# Does the design of a very large building have to account for the curvature of the Earth?
**URL:** https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455
**Category:** Factual Questions
**Created:** [August 24, 2021, 8:22pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455 "2021-08-24T20:22:14Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Drum\_God](https://boards.straightdope.com/u/Drum_God)
#### Post date: [August 24, 2021, 8:22pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/1 "2021-08-24T20:22:14Z")
This question is inspired by a facility being built by Tesla in southeast Austin. I drive by it from time to time and I am struck by how large it is. The building is not very tall, but it is going to cover a very large area.
Do the architects and engineers for this car factory have to account for the fact that the Earth is round when designing a building of such a large linear dimension? Is the floor of the factory designed to be truly flat even though the Earth below the foundation is not? Is the difference in size between the actual planet and the building so great that it is irrelevant? How big does a structure need to be before the fact that the Earth is round becomes important?
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### Author:  [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)
#### Post date: [August 24, 2021, 8:25pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/2 "2021-08-24T20:25:27Z")
Earth’s curvature is about 8 inches per mile, which would be trivial compared to local geography changes.
They just survey the site, then grade it flat. It doesn’t matter why it wasn’t flat.
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### Author:  [@Andy\_L](https://boards.straightdope.com/u/Andy_L)
#### Post date: [August 24, 2021, 8:25pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/3 "2021-08-24T20:25:52Z")
> **[Public tours | SLAC National Accelerator Laboratory](https://www6.slac.stanford.edu/public-tours#Facility-stops)**
>
> The tour destinations are designed to give you the most exciting and informative views of the lab.
> In 1962, in the rolling hills west of Stanford University, construction began on what was then the longest and straightest structure in the world, the Stanford Linear Accelerator, or linac. It took four years to build and was affectionately known as “the Monster” to the scientists who conjured it. Building the 2-mile-long structure was **an engineering challenge that required taking the Earth’s curvature into account (a 20-inch shift in the vertical axis)**. Electrons fired from one end of the gallery reached 99.999% of the speed of light in the first meter of their flight down the accelerator and collided with a target or particle beam at the other end.
Emphasis mine.
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### Author:  [@beowulff](https://boards.straightdope.com/u/beowulff)
#### Post date: [August 24, 2021, 8:28pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/4 "2021-08-24T20:28:19Z")
I remember being taught this as a kid:
> **[Do human-made structures account for the Earth's curvature?](https://www.spacecentre.nz/resources/faq/solar-system/earth/flat/structures.html)**
>
> If the Earth is round, some large human-made structures should have to account for the Earth's curvature. Do they?
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### Author:  [@steronz](https://boards.straightdope.com/u/steronz)
#### Post date: [August 24, 2021, 8:28pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/5 "2021-08-24T20:28:58Z")
But what does flat mean in this context? The surface of a lake is flat.
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### Author:  [@opiewan](https://boards.straightdope.com/u/opiewan)
#### Post date: [August 24, 2021, 8:29pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/6 "2021-08-24T20:29:27Z")
Also the Verrazzano-Narrows Bridge in NYC was built taking the earth’s curvature into account. According to Wikipedia, the towers are not parallel to each other, but are 1 5/8" farther apart at the top than at the base to account for the earth’s curvature.
> **[Verrazzano-Narrows Bridge | Description](https://en.wikipedia.org/wiki/Verrazzano-Narrows_Bridge#Description)**
>
> The Verrazzano-Narrows Bridge is owned by Triborough Bridge and Tunnel Authority bondholders who paid for the bridge at its construction. It is operated by the TBTA, which is an affiliate agency of the MTA, using the business name MTA Bridges and Tunnels. The bridge carries Interstate 278, which continues onto the Staten Island Expressway to the west and the Gowanus Expressway to the northeast. The Verrazzano, in combination with the Goethals Bridge and the Staten Island Expressway, cre
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### Author:  [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)
#### Post date: [August 24, 2021, 8:41pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/7 "2021-08-24T20:41:03Z")
> [@Andy\_L](#):
>
> Emphasis mine.
Specific to the Gigafactory in Austin, it’s supposedly going to be about 5 million square feet. That’s less than half a mile on a side, assuming it’s square. So the curcature of the earth over that distance would be about 4 inches, or 2" from the center to the edges of the building.
Four inches is a trivial elevation difference compared to the highs and lows of the area. The site will simply be graded flat as it would be no matter what size the building is.
The examples others gave involve more specialized issues, such as a very long bridge anchored to bedrock and needing supports perpendicular to the bedrock that are very high. In that case, the distance between the tops of the supports and the bottom will be different because of curvature of the Earth. But for a flat building, they just survey and grade, and having the center be 2" higher than the edges is easy to take out. Hell, in some places they have to remove elevation differences of many feet to build. A few inches is nothing.
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### Author:  [@crowmanyclouds](https://boards.straightdope.com/u/crowmanyclouds)
#### Post date: [August 24, 2021, 8:44pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/8 "2021-08-24T20:44:11Z")
Some people, flat Earthers in particular, can’t get it in their heads that _flat_ and _level_ are not the same thing.
If the site is large enough then grading it flat means it won’t be level and grading it level means it ain’t exactly flat.
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### Author:  [@bob\_2](https://boards.straightdope.com/u/bob_2)
#### Post date: [August 24, 2021, 8:49pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/9 "2021-08-24T20:49:33Z")
> [@crowmanyclouds](#):
>
> If the site is large enough then grading it flat means it won’t be level and grading it level means it ain’t exactly flat.
I never thought of that - so the floor will actually be a chord.
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### Author:  [@Riemann](https://boards.straightdope.com/u/Riemann)
#### Post date: [August 24, 2021, 8:51pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/10 "2021-08-24T20:51:04Z")
> [@Sam\_Stone](#):
>
> It doesn’t matter why it wasn’t flat.
> [@Sam\_Stone](#):
>
> Four inches is a trivial elevation difference compared to the highs and lows of the area. The site will simply be graded flat as it would be no matter what size the building is.
For a very large building, I don’t think it’s true that there’s no distinction between local topology and the curvature of the Earth. If the walls are built perpendicular to a foundation that is a very large flat plane surface, then they will not be vertical, as in the example of the Verrazzano Narrows bridge cited above. It seems to me that you want the foundation to follow a surface of equal gravitational potential.
It might be negligible at the scale of this example, but for a large enough building it can matter.
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### Author:  [@Drum\_God](https://boards.straightdope.com/u/Drum_God)
#### Post date: [August 24, 2021, 8:52pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/11 "2021-08-24T20:52:53Z")
Is “equal gravitational potential” really achievable given that the Earth’s density is not uniform?
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### Author:  [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)
#### Post date: [August 24, 2021, 9:12pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/12 "2021-08-24T21:12:42Z")
> [@opiewan](#):
>
> Also the Verrazzano-Narrows Bridge in NYC was built taking the earth’s curvature into account. According to Wikipedia, the towers are not parallel to each other, but are 1 5/8" farther apart at the top than at the base to account for the earth’s curvature.
They are farther apart at the top _because of_ the earth’s curvature. They are both built to be vertical, but diverge because “vertical” at one tower is not parallel to “vertical” at the other.
In the case of the Tesla building, assume a big concrete slab floor. If you build it _flat_ (i.e., in one plane), things will tend to roll towards the center of the building. If you build it _level_, then the building will be slightly wider at the roof line than along the slab (assuming vertical walls at each end) - just like the bridge towers.
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [August 24, 2021, 9:22pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/13 "2021-08-24T21:22:15Z")
I would imagine the elasticity of the building materials would negate any need to adjust for the Earth’s curvature for things like the gigafactory. For very large and also very tall structures (suspension bridge pylons) it sort of matters, but since these are joined by cables, it seems like that would provide the necessary capacity for adjustment.
The floor is an interesting one, but wouldn’t these buildings be constructed as a series of modules anyway? The floor isn’t going to be poured in one big slab.
I’m not sure there really are such things as materials that are rigid and inelastic at the sort of scale of the Earth’s curve.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [August 24, 2021, 10:26pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/14 "2021-08-24T22:26:34Z")
> [@Sam\_Stone](#):
>
> Specific to the Gigafactory in Austin, it’s supposedly going to be about 5 million square feet. That’s less than half a mile on a side, assuming it’s square. So the curcature of the earth over that distance would be about 4 inches, or 2" from the center to the edges of the building.
8 inches per mile is only 2 inches per half-mile. It’s quadratic.
And I imagine that it’s more important for a building’s floor to be level than for it to be flat, unless for some reason you have straight beams traversing the entire building (as you do for SLAC, and also for LIGO, the example I was going to cite).
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### Author:  [@rbroome](https://boards.straightdope.com/u/rbroome)
#### Post date: [August 24, 2021, 11:59pm UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/15 "2021-08-24T23:59:45Z")
Here is an example of the opposite problem. At the model basin they had to curve the rails to match the curvature of the earth since that is what the water does.
[https://mht.maryland.gov/nr/NRDetail.aspx?NRID=938](https://mht.maryland.gov/nr/NRDetail.aspx?NRID=938)
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### Author:  [@vbob](https://boards.straightdope.com/u/vbob)
#### Post date: [August 25, 2021, 12:08am UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/16 "2021-08-25T00:08:03Z")
I’ve always thought it would be great for an excavation company to advertise: “Some of you may believe the earth is flat, but we have the tools to make it so.”
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### Author:  [@Melbourne](https://boards.straightdope.com/u/Melbourne)
#### Post date: [August 25, 2021, 1:12am UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/17 "2021-08-25T01:12:31Z")
> [@Chronos](#):
>
> 8 inches per mile is only 2 inches per half-mile. It’s quadratic.
On this scale, it’s approximately linear. 4 inches per half-mile. 80 inches per 10 mile.
The difference between straight and true may be greater on a plan, because the corners of the map may be referenced to something even more than a mile away.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [August 25, 2021, 1:54am UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/18 "2021-08-25T01:54:04Z")
It is approximately linear, but the linear portion is 0 inches per mile. The lowest nonzero order is quadratic.
Think of it this way: If it were linear, and dropped 8 inches for every mile in front of you, then it’d have to rise 8 inches for every mile behind you. Which it clearly doesn’t.
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### Author:  [@bob\_2](https://boards.straightdope.com/u/bob_2)
#### Post date: [August 25, 2021, 9:20am UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/19 "2021-08-25T09:20:39Z")
That’s fascinating.
It then occurs to me that if the floor of Tesla’s building is flat, then if it was flooded, the water would pool in the centre. Weird…🙂
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### Author:  [@Andy\_L](https://boards.straightdope.com/u/Andy_L)
#### Post date: [August 25, 2021, 11:33am UTC](https://boards.straightdope.com/t/does-the-design-of-a-very-large-building-have-to-account-for-the-curvature-of-the-earth/949455/20 "2021-08-25T11:33:39Z")
Yeah. Somewhere I read about a rectangular pool that was long enough and flat enough that when full, water flowed over the long sides, but not the short sides.
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