Jesse James Garrett:

The interesting thing about galactic collisions is that because galaxies contain so much room between the stars, there’s very little actual colliding going on. The galaxies just sort of flow into one another, individual stars finding new places in the larger system developing around them in a process unfolding over billions of years. From the vantage point of someone living in one of these galaxies, even if you lived long enough to see the constellations shift and change around you, you still might not be aware of exactly what was going on.
A great metaphor for what’s happening with customer experience, service design and user experience design.