Number of Coordinates for Sphere Positions: Explained

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In summary, it depends on the specific characteristics of the sphere. If there are distinguished points on the surface, 5 coordinates are needed - 3 for the center and 2 for rotations. If the surface is blank, only 3 coordinates are needed for the center. If the sphere is given a radius, 4 coordinates are needed - 3 for the center and 1 for the radius. If the whole space is the sphere and it is a unit sphere, then 2 coordinates are needed for rotations using spherical coordinates.
  • #1
pivoxa15
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Homework Statement


How many coordinates are needed to know all the different positions of a sphere?

The Attempt at a Solution


Three, two for specifying every point of the sphere and one for rotating it to a different position. Is only one needed to rotate the sphere?
 
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Are there distinguished points on the sphere? And is the sphere of given radius?

If there are distinguished point on the sphere- that is, if you can distinguish one point from another (as on a globe of the earth), then you would require 5 coordinates: three to determine the center of the sphere, two angles to determine the rotations of the sphere in space.

If there are no distinguished points, if, say, the surface of the sphere is blank, then you would need three coordinates, to determine the center of the sphere. The rotations are irrelevant.

That is assuming that you are talking about a given sphere, with given radius. If you mean determine any (blank) sphere, then you will need four coordinates: three to determine the center of the sphere and one to determine the radius.
 
  • #3
HallsofIvy said:
Are there distinguished points on the sphere? And is the sphere of given radius?

If there are distinguished point on the sphere- that is, if you can distinguish one point from another (as on a globe of the earth), then you would require 5 coordinates: three to determine the center of the sphere, two angles to determine the rotations of the sphere in space.

If there are no distinguished points, if, say, the surface of the sphere is blank, then you would need three coordinates, to determine the center of the sphere. The rotations are irrelevant.

That is assuming that you are talking about a given sphere, with given radius. If you mean determine any (blank) sphere, then you will need four coordinates: three to determine the center of the sphere and one to determine the radius.


Let's assume the whole space is the sphere so the centre is the origin. Assume a unit sphere. Then two coordiates for the rotation?
 
  • #4
If you are now talking about the possible positions of the unit sphere, then yes, you need to coordinates for the rotations. One way to think about that is to use "spherical coordinates", [itex]\rho[/itex], [itex]\theta[/itex], and [itex]\phi[/itex]. Since the position of any point inside the sphere is determined once the points on the surface are fixed, we can take [itex]\rho= 1[/itex] and have [itex]\theta[/itex] and [itex]\phi[itex] left as variables.
 

FAQ: Number of Coordinates for Sphere Positions: Explained

What is the position of a sphere?

The position of a sphere refers to its location in three-dimensional space, usually described by its coordinates or distance from a reference point.

What are the coordinates of a sphere?

The coordinates of a sphere can vary depending on the reference system used. In a Cartesian coordinate system, the coordinates are typically given as (x,y,z) where x is the horizontal position, y is the vertical position, and z is the depth or distance from the reference point.

How do you determine the center of a sphere?

The center of a sphere is located at the midpoint of its diameter, which can be found by measuring the distance between any two points on the surface of the sphere and dividing it by two.

How do you calculate the radius of a sphere?

The radius of a sphere is the distance from its center to any point on its surface. It can be calculated using the Pythagorean theorem or by measuring the diameter and dividing it by two.

How do you convert between different coordinate systems for a sphere?

To convert between different coordinate systems for a sphere, you can use mathematical equations or transformation matrices specific to each system. Alternatively, there are online conversion tools available that can do the calculations for you.

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