of course absolutely true as i said above i could also construct a family of reasons for each of these more and more elaborate explanations increasingly detailed and complicated and byzantine rube goldbergian mechanisms however science has other requirements as well such as parsimony predictive success and of course most of those alternative explanations will fail those and other requirements it certainly can be amusing to try to construct alternative theories to explain this evidence and amusing to try to come up with more evidence it is all good mental exercise i would commend to anyone how many scientific facts observations pieces of evidence can one come up with to prove the earth is round i use prove loosely here since there is no proof in science only in mathematics and logic one caution i have is that some of these explanations are clever some are just silly like saying the earth is not warmer now than it was years ago however the measurements are the measurements and even when all kinds of corrections are taken acount of the temperatures now are warmer than they were years ago done using thousands of instruments of different types in different locations by different people who got consistent results incorrect theories are bad enough but bad data is fatal as to your other questions it is easy to measure the earth's free oscillations with a weight on a spring it is done all the time and has been done for decades and they have very characteristic temporal and spatial frequencies corresponding to oscillations of a rotating sphere a bit hard to wave your hands to make those observations go away you might be able to do it if you were really an excellent applied mathematician and willing to spend a few months in crazy speculative inverse theory computations currents of course are possible but these are very special kinds of currents that have special kinds of characteristics that match what one would expect from a fluid on a rotating spherical earth i have personally seen the curve of the earth when standing on a very high point now of course it could be an optical illusion but it is a very compelling one if it is however you can put it down to refraction or some other optical effect in fact you could even put photographs of the earth from space down to those as i said above and you nicely demonstrated my point you can explain almost anything away and maintain some pre conceived notion if you are willing to throw away parsimony and the demands of prediction etc