Space-time curvature (Score 1)

If my understanding is correct, although in all probability I could be completely wrong, then according to Einstein's general theory of relativity space-time is curved such that if I were to travel in a straight line across the breadth of the universe then I would eventually arrive at the same point in space from where I originally started.

Thus in respect to the galaxy cluster that is being pulled by an "unobservable mass" outside the observable universe relative to ourselves would not that mass, or at least the effects of that mass (if it is dark matter), be observable by looking for it in the opposite direction.

For example: Say I make an observation at the North Pole that galaxy cluster A, sighted directly above the North Pole, is moving away from us towards an unobservable mass B that appears to be outside of our universe. Then drawing a line from where I am at the North Pole through cluster A and mass B and on then by the curvature of the universe surely that line would eventually travel the circumference of the universe until it passes through the South Pole and back to where I am standing at the North Pole. So if I want to see B (considering it is visible or its effects) then by making an observation from the South Pole back along our imaginary line in the opposite direction then I would surely be able observe B inside our observable universe.