Google Maps and engineer Adam Davis now answer that question. The Google Maps mashup shows you the other side of the earth from your current location. Feel like doing the same but without any help from technology? Just do it yourself. Dig down deep in your backyard -- we mean really deep, like 7,926 miles -- and see for yourself. You might be covered with liquid hot magma but you'll be able to tell everyone you did it on your own.
I better go prepare myself. Davis's map shows that if I dug under my desk in Detroit, Michigan, I'd exit the earth in the middle of the south Indian Ocean.