Science in Christian Perspective

The Evaluation of Radioactive Evidence 
On The Age of the Earth*
ROY M. ALLEN, Sc.D.
368 Ridgewood Ave.
Glen Ridge, N. J.

From: JASA 4 (December 1952): 11-20.
Paper presented at the Sixth Annual Convention of the American Scientific Affiliation at Shelton College, New York, August, 1951.

Man is naturally an inquisitive being, ever anxious to know the answer to every question arising to vex his imagination. "How old is the Earth, and when J aid life begin upon it?" are two over which mankind has been pondering for many years. Ussher's chronology was but one attempt to supply the answer. It sufficed so long as believers in the inspired Scriptures interpreted the Genesis record to imply six solar days transpiring between Genesis 1:1 and the creation of Adam. Realization that the "yoms" of creation were "God's days," defined elsewhere in the Scriptures (Ps. 90:4, and II Pet. 3:8) apparently for the specific purpose of throwing light upon Genesis 1, together with unbiased analysis of the record itself resulted in a reorientation of Christian thinking. It should be emphasized in this connection that this has not been at the expense of belittling or questioning the inspired record. Rather does it serve to prove its literal accuracy when properly read.

It has not been primarily those accepting the inspiration of the Scriptures who have been responsible for pressing the birthday of the earth back into a remote past. Mechanistic evolutionists who require an enormous amount of time for the operation of any of their numerous theories have ever been the aggressors along this line.

Many are the approaches to a solution of the question tried out as yardsticks with which to measure earth time, among which might be cited: The salt concentration of the seas; the stabilization of the tides; the time required for the earth's crust to reach its present temperature; the rate of attrition of surface rocks; their re-deposition and solidification as sedimentary rocks, together with many others.

To apply any of these involves the making of certain assumptions but such procedure is common in scientific reasoning. The main objections to their testimony lie in the lack of agreement between them and their failure to indicate as great an age for the earth as mechanistic evolution requires. It is not surprising, therefore, that a "made-to-order" yardstick such as radioactive disintegration should be pressed into service. In the beginning, early estimates of the earth's age, as proposed by Kelvin, Rutherford, and others were around 400 to 500 million years although a few men of science went as low as 20 million. All figures were soon increased materially, Sir James 'Jeans putting it at 1450 million years. Later estimates went to 2000 million while the present tendency is to place a possible ceiling appreciably higher than this, even exceeding 3000 million years.

The Symposium on "The Age of the Earth" published by the A.S.A. in 1948 constitutes a fine presentation of the fundamentals involved in radioactive methods of dating. It makes unnecessary at this time a further review of the methods themselves, of which there are several. Briefly summing up the evidence on which radioactive dating is being accomplished, we can itemize it as follows:

1. All radioactive elements are continually decaying or decomposing (through giving off energy) into elements of lower atomic weight.

2. The rate of decay is specific for each element; some so slow their lives are measured by many billion of years; others, largely intermediate radioactive elements, may have lives measured in minutes (or less), hours, days, or years. The average life of radium, which is itself an intermediate element, is around 2500 years. To reach complete decay requires a much longer time than this. For practical purposes the rate of decay is expressed in half-life, that is, the time when one-half the original total energy would be gone, Then the average life is equal to 1.45 times this figure, a value derived by integrating the curve of total life.

3. It is possible to determine the half-life of all radioactive elements very accurately.

4. The rate of decay in every case has been found to be absolutely constant. These rates, so far as we are able to determine, are unaffected by any known external condition (e.g., such as temperature, etc.) and by such evidence as is available, identical in past ages to the present rates of decay.

5. The end products resulting from decay of natural radioactive elements have all been determined. In the case of those of higher atomic weight than lead the stable end product is some isotope of lead and the gas helium.

6. These conditions being so, we can understand the logic of assuming that an analysis of any rock or mineral originally containing a radioactive element, e.g., uranium for example, to determine the ratio existing between the element and its' lead isotope present with it (and perhaps the helium ratio also) will indicate the age of the rock or mineral in question.

Other conditions are also recognized, some of which will become evident later, but all in all, radioactive methods of dating appear, at least on the face of it, to have much merit.

The first issue will take us back to that time considered "the beginning." In what stage was the earth then, as indicated by radioactive evidence? That a beginning of some sort is predicated is apparent from the assumption that uranium (and other radioactive elements present at that time) had not yet evidenced any decay. This is equivalent to saying that radioactive elements did not exist previously. They therefore must have been formed at some specific stage in earth formation. This is certainly in accord with Genesis 1: 1.

Regardless of what theory one elects to accept as to how the solar system came into being, the fact remains that all evidence points to a common origin for the sun and its planetary system. The formation of all the elements, probably starting with hydrogen (since this still represents 81.76% of the total volume of the sun, helium accounting for 18.17% of the remainder) and progressing to those of higher atomic weight according to some fixed law ordained by the Creator,:must have been a part of the creative process.

As to the origin of radioactive elements, it is logical that radioactive decay be a reversible process. Just as the formula for decay is U238 - energy = Pb206 + He, so the formation of uranium in the beginning can be expressed Pb2106 + He + energy = U238. How the Creator brought about conditions in the beginning to effect this synthesis must be considered at this time, as far as positive knowledge is concerned, one of the "secret things belonging unto God," (Deut. 29:29). There is, however, in the known existence of cosmic radiation, perhaps millions of

times greater in earth's formative period, one suggestion of the means He might have employed. Also present processes for producing transuranium elements offer other explanations.

Presumably all the steps involved in the decay of U238 to Pb210G were reproduced, in reverse order. But notice this Involves the lire-existence of both helium and all the natural isotopes of lead. Stable isotopes 206, 207 and 208 frequently are referred to as radiogenic since they represent stable end products of radioactive decay. The assumption appears common that these came into existence through decay processes. There is not only no logic in this assumption but ample evidence it is not correct. Nor is it an assumption held by research workers in age determinations.

Of all known elements about three out of every four have from one to several natural isotopes. This is true of lead also. The atomic weight of ordinary lead is 207.21. This figure results from the relative abundance of all'stable isotopes of lead, usually found together in the following percentages (Nier's figures):

204 - 1.48%
206 - 23.59%
207 - 22.64%
208 - 52.29%

Helium and lead are both present in the sun but no radioactive elements of higher atomic weights than lead are known to exist in it. The sun apparently represents a condition where their presence is not possible, although the building blocks out of which they can . be formed are at hand from which they can be produced under proper conditions.

Regardless of the state of formation the earth was in when the reaction producing the radioactive elements was completed it would appear to be the time indicated by radioactive evidence as "the beginning." But.still an uncertainty exists.

In a reversible process such as under discussion there are obviously three stages to consider, all of which, conceivably might be included in the total age of the earthi viz--

1) the formative period during which energy was in excess And,utilized in the formation of radioactive elements. If this were a slow process, as appears logical, it might even be measured in terms of billions of years. This would mean nothing to an eternal Creator. This time would not be indicated by radioactive decay,

2. An equilibrium stage during which energy was not flowing in either direction. Here again might be involved a long time period.

Our reasoning thus far relates to the energy factor only. Others have to be considered. As stated, both lead and helium must be present, probably in abundance, judging from the percentage of both existing in the earth today. Since a natural process of producing radioactive elements is not known to be operable in the earth under present conditions (except for the formation of C14) the limiting factor must have been the supply of high potential energy. When this was used up, or conditions on the earth so modified radioactive element building could no longer continue, the process stopped, even though both lead and helium were present in excess. By analogy, the condition existing might be likened to the formation of silicate minerals in the presence of excess silica. The latter finally forms the free silica of acid type rocks. In a case of this kind, how are we to prove that some of the helium and lead isotope found in a given analysis are not in part residual, remaining in situ within the mineral from the beginning? A simple illustration may serve to make this possible condition evident.

I own a French clock, bought over forty years ago. It was guaranteed to run 400 days with one winding. Through the years I have proved this claim justified. A friend visits me and becomes interested in the clock. I tell him of the 400 day operation and by coincidence while he is at my home the clock stops. I see him take out a pencil and start figuring. Soon he announces that I must have wound the clock on or around July 1st of the previous year. He has believed me and had faith in the clock. No wonder he is surprised when I tell him he is wrong, for I remember winding it on Christmas day. Is the fault with his mental process or figures? Not at all; I explain that when I wound it I was in a hurry so did not take time to wind it all the way up! Just so, like the portion of unwound spring in the clock, the presence of untransformed helium and lead isotope (206, 207 or 208, as the case may be) associated with a radioactive element could throw all calculations as to the age of the earth entirely off; the indicated age would be too great. This condition has been recognized and all possible means to nullify its effect on accurate age determination have been employed. But still the uncertainty persists because the only indication of untransformed lead is assumed to be the presence of Pb2,04 also. When mass spectrographic analyses indicate the presence of Pb2104 the presence of ordinary lead Pb2O,7.21 is suspected.

Were it not for the fact that radioactive decay, comprising as it does three different radioactive elements altering the proportions of lead isotopes so that ordinary lead ratios presumably no longer hold good, it should be possible to multiply the percentage of Pb204 present by 66.5 (i.e., 98.52/1.48), then subtract this value from the total lead of all isotopes present, considering only the remainder as radiogenic lead. But this, of course, will not work. About all that can be assumed is that some of the lead present was not radiogenetically produced and that the true age of the rock is under that indicated.

It is interesting to note in Nier's classic work the common absence of Pb204. In only a few instances does it show up to confuse the determination. He assumes its absence to indicate all the existing isotopes of lead to have resulted from disintegration of U238, U235 or Th. But if the synthesis (we will call it that) of radioactive elements commenced with ordinary lead (Pb2107.21) it would be selective from the start and the various isotopes would soon cease to be lead, in their progress upward toward the end of the series. Unfortunately we cannot know the conditions existing in the formation of the earth at this time, hence can only theorize. Should the temperature have been high, as appears reasonable the lead would have been in a molten state but after a time the element under formation would possess a higher melting temperature. For instance, lead melts at 327'C (620'F), radium at 960'C (1760'F), and uranium and thorium at around 18500C (33600F). When freezing temperature of any intermediate radioactive element was higher than that of the earth or the rock magma in which it was located it would solidify. Unaltered lead (e.g., all of Pb204 and such portion of the other isotopes as remained) would still be fluid and might be dispersed elsewhere. In this case we would not expect original lead to be present. It is also possible, on other grounds, that radioactive element generation, even in its incipiency would affect a segregation of all lead isotopes, Pb2O4 being rejected while the others, having an affinity for helium in the presence of energy (especially if catalytic action played any part in the synthesis) were retained. Varying local conditions might result in different final results, hence, as in the case of one of Nier's analyses, the presence of 0.884% of Pb201 could be accounted for. It is the numerous uncertainties in the problem which render true interpretation of analyses, when translated into terms of earth age difficult and inconclusive.

Once it is realized that minerals like uraninite are not chemically pure combinations as we would expect, but (to employ a modern expression understood by all) contain a little of everything but the kitchen sink, the force of this line of reasoning is appreciated. Dana's analyses of 26 different specimens of uraninite emphasize this fact. They show in addition to lead,-iron, silicon, phosphorus, zirconium, manganese, magnesium, bismuth, copper, zinc, arsenic, sulphur, and elements of the rare earth series. But most suggestive of all is the universal presence of nitrogen in fairly large amounts. Of course anilyzing for helium was not done at the time these analyses were made, but assuming the accuracy of the determination we can see the strong possibility that nitrogen accompanied the helium. In this connection it should be noted that next to hydrogen and helium the elements occurring in the sun in greatest volume are respectively oxygen, magnesium and nitrogen. Since nitrogen is not in combination with uraninite it must have been occluded in its atomic lattice from the beginning. Of course there is a possibility of an ertor in determining the gas as nitrogen, it might have been helium. It was not until several years later that Ramsey discovered helium in the mineral uraninite.

Five analyses of Norwegian specimens in Dana's list average 775 million years while two more (Arendal) give a higher figure of 925 million years. These compare with Goodman and Evan's value of 1085 million years. Again a fair check but the same comments apply. It also suggests the present tendency to establish as high a figure as possible. Dana also gives an analysis for Colorado uraninite in which the PbO is only .70%, yielding an age figure of 52 million years. This figure compares favorably with one determination by Goodman and Evans of 54 (He) or 69(Pb) age, quoted by Professor Stoner in the symposium.

There yet remains another, and I believe more plausible, objection to figures derived from radioactive determinations as they are now accepted. If the premise of the origin of radioactive elements through reversible addition of energy to lead isotopes be allowed, the logic of a step-by-step build-up through intermediate elements is sound. Action and reaction should be equal but opposite in direction.

It is, of course, well known, that uranium does not transform directly to lead, but through a multitude of steps, or intermediate elements, all radioactive themselves, some with long life, others extremely short. Granted a reverse process, at any stage of build-up all these intermediates would be present after sufficient time had elapsed to allow the initial process to reach the last of the series, U238, or other, as the case may be. Stop the process at any instant and a portion of the element which started out as a lead isotope would be present in each transitional radioactive element. In other words, radioactive equilibrium should be present in a buildup process just as much as in decay. This means that should decay commence following the stopping of the process, every intermediate element would begin decay as a parent element in that their contained energy has never attained a higher level. Helium and lead would be produced which never originated in the beginning of the series. Consider the possibility that only a fraction of the additive energy had opportunity to reach the level of U238, with a correspondingly larger portion resided in U-11 (U234). U238 has a half-life of 4.51 x 109 years while U234 has a half-life of but 2.33 x 105 years. Still other percentages of Pb206 (and helium) would be located in Ionium (8.3 X 104 years) and in Radium (1590 years) and so on all down the line. Today we could be measuring the Pb2GG ratio and assuming it all originated in U238. This same situation could apply in principle to every radioactive method so  far suggested except the C14.

Let us consider the problem from still another angle. The fact that the Pb2O7'/Pb2O6 ratio in a given determination is employed as a check comparison (and considered as one of the most reliable of all radioactive methods) against U/Pb ratios is an implication that the origin of Ut238 and U2a5 was contemporary, both starting decay at the same time. Since both are first in their corresponding cascade series this seems logical, but raises another question. The average life of U2S5 is roughly only about 1/6th that of U238. Assuming that whatever energy formed U238 was also available for U205, the percentage of their corresponding lead isotopes available as building blocks being almost identical, (i.e., 23.59% and 22.64% respectively) the amount of each uranium isotope in the beginning should have been about equal. Due to their different rates of decay there now exists in the earth only .72% of U235 as against 99.276% of U238. This ratio of 1:139 is quite constant throughout the earth, wherever uranium is found. Does it not suggest the true yardstick with which to measure time is U235 and not U238 and the maximum age of the earth is nearer the average life of U235 than the higher figures set by other ratios?

Nier appears to have sensed the validity of this argument and by figuring backwards on the basis of relative decay rates comes to the conclusion that U235 originally was not present in so large a proportion as U238. However, granted a difference in the degree of complete synthesis to end products as I have suggested and also a tendency of one to commence decay at an earlier date than the other, his estimated original percentages may be entirely off. This is a line of research that should be followed up in every one of its possible ramifications.

An approach to the age problem, not primarily of the earth but of the universe as a whole has been via the constitution of meteorites. Apparently the original idea responsible for this line of research was the establishing of a firm basis for the helium method, since there should be no loss of helium from a meteorite. While this constitutes a valuable line of research and should yield important information of a cosmological nature, actually it is subject to the same factors entering into the origin of radioactive elements as earth studies.

Helium ages, as determined from some meteorites have exceeded those from terrestrial determinations, being appreciably higher than those derived by other means. Even here, however, the picture is not clear since recent evidence indicates that considerable of the helium of meteorites may have been derived from cosmic radiation. Such would nullify age figures derived from meteorites by the helium method. If age figures determined from meteorites can be considered as evidence of the time of radioactive element formation throughout the entire solar system (or the galactic universe) it raises questions of vital importance relative to age dating in the earth. For instance:

1. Was the general formation of radioactive elements simultaneous throughout the solar universe?

2. If so, what was the spread of time required for the operation of the process and was it completed universally at substantially the same time?

3. Did disintegration begin universally at approximately the same time? In other words, did age time clocks start ticking all together?

4. Can we agree that the time when radioactive decay commenced constituted the true birthday of the earth, that is, the greatest age indicated - by any radioactive age determination either on the earth or in a meteorite?

5. If so, is the age of minerals showing a great divergence from maximum age of two or three billion years to possibly as low as 20 million to be predicated on a re-crystallization of the radioactive mineral with partial or complete elimination of previously formed end products during a reforming of the rock masses in which they occur? Is this a logical assumption?

6. Is the alternate assumption of radioactive element formation simultaneously with the origin of the rock masses logical?

These should be thought-provoking to everyone interested in this age determination problem. It is not my intention to analyze them in detail. I shall merely mention some implications which must follow as a result of applying them to the dating of geological ages. Granting the premise of uniform radioactive element formation at some distant period in the past and subsequent initial decay, let us say roughly three billion years ago, then follows, pari passu that any radioactive mineral showing an age less than this has undergone modification and re-crystallization at a later date. Such processes can be demonstrated petrographically with practically every other known mineral, hence appear logical with radioactive minerals also. The problem then becomes one of demonstrating the degree of elimination of earlier formed end-products. Some of these must have been eliminated else all age determinations would be identical. But it does not appear possible by any known means to solve this problem. In view of this every age figure except the highest, determined from truly primeval rocks unaltered from the beginning, and the lowest, where elimination of previous end products has obviously been complete, can be viewed with suspicion.

If we take the other horn of the dilemma and assume original formation of radioactive elements to have occurred at the time of formation of a given rock we must admit that so long as radioactive element formation was taking place the earth was still in an embryonic state of development and therefore its true age is that of the youngest rock, possibly only 20 to 50 million years old. In this case the spread between maximum and minimum figures (three billion to twenty million) represents the time the formation of the earth was in a state of flux, a period of gestation, as it were, of an earth about to be born. Then figures for events transpiring on a substantially completed earth should be predicated on the minimum f age figure.

On the whole, the former premise appears more logical since it is difficult to conceive of radioactive decay going on for some billions of years while at the same time reverse build-up reactions are occurring at other places possibly not far removed. Nevertheless this provides no accurate dating for various so-called geologic ages. On the basis, however, that substantially consistent conditions prevailed in the formation of all rock masses, relative ages of various rocks can be correct even though the figures themselves be on the high side. On such assumption a complete new scale of rock ages copld be worked out independent of those established from fossil dating. Much has been made of the fair degree of correspondence in figures derived from various radioactive methods of dating (though Th/Pb208 and.U238/Pb2O6 often fail to agree) but if the same factors enter into all methods alike this should be expected. Errors should be consistent all along the line.

This analysis of radioactive age determinations has not been made with the idea of condemning the methods per se, but rather for the purpose of putting them on a more firm foundation. Properly interpreted they can be of great value in establishing geophysical facts. It Is these facts we want and proper methods of approach will ultimately yield them.

It would seem the past tendency to establish the age of the earth from the beginning, dividing this time into various 'ages, is the wrong approach. As pointed out, this beginning means little, if anything, from a practical standpoint. A far better method would be to establish recent dates accurately, then work backward into the past, little by little.

From the standpoint of the fundamental A. S. A. position there exists what might well be accepted as the basis on which to calibrate all types of pre-human dating. Reference has been made to the one exception to long-time dating on which we, and every Bible believing Christian must take an absolute stand. It is in regard to the time when the man created in the image and likeness of God came on the scene. Mechanistic evolution is more concerned in placing the origin of Homo sapiens in the far-distant past than in achieving any other single objective in its program. The reason is not far to seek. The great gap existing between man and the highest of the anthropoids (not on physical or anatomical grounds but on the cultural side) on the basis of an evolutionary development demands almost an eternity of time. Those of us who have followed evolutionary estimates in this respect can recall how the figure, starting years ago at around 25,000 years has been continually increased, to 50,000, 100,000, and now to many times this latter figure. And it has always been predicated on the gradual development of an entire race of beings.

Contrasted with this concept is the Scripture pronouncement that man did not evolve but was created a single individual from whom the entire human race came. This man, created in the image and likeness of God was endowed with God-like attributes from the beginning. Man, as he exists on the earth today is actually a degenerate, possessing in many respects only vestigial evidence of what Adam was before he sinned. And on top of all this he is spiritually dead, typically animalistic in nature, (See Ece. 3:18, 11 Pet. 2:12, Jude 10) hence the need for the new birth to restore what man lost in Adam.

The Scriptures provide only a rough estimate or approximation of the time of Adam's creation, such being deduced from a study of the complete written Word in the light of secular human history and archeological (not paleontological) evidence. On the basis of the genealogical record in Genesis 10 the date of the flood must be moved back to at least 3000 to 3500 B.C. to meet definite secular history. If the predeluge genealogies are incomplete (which on the face of it appears unlikely) the time of the beginning of the human race logically can be set at 7000 to 8000 years ago, certainly not over 10,000 years as a maximum. To concede more than this is merely accepting the unproved claims and assumptions of evolution.

The question might be raised at this point,-What has this figure to do with radioactive age dating? The connection is a subtle one and possibly overlooked, even by scientifically trained fundamental believers. It can be illustrated by a simple object lesson. Suppose we take an elastic cord, say 12 inches long in Its unstretched condition and on it mark off the inches with ink dots. Next we stretch it until it is three feet long. What is now the measure of an inch. It has become three inches.

Whatever the age of the earth from the beginning, evolution has divided it into time inches, or ages, ascribing to each a portion of the whole. We are not at this time interested in the relative percentages alloted to each so-called age although an obvious readjustment of these is possible. For instance, if preCambrian time actually were 95% of the whole instead of the 75% usually credited to it, it would modify all other figures accordingly. The point to be stressed here is the effect on all time values, especially that credited to man's advent, when the overall time is stretched beyond its correct figure. It is this correct figure, whatever it may be, in which we are vitally interested. To obtain it the first move must be to take the tension out of the elastic cord until an inch actually measures such.

In other words, let us repudiate any dating of positive human finds on which evolution places a figure in excess of 10,000 years as a maximum. Rough stone artifacts associated with obvious human remains need not testify either to a great age or to (,stone age" man in an early upward advance. With equal reason they can witness to degenerate man of the race of Adam, probably pre-deluge and of the line of Cain. The Scripture record puts Cain in the land of Nod (Wandering) from the beginning, hence he and his progeny may have reached the confines of all land areas of the earth in the Scripturally alloted time of 1650 years ante the flood. Certainly no one claims the stone artifacts in use by the American Indians less than 500 years ago to testify to stone-age man in an upward progress. The degree of culture evidenced by the Toltecs, Mayas, Aztecs and Incas a thousand or more years before, completely nullifies such conclusion. This entire concept is based solely on a mechanistic evolutionary belief.

It is not my intention to discuss the pros and cons of paleontological evidence but brief mention of it is pertinent to the complete picture. To one accepting the Scripture record of man's early history, devoid of all evolutionary bias, the travesty of mechanistic attempts to demonstrate a great age for man on the earth is pitiful in the extreme. First we have them digging up a lone tooth, a jawbone, or mayhap a portion of a skull-cap which often is not exhibited to all the world for examination and opinions as to its true identity. This is followed by some pronouncement claiming its human relationship, though often disputed by other authorities who do not agree. Sooner or later, however, contra opinions are forgotten or dismissed as of no value and it is read into the record as a definite proof of man's early origin.

On the whole the greatest argument against acceptance of such occasional finds as human links is the paucity of the finds themselves. On Scripture grounds alone the evidence should be more conclusive. From Adam on the record (Gen. 5) states "they begat sons and daughters." This implies an absolute minimum of four children for every generation, let us say an average of six. Granting a generation to be 50 years (i.e., longer than at presenO there would be 33 generations in the 1650 years between Adam and the flood. In 12 generations Cain's descendants alone would number nearly one million while in the remaining 1000 years before the flood the number would go Into staggering figures. Add to these the descendants of Seth and any other children of Adam and the population of the earth must have been large indeed. Where are the bones of all these? But the real argument is,"If man did not start with Adam but existed on the earth for countless ages prior to his time, where are the literal billions of remains of all these?" Let us stand fast on this one issue, though we concede eons of earth time prior to God's creation of man.

One of the best, as well as the most recent of radioactive methods is C11 dating. The results of late tests reported by Arnold and Libby (Science, Vol. 113, 29 27, Feb. 2, 1951) are extremely valuable and enlightening. It is to be hoped this method will not be suborned by those desiring to make it prove more than direct determinations indicate. It is easy to do this by tying together organic material and assumed human remains without positive proof they are of the same age.

It would seem desirable to make radioactive determination on uranium-bearing minerals completely altered from their original form, such as gummite, coracite, carnotite, autunite, torbenite, uranosphaerite, etc., as possible follow-ups of C14 dating. They might extend the range of the latter. Yet even with altered minerals consideration should be given to the question as to whether alteration has effected separation of earlier end products. A case in point is Nier's determinations on two samples of Bedford (N. Y.) cyrtohte giving figures of 300 and 375 million years. These are consistent with other values from the nearby Connecticut pegmatites, all of which should be of the same geological age. But cyrtolite is an altered zircon, changed during relatively recent years, so gradually as to retain all the original constituents of the parent mineral. Incidentally, in connection with uranosphaerite. because of its Bi2O9 content a study of this mineral might yield data on the 4n + I radioactive series and add knowledge of this group of elements, the existence of which in the natural state has been questioned.

A practice which should be adopted as standard is the blind determination of uranium-bearing rocks and minerals without knowledge of the supposed geological age of the specimum under test. This would achieve two results-nullify previous bias as to what ought to be expected, and with results freed from possible error, indicate the true age of the rock. The force of this suggestion is evidenced by a quotation from Goodman and Evans, "More specific geological dating is, needed in the formulation of a useful lead time scale." No comment is necessary.

It appears more attention should be given to the mineralogical occurrence of uranium and thorium minerals. For instance, why do they occur largely with the acidic rocks rather than the basic? Ordinarily one would expect them to be associated with the basic ferromagnesium rocks (like the metals of the platinum group) because of closer agreement in specific gravity. What of the over-all metallic content of the rocks in which they occur most abundantly? How about relative ages of the acid and basic rocks themselves and their relative position in the earth's crust? I am referring, of course, to the distinctly deep-seated plutonic series and not volcanic or hypabyssal rocks. Attention to such considerations might help to throw light on the age question through the correlation of all possible data.

Another suggestion might be made at this time. Radioactive age dating research has largely been confined to minerals found in rocks the ages of which are assumed to be indicated by basic stratigraphical evidence. It is generally accepted that sedimentary rocks themselves cannot testify directly. This assumption may be incorrect. All radioactive minerals originally present in the rocks from which the comminuted material was derived must still exist, even though widely disseminated. Because of their high specific gravity it should be possible to separate out enough of these comminuted minerals to test for U/Pb ratios. This type of test could be tried out through preliminary study of unconsolidated sands and detrital material. Even in this case some errors on the high or low side might be expected. Certainly tests on relatively pure zircon and monazite sands, also magnetically separated magnetite and ilmenite should prove interesting.

As a part of the complete picture it may be of interest to consider pleochroic halos and the help which might be derived from them. These are discussed in F. Alton Everest's contribution to the symposium. So far interest in pleochroic halos in relation to radioactive studies has been confined to evidence of the constancy of radioactive emanations over long periods of time. There is a possibility, however, that further study of them might provide age data also. Presumably this would have to be done on a petrographic basis, supplemented by microchemical methods.

While halos are frequently referred to in the literature, it would seem that much of the information regarding them is derived from Joly's work on them, supplemented by that of Henderson. Inasmuch as most of their work on them was done on split biotite rather than with petrographic sections, it is not at all complete.

Pleochroic halos are mentioned as occurring in about a dozen different minerals, a few of which may be questioned due to false interpretation of the petrographic slide. They are common in pleochroic minerals and those with marked absorption in one crystallographic direction, such as biotite and other micas, tourmaline, cordierite and some of the amphiboles. The halos invariably surround a nucleus of some other mineral of which there are also about a dozen recognized. The more common ones are zircon, titanite, cassiterite, thorite and uraninite. That the cause of the halos is the presence of a radioactive element was announced by Joly in 1907. Previous to this they were a mystery. That the extent of the halo beyond the nucleus represents the length of the paths of alpha particles of the various radioactive elements in the nucleus as they penetrate the matrix mineral is also known. A few items of interest regarding them which I have observed in my own study of them within petrographic sections may be of interest.

1. They occur only in rocks which are definitely acidic. With the disappearance of free quartz the halos are absent. Examination of many hundred petrographic sections in my own collection has confirmed this.

2. As already noted, they occur only in minerals which are themselves pleochroic or dichroic. No matter how acid the rock may be, if only quartz and feldspar are present no halos are evident. Yet the radioactive element responsible for them may be there since they show up as soon as biotite occurs in the same rock. This suggests a more common occurrence of radioactive minerals than evidenced by halos. One point I have not been able as yet to check as thoroughly as I should like is whether the feldspars in rocks containing halos always include some of the potassium series, orthoclase, microcline, or anorthoclase Should this prove to be the case it might indicate that formation of radioactive elements was brought about through catalytic action of potassium. Catalysis plays so important a part in straight chemical combinations, may it not also have been an agent in the synthesis of common elements and energy?

3. The radioactive element responsible for halos apparently can occur in any one of three forms, viz., (a) As a minute particle of a pure radioactive mineral uraninite, thorite, radium, or other; (b) As minute inclusions of a radioactive mineral within a secondary host mineral of larger size, evident as opaque particles in an otherwise clear nucleus; (c) As radioactive elements apparently dispersed within the atomic lattice of some host mineral.

4. The extent of the halos in every case must be measured from the outside contour of the nucleus mineral. The shape of the halos conforms to that of the nucleus. Most references to them call them spheres but this is true only when the nucleus mineral itself is an approximate sphere. They can be oval, angular, or extremely irregular.

5. While reference to halos in the literature refer to the nucleus as being extremely minute, actually they occur also around mineral grains of fairly large size.

6. The extent of the halos around the inclusions varies over a wide range, even with the same nuclear material in the same matrix, but all sizes fall into definite groups, My measurements are, in microns, 5, 7, 10, 17, 20, 23, 27. and 33. Joly's, figures correspond with these except he does not include the smaller sizes and does include 39 (38-40) which I have not run across. Halos sometimes show two, or even three definite rings or zones, indicating the presence of more than one radioactive element, each with its own specific alpha ray path. Another frequent condition, probably also explained by the same mixture of elements is the amount of diffusion at the border of the halo. The halo can be extremely sharp at its outer edge or very diffuse, with all gradations between.

7. Halos are manifested in two ways,-one which shows as a definite color or absorption when viewed in non-polarized light and independent of the rotation of the stage, and a second which is only evident in plane polarized light, varying in intensity with the rotation of the stage. In this latter case the direction of greatest absorption always corresponds with that of the mineral in which the halo occurs. These phenomena are associated with the crystallographic direction in which the matrix mineral is cut and are apparently independent of the radioactive element responsible for the halo.

8. There is a great range in the intensity of the halos, even surrounding the same nuclear mineral within the same matrix. This must result from the concentration of the radioactive element in the nucleus. It can be explained either by an old condition where the emanations are dying out, or, as appears more logical, it may result from the initial percentage of radioactive element present in a given nucleus. This latter view receives confirmation from the frequent presence of identical mineral grains (e.g., zircon) within the same matrix showing no halos whatever.

9. Joly refers to negative halos in biotite which he suggests are analogous to photographic solarization. These are areas where the maximum absorption, which in biotite is normal to the acute bisectrix, or crystallographic C axis, has been completely destroyed. The cause of it is at present unknown although several different theories have been offered to explain it. In rock sections this only shows up as a lighter area around an obvious nuclear inclusion, and is rather rare. More light should be thrown upon this when the relative ages of the blotite where they occur is known.

Discussion

After Dr. Allen's paper was read the session leader, Dr. 1. Cowpeerthwaite, called for discussion of the paper.

Dr. J. L. Kulp: I would like to divide my comments on Dr. Allen's paper into two parts. It really was two papers. The latter paper, on pleochroic halos, I would like to commend highly. I have looked over the literature on pleochroic halos and it appears that these pictures are the best compilation I have ever seen. I think that some precision densimetry on them could lead to very interesting results and possibly to some more precise data in the range that has not been obtained before.

The first part of the paper, however, had to do with radioactivity measurements. With all kindness, I would like to state that Dr. Allen's training was that of a metallurgist and therefore he might be excused from making errors of fact and concept in atomic physics. I am sure that I would make many more,

It is stated that the evolutionists are the people who wanted to push things back. Radioactivity measurement "was pressed into service" to save the day. Another statement was made to the effect that those engaged in this work have a natural bias for introducing the maximum time. Now these come in the first category of propaganda. I think they are quite unjustified. There is no conspiracy between the atomic physicist and the evolutionist in trying to discourage some poor Christian. The atomic physicist would probably delight in making paleontologists turn their fossil orders upside down. They are not in league and are quite independent scientists. They start from different premises and they get answers by entirely different means. The atomic physicist and the physical chemist uses quantitative measurement. There is no getting maximum time. This is very important because Dr, Allen referred to it a number of times, that is, that science has been pushing this date back. As a matter of fact, that is not true. Astrophysicists who are concerned about the beginning of things, Genesis 1:1, have brought the accepted time for the beginning of the universe, at least so far as they can measure, from 10¹⁰ to 10¹² years down to about 4 x 10⁹. That's a tremendous drop. At the present time the concurrent opinion is that the age of the universe is on the order of four billion years whereas previously-24 years ago-it was 10¹⁰ or more.

Thus the age of the universe has been brought down rather than pushed up. The age of the earth, however, has been pushed up a little bit. Twenty years ago it was still accepted that the earth was roughly two billion years old, from relatively rough data. Today, more measurements have been made and it is more probable that is is close to three billion. Nobody expects that this is going to continue to be pushed up. The nature of science is such that all of our answers are approximate but they gradually lead us to a mean which is sometimes approximate truth.

Now for the second point, Dr. Allen wants us to worry about the possibility that transformation from the nuclear equilibrium state to one of normal decay might have been so gradual as to retard the decay right at the beginning. He is perfectly right in pointing out that at one point in the history of the universe there was an equilibrium between the building up of uranium atoms and the decaying of uranium atoms. However, what he is worried about is this. He said if this building up process continued considerably into the history of the earth, then obviously if we ,simply measured the decay rate and used this to calculate the equilibrium time (age of the universe), we would have an anomaly because the building up of the uranium would add to decay. Now, offhand, this might seem like a reasonable objection except for two things: first, the temperature at which atoms are built up and, secondly, the temperature of the earth's surface since it was formed as a planet.

The temperature that is required for atoms to build up is on the order of one to ten million degrees. This is why, for example, you must use an atom bomb to explode a hydrogen bomb because you have to get a million degrees of temperature before fusion takes place, before particles will start sticking together to make bigger particles. Now I hope most of you are aware of the melting point of most silicates in the crust of the earth. It is on the order of a thousand degrees, Obviously therefore, once the earth was formed as a planet and geology started, there could not be any building anymore and that is the time that we are talking about in the beginning of the earth.

I do not think that we should take time to discuss the common objection to the method, since we have done it at other ASA meetings and answers are available in textbooks on nuclear physics. The method of age measurement is straightforward. Consider a series of sedimentary strata: a crack develops, some molten material comes in, and there your elements crystallize in their own particular minerals. Uranium will crystallize into uranium minerals and lead will crystallize into lead minerals. The uranium crystal which is formed at the time that the molten material crystallized is at the time that lead starts to accumulate in that uranium crystal. It is separated by chemical means prior to that. Now that this uranium crystal is in place with lead accumulating in it, the question is what can happen to that to give you an incorrect age. One obvious thing is that uranium might be leached out later In Its history by ground water. This is possible. But there are ways of measuring how much has been leached out. There are ways of measuring whether the uranium in a particular crystal is in equilibrium or not by quantitative methods.

In the introduction Dr. Allen stated that one reason we should mistrust these methods is that the methods of getting at the age of the earth give different answers, such as by the salt accumulation in the sea, radioactive methods, and accumulation of sediments.

Now let's take this one simple case. Suppose we have numbers and measurements of any physical property, the correct value of which is 41.00 and suppose we have one kind of machine that can measure this within plus or minus 0.1. Suppose we have another very inaccurate machine which can measure to plus or minus 10. If one method gives 40.95 plus or minus 0.10 and the other 32 plus or minus 10, the results would be in complete agreement. So the methods for estimating the age of the earth vary greatly in precision but are consistent within their degrees of error.

Another suggestion was that uranium 238 and uranium 235 at the equilibrium state should be equal. This is not true. They should be proportionate to their stabilities and their stabilities, to the first approximation, are proportionate to their half life.

One other thing that might be mentioned is the matter of the strong evidence for man having been on earth much longer than 10,000 years, as we have presented at some of the other meetings and as written up in the ASA Journal. There is abundant evidence of a qualitative nature that man is much older than 10,000 years. But quantitatively we can measure this now by carbon 14. Unfortunately we do not have as many measurements as we need to fix this to any degree of certainty. However, a number of measurements have proved that man was in North America at least 11,000 years ago. There are many geologists, archeologists, and anthropologists who readily agree that man is very recent, relatively speaking, in North America. If this is true, then quite obviously the attempt to hold a 10,000 year age for man is impossible.

I think it is also interesting, in this connection, that Dr. Allen left carbon 14 out of this problem because of the fact that carbon 14 was not in this original isotopic buildup at the early phase of the universe. In other words, carbon 14 is not subject to this particular objection which he raised.

There are several other methods besides uranium-lead. One very important one is rubidium-strontium. Another one is potassium-argon or potassium-calcium. The Rb-Sr is certainly equally good for old rocks and the fact that by the Rb-Sr method you can get exactly the same age within the experimental error as in uranium-lead, on different metals, from different pegmatites, in the same geologic situation is a very nice independent check on both methods.

Dr. I. Cowperthwaite: Is there further discussion of Dr. Allen's paper? If not I'll ask Dr. Allen if he wishes to comment.

Dr. R. Allen: The time is almost up and I didn't even make notes of all of the comments which Dr. Kulp had but I can show you perhaps a few on which we do not agree. Now, I think that I am absolutely correct in saying that the fundamental concept of the evolutionist, the mechanistic evolutionist, is to get time back just as far as he can for the operation of his theories. Now we're not primarily concerned here with the age of the earth.

He mentioned, for instance, or gave an illustration here as though the several different methods of evaluating time, apart from the radioactive, all agree if you allowed a sufficient variation in the degree of accuracy. Now, that is not what I had reference to at all. For instance, Lord Kelvin figured out the age of the earth on the basis of the time required for the stabilization of the tides and the announced figure, as I recall it, was 40 million years as the age of the earth.

The evolutionist raised such a holler when he announced that figure that they said they required at least 400 million years for life on the earth and therefore that his figure was wrong. They succeeded in getting him to re-evaluate it and he did boost it up to 100 million years or so but he said, "That's all I'm going to give you."

Now, you see, there is in these various types of evaluating time quite a variation. I didn't intend to go into that phase of the matter at all.

There are many other comments that he made, if I had jotted them down, that I would have liked to have answered. I'm rather surprised that he did not evaluate as well as I would have liked, the primary concept that I gave of the reversible process. It makes no difference as to the time when this occurred.

He mentioned, for instance, the fact that I said that the time could be longer because there could be perhaps a greater, that is a slowing down of the reversible process.

Now all chemists, I think, will agree with me that in a reversible process you have between reaction in one direction and reaction in another direction a period or a phase in which you have stability. For instance in the manufacture of sulphuric acid through a platinum catalyst, you build Up S0₂ in hyposulphuric acid to S0₃ by the addition of oxygen at a certain temperature. Now, when that temperature is exceeded, there is a range there where it is stable and if you go beyond that temperature, it starts to reverse and so you do have that period of stability and that was, in my estimation, a minor point.

I think the time is getting so short and I don't like to keep you any longer and I don't think I shall extend my comments any further. I certainly thank you for your attention.