Spin off of "Where are You"

joe shmo
Posers and Puzzles 30 Jan '18 19:00
1. joe shmo
Strange Egg
30 Jan '18 19:001 edit
What is ( appx. - 4 significant figures ) the radius of a planet from which you could begin at the North Pole, walk 1 mile South. Then 1 mile ( East or West ) completing a full circle, and 1 mile North again to return to the pole?

I figured I'd continue on with my oversight from the other puzzle.
2. HandyAndy
Non sum qualis eram
30 Jan '18 22:59
Originally posted by @joe-shmo
What is ( appx. - 4 significant figures ) the radius of a planet from which you could begin at the North Pole, walk 1 mile South. Then 1 mile ( East or West ) completing a full circle, and 1 mile North again to return to the pole?

I figured I'd continue on with my oversight from the other puzzle.
The radius of the circle you walk is one mile (the distance from the pole to the circle).
The circumference of the same circle is one mile.
How is that possible? Are we on the flat surface of a spherical planet?
3. joe shmo
Strange Egg
31 Jan '18 00:181 edit
Originally posted by @handyandy
The radius of the circle you walk is one mile (the distance from the pole to the circle).
The circumference of the same circle is one mile.
How is that possible? Are we on the flat surface of a spherical planet?
"The radius of the circle you walk is one mile (the distance from the pole to the circle)."

No, the radius of the 1 mile arc you walk in the southerly direction is unknown ( its the radius of the sphere). When you get to that latitude on the sphere you walk west (or east) a full circle that has a circumference of 1 mile.

"Are we on the flat surface of a spherical planet?" We are not, no tricks of wording. Its a math problem.
4. 31 Jan '18 00:531 edit
Originally posted by @joe-shmo
"The radius of the circle you walk is one mile (the distance from the pole to the circle)."

No, the radius of the 1 mile arc you walk in the southerly direction is unknown ( its the radius of the sphere). When you get to that latitude on the sphere you walk west (or east) a full circle that has a circumference of 1 mile.

"Are we on the flat surface of a spherical planet?" We are not, no tricks of wording. Its a math problem.
Do I understand the poser correctly?

The wording (“THE radius” ) implies that we are walking on the surface of a sphere whose radius, or distance from the center to any point on the surface, is the same at all points on the surface.

You walk for one mile from a pole along any one longitude line, to a point where it intersects a certain latitude line. The latitude line is therefor one mile from the pole (as the crow walks) and is given as one mile in circumference (same crow).

What is the radius of the sphere?

Is this correct?
5. joe shmo
Strange Egg
31 Jan '18 01:06
Originally posted by @js357
Do I understand the poser correctly?

The wording (“THE radius” ) implies that we are walking on the surface of a sphere whose radius, or distance from the center to any point on the surface, is the same at all points on the surface.

You walk for one mile from a pole along any one longitude line, to a point where it intersects a certain latitude line. T ...[text shortened]... one mile in circumference (same crow).

What is the radius of the sphere?

Is this correct?
Yeah, I believe you have the proper setup.
6. HandyAndy
Non sum qualis eram
31 Jan '18 01:23
Originally posted by @joe-shmo
"The radius of the circle you walk is one mile (the distance from the pole to the circle)."

No, the radius of the 1 mile arc you walk in the southerly direction is unknown ( its the radius of the sphere). When you get to that latitude on the sphere you walk west (or east) a full circle that has a circumference of 1 mile.

"Are we on the flat surface of a spherical planet?" We are not, no tricks of wording. Its a math problem.
Do we agree that the radius of a one-mile circle is 0.159 miles on a flat surface?
7. joe shmo
Strange Egg
31 Jan '18 01:26
Originally posted by @handyandy
Do we agree that the radius of a one-mile circle is 0.159 miles on a flat surface?
Sure.
8. HandyAndy
Non sum qualis eram
31 Jan '18 01:31
Originally posted by @joe-shmo
Sure.
And what we're looking for is the radius of the entire planet.
9. joe shmo
Strange Egg
31 Jan '18 01:42
Originally posted by @handyandy
And what we're looking for is the radius of the entire planet.
Yes sir.
10. HandyAndy
Non sum qualis eram
31 Jan '18 03:51
Originally posted by @joe-shmo
Yes sir.
Just an observation: It's a really small planet.
11. joe shmo
Strange Egg
31 Jan '18 04:051 edit
Originally posted by @handyandy
Just an observation: It's a really small planet.
Quite small indeed! More like an astriod.
12. HandyAndy
Non sum qualis eram
31 Jan '18 22:321 edit
Originally posted by @joe-shmo
Quite small indeed! More like an astriod.
To determine the planet's radius, do we first calculate the relationship between the one-mile
arc from point A to point B and the shorter (0.159 mile) chord linking point A and point B?
13. joe shmo
Strange Egg
31 Jan '18 23:513 edits
Originally posted by @handyandy
To determine the planet's radius, do we first calculate the relationship between the one-mile
arc from point A to point B and the shorter (0.159 mile) chord linking point A and point B?
No, and FYI your figure of a chord length ( 0.159mi) between A and B must be incorrect because you cannot find the chord without knowing the radius in this case ( we do not know the angle subtended by the 1 mile arc - that is to say "explicitly" ) Hint: We can know the angle implicitly as a function of the radius.
14. HandyAndy
Non sum qualis eram
01 Feb '18 01:57
Originally posted by @joe-shmo
No, and FYI your figure of a chord length ( 0.159mi) between A and B must be incorrect because you cannot find the chord without knowing the radius in this case ( we do not know the angle subtended by the 1 mile arc - that is to say "explicitly" ) Hint: We can know the angle implicitly as a function of the radius.
I believe 0.159 mile is the radius of a circle having a circumference of one mile, but apparently that's a non-starter.

We need a mathematician.
15. joe shmo
Strange Egg
01 Feb '18 02:47
Originally posted by @handyandy
I believe 0.159 mile is the radius of a circle having a circumference of one mile, but apparently that's a non-starter.

We need a mathematician.
There used to be many posters in this forum that had mathematical backgrounds maybe 8-10 years ago. Now, they seem to have found greener pastures ( perhaps the debates forum - ðŸ˜‰ ) If you have little to no math background this will probably be difficult. I guess the pre requisites to this problem are algebra, and trigonometry (calculus - if you wish to get fancy finding the zero of the function).