- 30 Jan '18 19:00 / 1 editWhat 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. - 30 Jan '18 22:59

The radius of the*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.*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? - 31 Jan '18 00:18 / 1 edit

"The radius of the*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?*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. - 31 Jan '18 00:53 / 1 edit

Do I understand the poser correctly?*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.

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? - 31 Jan '18 01:06

Yeah, I believe you have the proper setup.*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? - 31 Jan '18 01:23

Do we agree that the radius of a one-mile circle is 0.159 miles on a flat surface?*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. - 31 Jan '18 01:26

Sure.*Originally posted by @handyandy***Do we agree that the radius of a one-mile circle is 0.159 miles on a flat surface?** - 31 Jan '18 01:31

And what we're looking for is the radius of the entire planet.*Originally posted by @joe-shmo***Sure.** - 31 Jan '18 01:42

Yes sir.*Originally posted by @handyandy***And what we're looking for is the radius of the entire planet.** - 31 Jan '18 03:51

Just an observation: It's a really small planet.*Originally posted by @joe-shmo***Yes sir.** - 31 Jan '18 04:05 / 1 edit

Quite small indeed! More like an astriod.*Originally posted by @handyandy***Just an observation: It's a really small planet.** - 31 Jan '18 22:32 / 1 edit

To determine the planet's radius, do we first calculate the relationship between the one-mile*Originally posted by @joe-shmo***Quite small indeed! More like an astriod.**

arc from point A to point B and the shorter (0.159 mile) chord linking point A and point B? - 31 Jan '18 23:51 / 3 edits

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.*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? - 01 Feb '18 01:57

I believe 0.159 mile is the radius of a circle having a circumference of one mile, but apparently that's a non-starter.*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.**

We need a mathematician. - 01 Feb '18 02:47

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 - ) 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).*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.