.When we say "expanding" does that mean just spreading away from the center?
Angie, I thought I'd find a nice straightforward answer to your question. Wikipedia said:
In mathematical physics, n-dimensional de Sitter space (often abbreviated to dSn) is a maximally symmetric Lorentzian manifold with constant positive scalar curvature. It is the Lorentzian analogue of an n-sphere (with its canonical Riemannian metric).
They did flag it:
This article may be too technical for most readers to understand. "May be"!!! Ha! Ha! Even way back when I studied this stuff, that would have left me cross-eyed.
But science writer Marcus Woo answers your question succinctly:
The universe, in fact, has no center. Ever since the Big Bang 13.7 billion years ago, the universe has been expanding. But despite its name, the Big Bang wasn't an explosion that burst outward from a central point of detonation. The universe started out extremely compact and tiny. Then every point in the universe expanded equally, and that continues today. And so, without any point of origin, the universe has no center.