on meteorology, was referred to the author, who has never written to me.
With best regards, I am,
Sincerely yours,
Linus Pauling
mjh
July
1, 1965
