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How long would it take for light from the sun to reach the edge of the universe?

How long would it take for light from the sun to reach the edge of the universe?
Rhys Harniess from Hertfordshire (Aged 15-25)

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3 Responses

  1. Light travels at 300,000 km per second (186,000 miles per second) in space. Unfortunately the universe is also expanding at 300,000 km per second.
    Therefore light leaving the sun now will never reach the edge of the universe. It would be like trying to hit a car with a football as it drives away from you at the same speed as you you can kick thge football.

  2. Hi Rhys :).
    Logically, given that our universe is expanding and that the rate at which our universe expands is increasing continuously, a width measurement is applicable only to the instant at which it was made. However, accepting that constraint, we can draw on data collected by the Wilkinson Microwave Anisotropy Probe in 2003 to enable us to reach some conclusions. Firstly, our universe is flat (good news for mathematicians who can apply the ‘straight line principals’ of Euclidean geometry in large scale calculations) and secondly that it is reasonable to deduce such measurements as the radius of the ‘Observable Universe’ at that moment in real time.
    The mean radius of Earth’s orbit around the Sun is 149,476,000 km. (varying from a minimum in January to a maximum in July over a span of about 3%). A catalogue of some 18,000 stars has been assembled which records and locates their positions and a total of 28,000 stars have been listed within 300 light years of Earth. In one year a pulse of light, in a vacuum, would travel 9.4605 x 1,000,000,000,000,000 metres (a bit more slowly through other transparent media). It is not possible to measure beyond the furthest ‘observable’ star but it is thought that the oldest are probably between 11 and 14 billion light years away. Whether they still exist seems unlikely since stars do not burn forever – our Sun is about 4.6 billion years old and is thought to be nearly middle-aged -. However, if we imagine a condition of ‘selective suspended animation’ existed, then in the chosen circumstances, a pulse of sunlight
    ( that takes, on average, 489 seconds to reach Earth) would take 14 billion years to reach the furthest ‘horizon’ which we can detect —- probably.
    Our imagination is able to conjure with such scenarios but who can say if such travel will ever be possible in real life? ?
    I hope this slightly fanciful answer is adequate.
    Good Luck.
    Rockno3.

  3. How can the Universe be flat?

    If there was a big bang, surely there would be expansion in all directions.

    I still can’t see why light should keep going on and on anyway – and no-one seems to have answered the question I set regarding this – how can light have sufficient energy to keep going for millions of light years?? If it is particulate in nature it would certainly slow down. If it is a form of radiation, then it needs a source to keep it going, and the further it gets away from its source, then the less energy it should have. That, of course, assumes that the source is still there, and after several million light years, would it be?

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