Hitler used to tell a tale about sitting at a table some time in the First World War when he heard a voice telling him to move, so he obeyed it as if it was a military order, and a moment later the table was bombed and everyone sitting at it was killed. I don’t know whether this anecdote has been checked. On another occasion, which is well-known and can be verified, a British soldier called Henry Tandey, VC, DCM, MM, from Leamington Spa, is chiefly remembered for being the man who spared Hitler’s life. The story goes that on 28th September 1918 in the French village of Marcoing, a weary, wounded German soldier wandered into his gun sights and he chose not to shoot him. Hitler saw this and nodded his thanks. This may, however, be an urban legend and it may also be the second encounter between the two. Because it isn’t particularly wonderful to be remembered for that alone, although it shows he had a sense of decency and mercy, I should mention that Tandey was also given the Victoria Cross for restoring a plank bridge under fire on the same day, and was awarded the Distinguished Conduct Medal for, well, I’ll just quote the citation:
He was in charge of a reserve bombing party in action, and finding the advance temporarily held up, he called on two other men of his party, and working across the open in rear of the enemy, he rushed a post, returning with twenty prisoners, having killed several of the enemy. He was an example of daring courage throughout the whole of the operations.
Hence there seem to have been at least two occasions on which Hitler could’ve been killed before rising to power, and therefore it seems to be entirely plausible for him to have become yet another unknown casualty of the Great War, but of course this didn’t happen. I have to say that this suggests that he was in some sinister way protected from death during this period, and since I believe in the power of Satan as an personal evil force, I can easily accept that. However, how many other stories ended in potential future dictators of Germany being killed in WWI? I’m also unsure either anecdote is actually true?
But is Hitler really necessary? By which I mean, is a world without Hitler also a world where the Third Reich and Second World War didn’t happen? How much difference would it really have made to history if Hitler hadn’t existed or had died in the First World War? Might things actually have been worse?
Hitler was alleged to be a very poor strategist, basing most of his orders on never retreating, even tactically, and one result of that was that he lost a lot of battles which could potentially have been won otherwise. Consequently, in a Second World War where all other things were the same except that the Führer was a better military strategist, it might either have lasted longer or less long, and in a Nazi victory, and if it had dragged on, maybe the Nazis would have ended up acquiring and using the Bomb and winning that way, rather decisively and terrifyingly, going on to dominate the world. In the light of that, maybe it wasn’t Satan at all who protected Hitler those times. Maybe the protection was to ensure that an incompetent leader would lose the War. Of course, many anti-theists would say at this point that this is a funny kind of loving Deity because the Holocaust still happened, but perhaps we can leave the religious angle aside and just state the possibilities as they stand. Hitler surviving the First World War might have been a relatively good thing because it meant the Third Reich would lose the Second.
However, another question arises. The Holocaust and other atrocities are, morally speaking, central to the need to defeat the Nazis, even though they were apparently not the motivation for declaring war on Germany. Is it possible that a timeline where Hitler never rose to power would also not have had the Holocaust? A couple of scenarios have been popularly explored.
In one of them, Hitler died in the First World War at the Battle of the Somme and had no significant effect on the course of the War. The Treaty of Versailles is imposed in 1918 but instead of the Nazis coming to power, there is a Communist revolution in Germany and the Spanish civil war proceeds as it would’ve done anyway. Germany and the Soviet Union both invade Czechoslovakia and the USSR is thrown out of the League Of Nations. World War II happens anyway. After two years, there is a German-Soviet victory but then Pearl Harbor happens and Germany and Russia ally themselves with the US against Japan, and Canada and the US enter the war on opposite sides. There’s plenty more of this here, and it comes across as quite far-fetched. For instance, there’s no explanation as to the inconsistency of Germany going Communist while other countries become Fascist, and this is the crucial point.
My view is that if you look at the various European nations, many of them had successful Fascist movements, and only one of them had Hitler. Nazism is generally seen as a variety of fascism which emphasises the idea that there is a supreme Aryan race and a Jewish conspiracy. Other fascisms were not like this. For instance, Mussolini, the original founder of a Fascist party, focussed on the Roman Empire to encourage Italian nationalism and the Southern European fascisms generally stressed the centrality of the Roman Catholic Church. The Nazi version of Christianity, Positive Christianity, attempted to remove all Jewish elements from the faith, rejecting the Tanakh entirely, claiming Jesus was Aryan, supported the idea of an Aryan homeland and was hostile to Roman Catholicism. Mussolini had come to power in 1922 and therefore had longer to develop and enact his policies than Hitler.
It may also be instructive to look at the history of the Nazi Party. The Deutsche Arbeiterpartei (German Workers’ Party) became the Nazi Party as a result of Hitler joining it as a spy for the police in 1920, but that party was already anti-semitic and anti-Marxist. I don’t know much about the history but it seems to me that Drexler, the leader at the time, could have done the same thing, in which case the main difference would simply be that his name would have become symbolic of the most evil man in history instead of Hitler’s. Or maybe it wouldn’t. Maybe there were factors which would’ve led to his failure as a leader of the party, but this simply means either that someone else would’ve taken over and succeeded or another movement with similar aims would have arisen instead.
In a way, Hitler’s reputation is highly conditional and to some extent it plays into the cult of personality characteristic of totalitarian régimes. It may be that his life and interactions are important, but only because it helps one identify how precisely history took such a negative turn at that point. Specifically reviling him is to give him too much attention. It’s like constructing an elaborate cult around a serial killer or someone similar. It kind of feeds the myth and the kind of thing which makes politics seem to be about personalities. On the other hand, it is easy to take his actions personally when you’ve been directly affected by them, which applies by now probably to hundreds of millions of people if not more. The fact remains that there were any number of pathetic petty infantile moral vacua who could’ve taken his place if he had been killed in the First World War, and as usual it’s about the broad forces of history happening to converge on one person. Likewise, none of our leaders are that important today either. They’ve just been put there by the vagaries of economic and social forces and their lives are of no consequence.
Most of what happens is fairly predictable, and they say that in an infinite Universe, which this probably isn’t, everything is not only possible but inevitable. That is, everything that is possible must exist. This is not, however, so. For instance, at first glance it seems possible that the whole of space could be filled with diamonds one millimetre in diameter separated from eight other diamonds of the same side by one metre. Certainly this seems to be a stable arrangement, particularly if they’re all slowly orbiting each other, and the gravitational forces balance each other, but we can easily establish by observation that this is not so. Therefore there is an infinite set of things which are entirely possible but don’t exist, at least in this universe. Likewise, there could be quite a few things which we only believe are possible because we don’t know what rules them out, and it might be imagined that in fact there is really only one true way that things can be. However, this is not so.
Now there is this:
I’m not going to pretend that I can remember what any of the symbols in this equation mean, and without that information this is just an impressive-looking piece of technobabble. It’s also abbreviated and I may have written some of it down wrongly. Expanded, it would fill a sheet of A4. But this is in fact almost that famous Holy Grail, of a formula which written down fully explains everything physical in the Universe. What’s missing is gravitation, because gravity may not be a force at all, unlike the four used in the sequent above. But right now, that may as well say “abracadabra” to me because it means nothing to me.
There seems, however, to be a problem with the idea that that thing up there along with a similar account of gravity really would be a theory of everything. I mentioned previously (somewhere on here, can’t find it right now) that fine tuning is wanting of an explanation. As far as anyone can tell, there is no link between the relative strengths of the different forces, including gravitation, which make heavier atomic matter and through it chemistry, biochemistry, life as we know it and human beings possible, that means it has to be the case that things are the way they are, and consequently we live in a multiverse almost entirely consisting of very simple and boring universes incompatible with chemistry. There seems to be no cause for these proportions, and consequently there are a number of things which nearly are, but aren’t in this universe. I’ve mentioned these before, but not in as much detail.
Be warned, because I’m about to talk about nuclear physics, and I’m going to do so from a position of considerable ignorance, but not total ignorance.
It should go without saying that a convenient way of looking at atoms is that they consist of orbitals associated with electrons which have various shapes, such as a four-leaved clover or a dumb bell, balanced by a nucleus at the centre which “wants” to have the same positive charge as the total negative charge of the electrons. Hence helium has two positively charged particles, protons, and two negatively charged ones in its orbital, electrons. Hence chemistry. Atomic nuclei, with the exception of the most common isotope of hydrogen, also contain a similar number of neutrons, which are uncharged. The heavier the atom is, the more neutrons are needed proportionately to balance the protons in order that it remain as stable as possible. Hence with carbon and oxygen, with six and eight protons respectively, there’s a stable isotope with the same number of neutrons. By the time uranium is reached, there are no stable forms but the most stable has ninety-two protons and a gross plus two – 146 – neutrons. Even that isn’t enough. The issue is that like charges repel, so atomic nuclei struggle to stay in one piece since they consist of clusters of positive and neutral charges.
There are various factors and forces involved in atomic nuclei, not all of which I can easily call to mind, but two ways of understanding how they work are the shell model and the liquid drop model. No two otherwise identical particles in close proximity can have the same energy level. In atoms this manifests in the form of electrons having “shells” – they have different energy levels into which they slot, so there are for example two possible electrons at the lowest state and eight in the second, and then it gets complicated. This arrangement also applies to protons and neutrons in atomic nuclei, which can also be thought of as a kind of condensed version of the electron shells which make chemistry possible. The liquid drop model sees atomic nuclei as akin to droplets floating in space, and as such they have cohesive and adhesive forces and surface tension. Just as a drop of water has a skin round it which is difficult to penetrate and tends to hold the water together, so have atomic nuclei, and just as the interior of a drop of water consists of water molecules which stick together, so do atomic nuclei. Drops can coalesce and separate, and so can atomic nuclei.
The mass of an atomic nucleus is never an exact sum of the masses of its protons and neutrons because in order for it to hold together, some of their mass has to become energy. Exactly how much can be calculated by considering the nucleus in terms of the forces mentioned above, along with some others. This is known as the “empirical mass formula” and takes account of the nuclear volume, the surface area of the nucleus, the repulsion between the protons, the fact that nucleons need to be paired according to their spin (which I hadn’t mentioned before for simplicity’s sake), and the fact that they cannot occupy exactly the same energy level, which is known as the asymmetry term. All of these taken together, and there is a formula but I won’t bother you with it, explain much of what happens between and inside atoms, but there is a second property known as “magic numbers”. Certain isotopes and elements are more stable than they would be expected to be given this model and the associated formulæ, and consequently others are less so if you take these “magic numbers” to be “normal”. Therefore, the shell model is also needed. Both of them apply to real atomic nuclei and don’t contradict each other. If an atomic nucleus has a magic number of either neutrons or protons, it will be unusually stable. These numbers include 2, 8, 20, 28, 50, 82 and 126. Of these, element 126 has yet to be recognised, but the others are helium, oxygen, nickel, tin and lead, as far as protons are concerned, and as I mentioned before, oxygen-16, which is doubly magic, is particularly stable.
Incidentally, it’s fairly easy to demonstrate that elements have different isotopes, particularly chlorine, which is unusual in having two common stable forms, 35 and 37, of which the former comprises roughly three quarters of stable chlorine atoms and the latter one quarter. Careful measurement of weights of ordinary table salt in its reactions in solution with other substances such as sodium and potassium hydroxide reveal that the proportions involved don’t correspond to whole numbers. This can be demonstrated with ordinary household chemicals if you use large enough amounts and measure them precisely enough. It doesn’t require sophisticated equipment or hard to understand calculations. It could even come into making soap, particularly if the fatty acids have relatively short chains, such as the ones high in coconut or palm oil. The very easiest would be from certain substances in goat’s milk, but that wouldn’t be vegan, but coconut and palm are also ethically questionable.
One of the consequences of these forces and factors is the pattern of stability and instability in the periodic table. There’s at least one stable isotope of each of the first forty-two elements, then technetium appears to throw a spanner in the works. When the periodic table was first compiled, a number of gaps became apparent. Sometimes this was just because the element concerned hadn’t been discovered but wasn’t particularly unusual, as with gallium, although gallium is quite an unusual metal. However, in the case of element 43, it just seemed to be missing, and wasn’t officially discovered until the 1930s. By contrast, gallium had been discovered in 1875 and the actual metal was obtained a year later. It turns out that there is no stable atomic nucleus with forty-three protons, the element now known as technetium, which is universally and usefully radioactive. The same is true of the rare earth metal promethium, whose atomic number is sixty-one, but has stable elements either side of it, and in fact all other rare earth metals have stable isotopes. The heaviest nucleus which has a stable isotope is that of bismuth, whose atomic number is eighty-three. Bismuth and gallium share the unusual property of expanding on freezing, a very rare property crucially also true of water, which is another factor in making life of our kind possible in the Universe. Above bismuth lie polonium, astatine, radon and francium, all of which are exotic in various ways. Polonium is one of the most toxic elements known, completely down to its radioactivity. Astatine, along with tennessine, is a radioactive halogen, like chlorine and iodine. At any given time there are only twenty-five grammes of astatine in this planet’s crust. Radon is fairly abundant and the heaviest known gaseous element. Finally, francium is a radioactive alkali metal, slightly more common than astatine at thirty grammes. Francium and astatine don’t really have meaningful chemistry, partly because they’re so rare and partly because they’re too radioactive to be cool enough to have predictable reactions. It should probably also be mentioned that there’s another series of elements like the rare earths which are all too familiar and are again quite radioactive. These are the actinides, which include uranium and plutonium. One other element is worth mentioning here, although its situation is kind of the reverse of the others’. This is tungsten, which has five stable isotopes plus a further one, tungsten-180, with a half-life of two thousand million æons. The others can also decay but are around a thousand times more stable and have never been observed doing so. Tungsten is also the only third-row transition element which has a biological role, although it is also usually slightly toxic to animal life, so it’s conceivable that life’s existence depends on its near-stability.
The difficulty is in quantifying exactly how much the relative strengths of the strong nuclear force and electromagnetism could change before this arrangement of stability and instability would also change. The shell model would be unaltered by this, but the liquid-drop model would have different parameters if these were different. It’s tempting just to base everything around the inverse square law and the volume of the nucleus, but this wouldn’t take the surface tension factor into account, for instance. However, if the inverse square law were all that was required, the calculations look like this. For there to be a stable isotope of astatine, the strong nuclear force would only need to be relatively powerful enough to hold a nucleus slightly larger than bismuth together. The most stable isotope of bismuth is 209, and the most stable isotope of astatine is 210. If these atomic nuclei are assumed to be spherical, which they aren’t because nucleons don’t tessellate into spheres, and assuming the inverse square law is the only significant factor, a bismuth nucleus could be thought of as consisting of 209 units of volume each corresponding to a nucleon, and an astatine one of 210, which is 0.4% larger. This would actually mean the strong nuclear force would only need to be 0.2% stronger for this to happen, but in fact this figure is inaccurate. To be honest I can’t even work out in which direction. It certainly seems as though there would only need to be a small tweak for there to be stable isotopes of both astatine and francium, and since there are plenty of alkali metal-halogen compounds such as sodium chloride, there nearly is a salt called francium astatide. This would be a white, translucent substance with cubic crystals.
Technetium is more complicated. Both it and promethium have odd atomic numbers at forty-three and sixty-one, and odd-numbered elements are both rarer and less stable than even-numbered ones of similar mass. Even-numbered elements often form from the collision of α particles, or other elements previously formed in that way, and these, being helium atoms, have an atomic number of two, so the more common elements are even. Also, this allows particles to pair off inside the nucleus, again making them stabler. This is only a partial explanation though, because clearly an element like nitrogen or gold has stable isotopes in spite of being odd-numbered. Technetium decays to molybdenum (element forty-two) or ruthenium (element forty-four), both of which are more stable, so the issue is really why it’s less stable than either of those. All elements have radioactive isotopes, but technetium and promethium only have those. Technetium-99 has an odd number of protons but an even number of neutrons, which makes it more stable because of pairing: it has forty-three protons and fifty-six neutrons, making it the most stable isotope of that element. Less stable elements are also supposed to be furthest from the “magic numbers”, which would make the “anti-magic” numbers 5, 6, 14, 24, 25, 39 and 67 (and 103, which would be unstable anyway). Thirty-nine is close to forty-three, but is yttrium, not notably unstable. A light element without stable isotopes could, however, be expected to have a total number of nucleons close to 103 (which technetium-99 has), a total number of protons close to thirty-nine (also true), be odd-numbered (which it is) and have about sixty-seven neutrons, which is somewhat higher than technetium-99’s fifty-six. However, the liquid-drop model only includes approximations for quantum factors, and there’s a more sophisticated method called the Strutinsky Smoothing Method, invented by Vilen Strutinsky, which is more accurate, and can be expressed by this equation:
And yes, I know I haven’t bothered to specify what any of that means, but the point is, there is something out there which does seem to predict that there are no stable isotopes of technetium or promethium. Just considering promethium for a moment, this has an atomic number of sixty-one and its most stable isotope has a mass close to one hundred and forty-six, with eighty-five neutrons. At this point, it’s probably worth digressing slightly into my habit of using duodecimal numbers, because this is a good illustration of why it can be a good idea. Stating this in base twelve, promethium has an atomic number of five dozen and one and its most stable isotope has a gross and two nucleons with seven dozen and one neutrons. This shows much more clearly how these numbers are “unbalanced” than the relative mess of the decimal system can, because the occurrence of sloppy-sounding numbers like these is much rarer in the duodecimal, and focussing on these figures immediately suggests there is something up with them. They aren’t neat enough. The same can be done with technetium-99’s three and a half dozen and one protons, four dozen and eight neutrons and eight dozen and three nucleons, although it’s less glaring. Promethium is in fact the least stable of any of the first seven dozen elements, even less so than the notorious polonium.
The question is, then, could a different strength ratio of the strong and electromagnetic forces cause technetium and/or promethium to have at least one stable or metastable isotope? It occurs to me that both of them are in slightly the “wrong” place with regard to nucleon, neutron and proton numbers, which is apparently down to quantum physics in a way I can’t understand, but the classic “bad” numbers would be thirty-nine and sixty-seven, which are yttrium and holmium. Holmium has the distinction of being the most boring and useless element in the periodic table according to some chemists, and it’s notable that mentioning its name tends not to ring bells in most people’s minds. It’s just kind of “there”. It is a rare earth metal but not a particularly remarkable one, although it can be used to generate the most powerful artificial magnetic fields possible and can also damp down nuclear reactions, which actually sounds like an example of how boring it is. There would be technical differences in the design of nuclear power stations and possibly MRI magnets, but that would be it. It might not be possible to achieve the strength of magnetic fields found in certain circumstances.
Stable promethium is a similar prospect. Most of the uses of promethium depend on its radioactivity, for instance luminous paint and atomic batteries, but again there are alternatives to this, particularly considering that a different rare earth metal would be the radioactive one instead. It would probably have ended up in a phosphor on CRT TV sets and monitors. It would not, however, have the same name.
Yttrium is technically not a rare earth metal but is very similar to them. If it turned out not to be stable, it would not have been detected in the sample of rock from the Swedish village of Ytterby, and at least four different elements would have different names: yttrium, terbium, erbium and ytterbium. Since a relatively high-temperature superconductor was discovered as a result of a typo in the formula, confusing yttrium and ytterbium, this would have significant scientific and technological consequences. It might also have delayed the discovery of rare earth metals themselves. The newly discovered blue pigment Oregon Blue could not exist.
I’ve mentioned the possible Mandela Effect regarding technetium before. If technetium had not been radioactive, it would be called masurium, because of the irreproducible result in the 1920s which appeared to detect it, which in this case would be confirmed. The name “technetium” refers to the fact that it’s a manufactured element. Again, the uses of technetium in the actual world are based on its radioactivity. For instance, it’s used as a radioactive tracer in medicine. Stable technetium would be very different. Here’s a logarithmic graph of the relative abundance of the chemical elements in our planet’s crust:
A couple of things are obvious from this graph. One is that the odd-numbered elements are considerably rarer than their even-numbered neighbours, hence the zig-zag. Another is that there is a sudden plunge in abundance after element forty-two, molybdenum, and a gap where technetium, or masurium, ought to be. This seems to predict that technetium would be about as abundant as silver, although it would probably not occur native like that metal, meaning that it would probably be a minor precious metal like rhodium. It’s also significant that that plunge in abundance would be less severe because there would still be radioactive isotopes of technetium which would break down into ruthenium, an iron-like metal which would therefore also be more common. Technetium has a very high melting point, putting it into the category of metals like tantalum and tungsten, and is a powerful catalyst in the dehydrogenation of isopropanol. It would also be useful in the manufacture of stainless steel. Moreover, since it’s a relatively light element it might have a biological function, which molybdenum has for example. I can imagine it being used as an antidote to isopropanol poisoning. There are a large number of molybdenum-containing enzymes and it may have been essential to the evolution of cells with nuclei, so it’s conceivable that technetium would have a similarly significant rôle. Maybe life has actually struggled with the absence of technetium and would have evolved more quickly if it existed in a stable form, perhaps making complex life more common in the Universe. However, all this is speculation.
Astatine is a case which chemistry examiners are very keen for candidates to consider. The halogens have a regular and particularly predictable set of properties which change as they occur further down on the periodic table. Fluorine is a highly reactive and dangerous yellow gas, the most reactive element of all. Chlorine is still reactive enough to support combustion and is a green gas with a relatively high boiling point. Bromine is a fuming red liquid and iodine a dark purple shiny non-metallic solid. The colour changes are due to the absorption bands of the atoms moving across the spectrum as the electron shells increase in number. Astatine would therefore probably be a relatively inert black solid which looks like anthracite. Every other halogen has a biological rôle, so it’s possible that we’d require astatine instead of iodine for thyroid hormones. Astatine would be an unique halogen because it would be a metalloid. For example, it would be a fairly good conductor of electricity and might be a semiconductor, making it useful in electronics.
There appears to be a similarly predictable trend down the column for alkali metals, and of course cæsium is the most reactive of them all. This suggests that francium is highly reactive, but it has also been suggested that it isn’t, although I don’t know the argument for that. The low melting points of all the alkali metals also means francium could be liquid at room temperature, with a melting point of 8°C, and is about two and a half times as dense as water. Francium has never been observed as an actual lump of metal, or pool for that matter, since it’s radioactive enough to cause itself to vaporise instantly.
Between astatine and francium lies the radioactive and famous gas radon. This has a boiling point higher than any other elemental gas except chlorine, but unlike chlorine it is not very reactive, although relative to noble gases it would be. For instance, radon difluoride is entirely feasible, and in fact it does exist, as does radon trioxide, and there are thought to be higher radon fluorides. If it weren’t radioactive, it’s conceivable that it could collect as pockets of liquid in the ice near the south pole. It would be over four times as dense as water.
Polonium poses an interesting issue. It wouldn’t be poisonous, and it’s also alleged that tobacco contains trace amounts of polonium which make it more carcinogenic than it otherwise would be because of the radioactivity rather than the toxicity. If this is true, a world with stable polonium wouldn’t just differ in terms of Aleksandr Litvinienko not being assassinated that way or Marie Curie not dying of cancer quite as young, but possibly in altering the fates of millions of people, since tobacco would be marginally less carcinogenic, and this could mean various people lived longer and got to influence the world in untold ways. It would also not be called polonium as it wouldn’t’ve been Marie Curie who discovered it, who named it after her native Poland (and this also means Francium would have another name).
The question arises more broadly of whether there would be any other differences. I suspect that a different profile of radioactive elements would influence continental drift. Continental drift occurs because of convection currents in the mantle, heated by radioactive decay. The density of both the mantle and the continents would be slightly different if these stable elements existed, as they would be present in both, and the heating effect would be lower. I think this all adds up to slower continental drift, meaning that the Atlantic Ocean could be narrower, the Mediterranean wider and Australia slightly further south. The differences in world maps reported by those who believe the Mandela Effect is something other than confabulation tend to be in the directions of continental drift, and I find that slightly suspicious. Why would we misremember the locations of land masses consistent with their direction of movement rather than at right angles to them, or in some other way? This is one reason I suspect the Mandela Effect is more than just psychological, eccentric though it makes me. Of course it could also be that a slight difference in the relative strength of electromagnetism and the strong nuclear force would have a chaotic effect and end up producing a universe like this one, full of stars and galaxies, but not the familiar ones, because the early tiny irregularities in the distribution of density in space could be different and later become voids and superclusters which are
While I’m talking about the sky, I want to make one final observation. There are stars whose spectra show they’re high in technetium even though the element is unstable. It’s been suggested that this might be a signal sent by aliens, or at least evidence of alien technology tampering with stellar evolution. It occurs to me that although we generally believe the laws of physics are uniform throughout the Universe, this might mean they aren’t. Maybe there are, after all, planets out there in this universe where these elements are stable, but perhaps also whose laws of physics are incompatible with the survival of the human body, for instance because iodine could be highly radioactive. But the simplest and most boring, and therefore true, explanation is that these stars are high in technetium for some other reason. Nonetheless, there are alternate universes where the elements I mention are stable.