Outer space is not a very inviting place to visit.  We must take with us and entire life support system to make it even possible to visit space.  But we still cannot take gravity with us into space.  Spaceflight in microgravity conditions is harmful to humans because our circulatory system bones and other structures are designed to function in the gravity field of earth.  In microgravity, muscles may weaken and bones become more fragile  due to leaching of calcium out of bone.  These considerations should remind us that our earth environment and the needs of our human physiology are precisely matched and, while we may visit space, there is still no place like home.  Uplook Magazine March 2006, p. 4.  References: West JB.  Physiology of a microgravity environment: Historical perspective:  Physiology in microgravity. Journal of Applied Physiology 89:379-484, 2000.  Holick MF.  Perspectives on the impact of weightlessness on calcium and bone metabolism.  Bone 22(5)105S-111S, 1998.  LeBlanc A et al. Future human bone research in space.  Bone 22(5)113S-116S, 1998.  Burger EH and J Klein-Nulend.  Microgravity and bone cell mechanosensitivity.  Bone 22(5)127S-130S, 1998.