Perturbing Events in the Galaxy

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Sun orbits around in the Galaxy, are too investigation of the precision of the strati Perturbing events small to affect significantly the number of graphical dating have now been com comets perturbed towards the Earth by pleted. There are well-established and in the Galaxy interstellar clouds or by the variable gal reliably dated impact events and bio Gerry Gilmore actic tide. So could a solar companion - logical extinctions at - 35 Myr and - 65 planet or star - cause a comet shower of Myr ago, so that cometary impacts do sufficient intensity to guarantee a large indeed seem to cause mass extinctions. The Galaxy and the Solar System. Edited impact on the Earth? Given the low prob But earlier events are less well-dated, and by Roman Smoluchowski, John N. ability of such an impact, several billion the claimed periodicity, on which the Bahcall and Mildred S. Matthews. Uni comets would be required. One or more validity of the companion-star model versity of Arizona Press: 1986. Pp.483. per day would cross the Earth's orbit, relied, is not statistically significant. In $29.95. providing an entertaining spectacle at consequence of this, the exhaustive and least. repetitive discussion of the relevant argu FEW, if any, dinosaurs will read this A tenth planet seems unable to account ments in this volume becomes of mostly review. It is also well established that the for this. Reasonably detailed dynamical historical interest. While it makes fascina biological extinction at the Cretaceous - modelling shows that the comet showers it ting reading, the book is more appro Tertiary boundary about 65 Myr ago co caused would be too long-lasting and of priate for a long journey than as a text or incided with a period of increased impact too low contrast to the background rate. reference work. cratering on the Earth. Presumably these Thus we are left with Nemesis. Apparent All in all there is little evidence that the phenomena are related, though the cause ly this could do the job, but only if it were Sun has a companion 'Death Star'. But it and effect relationship between a comet allowed extremely contrived properties, does seem likely that the dinosaurs were hitting Earth and the extinction of species not least among which is the instability of treated to a spectacular warning of their is not yet clear. Nevertheless, astro its orbit. If the Sun has a companion, it is impending demise as several billion nomical events apparently have a direct just about to lose it for ever. The dino comets arrived - even if these were, as effect on biological evolution on Earth. It saurs were indeed unlucky to live when seems most likely, a consequence of the is of obvious (self-) interest to understand they did. random passage of a now-distant star. D There is, too, the question of period why large comets occasionally hit the Gerry Gilmore is at the Institute of Astronomy. Earth, and to predict when the next such icity in the record of biological extinc University of Cambridge. The Observatories. event will occur. One clue to this came tions. New statistical analyses and re- Madingley Road. Cambridge CB3 OHA. UK. with the announcement in 1984 of a periodicity of about 30Myr in the record of biological extinctions. Such a periodicity Wallach's stated intention in this book and its consequences dominate this collec Better reception was to bring together accounts of a variety tion of review articles, despite the some Gordon L. E. Koch of disciplines bearing on the interactions what misleadingly general title. between cells, especially at the molecular The current model for the origin of level. The bite-sized approach was there comets is that they are perturbed from a Fundamentals of Receptor Molecular fore particularly appropriate, and an large cloud, about 100,000 times the Biology. By Donald F.H. Wallach. Dek added concession to CTC is the use of a diameter of the Earth's orbit, which con ker: 1987. Pp.398. North America $85. simple and, presumably. inexpensive tains about 10" comets in its outer parts elsewhere $/02. print. It is this that has probably allowed and perhaps 10" in its dense inner core. the author to include some very contem These comets are stirred gravitationally ALTHOUGH one might not agree with all porary studies on receptors. In general by stars and giant clouds of interstellar his pronouncements, one has to admit that terms the book is a very satisfactory molecules passing at random, and some of Amstrad boss Alan Sugar's CTC (cut the description of the key areas relating to them fall close to the Sun (and to us). crap) philosophy has made the products of receptor function. A particularly impress So was the dinosaurs' fate due to a ran the microelectronics revolution more ive feature is the extensive bibliography, dom event? Not if such extinctions are widely accessible. So it is encouraging that which is a useful starting point for those periodic. similar ideas appear to be taking a hold in wishing to delve into such specialist areas Periodicity of extinctions requires peri several areas of scientific publishing. as hormone action, neurotransmitters and odic gravitational perturbation of the The CTC way of doing things is evident immune defence. comet cloud, which can be accounted for in the increasing use of a format in which The general format of the book is as only by the orbit of the Sun in the Galaxy, large and complex subjects are broken follows: it introduces the concept of infor or by the orbit of a companion planet or down into bite-sized sections, each of mation transfer between cells, examines star round the Sun. The prospect of a solar which can be encapsulated in a single the involvement of the cellular genetics companion - soon named 'Nemesis', or definitive statement. The experimental systems in responses to information trans the 'Death Star' - controlling the fate of basis of the statement is then presented, fer, moves on to the role of the plasma life on Earth led, in 1984, to a burst of together with an extensive bibliography to membrane and then examines a number interest in the popular press, and a rash of satisfy the demands of the more commit of systems such as the hypothalamus, speculation on the matter. ted reader. The great merit of this pituitary, thyroid, pancreas, G 1 tract, Now that the dust has settled a little, approach is that the book can be read at steroid hormones, neurotransmitters, Roman Smoluchowski and his colleagues several levels, or, perhaps more signifi phagocytosis and the immune system in have put together a well-presented collec cantly, its scope assessed at a glance. It is some detail, from the special perspective tion of reviews giving the data, the models particularly useful when dealing with sub of intercellular information transfer. I and their predictions, as well as several jects that require the coalescence of a thoroughly enjoyed reading Fundamen good accounts of the properties of the variety of separate but interrelated dis tals of Receptor Molecular Biology, and interstellar medium near the Sun. It is now ciplines under a single umbrella, such as learned much about subjects with which I clear that the variations in both the galac molecular biology; indeed, the outstand thought I was quite familiar. D tic tide and in the probability that the ing example of the success of this Gurdun L. E. Koch is a member of the scientific Solar System will pass very near a massive approach in recent times must be Molec staff at the M RC Laboratory of Molecular Bio cloud in the interstellar medium, as the ular Biology of the Cell. logy. Hills Road. Cambridge CB2 2QH. UK.