This paper (with minor revisions and additions) was read at the Fifth World Conference of the Ancient Astronaut Society in Chicago, Illinois, on July 28,1978 and subsequently published in Ancient Skies. It was later revised and published in Philosophy of Science and the Occult, Patrick Grim, Editor, by State University of New York Press, in 1982.
That extraterrestrial intelligences visited earth in antiquity and altered the course of human history is an old hypothesis, offered anew by Erich von Daniken. Although I am sympathetic to this thesis, the main thrust of this paper is a criticism of the behavior of critics, particularly scientists, in the broadest sense of that term. As a historical hypothesis, the merits of the ancient astronaut hypothesis should be weighed against the available evidence with rigorous scientific scrutiny.
Unfortunately, this has not occurred. Instead the scientific community has attacked both the hypothesis and von Daniken himself with outrage and abuse. His evidence has been dismissed with ridicule, and the hypothesis assailed with fallacious reasoning and an appeal to authority. Equally disturbing is the stony silence of “experts” regarding the evidence for the hypothesis. This silence, and the attacks of critics like Ronald Story, (1) supported by Carl Sagan, clearly show that a scientific evaluation is not forthcoming.
In what follows, I shall attempt to present the case for von Daniken. I shall then examine some of the criticisms frequently made against the ancient astronaut hypothesis.
It should be noted at the outset that this examination of such irrationality on the part of many scientists is in no way to be interpreted as a lack of faith in science. In point of fact, I have as much faith in science as some believers have in the existence of an anthropomorphic God. Religious faith, however, has evolved out of irrational hopes, fears, and reification of the unknown. It is a faith for which there is no evidence, in any reasonable sense of that term. It is indeed, more often than not, a faith in spite of evidence to the contrary.
My faith in science, on the other hand, has evolved from the achievements of science, from its rational and self-corrective method, and from the public evidence it has offered, however incomplete, in fulfillment of its predictions. It must be understood, then, that I am an ardent proponent of science. That is why I become so disturbed by dogmatists like Carl Sagan who destroy the credibility of science by claiming for it more than it can deliver and refusing to give the ancient astronaut hypothesis the scientific consideration it deserves.
The Case for von Daniken
The Case for von Daniken
It is common knowledge in our scientific era that it is both possible and probable that other intelligences exist elsewhere in the universe. To assume otherwise is to regress to the Middle Ages, when it was believed that the earth was the center of the universe and man the supreme creation.
Historian Will Durant, in his Story of Civilization, suggests that we are not necessarily the descendants of the primitive cultures to which archaeologists and anthropologists like to attribute our ancestry. His thesis, and the mysteries that science has not explained, strongly suggest the possibility that ancient space travelers visited earth. No argument based on such data as problems of intergalactic travel and the vastness of space has yet proved that superior intelligence could not accomplish what we, with our few centuries of limited scientific technology and theory, believe to be impossible.
It is both possible and probable that ancient astronauts did visit earth. This cannot be denied unless one holds that evolution is impossible, or that there is no evolution and God created only us (a point that raises questions on which no evidence could be brought to bear), or that such evolution as there has been took place only on earth, or that except for us there are no astronauts or other intelligences in the universe, or that the evidence is all in as to our origin, or that we have absolute knowledge about these things, and the like. Surely no enlightened person could hold such medieval ideas.
Unless we deny the possibility of evolution elsewhere in the universe or pretend to an absolute knowledge regarding our past, we must recognize at least the possibility that technologically advanced civilizations may have arisen elsewhere and that they may have visited us in the remote past.
The ancient astronaut hypothesis, then, is at least possible. As to proof of von Daniken’s theories, it must be noted that the ancient astronaut hypothesis is not a matter of natural science. It cannot be expected to follow the rigid rules and standards of proof set for natural science. Instead, its modes of proof are primarily like those in the social sciences, such as psychology, sociology, and anthropology. To expect formal rigidity in such informal disciplines is to demand what cannot be. Nevertheless, at the very least, one would expect scientists to permit von Daniken to extrapolate from his data, since they themselves accept extrapolation as one kind of evidence permitting further advances in science.
What could constitute proof for the ancient astronaut hypothesis? We are not likely to find an ancient astronaut. As von Daniken points out, “crashed” spaceships from the distant past would probably long ago have disintegrated or possibly have been carried away piecemeal. What then?
Von Daniken’s thesis explains many hitherto inexplicable mysteries none of which has received any elucidation from academic minds fettered by prejudices and preconception. Taken as a whole, von Daniken’s findings point convincingly to the likelihood of extraterrestrial interference in man’s distant past. That is not to deny that von Daniken manipulates many of his facts to adapt them to the ancient astronaut hypothesis. But what scientist does not do this when he formulates a theory? That’s why Mathematics, the language of science, is considered an art. Certainly we have little reason to believe that it in fact describes the universe as we conceive it to be in its natural “colors” and forms. It is also apparent in the fact that periodically science’s rules and principles are “refined” and that many of our scientists’ explanations are now taking on a metaphysical hue not susceptible to physical evidence.
The ancient astronaut hypothesis is little different from most of recorded history. The hypothesis requires only “validation” of the reported data though correlation of those data with the unexplained and wondrous technical artifacts of the distant past. The proofs of the ancient astronaut hypothesis are to be found in the logic of both possible and probable events, in the historical (even though predominantly religious) documents that are held in such high historical esteem throughout the world, and in the ancient artifacts that cannot be explained in terms of the supposed human knowledge and capabilities of antiquity. All these, studied as a body of coherently describable data, point to the likelihood of extraterrestrial intervention. Furthermore, the descriptions in ancient documents, when coupled with empirical data, considerably weaken the argument that terrestrials are responsible for those artifacts, which obviously were beyond their linguistic, conceptual, and technical abilities. Let us consider some of those wonders. A few should suffice.
Inscribed on over three hundred and fifteen square miles of a Nazca pampas, one can find, “Nazca ground drawings” so numerous as to stagger the imagination. Among them are huge depictions of a spider, a monkey, and a humming bird. They are so large I could recognize them only from the air. Other drawings could easily be mistaken for aircraft landing strips. Some are merely straight (often parallel) lines running across rough terrain and up mountainsides, without deviating a fraction of an inch -- sometimes almost ten kilometers (6.25 miles) long, as if cut by a laser beam from on high.
At the Bay of Pisco, south of Lima, Peru, there is an enormous trident (candelabra) engraved on the side of a hill pointing directly, according to a thorough search of Joseph Blumrich, at what is known as the Nazca Plains, outside the small city of Nazca. As to their source and meaning of these drawings, there are no universally accepted explanations. A NASA engineer, Robert Earle, claims to have determined that most of the lines point to important geographic locations on the earth. (2) A German Mathematician, Maria Reiche, who studied the lines most of her life and wrote Geheimnis der Wuste (Mystery on the desert), told our group of site seers that though she did not deny the existence of extraterrestrials, she doubted that their existence would explain all the lines and drawings. The enormity of the mystery can be fully realized only from personal experience.
Another unexplained mystery is that of the Terraces of Baalbek in Lebanon, where huge stone blocks sixty feet long, and said to weigh 2,000 tons, have been moved into place. They are so massive that even our modern technology cannot handle them.
Then there are the so-called “fortress” walls at Sacsayhuaman, outside the city of Cusco, Peru and lining the streets and walking “paths” within the city itself. They are constructed of thousands of enormous stones, many tons in weight, fitting together as closely and as neatly as the pieces of a jigsaw puzzle, without any kind of connecting adhesive. The thin edge of a sheet of paper could not be inserted between them.
Another marvel is the recessed quadrangular wall at Tiahuanacu outside La Paz, Bolivia. The inside surface is studded with sculptured faces apparently representing every racial type on Earth. There are many hundreds of other unexplained mysteries that most scientists show no inclination to investigate. I shall mention only one more: the mystery of the existence of models of sophisticated aircraft. Some of these models show a separation space indicating the possible existence of nuclear engines. Such models, which are in museums throughout the world, have been tested and found to be aerodynamically accurate in design (3) as was demonstrated at our Ancient Astronaut Society conference in Orlando, Florida, August 4, 1997. They are amazingly interesting artifacts because they correlate so well with the many scriptural descriptions of flying machines emitting smoke, fire, and thunderous noise.
Even if we accept the claim that all these things originated with terrestrial beings, we would be hard pressed to explain the disappearance of such superior civilizations. We have found no documentary evidence or, indeed, evidence of any kind to support a terrestrial origin for such technological achievements.
It seems, then, as von Daniken reiterates, that it is time to bring to bear on these fascinating mysteries, and on their descriptions in the languages of antiquity, new perspectives and viable hypotheses made possible by the more sophisticated language and knowledge of our day.
If scientific and religious institutions would allow it, and if governments or foundations would advance funds to support it, researchers could feed data from all over the world into computers to determine the comparative similarities among empirical descriptions of “gods from space” and to determine whether these descriptions are, as the critics prefer to believe, nothing more than the creations of insane minds or over-fertile imaginations. Supplemented by the computers, experts in comparative linguistics, translation, ancient cultures, and ancient languages should be able to determine whether the technical data, concepts, and achievements found in museums, existing at archaeological sites, and described in historical and religious documents could have originated with a pre-scientific people who spoke only non-technical and unsophisticated language.
As it stands now, the ancient astronaut hypothesis is primarily a historical hypothesis and peripherally a scientific one. It is founded on documentary and circumstantial evidence and, in some cases, on hard evidence that may not be denied except by stretching the facts beyond reason and probability.
Many professionals are sympathetic to von Daniken’s concerns. Among the million who read his books are scientists, philosophers, archaeologists, anthropologists, engineers, and scholars from every field. This is what apparently frightens scientists like Sagan, who seems to be making every effort to silence scholars who are inclined to take the ancient astronaut hypothesis seriously. He even goes so far as to suggest that if we do not agree with him, we are not reasoning persons. Such attacks are apparently calculated to intimidate the reader, particularly if he is a scholar. With such a modus operandi, it is not at all surprising to see that the critics of the ancient astronaut hypothesis find support from representatives of the church, an alliance that would surely amuse Galileo.
Much of the negative criticism of Erich von Daniken and the ancient astronaut hypothesis emanates from a relatively small number of scientists led, it seems, by Carl Sagan appealing to the fallacy of ignorance, who claims that there is not a “smidgen of evidence” for the hypothesis. The claim is that they prove, their theories -- logically of course. But verify?
I wish to remind Sagan and his followers that there are many kinds of proof. Sagan knows, but he appears to pretend otherwise, that proof can be not only empirical, observational, experimental, or inductive (as he seems to imply), but also theoretical, logical, mathematical, hypothetical, deductive, statistical, probable, and documentary.
These various forms account for much critical and fundamental examination within the sciences. The ancient astronaut theorists; use of many of these kinds of proof is no less valid than the sciences’ use of them. Here I must insist that evidence, proof, and knowledge must be possible, probable, public, and predictable. They must be directly or indirectly verifiable and compatible with a comprehensive body of relevant facts, theories, generalizations, and hypotheses. To the degree to which these elements fit coherently without contradiction, to that degree we can make legitimate claims to having evidence, proof, or knowledge.
A deliberate ignoring of the different kinds of proof is the modus operandi of those scientists who are guilty of dogmatism and prejudice. Are von Daniken’s scientific critics suggesting that there is no truth or knowledge except for that found in the natural sciences? They would do well to do a study of the various theories of truth. Would Sagan et al claim that there is not a “smidgen of evidence” that Lincoln was shot at Ford Theater, or that the History of the United States occurred substantially as recorded, on the ground that no one alive was there to see it happen? Would they question the documents that record Fleming’s discovery of penicillin, or Caesar having ruled Rome? Such knowledge cannot be absolutely verified by the techniques of the natural sciences, by experimentation, or by unfalsifiable or falsifiable claims.
Of course science must conduct its search for truth objectively. But science is not scientists. The latter are far from infallible and often far from objective; a few are even dishonest, prone to authoritarianism and dreams of scientific infallibility even when they admit they are speculating. They forget that the present achievements of science constitute little more than an embryonic development in the continuing search for truth. In elevating themselves to the throne of infallibility, they imply that they alone have the key to the mysteries of the universe. They display the worst kind of parochialism in failing to see that there are problems of a kind that cannot be solved by a study of molecular structures or subatomic constructs. To make matters worse, the technical achievements of science are often conflated with scientific certainty, misleading the layman into believing that the products of technology -- such as television, nuclear weaponry, and space travel -- are ample proof that what scientists say is ipso facto true.
Although von Daniken is no stranger to scientific concepts in this field, he has never pretended to be a scientist. His critics ignore this, however, and argue against their own assumption that von Daniken thinks he is a scientist. They then proceed to show what he himself admits, that he is not.
This straw-man approach is typical of much of their criticism. Indeed, it is probably to our benefit that von Daniken is not a scientist. As someone has said, “Science is too important to leave only to scientists.” The ideas von Daniken expresses have been posed, as von Daniken says, thousands of times in the past. No one before, however, was sufficiently daring or provocative to raise worldwide awareness to the possibility and probability of the existence of extraterrestrial intelligence
Various critics have referred to von Daniken’s research as “pseudo-science,” and claim that it belongs with occult literature. This can hardly be called scientific disproof of the ancient astronaut hypothesis. It sounds more like the voice of embattled authority proclaiming “truth” loudly and anxiously. Can such a response be attributed to von Daniken’s critics’ annoyance with his provocative style? It is, after all, very strange that they have not attacked with the same concentration and intensity any of the hundreds of other ancient astronaut theorists -- enthusiasts from Homer to Landsbury to Josef Blumrich (4).
Is it because von Daniken is shaming scientist and other authorities for their lack of integrity? Is it because they do not like having their self-limited search for truth exposed? Is it because they wish to ignore certain facts that abound throughout the world? Is it because they are afraid that the generous research appropriations they receive might be diverted to this cause?
Indeed, von Daniken’s persistence and his provocative and accusatory style of writing has not endeared him to the world’s scientists -- nor to its religious leaders. However, if his questions are not proper, it should be easy for those with knowledge to demonstrate that fact. Scientists certainly have not shown von Daniken’s characterization of them to be wrong, and what is worse, their unscientific responses support his contentions. Nor have devastating proofs against his hypothesis been demonstrated. Certainly character assassination and weak claims will not do.
The attacks and negative responses from religious institutions (and individuals like the contributors to Some Trust in Chariots, partly edited by the Reverend B. B. Thiering, chaplain of Cranbrook School) are easily understandable, in view of their special interest. One would expect, however, a more sympathetic attitude from the Sagans of the scientific community. Their approach thus far smacks entirely of dogmatic authoritarianism. Obviously science cannot be expected to preoccupy itself with unfalsifiable claims that can be shown to be filled with internal contradictions, ambiguities, and factually and intellectually meaningless” terms. But such is not the case with von Daniken’s thesis.
Consider, as a typical attack on von Daniken, Story’s The Space-Gods Revealed. In his foreword, Carl Sagan suggests that Chariots of the Gods? is “pop religion.” It is, in fact, an attack on religious claims. Moreover, Sagan sets the tone for disbelief before Story presents his so-called evidence. He makes it clear that -- in his view -- von Daniken is trampling where he does not belong. As Sagan has said on his “Cosmos” program, putting the cart before the horse, the amateurs scare away the professionals. But that is no more than a lame excuse for his failing to deal with the problem, certainly not an explanation. In fact, amateurs tread where the professionals refuse, or fear, to go. Someone has to investigate unsolved mysteries.
Further still, without discussing the extremely complex nature of the term ‘evidence,’ Sagan dogmatically states that there is no evidence for ancient astronauts. Both Story and Sagan put words into von Daniken’s mouth -- words like “dummies” in reference to our ancestors. Von Daniken does not claim that our human ancestors were “stupid,” or that they were not genetically similar. He merely suggests that they could not have had the knowledge implied by some of the artifacts from the past; however, they may have received some of the genes we have inherited. He is quite correct. They lacked a sophisticated technical language, concepts, and insights needed to solve such problems. Story and Sagan invariably associate von Daniken with strange ideas and mystic cults, branding him guilty by association.
Following Sagan’s foreword, Story’s book is permeated with carefully chosen emotional words and ad hominem attacks calculated to ridicule von Danken’s ideas; he resorts to laughter and derision when logic and conclusive evidence are lacking. His handling of von Daniken and his theories is a paradigm of sloppiness cleverly concealed from those who lack logical training. Story confines himself primarily to von Daniken’s earlier writings. Von Daniken was inexperienced with literature in matters of scholarly research (he did not even graduate from high school). He felt he would be better received if he colored his writings with a fictional style. Thus these works are vulnerable to attack. However, Story cleverly avoids criticizing hundreds of facts and data from other of von Daniken’s books. Here he would have been unable to draw on present-day accepted explanations, and on authorities with their pet theories to protect. Von Daniken insists we must marshal new interpretations based on present-day language, knowledge, and concepts.
The clearest indication of Story’s philosophical and critical incompetence is seen in his treatment of von Daniken’s explanations for the Nazca ground drawings. He says, sarcastically, “The runways are not needed for space flight. What were the ancient astronauts flying -- world War I biplanes?” Has Story not heard of our space shuttle, which requires a runway nearly three miles long? He implies that long landing strips would not have been needed. And, indeed, they may not have been. Nevertheless his remark assumes a great number of facts he could not know anything about, such as landing requirements, speed capacities, and so on. By suggesting that astronauts could have landed only in daylight, moreover, he is guilty of arriving at solutions in terms of our limited knowledge, precisely as von Daniken has charged.
The extraterrestrials might, among other possibilities, have been sensitive to a far wider band on the spectrum than are we, enabling them to see at night, or they may have had instruments to amplify other forms of light that appear as darkness to us. Story also refers to the “soft, sandy soil of the Nazca pampa.” But age and extreme weather conditions could have destroyed the original soil surface, and again he is assuming that their vehicles would be like ours having similar landing gear. Finally, story repeatedly appeals to the very authorities whose theories von Daniken places in question.
Story is unimaginative, and too comfortable with twentieth-century concepts to consider that the unthinkable may be true, as it so often has been. His speculations will seem reasonable to those conditioned to think within present-day parameters. But that is precisely what von Daniken brings into question. It is scarcely necessary here to rehearse the list of great pioneers hounded during their lifetime primarily because their insights and theories ran counter to the accepted “wisdom” of the establishment of their day.
Have today’s pundits learned nothing from their predecessors whose arrogance they unconsciously mimic”? They speak knowingly, however mistakenly: “knowing” that theories are facts; and “knowing” that there is no real, hard proof for the ancient astronaut hypothesis. From a philosophical and even a scientific standpoint, there is no such thing as absolute proof, not even in deductive logic or verification, not even in the most seemingly solid sciences for all claims to knowledge are predicated upon the following caveats;
1. Knowledge (and truth) is founded on some
assumption and the level of language used.
2. Knowledge is Subjective experience supported by evidence. However, not all Subjective experience (i.e., subjective -- non-public experience -- is not) is supported by evidence.
3. Knowledge is belief but not all belief is knowledge.
4. Knowledge is present experience of past events.
5. Knowledge cannot be acquired in the absence of evidence and a method for acquiring it.
6. Knowledge and truth are interdependent.
7. Knowledge and truth are dependent upon verifiable language.
8. According to available evidence, knowledge (and truth) is probable in nature.
9. All claims to knowledge (and truth) are preceded by an unspoken "IF" and "ACCORDING TO AVAILABLE EVIDENCE."
By “real” or “hard” proof, Sagan actually refers to unscientific proof, for he seems to mean proof that is immediately accessible to our sense faculties. This is exactly the kind of proof that once led the world to believe in a solar system with the earth at is center and sun visibly revolving around it.
Story accuses von Daniken of not being aware “of the archaeological and historical facts.” He will not accept that von Daniken is aware, and rejects them, refusing to accept hypotheses as facts. Yet Story himself claims to know the facts. He credits our ancestors with knowledge and common sense -- even with simple techniques and equipment for moving objects weighing many tons -- some up to eighty tons. He accepts their “empirical” descriptions of how they are supposed to have moved the huge statues (Moai) on Easter Island. He would deny that our ancestors’ descriptions of ships in the sky with flaming tails, accompanied by thunderous noise and tremors of the earth, are empirical descriptions. He does not explain his criteria for choosing one description and rejecting another. But more than that, he seems to suggest that there are no ancient mysteries – mysteries that the ancient astronaut hypothesis might explain.
In discussing the date of an ancient artifact, Story attempts to cast doubt on the accuracy of von Daniken’s information by use of the subtle technique of leaving out crucial terms from von Daniken’s comments, such as substituting “archaeologists” for von Daniken’s “some archaeologists.
Although there are endless examples of distortions, innuendos, and illogic expressed by von Daniken’s critics, we must not dwell on them longer.
Von Daniken’s critics seem to insist on one standard for him, that is, the empirical and positivistic methods, whereas they themselves rely heavily on theoretical or other methods. But they do not attack creationism in the Book of Genesis or the Christian belief in a non-material God. In this respect, we would do well to listen to P. E. Pothier of Bethesda, Maryland. In answer to an article that included attacks on von Daniken by Kendrick Frazier, published in Science News of June 9, 1976, Pothier said:
Scientists would do well, therefore, to admit that ancient astronaut theorists
have a right to use the same kinds of proof science uses in both the “hard”
and “soft” sciences. They would
do well to examine the evidence and data with the objectivity they claim to use
in the “hard” sciences.
Even Dr. Truzzi, who according to the New York Times has broken away from the “Committee for the Scientific Investigation of Claims of the Paranormal,” has said that that group was “more preoccupied with denouncing . . . than with investigating.” It is Truzzi’s conviction that claims to truth in those areas normally not considered to fall within the parameters of accepted science must “not be dismissed out of hand.” It is incumbent on science to be scientific about those hypotheses, “matters that present legitimate puzzle areas for science,” which some scientists and also philosophers are prone to denounce before investigating. They would do well to lend their interest, their methods, their techniques, and their moral and financial support in a serious search for historical knowledge relating to the ancient astronaut hypothesis. It has, too long, been not only ignored but unscientifically prejudged as improbable in advance of the needed research. If that is science, then I have long misunderstood what science is.
More power to Erich von Daniken. Let us hope his efforts will prosper.
(A summary of a paper read at the 24th Anniversary World Conference in Orlando, Florida, on August 4, 1997
(Criticism of the Ancient Astronaut Hypothesis revisited)
They continue to refuse to search for evidence in our own back yard at considerably less expenditure of funds. What they have succeeded, admirably, in doing, however, is to convince the world that they now believe what they formerly scoffed at; that is, that ancient astronauts did and do exist though our critics do not refer to them as such. They call them “extraterrestrials” with no regard to the historical age of the descendents’ civilizations.
At least in this, we have been vindicated, even if ancient astronauts never did visit Earth. And for this, we deserve credit. Certainly, Erich von Daniken does. He has led the way despite much vilification.
The good news is that criticism of our hypothesis is waning although not yet ceased. Our critics spend inordinate millions of dollars on pet projects, which though labeled “scientific research” are sometimes tinged with metaphysical claims and consequently are clearly on the fringe of credibility. It seems as if the kettle is calling the pot black. Science News, one of the reviewers of the book, the Edges of Science, by Richard Morris, refers to “ . . . some current science activity and . . . the controversy generated as the boundary between physics and metaphysics becomes blurred.”
In the past, the nature of scientific claims has been such that they must be falsifiable or verifiable, that is, they must be able to be tested. To the extent that science now resorts to metaphysical claims, they cannot meet those requirements -- the Ancient Astronaut Hypothesis does!
1. Ronald Story, The space-Gods Revealed (changed from The Space-Gods Hoax under threat of suit) (New York: Harper & Row, 1976).
2. Robert Earle, Proof of ancient Astronauts, Nazca Sketchbooks I, II, III, (Bay Village, Ohio: Robert Earle, I, 1975; II, 1976; III, 1978. In private correspondence, Mr. Earle has claimed that as a result of six years of study and six months of inn-the-field exploration in the company of archaeologists, he has discovered the real meaning of the Nazcan runway arrows: they are an astronomical chart of asteroids and comets -- on which the ancient astronauts hitched “piggyback” rides to take them to various places in their travels. No less than one-quarter of the Nazcan ground drawings, he states, are of hummingbird gods, which, he insists, are depictions of hovering spacecraft.
3. Dr. Struart W. Greenwood, aerospace engineer, member of the British Interplanetary society, and of the American Institute of Aeronautics and Astronautics suggested the nuclear separation space in private conversation.
4. Josef F. Blumrich wrote The Spaceships of Ezekiel (New York: Bantam Books, 1974). His initial intent was to disprove von Daniken’s thesis. Of his change of mind, he writes, “Hardly ever was a total defeat so rewarding, so fascinating, and so delightful.” Blumrich is a retired engineer, former director of Systems Layout branch of NASA, who contributed to the designing and building of the Saturn V booster. He has since taken out patents for designs based on Ezekiel’s “technical” descriptions.