When Jesus comes again to earth, all the righteous dead are resurrected and ascend to heaven with Him, along with the righteous living. After a thousand years (see Lesson #27, The Millennium), God’s throne inside the New Jerusalem, descends to Planet Earth, splitting the Mount of Olives. At the very site where Jesus made His final choice to die on our behalf, the New Jerusalem, capital of God’s universal kingdom, is established for eternity. JTL28 5.1
After the final destruction of all taint of sin, Jesus recreates the earth. The new earth then, is this recreated earth, not some alien place. It is new in the sense that God will remove from the earth every blemish that sin has caused. JTL28 5.2