It’s all very complicated :eek:
So Voyager’s speed is determined by “The dopplershift of the radio signals it transmits” or "speed relative to the “fixed stars,”
So while Voyager is hurtling away through space, the Earth is orbiting the Sun at 107000Kph or thereabouts and will sometimes be travelling in the same direction as Voyager and sometimes away from Voyager, therefore giving two different readings of Voyager speed relative to the Earth?
Another point with expanding Universe. Presumably the Big Bang worked like any explosion on Earth and flung bits of future Planets in all directions. So all the bits moving in one direction have a speed relative to the point of the Big Bang another speed relative to each other and yet another speed to bits of future planets going in the opposite direction?
Slight deviation, do we know exactly where the Big Bang happened and what is there now?
A lot of stuff to get my head round.