Relative position of a helicopter

If a helicopter takes off from a point on earth.(at certain altitude) and its still at that point in air.After certain time interval the observer whose position was same as that of helicopter’s take off point will see the helicopter right above him. The question arises is that how it is possible if [...]

Questions from Relativity

Sam asks “After the Sun, the nearest star visible to the naked eye is Rigel Centaurus, which is 4.35 light years away. If a Spacecraft was sent there from earth at a speed of 0.80c, how many years would it take to reach that star from earth as measured by observers (a) On Earth; (b) [...]