# If Earth were a cube

I was thinking about a situation where we lived in a cubical earth! (Gravity is such that people at each surface will still feel that they are standing upright). I came up with some interesting situations like when a ship crosses an edge or throwing a ball from the edge of surface... What would life be like, in such a scenario?

SteamKing
Staff Emeritus
Homework Helper
The Bizarro World ...

http://en.wikipedia.org/wiki/Bizarro_World

Staff Emeritus
2021 Award
Gravity is such that people at each surface will still feel that they are standing upright

Is that true? I don't think it is.

Dale
Mentor
2021 Award
(Gravity is such that people at each surface will still feel that they are standing upright).
No, gravity doesn't work that way. People on each surface would feel that they are climbing one of 8 giant mountains. They would not think that the surface is horizontal.

No, gravity doesn't work that way. People on each surface would feel that they are climbing one of 8 giant mountains. They would not think that the surface is horizontal.
Why can't gravity act perpendicular to the surface? Like field lines are uniform along positive x direction passing through the y-z plane?

DaveC426913
Gold Member
No, gravity doesn't work that way.
My interpretation of the OP's post is that he is declaring that gravity would be arranged that way - not that it would naturally be that way.

Thing is, as soon as he does that, he has to come up with the answer to his own question - because it's artificially constructed. To what resolution does the gravity remain normal to a surface? If you are standing one hundred yards from the edge, do you feel gravity normal to the ground i.e. no effect from the other surface? What about one foot from the edge? What if you straddle the edge? Would each leg be pulled in unique direction? Which way would your head be pulled?

DaveC426913
Gold Member
Why can't gravity act perpendicular to the surface? Like field lines are uniform along positive x direction passing through the y-z plane?
Are you asking why physics works the way it does?

If you stand on the side of a steep hill, which way would gravity pull you? Would you expect to stand perpendicular to the side of the hill?

My interpretation of the OP's post is that he is declaring that gravity would be arranged that way - not that it would naturally be that way.

Thing is, as soon as he does that, he has to come up with the answer to his own question - because it's artificially constructed. To what resolution does the gravity remain normal to a surface? If you are standing one hundred yards from the edge, do you feel gravity normal to the ground i.e. no effect from the other surface? What about one foot from the edge? What if you straddle the edge? Would each leg be pulled in unique direction? Which way would your head be pulled?
The situation is unreal. That's what I wanted to mean. It's hypothetical. Well for simplicity the field lines at one surface do not affect the other. If he is in surface 1, he will feel the gravitational pull of surface 1.
If he puts one leg on one surface and the other on an adjacent surface?? I don't know what's going to happen.

Are you asking why physics works the way it does?

If you stand on the side of a steep hill, which way would gravity pull you? Would you expect to stand perpendicular to the side of the hill?
No no. If a person stands on a mountain of inclination theta (mountain on surface '1') then he will feel mgsin(theta) along surface and mgcos(theta) along the normal to mountain surface.

DaveC426913
Gold Member
The situation is unreal. That's what I wanted to mean. It's hypothetical. Well for simplicity the field lines at one surface do not affect the other. If he is in surface 1, he will feel the gravitational pull of surface 1.
If he puts one leg on one surface and the other on an adjacent surface?? I don't know what's going to happen.
Right. So it's up to you to make up your own scenario. Decide how your fictional artificial gravity generators operate, where they are placed (presumably underground), and how their fields attentuate. Then your occupants will be able to tell where "down" is.

Nugatory
Mentor
Why can't gravity act perpendicular to the surface? Like field lines are uniform along positive x direction passing through the y-z plane?

If you actually calculate the gravitational force on the surface using Newton's law of gravity (you will need to do some integration here) , you will find that DaleSpam's response is accurate - unless you suspend the law of gravity, the gravitational field will not be generally perpendicular to the surface and walking to a corner will be like climbing a really high mountain.

If you do the calculations you will also find that the forces on the corners are so great that even solid rock cannot resist them so the corners will be pulled down towards the center. This is, of course, why the earth and all other planet-sized bodies are spherical.

Nugatory
Mentor
The situation is unreal. That's what I wanted to mean. It's hypothetical.....I don't know what's going to happen.

Nor does anyone else, as your question is basically "What do the laws of physics say will happen in a situation in which the laws of physics don't apply?". That's not going to be a productive physics forums discussion so the thread is closed.