The celebration is all about Jesus taking his leave of the disciples at the end of the forty days following his resurrection. During those days he has by turn astounded, comforted, admonished and encouraged his followers in a range of, often brief, appearances. There are two accounts by Luke, one in his gospel and the other in the Acts of the Apostles. And here lies the problem for modern readers - the accounts of the Ascension.
There is a remarkable contrast between the accounts of the resurrection and these accounts of the ascension. The disciples were convinced that Jesus had risen from the dead because they encountered him in a variety of ways and on a number of occasions after his death. These meetings persuaded them that Jesus was not dead but alive. This faith, this experience of Jesus, has been handed down by Christians from generation to generation up until today. Each generation of Christians has interpreted and understood the resurrection in its own way and in ways that make the experience of the risen Christ accessible and understandable. The reason that they have been able to do this is because there are no accounts of the resurrection itself. The resurrection had no witnesses. The post-resurrection stories are descriptions not of the resurrection itself but of the disciples' experiences of the risen Christ. Christians throughout the ages, and Christians today, have been able to describe their own experiences of Jesus as the one who is alive and they are able to validate those experiences by comparison with those of the first disciples.
By contrast we have a very vivid account of the ascension. In Acts 1.9 we read,
As he said this he was lifted up while they looked on, and a cloud took him
from their sight.
and in Luke 24.51,
Now as he blessed them, he withdrew from them and was carried up to
Theologians have argued whether these words describe the same event (Luke's gospel has the ascension taking place on the day of the resurrection, in Acts it occurs forty days later; many ancient texts omit the words "and was carried up to heaven," perhaps in an effort to avoid the problem) but there can be no doubt that the two passages both describe a physical ascension of Jesus into heaven.
These accounts of the ascension create problems for us today. There is, to modern eyes, something ridiculous about Jesus being taken physically up to heaven in a cloud. The image conjures up for us the thought of Superman soaring into the sky to save someone in peril. Indeed, artistic representations of the ascension are all slightly absurd, and as a result relatively few. The physical image we have tends to get in the way of our understanding of whatever the truth is of the ascension.
Hence, I think, the decline in observance of Ascension Day.
But there is an important truth about the ascension. The ascension offers closure to the first disciples and allows those who follow them in the faith the opportunity to feel that our faith can be validated by our own experiences of Jesus.
For the first Christians the experience of the risen Christ was a powerful and profound one. Having spent time with Jesus during his itinerant ministry in Galilee, and later in Judaea, and having witnessed his presence as one who is alive among them after his crucifixion and resurrection, they are now able to start afresh. The ascension and the later pouring out of the Holy Spirit at Pentecost inaugurate a new beginning for them. Now they are not simply disciples of Jesus but the Church. Now they are not observing and sharing Jesus's ministry, but they have one of their own. As long as they felt Jesus was with them they would look to him of leadership, inspiration, authority and validation; now they must find that within their own community.
The ascension changes the dynamic of the early church. No longer waiting for the new age to begin, but the creators of it.
And for us? Because Jesus took his leave of the apostles and first disciples we find ourselves in the same situation as them. Builders of the new age. We have the same ministry as them and the same resources as them - our faith, the gift of the Holy Spirit, the experience of Jesus as the one who has died but is alive.
The image of Jesus soaring into the heavens may not be helpful, but the fact of the ascension is central to our experience of what it is to be a Christian today.