Antimatter from Space

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130 Nature Vol. 282 8 November 1979 than isoleucine. From an alignment of the from energy in the form of subatomic In the past few years an exciting bovine COIl amino acid sequence with the particles, so modern cosmology provides a alternative picture has emerged. Ambitious sequence of codons in the human COIl natural mechanism for the origin of new theories that seek to unify three of gene, they observed that methionines occur matter: it was created from the explosive nature's four forces into a single opposite ATG at two and opposite ATA at energy associated with the primaeval mathematical description have predicted five positions. Provided there was no large violence. Paul Dirac gave a very heuristic that perhaps matter can be created without scale evolutionary interconversion of explanation of how this happens. The an exactly compensatory quantity of isoleucine and methionine codons it would equation that describes a particle such as an antimatter. If this is so, it opens up the appear that AUA codes for methionine in electron possesses two sets of solutions: one possibility of a lopsided Universe in which human mitochondria. There is not yet describing 'ordinary' electrons and the most of the antimatter has been annihilated, enough protein sequence data to determine other mysterious states in which electrons leaving a small residue of unbalanced matter whether AUA also codes for methionine in have negative mass-energy. As all systems that constitutes all the observed Universe. yeast mitochondria. tend naturally to seek out their lowest To test which of these theories is closest The structural grounds for the AUA to energy, nothing apparently prevents to the truth, physicists can search for Met and UGA to Trp codon assignments ordinary electrons from descending into antimatter in space. Although the nearest are presumed by Barrell et 01. to be these enigmatic negative energy states. As antigalaxy may be millions of light years nucleotide bases present at the wobble the energies can be limitlessly negative, away, perhaps high energy subatomic positions in the anticodons in tRNA~~and there is a sort of bottomless pit into which antiparticles can stream across the gap and tRNA~7. The presence of U or modified all matter can disappear amid a shower of pepper the Earth. Cosmic ray showers have U at the 5' end ofthe anticodon in each case energy. long been known to contain some might allow translation of AUA and UGA To preclude this apocalypse, Dirac antimatter (that is how the positron and by A-U base pairing and of AUG and UGG proposed that the pit is blocked with an antiproton were first discovered), but it has by wobble base pairing (Crick, J. molec. infinity of invisible electrons. If one of not hitherto been known whether these are Bioi. 19, 546; 1966). Recent sequencing these invisible negative energy electrons is merely by-products of high energy work by Sanger and Coulson (cited by given enough energy it will be promoted to collisions between ordinary particles Barrell et 01.) has established that the a real, observable, positive energy electron. among the cosmic rays and the Earth's anticodon of human tRNA ~f has a Thus, a new electron will suddenly upper atmosphere. Now an experiment has sequence consistent with these postulates. materialise in space. Furthermore, the been performed by a group of physicists These variations of the mitochondrial 'hole' left behind represents the absence of from Texas and New Mexico to search for genetic code from that which directs an invisible negative energy electron, which antiprotons among the primary rays (Phys. translation in E. coli illustrate that, once a Dirac reasoned is equivalent to the Rev. Lett. 43, 1199; 1979). From a high genetic code came into existence, it was not presence of a visible positive energy anti altitude balloon flight last 21 June, the immutably fixed in all its details. Will still electron, or positron as it is now called. The group detected 46 such particles, of which more exotic variations in the code be found positron is a sort of mirror image to the only about 18 are attributable to reactions in other organisms? For the answer, electron; like the latter, but with all its with the atmosphere. consult the dictionary in your favourite physical attributes (for example, charge, The ratio of antiprotons to protons dinoflagellate, protozoan or archae spin, magnetic field) reversed. coming from space works out at 5 x 10-4 in bacterium. D Positrons were discovered among the energy range explored, which accords cosmic ray debris in 1932, and since then, well with theoretical estimates based on the antiprotons, antineutrons and a host of assumption that no external flux of other antiparticles have been identified. antiprotons is bathing the Galaxy. They Until recently it was supposed that the can all be accounted for as by-products of creation of matter must always be collisions between ordinary cosmic rays Antimatter accompanied by an equal quantity of and the tenuous interstellar medium in antimatter of the corresponding type. This deep space. from space inevitably implies that for every atom of This experiment not only provides ordinary matter that we see, somewhere in important information for understanding from P. C. W. Davies the Universe lurks its opposite number. the origin and behaviour of cosmic rays in Because any contact between matter and the Galaxy, but it tightens up further the THE origin of matter is one of the great antimatter results in the matter falling back evidence against a matter-antimatter unsolved problems of science: the visible into the 'holes' and disappearing from the symmetrical Universe. If matter really can be Universe contains about 1050 tons of Universe, it must be supposed that created and annihilated alone, it will open material. Where did it come from? At one somehow the matter and antimatter have up whole new chapters in both cosmology time it was supposed that all this cosmic got themselves well separated. It is and subatomic physics. D stuff - from which the galaxies, the stars fashionable to suggest that there are whole and our own bodies are made - always galaxies made of antistars and antiplanets existed. Modern cosmologists, however, and, one may conjecture, antipeople. An believe that the Universe is not of unlimited antigalaxy would look, on the face of it, 100 years ago age, but came into existence about 15 indistinguishable from an ordinary galaxy. billion years ago in the hot, dense, When matter and antimatter annihilate In his last report from Saigon, Mr. Consul explosive eruption, popularly called the big each other their mass gets converted back Tremlett alludes to his having been ordered bang. into energy in the form of gamma rays, so by the Foreign Office to procure and send If this primaeval explosion marked the by measuring the flux of gamma rays from home a quantity of the bark known as creation of all the cosmic matter, physicists space, limits may be placed on the amount hwang-nao, which during the past four or five years has been exported from Tongking would like to understand the details: what of mixing that occurs between the two to Trinidad, and there seems to have proved precisely happened in the first microsecond species of material. This seems to imply efficacious in cases of leprosy. The tree from of existence? Since the early 1930s it has that almost complete separation has which it is obtained is hardly known except been known that matter can be created occurred, even on the scale of galactic to the missionaries, and is only found in the clusters. Presumably they were put asunder mountain forests of the north of Annam. in the earliest epochs of the big bang but P. C. W. Davies is in the Department oj Mathematics, King's College, London. just how this could have happened is still From Nature 21,6 Nov., 19; 1879. not completely clear.