Planetary POV

[Saber]

If  we have a completely flat surface on a  planet..........

 

 

What  would the inhabitants  of that  planet  see ???    A hollow  bowl like valley   with  4 mountain peaks @ the  4  corners ?

 

Like  this  *  but here the sides  are straight and perpendicular  in that  case they  would have slopes....  it was difficult to  design the  exact shape ....😁

 

And  if we  pour  some liquid  say water on that  flat surface  how would it  stand  there ? 

like a  water dome ?

And   again  how would  those  who  are on the  surface see that  water dome ?  a lake with flat surface in  the middle of that  hollow  bowl  valley ?

 

 

Edited February 11, 2023 by Saber

[studiot]

7 minutes ago, Saber said:

If  we have a completely flat surface on a  planet

Nice pictures.

Can I respectfully suggest you do some thinking for yourself here. You should be quite capable of ansering these questions yourself.

First just check up on the difference between a level surface and a flat surface.

[Saber]

1 minute ago, studiot said:

Nice pictures.

Can I respectfully suggest you do some thinking for yourself here. You should be quite capable of ansering these questions yourself.

First just check up on the difference between a level surface and a flat surface.

that  was a  question  i had in my mind   from when i  was    like 12 -13    years  old......i  have  dome my  thinking....i  just  wanted to know  other  people  opinions
 

[Sensei]

You have a 3D application, so make the right size of the globe i.e. 6370 km.

Then place a virtual camera e.g. 170 cm from the surface i.e. at the eye level of an ordinary person with a height of 180 cm.

Render it.

What do you see?

I bet there will be a straight horizontal line of horizon, not even 1 pixel away from "perfection"..

Edited February 11, 2023 by Sensei

[swansont]

14 minutes ago, Saber said:

If  we have a completely flat surface on a  planet

In addition to the clarification studiot seeks, the size of this surface relative to the size of the planet is likely important.

[Saber]

2 minutes ago, swansont said:

In addition to the clarification studiot seeks, the size of this surface relative to the size of the planet is likely important.

Say  very  large   just  like the  pictures i  sketched.....

And  about  flat vs  level  i  think  i used the  right  words  do  descibe  it.......i meant  a  flat surface  on a  planet  i didnt mean  a level  surface.....a  level  surface  would follow  the  spherical 3d  curve  of the  planet  right ?

[Genady]

A useful mental trick to qualitatively answer questions is exaggeration. Imagine the sticking out part as large as possible, e.g., the bases of the corners located at the equator, and the height equals the planet radius, so the center of the flat area is on the North Pole, and the northern hemisphere is almost entirely inside. The answers become quite clear, I think.

[MigL]

11 minutes ago, Saber said:

a  level  surface  would follow  the  spherical 3d  curve  of the  planet  right ?

Exactly.
Level means equal gravitational potential.

You should be able to use that information to answer your other questions.

[Sensei]

18 minutes ago, Sensei said:

You have a 3D application, so make the right size of the globe i.e. 6370 km.

Then place a virtual camera e.g. 170 cm from the surface i.e. at the eye level of an ordinary person with a height of 180 cm.

Render it.

What do you see?

I bet there will be a straight horizontal line of horizon, not even 1 pixel away from "perfection"..

Here's what I got:

 

 

[Saber]

4 minutes ago, Genady said:

A useful mental trick to qualitatively answer questions is exaggeration. Imagine the sticking out part as large as possible, e.g., the bases of the corners located at the equator, and the height equals the planet radius, so the center of the flat area is on the North Pole, and the northern hemisphere is almost entirely inside. The answers become quite clear, I think.

Not  that  big  though........in the  scenario  you   pictured  it  would  be a   cube.....not a planet any more...

2 minutes ago, MigL said:

Exactly.
Level means equal gravitational potential.

You should be able to use that information to answer your other questions.

Right   like  the  oceans  surface are level   but  they  are not  flat........they are spherical

2 minutes ago, Sensei said:

Here's what I got:

 

 

Thats  only a   plain  planet  can you  add  my  big flat surface  to this simulation  also ?

[Genady]

2 minutes ago, Saber said:

Not  that  big  though........in the  scenario  you   pictured  it  would  be a   cube.....not a planet any more...

Half a cube. The southern hemisphere would still be a hemisphere.

[Sensei]

4 minutes ago, Saber said:

Thats  only a   plain  planet  can you  add  my  big flat surface  to this simulation  also ?

Don't you see that it is not needed? From a human point of view, the Earth is not curved enough to make any difference to the human eye..

[Saber]

maybe  i asked my question with the wrong words......i  said  how would the inhabitants  see  it     lets  say  how  would  that  thing be perceived   or  felt  when your not looking from  out side the planet  but  rather are on its  surface..............

Never mind  i cant  understand  the  meanness in the  comments   have i  asked  a wrong  question ?    or  is it really   dumb   to  ask  ?   

[studiot]

I'm glad to see you are working at least some of this out for yourself.

So much more satisfying that way.

 

Here are a couple of practical facts or 'rules of thumb'  for you.

Cartographers and surveyors work in the '10k flat earth principle.'

That is, you can treat the earth as flat and the grid as rectangular, and trigonometric calculations as plane trigonometry within a region about 10 kilometres across.

 

Talking of flat earth we had a flat earth nutcase here who was trying to prove the earth is flat by surveying Lake Balaton in Hungary. He did not succeed, but the discussion did uncover some interesting geological facts about the alke Baloton region and also more generally, because glaciers creat flat bottomed valleys.

[Sensei]

I added 100m x 100m x 100m box. Its center is 0.01 degrees away from us. 2*PI*6370000m / 360 / 100 = 1111.8m - 50m = 1061.8 m. Approximately 1km from the camera.

Another view, but 0.1 degrees away from us.2*PI*6370000m / 360 / 10 = 11117.7m - 50m = 11067.7 m. Approximately 11km from the camera.

 

 

Edited February 11, 2023 by Sensei

[Saber]

1 minute ago, studiot said:

I'm glad to see you are working at least some of this out for yourself.

So much more satisfying that way.

 

Here are a couple of practical facts or 'rules of thumb'  for you.

Cartographers and surveyors work in the '10k flat earth principle.'

That is, you can treat the earth as flat and the grid as rectangular, and trigonometric calculations as plane trigonometry within a region about 10 kilometres across.

 

Talking of flat earth we had a flat earth nutcase here who was trying to prove the earth is flat by surveying Lake Balaton in Hungary. He did not succeed, but the discussion did uncover some interesting geological facts about the alke Baloton region and also more generally, because glaciers creat flat bottomed valleys.

So.... i felt  it  right.... by  the mean ness   of the comments   i  felt  that  maybe   they  think  im a flat earther.........
maybe  the society  had become  so  dumb  that  when im  asking a  question  some people  thnk  im one of those  people  who think  the  earth is  flat and the moons is a hologram and Hitler is hiding in antarctica......and  the  flat earth is  inside a  spherical  glass aquarium

This  question was  question i had in my mind  from when i was  in my  early teens   that how a completely flat surface.....(* not level but flat )  is  perceived  from the  point of view on a viewer  who is  on  the  planet......
The  4  corners....are further  away  from the planets center  so  they  are higher......and the  middle of the  flat surface is closer to the  planets  center.....so.  it  is   therefore.....lower......so a  flat  surface  on a  planet must   be  seen  or  perceived as a hollow  bowl.....with  4  mountain top  peaks  @ the  corners.....
but  i  wanted to  see other  peoples opinions   too...........

I didnt know the  society  has  come to a phase and  state  that  if  i  ask  such a question  people  would  think  im  one of those  people   who  think  the earth is flat......

[Genady]

4 minutes ago, Saber said:

lets  say  how  would  that  thing be perceived   or  felt  when your not looking from  out side the planet  but  rather are on its  surface

They will see the same as from outside, but close-up. The walls will stick out from the ground at an angle, tilted backwards. The top surface will look flat.

BTW, people on Earth can easily see its curvature by getting up to mountains, or by watching a ship disappearing behind the horizon, for example. I live on an island and the next island is about 60 km away. It is behind the horizon and not visible from the shore. But when I climb to our highest elevation, in a good weather, I see the island appearing into the view.

[Saber]

3 minutes ago, Sensei said:

I add 100m x 100m x 100m box. Its center is 0.01 degrees away from us. 2*PI*6370000m / 360 / 100 = 1111.8m - 50m = 1061.8 m. Approximately 1km from the camera.

Another view, but 0.1 degrees away from us.2*PI*6370000m / 360 / 10 = 11117.7m - 50m = 11067.7 m. Approximately 11km from the camera.

 

 

In  that  simulation can you  pleas  just make a  flat  surface  that  each of its  sides  length is like 35  or 40 %  of the  planets   diameter.....and  once again  with the  sides  20%   i want to  see how  the  camera  or  POV sees   it...

7 minutes ago, Genady said:

 The top surface will look flat.

 

maybe it would look  flat   but  i think  that  flat surface would be sloped  towards the  middle and center of that  surface  right ?   i mean  if  you  put a ball on thet  flat surface  it  would go  and  stay  right in the middle  point of that  surface  * after some  up &  down oscillations @  last it  would stay in the middle  point  because  thats  the point nearest to the  center of the planet aka lower....

right ?

[Sensei]

24 minutes ago, Saber said:

In  that  simulation can you  pleas  just make a  flat  surface  that  each of its  sides  length is like 35  or 40 %  of the  planets   diameter.....and  once again  with the  sides  20%   i want to  see how  the  camera  or  POV sees   it...

I created flat ground plane with 1km x 1km size.

Basically, you can't see the difference. The edge (the blue-gray transition, 1-2 pixels in the image) is 500m from the camera.

 

 

 

Edited February 11, 2023 by Sensei

[Genady]

12 minutes ago, Saber said:

maybe it would look  flat   but  i think  that  flat surface would be sloped  towards the  middle and center of that  surface  right ?   i mean  if  you  put a ball on thet  flat surface  it  would go  and  stay  right in the middle  point of that  surface  * after some  up &  down oscillations @  last it  would stay in the middle  point  because  thats  the point nearest to the  center of the planet aka lower....

right ?

The ball will behave like you describe, right. But the light rays will keep going straight and along the surface. So, if they just look at the structure, or make geometrical measurements, they will see that the top is flat. It would not be slopped toward the center.

[Saber]

2 minutes ago, Genady said:

The ball will behave like you describe, right. But the light rays will keep going straight and along the surface. So, if they just look at the structure, or make geometrical measurements, they will see that the top is flat. It would not be slopped toward the center.

In the  case  you  pictured  like that  the   sides length of the  surface is very very  large  in comparison  to  the planets  diameter........the  4 corners of the  cube  under the  surface  would also  produce some  gravity as  they  contain  a lot  of  mass....
im  thinking of a  surface  not that  big  so the  corners could produce  a considerable amount  of  gravity.........and not that  small  so  that  the corners would not be  high enough to have a slope inside.....

11 minutes ago, Sensei said:

I created flat ground plane with 1km x 1km.

Basically, you can't see the difference. The edge (the blue-gray transition, 1-2 pixels in the image) is 500m from the camera.

 

 

 

Thanx.....

[Genady]

2 minutes ago, Saber said:

In the  case  you  pictured  like that  the   sides length of the  surface is very very  large  in comparison  to  the planets  diameter........the  4 corners of the  cube  under the  surface  would also  produce some  gravity as  they  contain  a lot  of  mass....
im  thinking of a  surface  not that  big  so the  corners could produce  a considerable amount  of  gravity.........and not that  small  so  that  the corners would not be  high enough to have a slope inside.....

If they measure a shortest distance from one corner to another on the diagonal, they'll find that the line of the shortest distance goes along the surface, touching the surface all the way. Thus, the surface is flat, not slopped.

Another way is by drawing a large triangle on the top surface and measuring its angles. If the surface is slopped inward, the sum of the angles will be less than 180^o. If the sum is 180^o, the surface is flat. They will find that it is in fact 180^o. Not slopped.

[Sensei]

@Saber

Did you have trigonometry in school?

Use Pythagoras' triangle to find out how curvature changes with distance:

What you see here, 6 degrees, would be equivalent of ~ 670 km.

Edited February 11, 2023 by Sensei

[Saber]

I was  thinkning about  that  also   right now.....

 

On  each  point if you connect it to the center of the planet  the line ( would be  perpendicular to the surface of the planet )   on  each point it has a different angle

 

So   a person  on that planet walking on that   flat surface  would feel its angle   ( steepness ) gradually  decreasing as it  gets to the tangent  point....

I mean  for him  it would be felt like a curve  right ?    * not seen   but felt....

 

 

 

 

Edited February 11, 2023 by Saber

[Genady]

2 minutes ago, Saber said:

I mean  for him  it would be felt like a curve  right ?

Yes, he will feel like going down slope to the center and then up slope again. This is because our vestibular system detects gravity as a direction down. It is not very different from your ball example.