Most scientists think that the Universe began with a huge explosion called the Big Bang. A ball of matter smaller than an atom but at an incredibly high density and temperature exploded, producing a fireball what was the of matter and space. Bang? It is thought that the Big Bang happened BIG around 14 billion (thousand million) years ago. Redshift If you imagine that time reduced to just one year, a human lifetime would amount to less than one fifth of a second! Ever since the Big Quasar PKS 2000-330 Bang, the matter that was created has been s e A B C D In 1982, the most distant known s a moving apart at great speeds, a fact discovered e object in the Universe r c n by the American astronomer Edwin Hubble in i e c n the 1920s. a t s i When he looked at the light emitted by distant D galaxies for the spectral lines characteristic of particular chemical elements, Hubble found that Quasar 3C273 A B C D each line had moved towards the red end of the Three billion light years away spectrum, where the light has longer wavelengths. This implied that the light waves Edwin Hubble had been stretched during their journey. Not 1889–1953 only that, but the further away the galaxy, the The spectrum of radiation from distant Pleiades Cluster greater the movement of the lines – or ‘red galaxies shows peaks at wavelengths which are 400 light years away A B C D shift’, as the phenomenon is called. It was clear characteristic of various elements, especially to Hubble that this effect could only happen if hydrogen. If a galaxy is moving away from us, these characteristic peaks occur at longer the galaxies were moving away from us at wavelengths – in other words they are shifted great speed. towards the red end of the spectrum.This is The Sun A B C D the ‘red shift’ – an example of the Doppler Eight light minutes away The General Relativity Theory of the great Effect.The faster the galaxy is moving, the physicist Albert Einstein suggests that it is not greater the red shift. In the diagram,A, B, C the galaxies themselves that are moving but the Ultraviolet Visible light Infra-red and D represent four peaks seen in the spectrum of stars and galaxies. space in between them – the space–time Wavelength of radiation increases continuum – that is expanding. Hard as it may be to imagine, the galaxies are being forced apart rather as currants in a cake mixture are moved apart as it rises. This gives us a way of understanding what happened at the beginning of the Universe. It is not that all matter started squashed together at one point in space and then moved outwards to fill up the rest of space. Instead, all matter was created squashed up because all of space was squashed up – there The General Relativity Theory suggests that it is was no other space outside. At the moment of not the galaxies themselves that are moving but the Big Bang, time began and space started to the space in between them – the space–time expand. As it did so, it carried all matter with it. Albert Einstein continuum – that is expanding 1879–1955 more TheBIGBang Further Information Particle Physics and Astronomy Research Council If you would like to know more about the Big Bang theory and cosmology, the The Particle Physics and Astronomy Research Council following resources may help. (PPARC) is the UK Government-funded body that exists World Wide Web sites to support research in basic science: Particle Physics BBC Science Astronomy www.bbc.co.uk/science/space/ Space Science origins/bigbang/index.html This support is provided by funding UK researchers Cosmology links and by ensuring that they have access to world-class http://www.damtp.cam.ac.uk/ facilities in the UK and overseas.The Council pays cosmos/Public/index.html the UK’s subscription to the science programmes of the European Laboratory for Particle Physics (CERN) DAMTP www.damtp.cam.ac.uk/user/gr/ and the European Space Agency (ESA). public/bb_home.html PPARC recognises the importance of its science in assisting wealth creation; in post-graduate training; and in MAP motivating young people towards an interest and career map.gsfc.nasa.gov/m_uni.html in science generally. Books Russell Stannard Our Universe – A Guide to What’s Out There Kingfisher1996 Stuart Clark The Encyclopedia of Stars and Atoms Particle Physics and Astronomy Andromeda Oxford 1994 Research Council Robert Snedden Particle Physics and Science Horizons – Space Astronomy Research Council Belitha Press 1995 Polaris House North Star Avenue Swindon Wiltshire SN2 1SZ Tel:+44 (0) 1793 442000 Fax: +44 (0) 1793 442002 Particle Physics and Astronomy Email: [email protected] Research Council PPARC also publishes information on a variety of topics related to physics and astronomy, to help increase public Acknowledgments: awareness of the UK’s achievements in Photos supplied by: Cavendish Laboratory, CERN, ESA, Hulton Deutsch, Lucent Technologies, NASA, Popperfoto, ROE, Exploring the origins of our science and technology. Find out more by Science Museum, UMIST. visiting the PPARC World Wide Web site: Design and production Joint Reprographics Service www.pparc.ac.uk Version May 2004 Universe BIGBang OR STEADY STATE? Fred Hoyle Support for Big Bang Theory 1915–2001 was discovered in 1964, while using a horn radio antenna in Holmdel, N.J. to isolate, identify and measure sources of Hubble’s discoveries of an expanding Universe noise in the led a Russian-born scientist, George Gamow, to atmosphere, Bell Labs argue in the late 1940s that there must have scientists Arno Penzias been a point when the Universe started to (right) and Robert Wilson expand. Soon after Gamow published his idea, discover faint cosmic radiation the English astronomer Fred Hoyle gave a radio from the farthest reaches of talk in which he dismissed the theory as ‘some sort of big bang’. Although Hoyle had meant the known space. phrase to be insulting, it stuck, and from then on, George Gamow as far as most people were concerned, Gamow’s idea was called the Big Bang theory of the COBE (Cosmic 1904–1968 beginning of the Universe. Background Explorer) For almost 20 years, arguments raged between Satellite revealed tiny Big Bang the believers in the Big Bang theory and Hoyle’s temperature differences supporters, who believed in the rival ‘steady- that reflect early state’ theory, in which the Universe has always existed in much the same way as we see it now, variations in the density Supporters g with no beginning. Strong evidence for the Big of matter, the seeds of Bang, and a tough challenge to the steady-state galaxies. theory, came from the new branch of science called radio astronomy. It was discovered in the 1930s that galaxies emitted radio waves, but the first map of the sky’s radio sources was made in the 1950s by Boomerang is a balloon-bourne Martin Ryle, the Cambridge radio astronomer. millimetre-wave robotic If Hoyle’s steady-state theory was correct, Ryle telescope, built to observe should have found an even distribution of structure in the Cosmic galaxies through space. But he didn’t. The Microwave Background further Ryle looked into space with his receiver, the more sources of radio waves he found. Since radiation. It takes both the light and the radio waves from distant advantage of the wind galaxies have taken billions of years to reach us, pattern that circulates we see them as they were in the distant past. around the Antarctic Ryle was detecting galaxies that were closer in continent to run a long Martin Ryle time to the Big Bang. The fact that there were duration flight, arriving more of them suggested that the Universe had close to its launch site. 1918–1984 been much denser then than it is now. This was tremendous support for the Big Bang theory. Then, in 1964, two American scientists, Arno Penzias and Robert Wilson,made a discovery A new development is the Very that finally tipped the balance in favour of the Small Array, designed Big Bang theory. They were using a radio to help build up a more- antenna to look for interference to satellite broadcasts when they accidentally picked up detailed microwave microwave radiation coming from all areas of picture of the early the sky.This is the same form of energy that we Universe. It will consist use (at a much greater strength) to cook with of 15 small horns and in microwave ovens. The radiation had a reflectors, each temperature equivalent to 2.7 degrees Kelvin – connected to an less than three degrees above absolute zero, the extremely sensitive coldest temperature possible. One of their receiver, and will be colleagues, Robert Dicke, guessed very quickly constructed among the Arno Penzias that they had found the remains of the vast conventional telescopes b 1933 amount of heat energy released at the time of already operating at the Robert Wilson the Big Bang – the lingering afterglow of Teide Observatory, in Tenerife. creation.This would make it quite clear to the b 1936 reader what the modern view of cosmology is. more utrons d ne fus an e to ns ge to th ro e P r d neutrons fus evidence for the an e to ns ge to th ro e P r Q utrons s d ne fuse u n an t -50a o o 10 r t s g kseconds o n e ? s r to th fo p o e rm nd r r i s a P nto neutron - c 40 r i 10 Q e seconds e l s a u c n t a u o tron i r t neu s fu n k n o nd se g s t r a to h f h p ns g el or lig d o et ium mer an t h and oth into ons Bang Q o e neutr -35 r s r c n i 10 u P r seconds a o e r t e l k o a c s r t u fo p in n BIG rm nd g t Quarks i s a h h nto neutron el lig c ium er r i and oth Leptons e le a c t u Q in n s g - u n ht Neutrons & Protons 12 a o h g 10 r t e li k