I spend a lot of time looking at the sky these days. When you look up, you see the border between "here" and "not here" is invisible. Where do you cross that line and suddenly find yourself "no longer here"? But when you see a cloud, it suddenly makes "not here" seem much more noticeable.
I think Ascension Day is a holiday that is sorely neglected. Of all events, this one should help us see this distinction much better. According to sources, Jesus spent about 40 days with his followers after his resurrection. Then, while they were standing with him, he - that is, he and his physical body with the wounds from his crucifixion - rose up and up into the sky and left their sight. Here is no room for neo-platonic separation of (good) spirit and (evil) matter - spirit and matter rose into the realm of God as a unity.
The man who stands in for us - he and his body crossed that border and went up next to the creator of everything anywhere and sat down next to him - he still sits there now with the same wounds from his execution, reminding us every moment that true love is eternally stronger than death, for true love seemed to tear up all our biology and chemistry teaches us about what happens to a life form when it "dies." Yet true love is also the author of all the real rules of biology and chemistry that we will never excavate entirely.
In the western (that ist, between Roman Catholic East Europe and westward) Christian world, we see many crucifixes - Jesus suffering on the cross. But that leaves us standing in Good Friday waiting for what comes next.
The earliest Christians had it right; in their catacombs in Rome they gave us "graffiti" not of Jesus suffering on the cross, but of Jesus, the Lord of all the universe, reigning with all power. They knew what they were about to see when they closed their eyes the last time - the blood had already flown, that was over. They were about to see the real ruler of all. Ascension Day reminds me, at least, that it is not death but life that enters into the ream of God, because true love is stronger than death.