Hannes Alfvén (1982) - How Space Research Changes our View of the Universe

I am going to report about the achievements of space research, 25 years of space research, and its application to the more distant regions of space. And I will concentrate on the change it has produced in plasma physics. I think this is an illustration of what Professor Nagel said, that you should not believe in what is accepted today because that may very well change very rapidly. First of all, you may ask is plasma physics of very much importance in astrophysics? If you read the usual text books in astrophysics, you don't think this is the case. But in reality, the stars consist of plasmas and the interstellar medium also of plasmas. And it seems that the universe consists to more than 99% of plasma. In fact, at least by the volume, more than 99.99999999% of plasma. So plasma physics should not be considered to be completely irrelevant to the research of how the universe is structured. To be more specific, plasma physics extends from the laboratory. Typically, this is in a logarithmic scale, that is typically, 1/10 of a metre for a normal experiment. Up to the magnetospheres, the magnetic fields surrounding the earth and the other planets and the sun, that is about 10^8 metres. And then we come up, this is a jump of nine orders of magnitude. By another jump by a factor of one billion, you come up to the galactic phenomena. And a third jump, this is a cosmic triple jump, brings you up to the Hubble distance which is what the big bang believers call the size of the universe. This is 27 orders of magnitude. And laser fusion has extended it downwards by five orders of magnitude more. There are reasons to believe that the basic properties of plasma are the same in the whole region. This is by no means certain. We can trust that it is so in the laboratory and in the magnetospheres because there we have reliable measurements out to this limit. Outside this, the field is necessarily more speculative because of what is called high quality diagnostics. That is, an investigation of the properties of a plasma is possible in the laboratory and as far out as the spacecrafts go. But it is not possible further out. Whether we should believe, accept that plasma changes its properties at the outer reach of space craft or not, this is a thing which we cannot prove. But I think there are good reasons to suppose so. What has happened in this field during the last years? It is especially that the space research has made the magnetosphere accessible to detailed analysis by high quality instruments which are sent out here, and going up and down, up and down and sending signals to the earth which have been interpreted in detail. The result of this is at the same time laboratory research has made a great step forward. To some extent favoured by, to a large extent favoured by the fusion work which is going on there. So far, the fusion research has not given us any energy but it has given us very valuable information which can be used for clarifying the structure of the universe. There has also been much work spent on the translation between laboratory work and the magnetosphere. And the result of this is that we have got a drastic change in our concept of what the plasmas out in space are like. In reality, there are half a dozen different respects in which this change has taken place. And I am going to select a few of them and try to discuss them more in detail. One of the important things is that our concept of the structure of interplanetary, interstellar and intergalactic space has changed drastically. was absolutely empty. It is from that point of view absolutely empty. But not absolutely empty, it is rather empty but the little matter which is between is very important. and this was then considered to be a homogeneous, nebulous gas with dust in it. Space research has given us a new view which you can call the space age concept of space. Namely, that space is highly structurised. It is penetrated by a network of electric currents. And this is something which is of importance in all fields of plasma physics. We know that this is so after this limit there are good reasons to suppose that the whole universe is penetrated by, has this structure, highly structured, penetrated by electric currents. More specifically, what does structured mean? It means that we have discovered a number of phenomena which are strongly inhomogeneous. There are electric double layers which you'll find everywhere in space. These were not believed to exist up to something like five years ago. Now they are very popular. There was, a few weeks ago, a symposium in Denmark where there were 50 of the most prominent people working in this field who discussed the properties of double layers. What is a double layer? If we have an electric current in this direction, then under certain conditions we have the density of the plasma which is fairly homogeneous. This is the density and this line gives the electric potential, the voltage which increases slowly. There is an electric field which drives the current through the plasma. However, when a double layer is produced, the conditions are changed like this, here is the voltage, it makes a sudden jump and then has another constant value and the density changes in a corresponding way. Such double layers were well known in the laboratory since the time of Langmuir about 50 years ago. It was denied that they could be of any importance in space until they were actually discovered. There are such double layers at a height of something like one or two radii above the earth. And this is a picture of the earth and these are magnetic field lines. And here in the equatorial plain at a distance of five or six earth radii you have a plasma flow, sunward plasma flow. This is seen from the night side and that produces an electromotive force here. And this produces electric currents which flow along magnetic field lines to the earth, then through the ionosphere and back again to the equatorial plain. So we have, we are here discussing an astrophysical problem, not in terms of magnetic fields as has usually been done but to the same extent in terms of electric currents. And these electric currents may produce double layers. In here is a double layer at one or two radii. And that means that we have a sudden jump in the voltage there which produces, in which auroras or aurora electrons are accelerated. Here, we have the electromotive force, here the auroral electrons are accelerated and the energy is transferred by the circuit. This is not a hypothetical, theoretical hypothetical picture; it is something which is actually measured by space crafts which have penetrated many times. Of course, there are many details which are still obscure. These double layers may have voltage differences of kilovolts, which you have here, solar flares, it is megavolts or gigavolts and they may be still higher. Then the currents produce filaments. In cosmical physics we are accustomed to the Newtonian attraction. The general gravitation which typically produce, aims at producing spheres, like stars and planets and so on. However, we have also electromagnetic forces. And these electromagnetic forces, they tend to produce filaments. The basic phenomenon is known for a very long time. It is actually, that two parallel currents attract each other. And this produces electric pinches and filamentary structures. And such filamentary structures are common in the universe. Can I have the slides here? And we have good reasons to suppose that whenever you observe a filament, that is just an indication that we have electric currents pinching electric currents there. Can I have the first slide? Yes, this is the sun, this is the solar corona and if you sharpen the picture a little you will see that this has thin, thin, thin filaments in every direction. The sun goddess actually has beautiful hair which you see here. And these filaments are likely to be due to electric currents which produce the so called pinch effect, produce filaments out of it. Next slide. Here is a comet and here you see striations, filaments of the same kind. The tail of a comet is obviously a plasma phenomenon. This was first pointed out by professor Biermann here in Germany. Next slide. Here are photographs of interstellar space, far out in the galaxy. You see thin filaments everywhere. Next slide. Here are other filaments of the same kind. Next slide. Here is an ordinary cosmic cloud which seems to be a homogenous structure. But if you subject it to what is called contrast enhancement technology you get this picture. That is, you put it into a computer and ask the computer to look for contrast. And then you see it is penetrated by filaments, which is a strong indication that there are electric currents also there. Can I have one more slide? Here you have dark lanes which probably are also due to filaments. These are just some arbitrary examples to show you how important the formation of filaments is and what it is likely to be due to. Then come surface currents in space which are also very dramatic. It is actually, to me it was the most important, the most shocking discovery. Namely that if you go out from the earth, measure the magnetic field out from the earth you observe, this is now the distance from the earth, this is the magnetic field. You will observe that it decreases approximately as r ^-3 as it should do, out to something like seven or eight radii. Then it may suddenly change its sign. And this is made very abruptly, in a very, very short distance, some 100 kilometres, less than the distance from here to Paris, for example. And what a space craft records here is that you have constant value here with some fluctuation and then suddenly it jumps over in this way. This demonstrates that there is a thin current layer which separates the plasma controlled by the earth's magnetic field from the plasma controlled by the solar magnetic field. And such double layers, they are found in many places. On Jupiter, Saturn and quite a few other places, comets and so on. We have something like ten different cases where we have such thin, thin filaments. And they separate regions which may have different magnetisations. It goes here like that and outside it goes like this. The regions may also have different temperature, different density, different chemical composition. And if we go out in space, further on, it may be that similar layer separates regions of ordinary matter from anti matter, if we extrapolate it. The awkward thing with such a layer is that you cannot observe it until you penetrate it. I attended a meeting, I attended the arrival of the space probe to Saturn and then it was dramatic, no one saw it and suddenly everybody, the big hole, saw it, here it comes. And this makes it awkward too because if you go out to the interplanetary, to the intergalactic, to the interstellar and intergalactic regions, you may have similar structures there. And they cannot be observed. Now, it is very unpleasant to introduce such a concept if you cannot observe it. But it is still more unpleasant, at least to me, to postulate that at the outer edge of the reach of the space craft, space changes its properties. And this has far reaching consequences for astrophysics in general and not the least for cosmology. If we try to apply all this, to see what changes this makes for astrophysics in general, I think many people are mostly interested in the application to cosmology. And I have tried to concentrate on it. I don't think there is time enough to develop and present a new cosmology here. The application is first of all that space has a cellular structure. And this means that the existence of anti-matter is not excluded. There are a number of very nice arguments against the existence of anti-matter in the universe but these are all based on a concept which we know now is not valid. So we cannot exclude the existence of anti-matter and the universe may very well be symmetric with regard to ordinary matter and anti-matter. Then comes an analysis of the red shift. The red shift demonstrates without any question it must be a Doppler shift and I think it is impossible to avoid that. The red shift demonstrates that the universe or to be more correct, to use the old term, metagalaxy, that means all the galaxies we can observe. It is a synonym to what the big bang believers call the universe. If you plot the red shift, that is the velocity of galaxies and here is the distance to the galaxies, you get this famous Hubble diagram. And people conclude that this proves that there is a linear relation between the expansion and the distance. And that the deviations from a straight line here are due to observational errors. This may very well be so but it is not necessary to make such a conclusion. If you take each individual point and extrapolate backwards in time. You see here that this is now and from here you extrapolate backwards in time and then this is the distance from the earth and in the reference system you see that these do not necessarily coincide in one point. They spread here over a large region and it does not exclude that everything could converge in one point but it does not prove it. It proves that the metagalaxy at present is expanding and that it was once, about ten billion years ago 1/10 of the present size. That is one billion years ago, one billion light years. But this is not proved at all. Furthermore, it has been discovered that space has a hierarchical structure. The hierarchical model was introduced by Charlier long before the big bang, around the beginning of this century. And it's said that stars are aggregated to galaxies, galaxies to what we now should call clusters of galaxies and clusters of galaxies to super clusters and super clusters to some larger units. If this hierarchical structure follows some general law then we can satisfy some conditions the Albert objection and the Seeliger objection to an infinite universe. This was not believed in until 1970, de Vaucouleurs demonstrated, he is a very famous observer, that this really is true. The universe has the galaxies, metagalaxies and so on which are arranged into hierarchical structure. And this is how de Vaucouleurs' diagram looks actually. It is plotted in different coordinates. This is the size of a structure and this is the mass of it. Here you see that the stars are here. This limit, which is very important, that is the Schwarzschild, the Laplace Schwarzschild limit, it means actually that on the other side up here we have black holes. You see here that stars go down and neutron stars may approach the Schwarzschild limit rather much. But if we go out to galaxies and clusters of galaxies and so on, they are very far from the Schwarzschild limit. This is actually given an escape velocity, it's actually two orders of magnitude in density here. So they are four or five orders of magnitude from the Schwarzschild limit. It means that the general theory of relativity comes in here as a correction which is negligible, Then if we extrapolate to the metagalaxy using the same formula, it comes here for orders of magnitude in density from the Schwarzschild limit. So the hierarchical structure of space which de Vaucouleurs introduced in 1970 that was not believed until in the end of the '70's, it was generally pupils and collaborators who made highly sophisticated statistical analysis and did confirm this. So you can say that the hierarchical structure of space is now an observationally confirmed structure. And there is a large void region here which makes it very unlikely that space is closed, which it should be if it is on the other side of the Laplace Schwarzschild limit. I think this is approaching its end. This is the Sand Reckoner which Archimedes has as a title for one of his most famous books. And if I should conclude this, I think that we should not take the generally accepted big bang hypothesis as confirmed by observations. Instead I should like to quote once again what Professor Nagle said and I think that space research has given us so much new information about what the space structures are like. And it is, as far as I can see, unavoidable that this will shake the concept of, the basic concepts of astrophysics in a rather drastic way. So if I should conclude this by giving an advice to the 500 students here, it is that those of you who are interested in astrophysics, should not take the curriculum in the general theory of relativity but instead a very good course in modern plasma physics. Thank you. Applause.

Hannes Alfvén (1982)

How Space Research Changes our View of the Universe

Hannes Alfvén (1982)

How Space Research Changes our View of the Universe

Comment

Three years before the present lecture, in 1979, Hannes Alfvén gave a talk on ”Observations and Cosmology” at the Lindau Meeting. In his talk, he rejected the Big Bang theory and instead advocated a model of the Universe symmetric in matter and anti-matter. In 1982 he came back to Lindau, this time with a more general lecture title about space research and its results. In particular he wanted to describe the implications for cosmology of the discoveries made in 25 years of space research. In his introduction, Alfvén quotes the Chairman of the session, Bengt Nagel, at that time the Scientific Secretary to the Nobel Committee for Physics, as saying ”one should not believe in what is believed today, because that may very well change rapidly”. Even though I was not present at the lecture, I think that I can warrant that this is a correct quotation. Nagel was my predecessor as secretary to the Nobel Committee and it is true that he used to say things like that. After the introduction, as a true plasma physicist, Alfvén then spends most of his lecture describing and explaining electric currents and magnetic fields in space. In particular the emphasis is on the then recently discovered electric double layers. These were well known from laboratory plasma physics, but had only recently been discovered by spacecrafts exploring our solar system. He then makes a rather large extrapolation from these interplanetary discoveries to space in general and in particular to a hierarchically structured universe, with stars, galaxies, galactic clusters and superclusters, etc., etc. If this extrapolation is accepted, there is a mechanism that would give rise to a cellular structure in space, where the matter content of each cell would be separated from that in the surrounding cells by double layers. So the main result for Alfvén turns out to be a physical mechanism that would allow a universe symmetric in matter and anti-matter, as described by him in 1979. Always somewhat of a showman, at the very end of his lecture, Alfvén again quotes the Chairman and ends by giving as advise to the young 500 students in the audience: Don’t go for a curriculum of General Relativity but chose Plasma Physics instead!

Anders Bárány

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