Photography becomes art when it becomes unphotographic.
"Post processing" refers to what you do to your image files after you retrieve them from your camera and put them on your computer. For some, this means tweaking the image to make it as "photographic" as possible. Sharp focus, extreme detail, accurate color, contrast, exposure, low noise, and so forth. You get the idea.
For me, what comes from the camera is just the starting point down a path where the end is not always in sight. The example below shows just how far off the beaten path this quest can lead.
We'll start with the first photo, taken with my trusty Panasonic DMC-FZ5. It's a photo of the stairway at the Phillips Collection, an art museum in Washington DC. Then we'll follow its progress until it becomes something out of a science fiction movie. And you'll see where the title for this article comes from.
And that's how it was done. A trip from the stairway to the stars.