NHI Starmaps

[chr0naut]

Two points, my star chart book is a professional one dated, I believe, on the 1955 sky.  Most stars are still right there!  My application of comet aphelion points to those areas is based on the scientific orbits provided by astronomy professionals to those locations.  You really need to go read the 49 pages of the info I suggested.  It goes into scientific detail how the GPS would work for star travellers with very fast ships.

GPS uses radio signals and multiple satellites allowing things to be located on the Earth by the doppler differences in the radio signals from multiple satellites.

The light from Proxima Centauri takes 4.2 years to get to the Earth. Light travels at the speed of light in a vacuum, so if it takes 4.2 years, the distance in miles is very big. The distance of 4.2 light years, in miles, is 24,690,150,000,000 (roughly 24 million, million miles).

From that distance, the entire globe of the Earth and out to the orbit of the Moon, including the atmosphere and all satellites near it, would be a tiny, almost dimensionless, point. Optically invisible from Proxima Centauri.

GPS wouldn't cut it because from that distance, there's zero discernible distances between the satellites and the radio signals themselves would have travelled for 4.2 years in a near parallel beam. The phase differences would still be there, but they'd all be coming from exactly the same point, and therefore the GPS satellite system in orbit around the Earth is useless at any real stellar distance (even for the Sun, which is only 52 million miles away).

Proxima Centauri also happens to be the nearest star to the Earth after the Sun. Most other stars are thousands, millions, or billions of times even further away. If GPS is inadequate for locating the earth from Proxima Centauri or the Sun, then imagine how impossible it would be from other stars.

And the GPS radio waves are only passing through the fairly even 1G gravity field of the Earth when we 'read' them on the Earth. Spacetime itself is warped around stars and heavy stuff, so much so, that some stars 'lens' the light coming from behind them, scattering it enough to produce multiple ghost images of the background stars and galaxies.

So, a GPS radio wave would not be relied on to travel in a straight line in deep space, it would be bent and warped everywhere and would even interfere with itself traveling a different path, and all those radio photons travelling multiple paths would all travel different distances even though they came from the same source. Trying to make sense of that would be a real mess.

But you could theoretically set up positional transponder beacons throughout deep space, which would be a very, and exponentially more expensive, project as the region of potential travel and mapping gets larger (in multiple dimensions).

You would know these kind of things if you got out and off planet more. I mean, you've hardly left your solar system at all, ever. The majority of 'space stuff' you have done is so far is within 120 miles of home. LOL.