Is There Evidence from Space of Man on Earth?

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!

February's Lunar Eclipse: Report

The next lunar eclipse visible from North America won't occur until December 2010, so hopefully you got a chance to see this last one in February.

Sadly, here in Orange County, California, it was cloudy for most of the event. However, at one point just before the Moon completely entered the centermost, reddish portion of the Earth's shadow, the clouds broke at my location and I was able to watch the eclipse for about five minutes. So I was reasonably happy with that.

Apparently the northern part of the county, as well as Los Angeles County, had somewhat better conditions. Here are some images taken by members of the Orange County Astronomers in those locations:

Lunar eclipse in Fullerton, taken by Cor Simons.

Lunar eclipse and the Queen Mary, in Long Beach (L.A. County), taken by Wally Pacholka.

Lunar eclipse mosaic, very nice! Taken from Cerritos (L.A. County), by Dave Kodama.

Astronomy Picture of the Day can usually be counted on to post some of the very best images from around the world of each astronomical event. I liked this one, which demonstrates the snowflake principle in effect: no two eclipses are exactly alike! And this photo, although a composite, in my opinion does justice in capturing the effect of a darkened moon and the resulting stars that become visible around it. (To appreciate this, you have to be an observant enough skywatcher who's familiar with the view we normally have of a (non-eclipsed) full Moon: it's so bright that it completely drowns out the majority of stars around it).