Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Two spheres and three spheres

  1. Mar 17, 2005 #1
    Just a couple of questions:

    1. If we imagine space to be curved over a sphere is it possible to travel in one direction and eventually end up where you started, assuming that the sphere it self is not expanding.

    2. What's the difference between a two sphere and a three sphere? I find it hard to grasp the idea of a three sphere, because if there is now a radial or z coordinate then it's not really a sphere is it? :confused:


  2. jcsd
  3. Mar 17, 2005 #2


    User Avatar
    Science Advisor
    Gold Member

    If you're thinking about something analogus to an explorer circumnavigating the globe, then yes certaily.

    -The main difference between a 2-sphere and a 3-sphere is their number of diemsnions (this is obvious I suppose).

    -The idea of a 3-sphere is hard to grasp, the best way is by analogy to a 2-sphere.

    -'the radila coordinate is something that is only really a coordiante when you embed the 3-sphere into a higher dimensional space, in the context of the space of the three sphere itself (assuming enough structure is defined) the 'radius' of the sphere is just a parameter that differentiates it from other simlair spaces.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Two spheres and three spheres
  1. Dyson sphere (Replies: 1)

  2. Cooling sphere (Replies: 2)

  3. Disks and spheres. (Replies: 3)

  4. Celestial Sphere (Replies: 0)

  5. The corona sphere. (Replies: 2)