Gravity

[Snes31]

So recently i have bean thinking about earth's gravity, and i have more of a theoreticall question, for people who understand more then me. What if some one reacreat a small round sphere, whit the same elements that are found in earth, and apply the same rotation speed, layers and magnet like north and south pole, but just smaller in scale. Including the magma close to the real thing but smaller, like a baskerball. 

Would it create the same gravity ore earth is mutch complex then this ?

[Ghideon]

34 minutes ago, Snes31 said:

So recently i have bean thinking about earth's gravity, and i have more of a theoreticall question, for people who understand more then me. What if some one reacreat a small round sphere, whit the same elements that are found in earth, and apply the same rotation speed, layers and magnet like north and south pole, but just smaller in scale. Including the magma close to the real thing but smaller, like a baskerball. 

Would it create the same gravity ore earth is mutch complex then this ?

The gravity for any body is related to the mass of the body. So by recreating a scale model, the small earth you describe, your model will have a tiny fraction of earth gravity since the model has less mass. The magnetic fields, magma and the rotation does not have a great effect on the gravity here on the surface. 

But that said, gravity as physical concept, is the same "thing" everywhere. Gravity has different magnitude and direction, for instance the surface gravity on the moon is weak compared to earth. But it is the same kind of gravity, described by the same physical rules, even if the moon has a different internal composition.

Feel free to ask follow up questions.

 

Edited October 18, 2020 by Ghideon

[michel123456]

1 hour ago, Snes31 said:

So recently i have bean thinking about earth's gravity, and i have more of a theoreticall question, for people who understand more then me. What if some one reacreat a small round sphere, whit the same elements that are found in earth, and apply the same rotation speed, layers and magnet like north and south pole, but just smaller in scale. Including the magma close to the real thing but smaller, like a baskerball. 

Would it create the same gravity ore earth is mutch complex then this ?

No. It was shown by Galileo Galilei in 1638.

When you scale down (or scale up) you must take account of the square-cube law. https://en.wikipedia.org/wiki/Square–cube_law

[Halc]

4 hours ago, michel123456 said:

No. It was shown by Galileo Galilei in 1638.

When you scale down (or scale up) you must take account of the square-cube law. https://en.wikipedia.org/wiki/Square–cube_law

Gravity for a fixed mass object scales with the inverse square law (shown first by Newton, late 1600's), not the square-cube law, which instead relates area to volume, and also orbital periods (Kepler, around 1600).

We're not talking about a fixed mass object here, so yes, the square-cube law is relevant, but only when Newton's work is applied.  A planet of half the radius would have 4x/8x the gravity (8th the mass, half the radius squared).

Ghideon gives a good answer to the OP.  A basketball sized Earth would exert as much gravity as a basketball sized rock, which is negligible in comparison to what we're used to.

[MigL]

6 hours ago, Snes31 said:

What if some one reacreat a small round sphere, whit the same elements that are found in earth, and apply the same rotation speed, layers and magnet like north and south pole, but just smaller in scale. Including the magma close to the real thing but smaller, like a baskerball. 

Would it create the same gravity ore earth is mutch complex then this ?

No.
A 'scale' model would be vastly different, as Gravity affects the Earth in many different ways.
Some obvious examples, a smaller Earth might not have enough gravity to hang on to its atmosphere, and there may not be enough pressure to keep magma flowable.