Letters to the Editor

Astounding maintained a lively forum (sometimes called "Brass Tacks") for readers, writers and editors to discuss stories and anything else. Many letters concerned Campbell's series, here are some with JWC's responses.

November 1936

Dear Mr. Tremaine:

Received my Astounding on Saturday and have not finished it yet, but have two comments to make:

The Incredible Invasion is A 1 - although I got fooled last month by not noticing it was a serial and starting it before I had all the installments.

So much for the roses, but-- Please take up that copy of Astounding on your desk and turn to The Veiled Planet, Page 102, first paragraph. "--pressure applied to either bromine or iodine immediately restores it to liquid --" Maybe my chemistry teacher was fooling me all the time, huh?

I like John W. Campbell, Jr. -- he's a swell author, but as a chemist he's a good astronomer.

This would be inexcusable coming in a story, but in an article -- wow! Words are feeble! It can't be expressed.

Randy Vickers, 626 Constance Avenue, Victoria, B.C.

January 1937

Dear Mr. Tremaine:

In answering Mr. Vickers, who objects to my statement, made in the article, The Veiled Planet, that "pressure applied to either bromine or iodine immediately restores it to a liquid," I am somewhat handicapped in that I am not certain as to his point of objection. I imagine, however, that it may be a question of the physical state of iodine.

At Earth-normal temperatures, iodine is a solid forming steely, flat crystals, but having quite a high vapor pressure. Like a number of other substances -- camphor, solid carbon dioxide, and other less well-known substances -- iodine cannot exist in the liquid state under Earth-normal conditions.

The statement quoted above was made in connection with the discussion of the possibilities of life on planets under widely different conditions. I had suggested that bromine or iodine might serve as the active gas in the atmosphere, with the proviso, however, that the temperature of the planet must be higher than that of Earth, about 200° C. in the case of iodine. Farther on, I added that in the case of such gases as hydrogen and oxygen, immense pressure would increase their reactivity, thus making high temperatures unnecessary, though pressure applied -- and so forth. Under those non-earthly conditions -- a temperature of 200° C. and great pressure -- iodine can exist only in the liquid state. Consider it this way: on Earth, in an open room, carbon dioxide can exist in only two states -- the solid or the gas. Liquid carbon dioxide is impossible then? Under normal Earthly conditions, it is. But most of the carbon dioxide sold is in the liquid state, because, at room temperature, carbon dioxide cannot exist as a gas, when under a pressure of 1,000 pounds per square inch. It becomes a liquid.

So with iodine. At 200° C., under great pressure, iodine becomes a liquid. Any handbook will give you the melting point -- 113.5° C. -- of iodine, which would be impossible if it had no liquid phase. As a matter of fact, every element must have all three phases, even the most stubborn, helium at one end of the scale, and tungsten at the other. Though helium is solid only at a temperature within a hairbreadth of absolute zero, and tungsten a gas only above 5,500° C., at various points in these articles, just as at various points in the universe, we will encounter both.

Actually, had I said that "iodine is restored to a solid" that would have been a slip, for, under the conditions named, iodine could not have been a solid.

If I've missed your point, Mr. Vickers, let me know. I think I can guarantee all information in the articles within the limits of our present knowledge, and the limits of practicable explanation. By the latter, I mean that, for instance, Newton's law of gravity -- F=kMm/d2 -- is not exactly accurate, of course. It should be corrected to Einstein's laws. The change, however, is so slight that for only the most exceptional cases, such as very near suns and in the whole sphere of space, is it important. The explanations, further, are impracticably difficult.

However, there will be now gross errors, if I can possibly avoid them.

John W. Campbell, Jr.

June 1937

Dear Mr. Tremaine:

In answer to the questions raised by the correspondents in Science Discussions:

Mr. Duncan: though Moulton does not believe that life exists on the Jovian worlds, neither does he believe that man will ever succeed in leaving Earth to cross space. In both instances I personally disagree with him. Since both are equally controversial, and since neither of us can bring proof to bear, I maintain the right to my belief.

Further, I suspect that Moulton's argument against life confines itself to the low temperature of Jupiter, and to the high-velocity winds. I included the low temperature as a necessary basis for life on a different scheme all together. The terrific cyclones of the extreme upper atmosphere, which is all that is visible to us, probably do not reach to the surface of the planet. The dense atmosphere could not rush by the solid or liquid planet at any such rate; fluid friction would break their force, forming a layer of relatively dead air in the altitudes wherein I propose life may exist.

Mr. Spencer: Planets do cool to the core, it is now believed. In the first few miles of descent so rapidly that a continued rise at this rate would indicate an average temperature for the entire planet of something of the order of 50,000° C. Volcanic material and geysers indicate heat beneath the surface, but we cannot assume this to be general. The present belief is that radioactivity accounts for the observed heat of the crustal rocks, and for the volcanic action. Minute as the quantity of radioactive elements in the crust is, it is still too great for general distribution.

Practically all the radio matter on Earth must be in the crust, for if it were distributed throughout the planet in the same concentration, low as it is, the heat released by the disruption of the radium, thorium, uranium, and similar atoms would fuse the planet completely in a comparatively short time, let alone preventing it from becoming solid originally. Local concentrations of not impossibly high degree, taken in consideration of the low heat transmission of rocks, would readily account for volcanic action. Radium is tremendously potent stuff, and a little natural atomic power goes a long, long way.

Mr Widmer: Telephones continue to function, despite failure of city power. I answer this only because I have a relative connected with that end of the business. Every telephone office is equipped with emergency power sources, generally a series of perfectly Gargantuan storage batteries. They come as tall as a man, 5 feet across and 4 feet wide for each cell, with about two dozen cells to a battery. Further, many stations have power plants for emergency use.

Though the Pittsburgh floods cut off city power, and forced the telephone system to conserve their powers by reducing the number of telephones in operation, at no time was service suspended. In operation, at no time was service suspended. In one of their stations, a four-hundred-ampere fuse blew several times in rapid succession, due to the sudden increase in calls, and had to be shunted with a buss bar. Within a short time the restriction on the number of operating telephones was lifted, as the united efforts of the Bell companies sent everything from Delco light plants to a Diesel-electric mobile generator unit to tide over.

Mr. Hall: In the article, Other Eyes Watching, in the February issue, I stated that the entire process of stellar collision and formation of the planets took not more than three hours, and at that I was toning down the statement of my authority.

Henry Norris Russell, in his book "The Solar System and It's Origin," states that for stellar bodies of the same order of size, and of about the mass of the Sun, meeting in glancing contact, the time cannot exceed one hour. This time limit is derived from purely astronomical calculations, and is indisputable since it is based on orbital calculations which are perfectly simple and extremely accurate. If the bodies involved were like our sun, and if they made glancing contact, that so limits the question that the time cannot have been more than an hour. I made it three hours, to take into account the possibility of very close passages not quite making contact.

An extremely close passage is necessary, to allow the strains to become sufficient to tear out the immense masses evidently erupted, and existent now as the planets.

For a complete discussion of the mechanism, I suggest that you read that excellent book, I mentioned above, and Russell's later articles "New Light on the Origin of the Planets" and "More About the New Lyttleton Theory of Planetary Origin," in the October and November numbers of the "Scientific American" for 1936.

Since the problem is so widely astronomic, rather than geological, the truly astounding picture of the two titanic masses that caused the solar system circling in that catastrophic meeting in less than an hour is not given the prominence its interest warrants.

John W. Campbell, Jr.
418 Central Avenue, Orange, New Jersey.

July 1937

In Explanation ---

Dear Mr Tremaine:

In connection with the low-temperature work mentioned in the enclosed letter on Pluto, it may be of some interest to understand the present technique of producing the extreme low temperatures available in laboratories, and some of the remarkable effects occurring under those circumstances.

The process of producing liquid air is reasonably familiar, and liquid air is itself the first step in a long series of operations required. In a complete cold-laboratory equipment the following steps are usually used: either a liquid-ammonia plant, or an air-liquefaction plant. This, in turn, is used as the cooling medium for a hydrogen liquefier. The liquid hydrogen is used to cool and liquefy helium. The real work does not begin until the liquid helium is available, for the boiling point of liquid helium is now regarded as a quite high temperature.

The problems involved in this work are interesting. Metals tend to become brittle at low temperatures. What, then, should tanks containing helium under two hundred pounds of pressure at a temperature of 260° below zero centigrade be made of? And what could you use to lubricate the compressor cylinders of an air liquefier? (Even if oil weren't a solid at that temperature, it forms an explosive mixture with liquid air.) Alloys have been developed, and tricks take care of the rest. The air liquefier is, incidentally, lubricated with liquid air, which happens to have lubricating properties. The expansion engine used in liquefying helium can't be lubricated; helium is not a lubricant, and nothing lubricates at that temperature. Therefore, they do without it by mounting the piston on a long, nonheat-conducting piston rod, and lubricate the remote bearings. There are plenty of other problems of purely mechanical nature, however.

Finally, we do have our liquid helium, to produce which we have used about a hundred thousand dollars' worth of apparatus. The temperature of even this . . . . . . . . . . . or four degrees from the absolute zero we want to attain. From this point on, however, the centigrade scale is almost entirely dropped from the reckoning.

The next step throws over all conventional cooling methods; it has to, because no substance exists which will extract heat at this temperature. The method employed instead is one of the most fascinating operations of modern physics; the heat is pumped out by magnetic force.

Not only iron, and such elements as cobalt and nickel, are magnetic; every element reacts more or less, positively or negatively, to magnetic lines of force. There are three types of reaction: the tremendous, almost violent attraction of iron, nickel, and cobalt -- the so-called ferromagnetic bodies -- and certain ores also exhibit this property; paramagnetic elements are very weakly attracted by magnets; diamagnetic elements are repelled. These last two forms of reaction are generally extremely weak, so that even the most powerful magnets will not actually pick up a mass of paramagnetic material.

However, paramagnetic elements arrange their atoms in a magnetic field into definite, oriented positions. This is the important property. A paramagnetic salt, such as gadolinium sulphate, may be placed in a magnetic field, whereupon all the gadolinium atoms arrange themselves in ordered, regular files and rows. The basic fact of importance is that in a magnetic field, gadolinium are not moving at random.

Now suppose that a piece of gadolinium sulphate is cooled in liquid helium, boiling under extremely low pressure, to a temperature of 4° absolute. A powerful, magnetic field is applied to the apparatus, and the atoms immediately arrange themselves, losing their heat of random motion to boil further liquid helium. Suppose that the gadolinium is "diluted," by being used not merely as a sulphate, but as the compound hydrated gadolinium naphthalene sulphonate. Before the gadolinium atoms can be arranged neatly and self-satisfyingly they must calm out (by absorbing) the motion of all the . . . . molecule. Finally, an equilibrium is reached, and the last of the helium boils off the now-cooled, magnetized gadolinium compound.

Then -- the magnetic field is withdrawn. Immediately, the gadolinium atoms fall away into random motion, as rapidly as possible. But -- there is darned little random heat motion in that stuff already cooled to 4° A. They attempt to pick up energy of motion, try hard to find it, but there just isn't much to be had. The result is a further, terrific drop in temperature, down, down to the lowest levels reached. Practically the last, faint dregs of energy are absorbed by atoms trying to fall away from their rigidly held, magnetized positions, but unable to get energy sufficient to escape. The very magnetic field that once forced them into place has, in effect, been frozen into them. The temperature drops to 0.004° A.

Normally, when an electromagnet is cut off from its current supply, the magnetic field drops instantly to zero. But when these ultra-frozen magnetic fields are cut off from the source of current the magnetism cannot escape; only as heat leaks in does it fall off. Almost, the magnetic field acts as a substance boiling at a temperature exceedingly close to absolute zero. At absolute zero, a magnetic field will not collapse. Above that temperature it "boils away" more or less rapidly, and is completely "volatile" at even 4° A.

At those temperatures in the thousandths place on the absolute scale, specific heat approaches zero. Normally, it takes six calories of heat to raise the temperature of liquid hydrogen one degree absolute. At those ultra-low temperatures, almost no heat at all is needed to raise the temperature a comparatively large amount.

That substances become superconductors well above this temperature is widely known; perhaps at the temperature of Pluto's poles, lead power lines thinner than human hairs could carry hundreds of amperes of current without resistance.

The possibilities of atomic research in this range are, to-day, attracting wide attention, although the immense amount of labor and the huge investment required for apparatus makes the work very costly. We have not begun to explore the range below 4° A. and barely touched that temperature. Were Pluto's temperatures available, immensely important data would result.

Sincerely -- John W. Campbell, Jr., 418 Central Avenue, Orange, New Jersey.

Concerning Iodine.

Dear Sir:

I was surprised to learn that the dispute concerning the physical properties of iodine is still waxing strong. Surely the obvious method of deciding is the same as that used for settling all scientific controversies -- experiment.

Any one who takes the trouble of carefully heating a few crystals of iodine in a test tube will find, beyond all question of doubt, that the iodine melts, and can be poured from the tube.

In 1898 the melting point of iodine was determined by Lean and Whatmough to be 113.5° C, and two years later, Drugmann and Ramsey found the boiling point, at normal atmospheric pressure, to be 184.4° C.

Let us turn now to the supposed conditions on Venus. The iodine exists, according to Mr. Campbell, at a temperature of 200° C, and under a large pressure. Since the melting point is 113.5° C, and is only very slightly affected by changes in pressure, the iodine can obviously not be in a solid state. Again, as the vapor pressure of iodine at 200° C is about 100 cm of mercury, any pressure exceeding this -- as the "high pressure" would -- would be sufficient to produce condensation.

Consequently, the only state in which the iodine could exist is the liquid state, as Mr. Campbell originally stated.

Douglas W. F. Mayer, 20 Hollin Park Road, Roundhay, Leeds 8, England.

jolomo.net | atlanta | pkd | fusion | recipes | email