Middle-earth is an historical term. It is a literal translation of the Old English term middangeard, referring to the real world, the habitable lands of men. Less formally, the term "Middle-earth" often refers to the lands where the stories of J. R. R. Tolkien take place. Tolkien said that his Middle-earth is our Earth, but in a fictional period in the past; estimating the end of the Third Age to about 6,000 years before his own time.
http://en.wikipedia.org/wiki/Middle_earth

In fact Middle-earth, like the variants in other Germanic languages, is simply a reference to this earth, versus the worlds above and below; Middle-earth is the earth in the middle. http://www.greenmanreview.com/book/book ... earth.html

Here we should pause to consider what is "middle" about Middle Earth. Heaven and Hell, according to the medieval English lyric, are eating into merry middle-earth—Heaven from above, Hell from below. Middle-earth is not permanent in its present incarnation, neither in Tolkien’s world nor in ours. We can expect, some day, a new heaven and a new earth . . . [quote Galadriel and Fangorn’s conversation about reincarnation]. In fact, Tolkien’s Middle Earth is not three-tiered so much as three-directional. If the West is Heaven (or Paradise), then the East in some sense approaches Hell, even though the symmetry is incomplete, and Middle Earth is middle because betwixt West and East. http://users.bestweb.net/~jfgm/Encyclop ... 0Notes.htm

I haven't really tought of that before. I knew that Tolkien wanted to create a mythology for England but I never tought of it that way. I think it's a good teori that when the elves leave, Middle Earth looses it's magic and eventually turning into the world as we know it. But it dosen't feel right to me. I think it's a bit sad if it is that way. I like to think as Arda as an whole other world far from here. It's a hard to believe that Middle Earth should turn into this strange world

Aftenstjerne