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Birth, Age and the Future of the Universe

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Birth, Age and the Future of the Universe INTERNATIONAL SPACE SCIENCE INSTITUTE No 3, May 1999 SPATIUM Published by the Association Pro ISSI Birth,AgeBirth,Age andand thethe FutureFuture ofof thethe UniverseUniverse Recent results of space research tell us a story of unlikely events. Life emanating from the vaste of exploded stars is but one of them. Editorial We are here. There is no doubt Impressum about it.– Research, however, has shown that life, our solar system and all the SPATIUM galaxies interrupting locally the Published by the voidness of space have been caused Association Pro ISSI by tiny unbalances, which seem once or twice a year very unlikely a priori. Recent results of space research tell us a story of unlikely events. INTERNATIONAL SPACE SCIENCE This fascinating history of our INSTITUTE universe was the subject of the key Association Pro ISSI note address by Professor Gustav Hallerstrasse 6,CH-3012 Berne Andreas Tammann,Director of the Phone ++41 31 631 48 96 Institute for Astronomy of the Fax ++41 31 631 48 97 University of Basle on the occa- sion of the third anniversary of President the International Space Science Prof.Hermann Debrunner, Institute on the 27th of November University of Berne 1998. Publisher Dr.Hansjörg Schlaepfer, It is with greatest pleasure that we Contraves Space,Zurich devote this issue to Professor Layout Tammann, who has actively con- Gian-Reto Roth, tributed to the understanding of Contraves Space,Zurich our universe over the past 40 years. Printing Drucklade AG,CH-8008 Zurich Hansjörg Schlaepfer Berne,May 1999 Front cover Rings of glowing gas encircling the supernova 1987A. (Hubble Space Telescope, NASA/ ESA,February 2,1994) SPATIUM 3 2 Birth,Age and the Future of the Universe G.A.Tammann, Director, Institute for Astronomy, University of Basle Key note address at the third anniversary of the International Space Science Institute, November 27,1998 The sciences have fundamentally For thousands of years the human is gained, a new paradigm is born. changed the views of our world life has been an interval of 40 years These are the great discoveries during this Century. They have of suffering of hunger and freez- which influence our understand- brought a cultural revolution by ing. Science has doubled its length ing, thinking, and culture. affecting technology,medicine,civil- and it is now expected to be pain- isation and, perhaps most impor- less, comfortable and pleasurable. A few examples will be given in tantly, the thinking of men. At the end of this century man the following from the realm of finds himself in a world which has astronomy. They are to illustrate Man has explained the origin of all been fundamentally changed by how the scientist works on a life, i.e. the energy source of the the sciences from what it was gigantic mosaic that suddenly Sun which had remained a total at the beginning of the Century, reveals a face or contour. mystery up to 1930. He has estab- – and not only the world has lished a worldwide net of commu- changed but also man himself, nication and transportation such – and were it just in physical size. that he partakes almost instantly in occurrences all over the world. It may seem surprising that this Humans have left the Earth’s grav- radical change has been brought ity field and have seen that the about by the sciences which are Earth is round. The Moon has believed to progress step by step by been occupied – so far temporarily a painstaking method dominated – by men and the planets have by mathematical logic and bare of been visited by spacecraft. The fantasy.While it is true that all sci- triumph of rational thinking has ences proceed in minute steps, it even brought an unprecedented happens once in a while that the 50-year period of peace in Western understanding jumps suddenly on Europe. a higher level. A broader insight Lines from galaxies Lines from Earth atmosphere Figure 1. The spectra of 16 galaxies.They are perfectly aligned as seen from the lines originating in the Earth’s atmosphere. However, the galaxy lines (originating from different chemical elements) are progressively shifted toward the red.This redshift effect is caused by the expansion of space stretching the light to longer wavelength. The different redshifts correspond here to recession velocities of 3000–16,000 km s –1. (From P.Stein, Basle). SPATIUM 3 3 The expanding Universe In 1912 Vesto M. Slipher took the first spectra of what was then called spiral “nebulae” (now known to be galaxies). It was a tedious process with small tele- scopes and slow emulsions. He found the spectral lines shifted toward the red (Figure 1) and he Figure 3. A yeast cake as a model for the expanding Universe. As the cake increases in concluded correctly that the size the distances between the raisins become larger. Close raisins get separated by small objects were hence receding from (absolute) amounts, distant raisins by large amounts.The aspect is the same for all raisins. us, – yet faster than any known star (Neglect the rim).The model has the disadvantage that one can oversee it instantaneously while the concept of simultaneity fails in the Universe (see page 5). in our Galaxy.The large recession velocities became a puzzle which many astronomers tried to solve. Finally Edwin Hubble, after hav- also that their velocities were pro- cluded that the whole Universe ing proved in 1925 that the “nebu- portional to their distances! (Figure was expanding like a yeast cake lae” are distant galaxies, consisting 2) The picture was like that any and that there must have been a of hundredthousand million stars raisin has in a growing yeast cake: time where the Universe was arbi- like our Milky Way, realised in all other raisins are moving away trarily small. The Universe had a 1929 that not only (almost) all and the faster the further away beginning, now known as the Big galaxies move away from us but they are (Figure 3). Hubble con- Bang! In the last seventy years the Big ] 1 Bang has become a physical fact. – The most distant galaxies have Distance 100.000 redshifts corresponding to almost the speed of light. Several inde- pendent experiments prove beyond 30.000 doubt that the young Universe Recession velocity [km s must have been tiny, extremely dense, and excessively hot. 10.000 The expansion of the Universe gives us a simple tool to determine bright Apparent Magnitude faint bright Apparent Magnitude faint its age. At a very early epoch all Figure 2.The demonstration of the linear expansion of the Universe. Left: Standard can- galaxies (or the matter or energy dles (e.g. 60 W light bulbs) get fainter as the distance increases. Right: The brightest they were later made of ) were galaxies in clusters of galaxies are good standard candles (note the relatively small scat- compressed in one place. When ter!). As they get fainter they must be more distant, but at the same time their recession velocities increase. (Linear expansion requires in this logarithmic plot a slope of 0.2, the expansion began some were which is shown). slowly carried away; they are today SPATIUM 3 4 our neighbors. Others were car- travelling through space cannot by our yeast cake: not the raisins ried away with high speed; they be correct. In reality space expands move apart, but the dough ex- populate now our horizon.All had and carries the galaxies along. pands and increases the distances the same travel time, i.e. the age This is perfectly reasonable with between the raisins. of the Universe. Therefore one Einstein and is again exemplified must determine “only” the dis- tance to one galaxy – or much better to many galaxies, which is technically not easy (Figure 4) – and divide this distance by the reces- sion velocity.The result is nothing else but the expansion age of the Universe. Measured redshifts and the corre- sponding recession velocities plus the best distance determinations give an expansion age of 14 (±2) Gigayears (1 Gigayear = 1000 mil- lion years). This time may appear long, but when one realizes that life began 3 Gigayears ago,that the oldest rocks on Earth have an age of almost 4 Gigayears, and that the oldest stars in our Galaxy were formed 12 Gigayears ago,one can- not but be impressed by the youth of the Universe. Imagine you take a very old rock in Greenland into your hand and it has almost one third of the Universe’s age! The expanding Universe revises in several ways our thinking. For instance, the fact that all galaxies are receding from us makes us falsely believe that the Big Bang has taken place here. In reality any galaxy, like any raisin in the yeast cake, sees all other galaxies (raisins) in recession. There is no preferred, absolute point in the Universe. Our thinking is unjusti- Figure 4.The Hubble Space Telescope has a mirror of “only” 2.5 m diameter, but since it fiably egocentric.After some more orbits the Earth above the atmosphere it provides exceptionally sharp images. It has thought (concerning the “edge” greatly helped to determine galaxy distances and hence to determine the expansion age of the Universe.The telescope was built and is operated by NASA with a 15% share of the problem of the Universe) one European Space Agency (ESA).The telescope is here docked to the Space Shuttle during realizes that the picture of galaxies a repair mission involving the Swiss astronaute Claude Nicollier. SPATIUM 3 5 Evolution stituents annihilate each other to form energy again. It therefore in the Universe seems that the Universe cannot ever create lasting matter.
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