http://www.churchyear.net/ascension.html
Frequently Asked Questions
1. Isn't the Ascension of Jesus based on Outdated Science?
This question is not about the Ascension holiday per se, but related to the truth of the historical Ascension. However, since belief in the ascension is directly tied to celebrating its feast, it should be addressed. Some theologians and philosophers have claimed that modern people cannot believe in Jesus' ascension, because the story assumes the outdated science of a "three-tiered universe."
It is true that many Biblical authors likely perceived the universe as three-tiered, in which heaven is spatially "up" above a sky dome (and hell is below the earth). Luke may or may not have had this cosmology in mind when writing about the ascension. Even if he did, this does not discount the truth of the ascension. What ultimately happened at the Mount of Olives that day was that Jesus returned to the Father, to a reality that is outside of space and time as we know it. Assuming this return was miraculous, it likely wasn't a spatial/material act at all. It was an event above human perception and explanation. However, the witnesses had to render the event in terms they (and we) could understand, using the tools, knowledge, and science of the day (as we would do as well; we can hardly be expected to explain events in terms and frameworks beyond those of our day!). As such, the miraculous event was recorded as a spatial ascension, because we humans live within space-time, and conceive of reality spatially and temporally.
These ideas owe a debt to C.S. Lewis. In a 1942 sermon, Lewis described the Ascension as:
…a being still in some mode, though not our mode, corporeal, withdrew at His own will from the Nature presented by our three dimensions and five senses, not necessarily into the non-sensuous and undimensional, but into, or through, a world or worlds of super-sense and super space. And He might choose to do it gradually. Who on earth knows what the spectators might see? If they say they saw a momentary movement along the vertical plane - then an indistinct mass - then nothing - who is to pronounce this improbable?" (God in the Dock, p. 35; also see "Horrid Red Things," in Ibid. pp. 68-71)