I took this photo of the Forth Bridges from about 19 miles away in Longniddry and I found it very interesting that the bottom of the Forth Bridge isn't visible.

Anyone able to explain? Is it due to the tides somehow bulging in between (tide was just about half way going out) or Earth's curvature?

Can someone do the math? 😅

by piggledy

16 comments

  2. You would need to know the height of the observer, and the closer you are to the surface then the more will be obscured by the curve.

  3. there’s a [distance to horizon calculator](https://www.ringbell.co.uk/info/hdist.htm)

    So here we go. The rail on the forth rail bridge is 46 metres high. Using that calculator, the horizon from there is 24.2km.

    Longriddy is about 30km away, so the bridge’s horizon is 5.8km away from you. So you need to be high enough up to have a 5.8km horizon. (eg, just as you’re seeing the bridge poke over the horizon, you need to be high enough that you’re poking over the bridge’s horizon too. They’re the same thing, just I can google the bridge’s height and I can’t google yours.)

    You need to be 2.5 metres above the water to meet that. So if the higher you are above 2.5 metres, the more of the bridge’s legs you’ll see. Below 2.5 metres, the rail level is going to disappear behind the horizon.

  5. This is why even medieval peasants knew the world was round. Flat Earth theory is an entirely modern kind of stupid.

  6. Yes, curvature. The math is slightly beyond me bc you have to take into account refraction, which means essentially that you see a bit *more* of the bridge than you would expect by naively drawing a straight line from you to the bridge.

    it also means our sunrises and sunsets take slightly longer. like when the sun touches the horizon, without refraction it would have already just dipped below the horizon. for shorter distances like this it’s obviously not as much, only a few metres

  8. You just need to hold the phone a little higher. Say maybe a few hundred feet?

  9. Guys, let’s not forget it’s *mathematics* and therefore MATHS, not this lazy American slop ‘math’

  11. My money is on:

    [https://en.wikipedia.org/wiki/Fata_Morgana_(mirage)](https://en.wikipedia.org/wiki/Fata_Morgana_(mirage))

    The [optical phenomenon](https://en.wikipedia.org/wiki/Optical_phenomenon) occurs because rays of light bend when they pass through air layers of different temperatures in a steep [thermal inversion](https://en.wikipedia.org/wiki/Temperature_inversion) where an [atmospheric duct](https://en.wikipedia.org/wiki/Atmospheric_duct) has formed.[^([1])](https://en.wikipedia.org/wiki/Fata_Morgana_(mirage)#cite_note-An_Introduction_to_Mirages-1) In calm weather, a layer of significantly warmer air may rest over colder dense air, forming an atmospheric duct that acts like a refracting [lens](https://en.wikipedia.org/wiki/Lens_(optics)), producing a series of both inverted and erect images. 

    —

    Sometime from Kirkcaldy I can see out to Bass Rock really clearly, other times it looks like it’s floating. It’s because of this.

  12. Jesus Christ. So many wrong answers… yes it’s the curvature of the earth. The bottoms of the bridges are disappearing over the horizon.

    Here’s a fun simulator using boats.

    https://shipbeyondhorizon.com

  13. 🤯

    I love Reddit for this type of irrelevant nonsense .😂😂

  14. No, the earth is flat. What you’re seeing is just atmospheric distortion.

  15. the wires from the suspension bridges in the back look really really cool

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