Professor Sir Fred Hoyle, astronomer and a mathematician at Cambridge University in England, speaking at Nobel Conference XII - The Nature of the Physical Universe held at Gustavus Adolphus College in St. Peter. Hoyle's speech was titled "An Astronomer's View of the Evolution of Man." Hoyle is also known for his books which popularize astronomy and for his science fiction stories. The speech broke for questions, which were introduced by the moderator.
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Do a young child and now it seems a long time. The week seems an age in a year and Eternity. That wasn't man sees time somewhat similar. They 4 years from one election to the next seems a long time to our government. A human lifetime seems an age to each individual and a few centuries seems an eternity. Yet just as a young child experience of life is very short. So the total time span of civilized man is very short. This being only about two hundred generations of human civilization. Where is there a upwards of ten thousand generations of human prehistory? And if you can't 30 years do generation life has existed on the earth for more than a hundred million Generations. There's another characteristic which button civilize man. She has with a young child. With the impression of a future in which almost anything seems possible. What does a child reaches the age of about eight years he begins at last to see that not everything is really possible. It begins to distinguish between what might be And what can never be? Civilize man hasn't yet quite reach the comprable age of discrimination. Although the first seeds of Doubt appear to be forming a right now in the second half of the 20th century. I need dating Mike talk tonight. I'm going to discuss what I believe to be a major constraint on the future or constrained which I think in its very nature seems inescapable. It may seem rather strange to you. That one can accept a limitation not just for the present moment, but for all time change their however far we wish to go forward into the future strength comes from the materials in the world around us materials that it taken on a cosmic scale. The relative abundances of the elements as they exist between the stars and probably also galaxies other than our own they shown here. It's quite true that when you look at different stars in the sky there very little one from another in that makeup in the chemical makeup, but not by factors that will make much of a change if you showed them on a diagram such as days. So they most abundant of the elements the ones that are up here are some thousand billion times more abundant than the least abundant elements which are out here in the region of large atomic weight. Let me give you a few examples of the economic importance of these abundance is the commonest and least expensive of the metals such as magnesium aluminum ion. Have Rhonda High abundance is zinc and copper being less abundant valuable is still less abundant in Steele Mo valuable and the precious metals silver and gold Platinum Palladium rhodium iridium that sort of thing Cosmic play very rare elements. Of course, the relation between economic value in Cosmic abundance isn't entirely strict is also some of the economic value on the particular physical properties that an element happens to have under the defendants on the processes in the earth, which of lied to the formation of deposits here on the surface of the some elements tend to concentrate into competitive the rich deposits and others remain more diffusely distributed and distributed or economic a more expensive to extract from the Rocks. So I didn't call you this relationship isn't quite strict. It's interesting and important that life itself is based on the coming is to the elements particularly hydrogen carbon nitrogen and oxygen. Of all substances water is perhaps the most essential to life in the molecule of water. H2O is composed of the cosmic play most abundant element hydrogen and oxygen the third most abundant element and carbon and nitrogen which form the Mainstay of Life the fourth and fifth most abundant element important elements to life like calcium in our bones iron in the blood magnesium in the green chlorophyll Health Plan sulfur and phosphorus element around a high abundant. So you can say that life is built from the simplest molecules containing the complex, these two elements. Which suggests that life on a on a cosmic scale may be very abundant indeed. It just comes from the Communist materials basic life forming elements found in Cosmic gas cloud. But to the surprise of most astronomers the elements of themselves Associated into molecules and not merely into molecules with into organic molecules. That's the same involving carbon in an important way in the denser parts of clouds like this. At the last count which I made myself some 36 different organic molecules in between discovered by one of the new techniques of modern astronomy Circle millimeter-wave astronomy. I mostly these molecules which have been found. I made up from hydrogen carbon oxygen oxygen precisely the mine life warming elements. The discovery of organic molecules within dancing to sell a cloud which tend to be small regions in these larger clouds of the cloud hear the discovery of organic molecules in in these clumps within clouds of this time. I did impetus to the idea that life may have proceeded to the formation of our own solar system. The Sun and all planets have ages of about four and a half billion years. What does our galaxy the whole system of the Milky Way age of about 12 billion years. The salt is that life here on the earth could have been derived from biologically important molecules, which existed already in the gas cloud from which our solar system fault. Is this for sell just the same biological conditions would apply for many of the newly forming stairs? With the implication that life in our own system may be related to life in other systems. According to this point of view life wouldn't be required to originate independently in every star system. These are the next slide please these dents interstellar clouds also contain myriads of fine grains. If you took a centimeter a divided into a hundred thousand million pieces then a typical size for one of these pieces. Organic molecules that stick to the grains the small grains that exist in the clouds can stick together and it's interesting that the joining of two such molecules molecule of formaldehyde and resending mean both of which are known to exist in large quantities of the amino acid glycine. High temperatures within the clouds with temperatures which are actually determined chemtech values at which amino acids into chains are the resulting polymers are known to have a sticky quality there their they're sticky things that would cause grains it coated on the surface of grains when two of them come together. What caused the Grange to stick together Ace of considerable interest. I think that the perimeter the distance around the single grain happens to be comfortable to the scale of a biological Gene. While the clumps of grains that can be caused by the sticking together turns out to have a scale when you lucky doubt comprable to the size of the simplest biological cells the scale of a few microns. And furthermore The Matrix are solid grains in could be formed in such a clamor. She stuck together. Would beat will provide an important Shield against radiation, which would otherwise otherwise tend to break up these comparatively fragile complex organic structures. These considerations make the suggestion of an Interstellar origin for life more plausible than it seemed only a few years ago. Indeed. I think one might say that it is become significantly less difficult to see how the simpler organic molecules might get together and build themselves into complex molecules within dense interstellar clouds like this, then it is to see how the getting together of the simple molecules might have happened here on the Earth. And in further support of this idea, both amino acids and Interstellar green plums have actually been found in a certain class of meteorite the so-called carbonaceous chondrites. So you might say that the interstellar Theory begins to look rather like the front-runner Rosen the Mille acquaint speculation. But now you may wonder why the abundances you may wonder why they sell Universal why they seem to be in same in all all stars in similar in different galaxies what made abundances with this particular distribution for most of the elements of small atomic weight and low for elements of large atomic weight the answer to this important question lies in two parts, the first part concerns a state of the whole universe is one which we've spoken about it earlier today with your kid about 15 billion years ago when all material was highly compressed and very hot are the second part has to do with detailed physical processes that take place within the star. So let's take these two parts in Dunn. The hot dense state of the universe is often called the origin of the universe, although whether it really wasn't already in the origin of all things. He's perhaps but I'm not going to get into that debate tonight. What I'm going to be dealing with something that isn't a matter of debate and that is the very high temperatures which existed time would prevent protons and neutrons from associating together. If one is near enough today early later today show called origin of the universe. The forces that dr. Gelman was was talking about those horses that too weak to withstand the intense radiation failed at that time protons and neutrons would have been evaporated immediately by the intense radiation field. The high temperature of the radiation failed also has a second interesting fact because he's a spitting out of interchange relationships between neutrons and protons this day weekend direction is it was a call this afternoon so that a balance between protons and neutrons comes to be set up the universe revolves. So the temperature of the radiation field Falls and eventually stage is reached when those neutrons at the present are for the most part able to join with protons. I want happens then is the ultimate out. So he's only it is he's very largely he live. But a considerable excess of proton Still Remains. After after all, the new phones are so dried out and it's this excess that you use the hydrogen and it's in that way that the hydrogen comes to be the most abundant of the elements. So in this why what what what appears out of this early moment is an excess of hydrogen and helium hydrogen and helium. What are the main elements to emerge from the origin of the universe? It's true that also that small traces of all the elements may have been priced. I don't want to say it all hydrogen helium, but for the main concentrations of the other element we have to now to tend to the Stars till they second thought that I mentioned a moment ago, but let me go the first part by summing up the effect of the origin of the universe some 15 billion years ago as being immersed in a predominantly hydrogen helium environment. From a cosmic point of view has provided us will see as we go along for the energy of the Stars complex of processes to occur within the stars that have the effect of synthesizing the rich variety of items that we find in our everyday world all the time. And in inside the condensation to this song causing a rising temperature within it due to the compression eventually the rising temperature leads to energy production by nuclear reactions. And you couldn't ask the weight the natural question to ask you to walk out these these reactions. What do they consist of this is very easy today hits the hard one for scientist to answer earlier in the reason why it was so hard. It was a wrong 19th century belief that one kind of atom can be changed into another kind of every separate kind of indestructible and itself the discovery of the natural radioactivity of the heaviest elements around the beginning of this scene indestructible of the right idea for explaining the source of the energy that Yet the natural radioactivity of the heaviest elements elements like uranium and thorium couldn't possibly be responsible for the energy of the sun is Dallas just because the abundances of these heaviest element is so small. And it was this difficulty that cause J perin in 1919. suggest quite a different idea and this was to the effect that if 4 atoms of hydrogen could get together and become converted into one active energy on an appropriate scale aspiration scale could be released precisely because Richard Ayers turned out to be right indeed have to be right because there's no other way that's consistent with the abundances that I showed you for the element there explain the energy Supply with the Stars clearly of God. Unlike the situation in 1919 today. We understand how hydrogen can be changed to helium other two main ways for doing this. We should go by the names of the proton-proton chain and the carbon nitrogen cycle, but I'm not going to get them. I don't need to get into the details of that for my purposes tonight generation of energy inside Stars has that kind of inevitable quality about it these stars in the making the Protist form with in gas clouds like the like the ones we've been seeing and the Drawn Together by gravitation. Until compression raises their internal temperature high enough for nuclear reactions to change hydrogen and helium at the rate that is sufficient for an energy balance to be set up a balance between what is being produced by the nuclear reactions of hydrogen into helium and what's being lost at the outside of the Star by radiation in space. I want not stages Richmond that balance comes to be set up. What we say. Is that the star rather than approach to stuff his phone. What happens? When is Ka what happens during can be seen in the next size little technical afraid, but I think we can get through it to the next song, please. What we have on the left hand scale is the amount of visible light which the star emits measured in terms of the visible light from the sun is the unit what you can see on the bottom scale is the temperature of the outside of the stuff which is essentially determines the color of the Stars. We see it in the sky. No one tells you is the relation of the kind of color of the star to how much energy it submitted for various different masses of the star. although a very great deal of energy enormous by human standards can be got from this hydrogen to helium conversation that I've been speaking about. There's no limit to it don't go on forever and that's imposed by the availability of the hydrogen sooner or later. The hydrogen gets used up and particularly as they sell stars of large mass. That is a very luminous ones with very large and making very large amounts of energy the ones that are particularly cute from them as hydrogen becomes exhausted in the central region 2 Stars. I need evolution of a Kind what you can see in the next slide begins to take place. But what happens if it goes along a track which is shown schematically like this in the diagram. But more lies independent of the mass it goes over to a region over here, which is characterized by the still having very large size and a very low surface temperature which means it is very red in color and set stars as you can see the diagram a known as John's. By the time this happens that you can see here is effectively and its death throes. The detail but I I must stress. However, the detailed behavior of an individual still is a good deal more complex than it might seem on this schematic Slide the cause of this complex Behavior. Is that with the hydrogen becoming exhausted and with energy from hydrogen to helium conversion becoming less and less available to this job? It seeks to derive energy from other nuclear processes by which the first two produces carbon and oxygen from the helium the first of the processes the helium, which is being made from the hydrogen then then makes these these things that you're in here. That's the first stage then the carbon nitrogen and oxygen in the witches in here. themselves serve as fuel Call building still more complex elements elements sodium magnesium aluminum silicate the name the most important one is the last step is for the Silicon which is being mocked here to itself and gauging reactions, which produce is all the things that you can see in about this region here of the doctor that. That region. These successive steps as you can see into connected with the product of 1 stage serving is the fuel for the next day. So we have a set of steps in the chemical evolution of material. List of Jester question was just a question. You made it your mind what happens after the last of these stage is the one in which the Silicon says is the fuel building only to about here. I only I only took about about here. What happens is that? Is any further Eeveelution perhaps the still larger values of the atomic weight out of over here possible answer to this question is basically no one silicon is being consumed. We reach is a situation in which the original material the hydrogen helium environment that we started with as being entirely converted into nuclear actress. No further energy can then be obtained indeed. If you want to go any further Beyond here Beyond about this point you want to build with nuclei containing still more protons and neutrons energy is actually got to be supplied and this happens in only in very very rare cases very rare condition vents because of their Rarity of these conditions that the atoms that you can say that I actually have being built. Because of the Rarity that those atoms have such very low abundances as you can see here. I'm it's because of the time because of their Rarity these exceptional situations are no help at all the lights please that says that no help at all to the stars in that average search for continued sources of energy on a no-win course. However, complicated Its Behavior, there's no gainsaying the fact that the energy supply of a star is limited, but it tends to exhaust its supplies at an ever-increasing right and the energy production from nuclear reactions must eventually fail to make God what is being lost from the outside into space. This raises the problem of the final fate of a graveyard. Before I come to this problem, I'd like to show you that this isn't Theory and. It's probably Theory agrees with what we observed observation Nissan Ancira to supported a small Mass like the song. I'm very few of them appear as bright stars in the sky the brightest star at the ones we are the ones that are undergoing precisely the kind of evolution that we just been talking about this business. So kind of going over here and this other company which for any individual star is a very complicated Behavior. In other words many of the brightest stars are in the Deathstroke's. The problem of the ultimate fate of the Stars especially if there is a large mass for which question is is very cute is a fascinating one complex one till they start number he likes to work out all the details. All those wiggle is until fall, but I don't think it need consent is tonight. What you want to know is why this road ultimately leads in some cases. It might lead to the mysterious objects, which have achieved wide popularity of not notoriety in which a neuron is black holes. You know that Casey is the road leads to explosions which disintegrate most if not all of the stuff. the violence of these explosions with an illness supernova can be compared with the most violent man-made blasts an h-bomb and it would need something like a hundred million million million million h-bombs all exploding together to equal one of these chaps. From our present point of view the disk solar explosion serves the broadcast far and wide in Space the complex massage with in the still at the table in The Notches in the movie ACM in Charlotte and many many others that we we actually haven't discussed. I don't want to give you the, once this thing of complex antonyms through space sets up a situation which side This is a situation in which you got to sort of cyclic process setup in which we discuss this business of material from the interstellar gas going from right to left. I'm falling into stars. But now we seen that stars can go off with a bang and they return the material over here back to back to the to the gas. So it kind of this whole thing goes round in the loop. Through this Loop way now in a position to understand how it comes about that alone nuclear processes it inside the Sun a limited to hydrogen to helium conversion with no production inside the son of elements like carbon or silicon the explanation of this is that all these other elements were produced in Stars, which completed the revolution before the sun and our planetary system was formed. Galaxy that's to say the system of the Milky Way is about 12 billion years old as I said a little while ago nearly three times the age of our solar system. So the preceding generation are generations of stars. What happened with the Day broadcast that synthesize materials throughout our galaxy through business that we've got here. They said they saw the the loop and the deer into the gas clouds were there for president in the particular gas cloud from which the Sun and our planets were formed. Could have the light symbol for a little while, please. I begin tonight by asserting that whatever uncertainties that may be about the future of mankind. One thing is certain name of the chemical environment in which we must operate and now you see why this has to be so our environment determined by the abundances of the elements is being produced by the grand scale March events. The scene for it was said in the first place by what I referred to as the origin of the universe into this we've now added a wide sweep of the evolution of the Stars. So it's useless to think that we can escape from our chemical environment by going to some other place that just isn't any other place where it's any different. It's true. By the way that the Earth itself isn't an Intel isn't quite a difficult place. There isn't the enormous preponderance of hydrogen and helium here on the earth and thickness a whole the Earth is rather deficient in all that biological biologically important elements like carbon and nitrogen. What day is deficiencies mean? Is it in the process which led to the formation of the earth it somehow happened that there was a selection against the lightest of the elements most precisely I think against volatile elements exist as gases rather than the solids that's what this election was. But these difference is a largely made good from our point of view by the fact that we humans live at the surface of the Earth in the biosphere cuz it's called where they are hydrogen carbon and oxygen are concentrated. So the Deficiencies in our everyday world the world. We actually live in that far by any means as great as they are for the Earth is a hall in affect the biosphere return just 20 Century Custom environment. As I said before this era did the Mayweather iwabe this Cosmic environment in which life started in the first place. Well, I come now to the last part of what I want to say tonight. Give me then that chemical environment can't be much changed. What does this tell us about the long-term future of our species big question of God, but one about which I think you can say quite a surprising America. All chemical environment that sinking posies constraints which can be summed up in three rules the first role is that any material which man uses in large quantity must be made up of elements of large Cosmic abundance. The second rule would be that elements are present in lower abundances can still be important economic play provided. They are used in what is he often called high-technology. We're a small quantities of a material with special properties are very important as you might have on surfaces are contact points. I said rule is that elements present in lower abundance is can also be important economically. It's our sources of nuclear power because nuclear processes are on the order of a million times more energetic than chemical ones which multiplies a million for the effectiveness of nuclear materials like uranium and thorium Well before we go on to think a bit more about about these Rose, let me outline what can happen when the first of them is contravened suppose you and Jenna water solution a mineral substances within their fairly considerable depth within the Earth's crust when squeezed at high pressure through into feces in the assault laid, but quite hot Rocky Matrix. We know that conditions for the precipitation of various minerals materials can be exceedingly specific and conditions happen. We were supposed to be in place for the precipitation of a particular element. What's a gold? Tell a vinyl precious metal comes to be formed an earth movement large-scale movements over hundreds of years. They out the rocks in the Earth's crust around causing the vine of girl to be brought to the surface or near the surface. Weathering ordinary weathering at the surface now precedes on a much shorter time scale eventually washing some of the gold into a bed of a river where some enterprising prospector happens to notice it what happens then of course is this a gold rush and shoes 1848 whatever it was grow explosive Lake close by that River. But the boom has to be short-lived. Although people that are actually in the the bull believe the prosperity will never end. It's got to stay human property that when you're in in the short life situation, you don't quite see it's going to be short, but it has to be a large towns in populations soon wither away unless the economic capital provided by the gold is being widely used. Why is it used to establish a different than most stable activity for the people that live there I decided to live there. What are the reason for my giving you this look like John plays at the oil boom of the presents and she has the quality of a gold rush about it, but affecting the whole world rather than a small particular area. By growing rapidly on The Limited resource accumulated geologic play all the tens or even hundreds of millions of years man has contravene the first about rules with a class right to sell my car goes down in the whole world. And it's also clear that they threat will actually will become a reality unless the technical impetus supplied by the oil can be can we use to provide us with access to some new how much longer lasting source of energy? That's just Elementary Common Sense. I'd like to show you the next side, please. This slide relates the use by the United States in the year 1970 of economically important material is to the way in which they're available in the Earth's crust in in the oceans in the air. The name of the fat guy is today Stingray plentifully available materials from those that the more rare. I don't understand life time scale that you can see here is logarithmic and it's been standardized with respect to a very common material, both in the sun in our use of Internet is silica silicon. Dioxide up here indicate High abundance has a low values indicate deficiencies in The crucial deficiency overwhelming deficiency. Is that for the hydrocarbons are given these is the former chemical formula for methane, but that's intended to include all of the oil coal and natural gas. You can see this is ridiculously low him another way of displaying this information is shown in the the next and final side. What this does is to give you the length of time in years again logarithmic play. So this is 10,000 years. This is a million years. This is a hundred million years until the length of time in years for which resources of available materials will last. I'd like just to say that this estimate for call over here is almost certainly quite a gross over instrument. Because it assumes all the call in the ground to be recoverable at zero energy cost. Where is most of the coal would actually use much energy or more than it then it would deliver and it would you go when it was burnt to the surface by present-day techniques in contrast with this that did this miserable situation for the oil and gas in and at least doubtfully High position for the coal all the other estimates on the air here. Quite considerable underestimates. They refer only to the most conveniently recoverable material. Example there is much more uranium and thorium present in the corner granitic rocks than there is in in seawater, but I be of use Seawall to hear because he happens to be easier to extract uranium and thorium by precipitation from seawater. Then it is by crushing in huge quantities of a rock with rather low grades of uranium. I just to show you what is involved in the in the economic energy value all the well It is quite expensive to extract uranium and thorium from seawater compared to the prices that are being played today in the world for those substances in otherwise about $100 a pound is that is being the estimated values in a proportion of about 1 pound of uranium-238 pounds of thorium a phone could get the total energy out of a pound of uranium and thorium. This would have an economic value of about $20,000 so you can see that the prophet in doing this is actually enormous another reason for my giving seawater is this happens to be material which is readily available to almost all the nations of the Earth. Could I drink lots of coding the energy that we need the the lifetimes are running in the region of millions of years as I say these kind of minimal instruments. Could the lights up now, please excuse. I think I ought to say to energy programs based on uranium and thorium let such opinions. I think I'd only possible because we happened to enjoy the great luxury, but still living in the hydrocarbon the era. What is generally agreed that this area must be quite short-lived replacements for they hydrocarbons when they're exhausted mankind would have to return to a pre-industrial civilization which would mean a population level of props at ten of what we used to play in living in the world would have to die for Billy and piglet present-day population-level, perhaps 10 billions in the future and it's against this enormous Dimension that I think one has to say that energy from uranium and thorium. Is it only replacement for the hydrocarbons that's presently known to be possible. maybe some other in the future, but but presently that that's the only one which is which is no I come now to a few final remarks. Referring to my life slide which which gave these these lifetimes ranging up to millions of years. That those lifetimes were calculated for the consumption of materials at 1970 rights rights over only the past six years consumption has moved appreciably. If the world population with A continuous present out of control increase the lifetimes that we saw in that last side, what's him become meaningless conceivable availability of materials confirm it for the long sustained rise in the number of people living in the world even say this in the following way. It's a present rate of increase with the continued for a further twenty to Thirty generations. And I told you this is very little compared to the number of there already being the human population with them become so large that the whole of the Earth's atmosphere would only be careful of supplying a ration of are a one breast itch. So plainly then population limitation must come at no very distant day. He might come forcibly and painfully so overcrowding and material shortages what it may come through common sense and voluntary action. Indeed by reducing bus rights everywhere to equality with death rates. He could actually come not by the middle of next century is many people talk about fight fight it by the end of next year. That is quite possible. No impossibility back. And the lifetimes that we've seen here would then become applicable and if it's what the happen then I would say that nothing concerning the future of our species would then look unfavorable? Thank you. I have a deformity of what may be an interesting question from the audience directions to dr. Ho. You see the favor the use of fissionable materials is a major source of energy. Are you worried about the hazards of fission reactors? And what is your comparative evaluation of Reliance on solar energy? Could I put it stock play? I think this is the worst accident that I can see happening to reactor. Then this is to the least reactive State branches of the can do the Canadian. I think a good deal safer than I'm speaking that they might kill it's how some people is on the Boise State. A technical mistake occurs in the reactor up to technical mistakes of the time. There's an earthquake. Is that sort of calculation? I think I'm much bigger danger is fissionable material falling into terrorist hands. But here I would say this is not a reason at all to say we mustn't have nuclear energy. It's a reason to stop terrorism. If a terrorist bomb to to be exploded in a big city, I think about a hundred thousand people month. I think if political considerations like to situation like the first world war and this is a political problem and I don't want a nuclear energy. That would be against you could dance to fit on an enormous scale. But I wanted to give you the orders as I have seen them in the head I think about five hundred million people might die. But if we fail in energy, this is how I take at least four billion people like them to death. That's that's the scale of the problem now. Having said that there are also two ways that one can can proceed to minimize the justifiable phase one is to use the kind of react to that. I mentioned a moment ago, which may very well be adaptable to the consumption of thorium. So what happens when you when you work with sorry I missed it the fissionable material which is produced is a form of uranium. It isn't plutonium, which I agree is a very dangerous material and a fact fissionable form of uranium. It's not the usual fictional form. Its uranium 233 is that is mixed with uranium 238. It's very different and difficult for a lower-level kind of technology to unscramble in a fuel cell is a commercial reactors. It would be around the back way of doing it. I personally think that saying we will rely on solar energy. Is a failure to take account of the magnitude is a problem because there is no guarantee it talk. That's our energy will prove inadequate sauce. And I myself believe that solar energy world would be very dangerous more dangerous than than reactive. What is the most innocent form of solar energy you can think of but by gosh, if you take account of all the trucking of the world all the chainsaws that you going to have if you going to supply the world's industrial wood you'll soon find it a lot more people are killed every year from the drawing of wood then from nuclear reactors. if you take call, I think it is sadly the case that it almost no minors but worked for upwards of twenty years of Coffey. So don't suffer in some degree from pulmonary disease. In my own country, not the single clinical case from working in the nuclear power industry for upwards of twenty years has yet come to like I don't know how it is in this country, but that's that's the situation in the UK safety factors that you're involved in it. It doesn't amount to much unless it's taken from over a wide area. That automatically means that one has to have a concentration of mirror. Isn't that what I am sure that is the most importance of not allowing this problem to write until the hydrocarbons become exhaust and the only will only way around at the moment is this is the uranium and thorium nuclear fission. It'll be found that would be marvellous, but I don't think we're going to find out.