Visible items from outer space?

Cecil seems to think long thin things like highways, canals and Great Walls would be the most visible man-made objects from space. I would offer the largest man-made lakes, such as Powell, which would reflect much more light than a narrow highway, and could be the first thing that come into view as one approached the Earth would be one of these lakes. What does visible mean anyway – a few photons/sec, recognizable color spot, identifiable shape, type of object deduceable? When no definition of the question is given, any old answer is good enough.


Link to Cecil’s column, edited in by CKDext, Admin: Is the Great Wall of China the only manmade object you can see from space?

[Edited by CKDextHavn on 07-14-2000 at 07:09 AM]

Well, visible in this context generally means recognizable by the nekkid human eye. If you can point and say “that’s the great wall of China” then it’s visible from space.

As for manmade lakes, I believe the column was referring to manmade structures, and a lake probably doesn’t count as a structure. It’s the result of a structure :slight_smile:

Welcome to the SDMB, and thank you for posting your comment.
Please include a link to Cecil’s column if it’s on the straight dope web site.
To include a link, it can be as simple as including the web page location in your post (make sure there is a space before and after the text of the URL).

Cecil’s column can be found on-line at the link thoughtfully provided by my esteemed colleague CKDextHavn.

The column (including Slug Signorino’s illustration) can also be found on pages 92-95 of Cecil Adams’ book “More of the Straight Dope”.

Does the hole in the ozone layer count?

I think that falls under the category or man-made lake, i.e. it is not a structure.

What I am wondering about is the international space station, currently under construction at KSC. On the tour, we were told that the space station would be visible from earth. Then wouldn’t the station while still on earth be visible from space? What about the building it is being assembled in (since that would be bigger than the station itself)?

Did they say the station would be visible with the unaided eye? A lot of these discussions revolve around the method you use to look at something.

On the other hand, the station might be “visible” as a “star” at dusk and dawn as sunlight reflects off its surface when the actual shape and outline could not be determined without a telescope. There are a number of satellites that are visible, even though they are only 20 feet, or so, in diameter. No one could identify any part of them without a telescope, but they reflect sunlight very well.

And, of course, for any of these questions, “what is space?”

Is a low Earth orbit space? Then a number of man-made structures can be seen. Do you have to be halfway to the moon to be “in space”? Then far fewer, if any, structures can be seen.

 A couple of big problems here:

 First, a structure in space can be visible when *FAR* smaller than the reverse situation. In space, it will be a point of light against a dark background (assuming the correct viewing conditions--night, but the target still in daylight.) Seeing the point of light at the correct spot at the correct time is sufficient for identification.

 Second, to add to the problem, the station is being *BUILT* in space, not on Earth. Pieces that are small enough to fit on the shuttle or the big Russian booster whose name eludes me at present are built, sent up and fastened together.
 Not only do we not have anything powerful enough to lift the whole thing, it is not possible to lift it even with a sufficiently powerful rocket--it would fall apart. Structures in space do not need to resist gravity, there's no need for such heavy engineering unless there's some other force involved (ie, the walls still need to be strong to hold air pressure.) Parts of the shuttle itself aren't even capable of functioning on Earth--the bay doors and the arm are both too weak to use in gravity.

I have seen the russian MIR several times with my naked eye at dusk crossing the sky slowly (or very fast, depending on how you look at it) overhead. It is just a dot like a star so what I am seeing is some reflected light. If I were where Mir is I doubt I could see a truck on earth.

As for what you can see from space, you can see the light of the cities at night. I recently saw two very impressive graphics made with photos taken from space. One was the USA and you can see the shape and all the cities perfectly. The other one was of Europe and it was the same. This was less than a week ago, now (of course) I cannot find the link for the life of me. I recall vaguely it might have been some site about weather satelites. Maybe someone can find it… now I am going nuts trying to find it

sailor, see here for a variety of nighttime images from satellites. It has images from all continents at both high and low resolutions.

dtilque, thanks, those are not the ones I saw but very similar.

Thanks and a tip o’ the hat to Dtilque for a nifty website, which I have now added to my Favorites.

One question–on the Earth at Night map, it looks like there’s stuff lit up where there isn’t really a city, like two big bright dots northeast of Vancouver. I didn’t realize British Columbia was such a hot destination. Are they showing snowfields or something, besides just electrical lights? I notice the north polar ice cap is brilliantly lit up, too, but not the south.

Just wondering.

The spots NE of Vancouver look like they’re about right for Calgary and Edmonton.

The bright stuff up north is the Aurora Borealis.

I am writing a dissertation and included the fact that the Great Wall could be seen with the naked eye from earths orbit. What a dumbass I felt when I bothered to check my facts and discovered that it was untrue! Anyway, there is another rumour going around that Chep Lap Kok airport in Hong Kong can be seen with the naked eye from a jet in the outer atmosphere. Could this be true? The airport is so new that I couldn’t find any info on this.

Page doesn’t work for me - says it can’t be found. Is it just me? :frowning:

By the way, not only is the ISS visible from Earth, but under the right conditions, it’s actually brighter than Venus, putting it into third place in the sky.

But no, you can’t resolve any detail.

dantheman - if you’re referring to dtilque’s link, then with a little initiative you can find the pictures.
Try here.

wiz, if “space” means low Earth orbit, then the Wall is visible (at least parts of it). If “space” means the Moon, then no. Points in between vary depending upon how far.

As far as the airport, do you mean the whole airport, or the terminal building? The terminal building is 1.2 km long. I’m sure that is visible from low Earth orbit, much less high atmospheric planes.