The analogy I use to explain this to people is simply how it is impossible to go further south than the South Pole. There is no physical barrier stopping you f

The analogy I use to explain this to people is simply how it is impossible to go further south than the South Pole. There is no physical barrier stopping you from moving in any direction, but due to the shape of the Earth you have reached the southernmost point. It is likely the same with our universe, and its inherent morphology, too.