When a "layman" hears of the cosmic microwave background, and this layman also has a passing knowledge of big bang theory, it can be difficult for said layman to wrap his head around what the CMB really is. That layman might ask, wouldn't this primordial radiation have "passed" us by now, and we wouldn't be able to see it? In other words, the universe originated in a "big bang" and has been expanding since then at some speed less than the speed of light. Therefore this primordial radiation would exceed the boundaries of the matter which comprises the known universe, and you wouldn't be able to see it any more. Obviously this is an oversimplification of big bang theory and CMB, and I was wondering if those of you knowledgable about the details of cosmology can elaborate for me. I.e., debunk the idea that the CMB would have passed us by now. Or, explain why the CMB has not passed us. Thanks. -Scott V.