Let us optimistically assume that sooner or later a workable interstellar propulsion system will be found, and also be built and successfully tested in space. While this would be a great advance toward making interstellar travel possible, it nevertheless does not automatically follow that a voyage to the stars will in fact be attempted. There are a few other issues that must also be settled first: for example, a habitable exoplanet must be identified. It must be suitable for human colonization and ought to be a reachable distance away from Earth within a reasonable period of travel time. Second, engineers must provide a plausible space vehicle design architecture, and a spacecraft of that design must then be constructed, and tested successfully. Such a craft does not exist as yet, one among many reasons being that the specifications for it depend in turn upon the size and makeup of the likely boarding population. But both of those factors are still unknown. In addition, and perhaps most important of all, an unprecedented level of funding and resources must be allocated to the project.

Most of us don’t build muscle mass after young adulthood. After we turn 50 our muscle mass decreases 1-2% per year. From our 20s until the age of 80, our muscle mass decreases by 30 – 50%! This becomes increasingly noticeable after age 70.Our strength declines by 10%-15% per decade until age 70, when this loss accelerates to 25% to 40% per decade. Sarcopenia, or muscle loss, often serves as a harbinger of frailty. But frailty is not normal with aging. The five factors of frailty (three must be met to be considered frail): Unintentional weight loss; exhaustion; muscle weakness; slowness in walking; low levels of activity. Multiple studies show that a good exercise program, including aerobic, strength, and balance regimens, preserves muscle mass in older generations. Chapter explains how frailty is a group of symptoms that can be effectively avoided or treated.