Above And Below

Why was Moshe the one to serve in the Mikdash for the first 7 days (Rashi 8:28) and only afterward did Aharon take over?  Why for the first 7 days was the Mishkan taken down every day but only after the 8th day did it last?  

The Mishkan is an other worldly building meant to bring the presence of the Shechina down into this world.  It does not fit into the natural barriers of the world.  The first 7 days of the inauguration where to adjust the Mishkan to this world.  That is why it was 7 days, the complete cycle of a week of nature.  That is why the Mishkan needed to be taken down every day for it did not fit within the order of nature.  It took the power of Moshe Rabbenu, who was always connected to the higher realms to be able to connect the Mishkan to the world.  Only after the first 7 days did the Mishkan now become incorporated into the nature of the world (not that the Mishkan became lower, but that nature was elevated to be able to contain a Mishkan.)  Now, on day 8, the day that is above teva, meaning not that teva was broken but rather teva was expanded and elevated, can the avodah be given over to Aharon to do to the avodah on a daily basis.  Moshe has to serve the first 7 days because at that point the Mishkan can not fit in the world without the avodah of Moshe, who is simultaneously connected to this world and above.  Then the super natural Mishkan can become incorporated into the world (based upon Shem MiShmuel 5671, see also Sfas Emes 5639, Imrei Emes Shemini Atzeret 5761.)  

That is why on Yom Kippur the sprinkling is 1 +7, the above teva, 8th sprinkle gets incorporated into the teva.  The אחת למעלה unites with the שבע למטה.  The teva expands to include that which is beyond it.

וירד מעשת החטאת והעלה והשלמים.  The Apter Rav says this hints to the idea that even the great leaders who are busy atoning for people and raising the worlds to higher levels have to at times go down from their lofty thoughts in order to connect to people.  But this going down leads to greater heights.  The above teva becomes etched into the teva.   

החדש הזה לכם.  Nissan is the time of great miracles, it is a time ripe for above nature revelations.  However, even great miracles have to become incorporated into the boundaries of time.  We incorporate the miracles to fit into nature by elevating our nature.