• Question: how far away is the horizon

    Asked by lukefleming to Alex, Amy, Andy, Georgia, Ollie on 21 Jun 2011.
    • Photo: Amy Reeve

      Amy Reeve answered on 21 Jun 2011:

      Hi Luke

      Awesome question. If you are about my height (5ft 6 inches) then if you stand on flat ground, level with the sea then the horizon is nearly 3 miles away (2.9miles to be exact). The distance to the horizon depends on how tall you are and your height above sea level. the higher up you are the further you can see. 🙂

      the height of the horizon also has an effect……you can see mountains on a clear day across ground up to 100miles away…how cool is that?!!! 😀

    • Photo: Ollie Russell

      Ollie Russell answered on 21 Jun 2011:

      Hi luke,

      If you go high enough (around 60000 feet) then you can actually see the curvature of the Earth! Although to do this I think you’ll either have to join the RAF of become an astronaut!

    • Photo: Andy MacLeod

      Andy MacLeod answered on 21 Jun 2011:

      Hi Luke. Turns out you can prove it with geometry!

      D = sqrt {(R+H)^2-R^2}

      D is the distance you can see, where H is your height, and R is the radius of the earth. There’s a picture on the Bang Goes the Theory site here that was apparently drawn by one of my colleagues in Edinburgh: http://www.bbc.co.uk/bang/ask_yan/how_far_away_is_the_horizon
      (Dan was one of the physics-y guys who failed to come up with an answer to this: http://ias.im/52.117)

      Yay geometry! Here’s looking at Euclid! This is why ships have their lookout posts up so high, so they can see further – they’re trying to increase H, and hence D. That’s also one of the reasons I enjoy climbing mountains. You can see much further from the top. http://www.flickr.com/photos/nailest/5697121927

      And I may have used it before, but it’s one of my favourite scientific quotes. Newton made it famous, but it had been around in various forms before he used it:

      “If I have seen further than others, it is because I stand on the shoulders of Giants”.

      He was using it metaphorically – individual scientists may only see a little bit more of the Truth of the world, but we’re all building on what’s come before us. Every little helps. 😀

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