Perfectly flat bridge vs round earth
« on: December 09, 2013, 12:49:32 PM »
I'd like to see the opinions of both the round earth and flat earth Stance of the following situation.

Please note this features a lot of hypotheticals but I imagine the fundamental science will still hold true.

Imagine a Bridge is built from England to America. This would obviously be slightly curved in order to follow the earths curvature.

However, if the bridge was built perfectly flat, would you agree that one end of the Bridge would end up in space?

With This said, would it appear flat or would it appear to gradually slope upwards? (To someone standing at the base in England.

Also if someone was to attempt to walk along this Bridge, would they Eventually struggle with the gradient and require a ladder?

I have a few more questions with this but would like to see people's opinions on this scenario first.

If it doesn't make sense please let me know and I'll attempt to reword.

(Also I know it's unfeasible to build a Bridge that long and utterly nonsense to then walk across it, but this is besides the point).

Thanks! !

Re: Perfectly flat bridge vs round earth
« Reply #1 on: December 09, 2013, 01:25:18 PM »


(Also I know it's unfeasible to build a Bridge that long and utterly nonsense to then walk across it, but this is besides the point).

Thanks! !
If this bridge was built, I am sure someone would walk across it. After all, people row across the Atlantic in silly little boats...
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Re: Perfectly flat bridge vs round earth
« Reply #2 on: December 09, 2013, 06:28:28 PM »
If you presume a round earth, this bridge would slope linearly into space as it would be a tangent line.  A person attempting to walk across this bridge would notice their altitude increasing exponentially and would eventually be forced to climb a nearly vertical surface.

However, a person would be able to walk across a perfectly flat bridge in reality due to the flatness of the earth.

Offline Khris

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Re: Perfectly flat bridge vs round earth
« Reply #3 on: December 10, 2013, 02:36:22 AM »
Hey everyone :)

Quote
would it appear flat or would it appear to gradually slope upwards?

If the bridge is perfectly flat, it would also appear perfectly flat. It's just that if you presume a round earth, as you walk along the bridge, the earth's gravity vector will turn more and more, pulling you not just towards but also alongside the bridge. So the bridge would only slope according to the reference frame of up and down as created by gravity.

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Offline spoon

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Re: Perfectly flat bridge vs round earth
« Reply #4 on: December 10, 2013, 03:02:55 AM »
In RE, I think by the time it was "uphill" enough for you to feel it, you'd be in space.
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Offline Scientific Method

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Re: Perfectly flat bridge vs round earth
« Reply #5 on: December 10, 2013, 10:26:43 AM »
Mind if I throw in some numbers?

Distance from London to New York: 5,600km
If you built a perfectly straight bridge this long, the end of it would be at an altitude of ~2,100km above the surface of the earth, and an angle of 48.7° to the gravity vector (apparent uphill slope of 41.3°), making it a very tough climb!

How far along this bridge would you need to travel to officially be in space? 1,133km, at which point it would feel like an uphill slope of about 10°.

Would it appear to slope upwards? Well, actually, it would just a bit. Thanks to the fact that air density falls as altitude increases, light bends down slightly, which would make a completely flat surface appear to slope up gradually. How much would depend on the density gradient at the time.

Of course, this is all assuming a round earth. I've no idea what the distance is supposed to be on a flat earth, as there is a lot of conjecture as to the proper layout of the continents, but a flat bridge would follow the surface in this case. Note: it would still appear to curve upward slightly (as would the ground beneath it), thanks to the density gradient of the atmosphere.
Look out your window. Better yet, get up and go outside for a while.

Re: Perfectly flat bridge vs round earth
« Reply #6 on: December 10, 2013, 02:57:29 PM »
ITT: An REer just admitted to bendy light.

But since I am also RE, I agree that it would appear to slope upward gradually.  If you took a telescope and viewed as far out as you could, you would probably see the increasing gap between the water and bridge.
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Online markjo

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Re: Perfectly flat bridge vs round earth
« Reply #7 on: December 10, 2013, 04:27:58 PM »
ITT: An REer just admitted to bendy light.
Sorry, but RET's atmospheric refraction is not the same as FET's bendy light.
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Offline Scientific Method

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Re: Perfectly flat bridge vs round earth
« Reply #8 on: December 10, 2013, 09:08:10 PM »
ITT: An REer just admitted to bendy light.

But since I am also RE, I agree that it would appear to slope upward gradually.  If you took a telescope and viewed as far out as you could, you would probably see the increasing gap between the water and bridge.
ITT: An REer just admitted to bendy light.
Sorry, but RET's atmospheric refraction is not the same as FET's bendy light.

Quite right, atmospheric refraction generally causes light to refract downwards, sometimes so much so that an object on the surface of a body of water can still be seen by an observer 6 miles away whose eye level is only a few inches above the water. It has been thoroughly studied, and well explained. 'Bendy light', however, requires that light consistently bend upwards, as well as left and right, at varying rates depending where on the earth you are, and what time of day it is. It requires consistent inconsistency, as someone so eloquently put it! In short, refraction has been observed and explained, 'bendy light' has not. I'm not even going to get into the 'Bollybill effect'... :)
Look out your window. Better yet, get up and go outside for a while.