<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I really appreciate the information. However, one thing I wanted to know more about is that moons calculation can vary right (for example if you change the reference point). So in that case, how would you be sure and saying with 100% certainly that moon can not be seen. It actually did happen a couple years back when an organization changed their reference point in the calculation, for which they had to change their already published calender, on a few dates.Also, we know that every scientific theory is based on a probabilistic model for its accuracy or occurrence. That is why every single scientific theory, when it is proposed, is verified with model studies or model fit with real life data. Only after that, the theory is published. Typically from what I have experienced and heard, scientific journal and the scientific community will not value much a theory, when presented just as a theory. Only after extensive validation, the theory gains credibility. And on top, even after extensive validation, no one denies that the basis is still on a probabilistic model. Meaning, a scientific theory does not confirm with 100% certainty. It could be say 99% probability of occurrence, but that 1% chance still remains. On top, that 1% chance really does not mean that out of 100 times, only 1 chance of odd can happen. Rather, that 1 chance can happen even in the very next occurrence, and much more, can happen again consecutively on two occurrances. I am not sure if I am able to explain well here. For an example, although unrelated, we had two 50 year rain events in San Diego on two consecutive years, a couple years back. It does not mean that the 50 year flood calculation is wrong, however, it also does not mean that the calculation is decisive. What is decisive is a real life event, in this example, it was the actual rain that was observed and measured. To make the analogy complete, in this case, isnt an actual visual sighting a confirmation with 100% certainty, which may actually happen based on the above discussion (I am assuming the person who said he saw the moon did not lie, because that will end the discussion right there). It is hard to believe that a person after fasting for 29 days, cannot fast one more day.Oh, I also found a beautiful photograph taken by an amature astrophotographer, which shows the moon crescent, venus and mercury (the one on the left of the chimney about mid height, you really need to zoom up to see it). I though I'd share it here. <br />Posted by Shaheed</DIV><br /><br />My calculations were based on San Diego on the night in question. My astronomy program allows me to set the location and time easily.</p><p>In this case, it is not theory, but easily reproducable calculations of the positions of astronomical bodies. They are extremely precise. Not perfect, but good enough that any difference would be too small to see witrh the eye or ordinary telescopes. I can say with 100% assurance that what I posted is correct.</p><p>Weather is much different. It is a chaotic process, based on using models whose input is imperfect to begin with. It's a much more difficult problem, and the output from the models are quite imperfect as well. Odds are very important in weather forecasts since it is an imprecise process.</p><p>That is not the case for the motion of the planets or the moon for periods up to hundreds or thousands of years.</p><p>If you go to millions of years in the future or past, the tiny measurement uncertainty that exist can make a measurable difference.</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>