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How large is the universe?

How large is the universe?



3 Responses

  1. HI Collin :).
    The most generally accepted estimate for the width of the observable universe is 156 billion light years. In one year light travels 94605- and 11 noughts metres! This is a basic unit of measurement but other units have been created to enable astronomers and cosmologists to assemble theoretical models on which to base their conclusions.
    This best estimate has a recognised error factor of 1% and all data is subject to error due to measurement and other inevitabilities. The most reliable information was obtained from a mission by a deep-space telescope ‘WMAP’ and further confirmed by other paths of inquiry combining it’s shape, age, acceleration, and total mass. All these considerations make scientists very confident of this figure. In 2003, the Wilkinson Microwave Anisotropy Probe sent back data which indicates our universe is flat. Beyond this ‘horizon’, who knows?
    I hope this answers your question but if you would like a more detailed description of the universe as it is pictured, then do please e’ mail me.
    Good Luck

  2. From Jenny at the BA,

    We usually don’t publish email addresses but here is Rockno3’s –



  3. HI again Collin :).
    From opposite poles of our 300 million km. (186 million mile) diameter orbit around the Sun astronomers have been able to peer out into the void of space and that IS, mainly, what seems to be out there! There are many rocky and gaseous objects of course, spread through possibly over 80 billion galaxies. The distances between them are so huge – and growing all the time – that the task of creating a catalogue of them is a major challenge. Our own galaxy, the Milky Way, for instance, is about 100 light years across! Astronomers and Cosmologists have needed huge scales of measurement, very sensitive devices and complex mathematics to locate the positions of these masses. It is only by being able to ‘see’ their light and by detecting their other electromagnetic radiations that we can discern these objects. We believe that some 23% of the mass out there is composed of ‘dark matter’ which we cannot monitor directly and the likely existence of some objects has to be inferred from the resultant behaviour of nearby stars which we can see. Since there is no ‘perimeter fence’ as such we can only look for the most distant of stars and conclude that the ‘Observable Universe’ is as big as that and the whole universe is probably much bigger! (So says ‘cosmic inflation theory’- and the ‘Cosmological Principle’ casts doubt on claims that the Earth could be at the centre of the universe so it is unlikely that we can observe all of it anyway.
    The mean radius of Earth’s orbit around the Sun is 149,476,000km or 92900000miles
    (91.4 to 94.4 million miles between January and July respectively). The mean Earth to Sun distance provides the chosen ‘Astronomical Unit’ or ‘1AU’. For other measurement methods, employing parallax and triangulation, the ‘Parsec’ or ‘pc’ is used. By comparison 1pc is equal to 206,265 AU. The Parsec is useful because distance in pc is simply one over the parallax. Geometry enables mathematicians to interpret parallax as a location technique and 118,000 selected stars have been mapped from data received using a dual telescope / grid arrangement on a probe. In fact, 28000 stars have now been logged within a distance of 300 light years. The nearest star, beyond our Sun, ‘Proxima Centauri’, is some 4.2 light years away and that distance is known to an accuracy of better than 0.1 light year. This measurement was made by using the ‘Cephoid Variable’ method. This most famous Cephoid has enabled mariners to navigate our waters for centuries past by it’s northerly location in our night sky. The precision lessens as the distance becomes greater e.g. the bright star ‘Deneb’ is about 1600 light years away, based on brightness and spectral type but this estimate could be as much as 25% wrong either way. However, as a result of the success of the mission in 2003 by the Wilkinson Microwave Anisotropy Probe we can deduce figures such as the radius of the universe to within a 5% error. Seemingly minute by comparison, the reflected sunlight we call ‘moonlight’ takes just over 1 second of real time to reach Earth from 239,000 miles away – or about 1/400th of the distance from the Sun itself. At the other end of the scale, light from Polaris, the ‘Pole Star’ travels about 300 light years on it’s journey – that is 300 X (9.4605 x 1,000,000,000,000,000 metres)! The values claimed are consistent with everything else we know about the universe e.g. the ages and positions as measured for stars do not exceed the largest distance light could have travelled, so a high degree of confidence is held in the accuracy of these estimates.
    Thus a picture of our universe has been envisaged and continues to be improved upon.
    Many more facts than these are ‘known’ but I hope that the information included above provides sufficient detail to answer your question.
    Good Luck.

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