By Julian Gavaghan  
    Last updated at 11:28 AM on 27th February 2012  
    Since the invention of radio more than a century ago, man    has been broadcasting into space in the hope that any listening    aliens could learn of our presence.  
    Yet, despite waves travelling a distance of 200 light    years in all directions, they still have 118,800 light years to    go until the entire Milky Way has heard the word.  
    In the photograph below, the small yellow    dot - with the even tinier Planet Earth buried somewhere in its    centre - reveals the limited extent of broadcasts since Marconi    invented the radio in 1895.  
      A long way to go: The yellow dot shows the 200 light year      radius of how far radio waves have reached into the Milky Way    
    And, when you consider there are billions of galaxies    like ours in the universe, the quest for extra-terrestrial life    is not likely to end any time soon.  
    Science blogger Adam Grossman, who created the diagram of    ‘Humanity Bubble’ using a Nick Risinger’s famous image, quipped    on his site: ‘This makes me feel small, sad and    alone. Hold me.’  
       
    Yet, given that it would take just four minutes to get to    Mars when travelling at the speed of light, the distance of 200    light years is no small feat.  
    And, given recent evidence of a possible earthquake on    the Red Planet that indicate life there, perhaps all we are    waiting for is for Martians to invent a radio set.  
       
       
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Earth calling: Tiny yellow dot shows distance radio broadcasts to aliens have travelled