ubiquitin,
Although I said I wouldn’t be posting anymore on this, the recent signs of progress in your understanding are encouraging, so I’ll give it one more shot. PLEASE, PLEASE, read slowly and carefully.
Let’s go to your meaty/milky example. If I redefine my seconds as only five sixths of the length of a real second, AND HAVE MY CLOCK TICK THESE NEW SMALLER SECONDS, then surely you agree that I may not yet eat milky when 6 hours are up on my clock, as in reality only 5 hours have passed. The fact that I have changed my second does not affect the halacha.
What I would need to do to in order to fix my problem (so that the true time I can eat milk will indeed be when six hours have passed as indicated on my new clock), would be to add a leap second every five seconds. Every time five seconds are up on my clock (which are only 5*5/6 = 4+1/6 real seconds), I would have to wait an extra leap second (of my kind of second, 5/6 of a real one) before ticking on again, in order that five real seconds should have passed while my clock still indicates “five seconds”.
This is exactly what is happening with the real leap seconds. The second since antiquity, and certainly the second of chazal, is defined as 1/86400 of a day, whatever the length of the day may be. Then scientists discovered that the length of the day is slowly changing, so they redefined the second to be a certain fixed amount of time. This redefinition does not affect the halacha, which still uses the old definition even though it isn’t exactly constant as compared to nuclear radiation. Since the length of the day has continued to change, the new second as defined by the scientists is now LESS than 1/86400 of a day. THIS IS THE NEW SECOND THAT OUR CLOCKS NOW TICK. Our clockfaces still have 86400 seconds to 24 hours, so with the redefinition of the second comes the redefinition of a day too! If we didn’t add leap seconds, in about 20000 years average midday would be at 3 o’clock in the afternoon on our clocks! Obviously this would be uncomfortable for people, so they add leap seconds every so often to keep atomic time in line with solar time. The time AFTER the addition of the leap second is the true halachic mean solar time that chazal meant.
When chazal said that molad to molad is 29.5 + 793/(1080*24) days, they meant halachic days, not the new days which are slightly shorter. The answer to the question at the end of your post is ABSOLUTELY YES. No matter how many leap seconds have been added over the 140 years, the time to say kiddush levana will be at 12:17:03 on my internet-connected clock. This is because the rules are that leap seconds are only added as necessary to keep atomic time in line with solar time. When we add a leap second, it means that the accumulated error of our clocks ticking the new atomic seconds, over a true solar clock, has reached a second, and we are CORRECTING for this. Please say you understand now!
(I won’t go back into the other tzad, as you seem to be having enough trouble with this one.)