There is an image of "Earth at Night" that circulates widely--perhaps you've seen it. If you think there is something unrealistic about this image, you're not alone. The reason for its perceived unrealistic quality is the fact that it is a digital composite. Composites combine and vertically "stack" multiple images, a process which enhances the detail of the phenomena or object being viewed.
When I was home at Christmas, my father and I had a spirited debate about the extent of lighting revealed realistically in that image. He pointed out that even small cities are distinguishable as dots of light in the image, something that he regarded as certainly impossible to detect from space.
Is that impossible? And is the "Earth at Night" composite realistic? Or is the composite process in effect a form of doctoring a photo?
To get to the bottom of this, I think it's necessary to specify what attributes we mean by "realistic" as opposed to "doctored". To that end, I'll offer this opinion: we can say that the "Earth at Night" image is unrealistic insofar as it does not represent what a human being could see with the unaided eye at a single time and single field of view.
However it is realistic insofar as those little dots of light are not simply "colored in" by some person playing around with Adobe Photoshop--they are the recorded photons captured by cameras using time-exposure photography and other techniques. (These other techniques include creating a 'mosaic' of the entire Earth from smaller photographs, each one cloudless and night-fallen).
That leaves us to wonder, though: what would the Earth actually look like to the unaided human eye from Earth-orbit? Finally it's easy to find out, thanks to astronaut Don Pettit, a member of Expedition 6 to the International Space Station. He presents this video: Cities At Night, an Orbital Tour Around the World. It's about 10 minutes in entirety; if you don't watch the entire thing, it's worth at least checking out the first minute or two!
1 comment:
It's a cliché in our time to be pessimistic and negative about technology. And even though I think that much of the lighting which is holding our cities and suburbs celestially barren is senseless and deserves disapproval, if for no other reason than for saying something new I'd like to say that I find the fact that you can see the lights on Earth from space an inspiring tribute to human ingenuity, that attribute, after all, that makes our survival and our happiness possible.
Post a Comment