To say the least, Luke's version of Jesus' ascension creates problems. He's the only evangelist who describes a definite departure of Jesus from the earth. (To put it in our terms: Jesus changes his zip code.) Luke's two gospel predecessors, Mark and Matthew, end their writings with the risen Jesus somehow still "out there" among us. Leaving out the 12 verses tacked on to Mark's original gospel, neither mentions a resurrection. Even John, whose Jesus ascends to the Father on Easter Sunday, returns to the disciples' upper room later that evening, and again a week later. Eventually he follows his disciples back to Galilee, appearing to seven of them while they're fishing, helping them haul in a miraculous catch of fish, and even prepares breakfast for them.
Luke actually seems to narrate two separate ascensions: one at the end of his gospel; the other, at the beginning of Acts. The first seems to be, like John's, a temporary departure; the second a permanent leaving.
Because of these contradictions, we're obviously dealing more with theology when we discuss Jesus' ascension than with actual history.
This ascension theology comes through clearly in today's second reading from Ephesians. The disciple of Paul responsible for this particular letter is trying to show his community the significance of everything Jesus did: his whole ministry, culminated by his dying and rising. It isn't that God simply resuscitated the historical Jesus. The risen Jesus is among us in a completely different form.
God, who has worked in Jesus, and raised him from the dead, continues that work by "... seating him at his right hand in the heavens, far above every principality, authority, power and dominion, and every name that is named not only in this age but also in the one to come. And he puts all things beneath his feet and gives him as head over all things to the church, which is his body, the fullness of the one who fills all things in every way."
In our gospel pericope, Luke's Jesus shares his/her risen uniqueness with his followers. "Behold," he promises, "I am sending the promise of my Father upon you . . . ." What Jesus once did, his disciples will continue to do. The Spirit will see to that.
Luke's emphasis on the presence of Jesus' Spirit in the community seems also to be behind his Acts narrative of Jesus' definitive ascension. From that point on, people who wish to imitate Jesus' faith must be instructed in that faith not by Jesus, but by one of his followers who is empowered by the Spirit. Paul's conversion gives us a great example of this process. Though the risen Jesus personally appears to him on the road to Damascus, Paul still must receive instruction and baptism from Ananias before his conversion is complete. (Couldn't Jesus have finished the job himself before Paul ever went through the Damascus city gate?)
Luke's Jesus really means it when he proclaims, "You will receive power when the Holy Spirit comes upon you, and you will be my witnesses in Jerusalem, throughout Judea and Samaria, and to the ends of the earth." Besides giving us the geographic outline of Acts, the evangelist is also presuming Jesus' followers are now taking over Jesus' ministry. In a theological sense, Luke must "get rid" of him before they can step in and do his work.
If we look at today's feast as just one final step in Jesus' ministry, we're really missing the part we play in that ministry. It's now our faith that people are expected to imitate; our lifestyle that people are expected to copy.
Knowing this, perhaps it would be better for some of us if Jesus never ascended.