A drop of water falls in an endless, still lake. The ripple spreads out, leaving a circular wave spreading out endlessly. Tiny disturbances create their own ripples; one side travelling with the main ripple, causing wonderful interactions in the wavefront; but the main ripple grows faster than these disturbances spread across it.
The beings of the ripple look across the main ripple, seeing the disturbances as their interactions propagate across the main ripple. Looking back far enough to the earliest disturbances, one thing becomes clear; the entire ripple comes from one drop, and most of the ripple is moving away faster than a disturbance can propagate.
An expanding universe where every point of the universe started from the middle is pretty easy to conceptualize with the right analogy.