I have been wondering, maybe some one could enlighten me as to the answer I have been looking for. I have googled, but I am after a more direct answer to this question.
If light takes X time to travel a distance, and some of these distances are so vast it would take so called millions of years for that photon to travel, how can we possibly have measured that since our technology really has been good enough in the last 20 - 30 years to get any real accurate measurements?
The other problem I have with the question is if we don't send the original light emission for the bounce back how can we possibly be sure what data we have is even remotely accurate?
If we can't be accurate or the data is corrupted due to false or innacurate data collection how can we truely know where we are for accurate space exploration beyond our region of viewable space (our set of planets, not the Milky Way as a whole) as we could not possibly guage the speed at which we - the Earth or the opposing planet - is actually travelling or rotating axis based on their own centre of galaxy or orbit>?
Is there an answer for this, or am I thinking about this way too hard?