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sbisson at 04:55pm on 07/05/2002
sbisson at 04:55pm on 07/05/2002I was doing some thinking about the Big Fermi Paradox Space Opera idea I'm playing with (those who've heard me discuss the Deepships idea will know the story I'm talking about) at lunchtime, and realised I'd completely lost a whole pile of mathematical knowledge. While I can design architectures for complex web systems, I don't seem to be able to recall how to calculate how big a 65km long artifact in a 100 Km orbit will look...
Especially as I need to think of it in terms of spherical geometries. I've worked out that it will cover 32 degrees of sky when viewed from the equator using simple trig after a quick web refresher (and some emails with Charlie), but the tricky bit is trying to understand how big it will look when viewed (for perfectly valid plot reasons) from the Canary Islands. I think it will still be a "chicken little" moment for the characters though, especially as the artifact was an asteroid only a few minutes before.
I'm now thinking if one of these shareware/freeware 3D astronomical viewing tools will help me out. I remember looking at one a while back that allowed you to place viewpoints and objects anywhere, and that handled most of the 3D graphics formats around.
But I'm still left wondering what happened to my mathematics O-level...
Especially as I need to think of it in terms of spherical geometries. I've worked out that it will cover 32 degrees of sky when viewed from the equator using simple trig after a quick web refresher (and some emails with Charlie), but the tricky bit is trying to understand how big it will look when viewed (for perfectly valid plot reasons) from the Canary Islands. I think it will still be a "chicken little" moment for the characters though, especially as the artifact was an asteroid only a few minutes before.
I'm now thinking if one of these shareware/freeware 3D astronomical viewing tools will help me out. I remember looking at one a while back that allowed you to place viewpoints and objects anywhere, and that handled most of the 3D graphics formats around.
But I'm still left wondering what happened to my mathematics O-level...
frustrated
So how big *is* 32 degrees ....
Found here on Space.com
So I reckon that if a fist is 10 degrees, then the size of a 32 degree object should be about the size of a shoebox at arm's length (or perhaps a better example would be the size of your computer monitor at the normal working distance, if you don't have a big screen like this one!)
Definition of terms ...
1) circular orbit, with a radius of 100km
2) same but with a diameter of 100km
3) same but with a circumference of 100km
4) same but at 100km above the earth (or whatever)'s surface
Also, how far north are the Canaries? Do you have to allow for refraction through the earth's atmosphere (the stuff that makes the moon so much bigger at moon rise and moon set could be wonderful when applied to a space craft)
So let's think about this another way ... lying on your back in a field with no buildings, the world appears flat, which basically means you can see 180 degrees above you if you don't move your head (and depending on your peripheral vision and whether you're wearing glasses, possibly a fair bit less) so 32 degrees would be 1/6th of the sky.
I've just done a quick test with my glasses and my fist and I reckon that I can get seven fists (so 70 degrees) without moving my head using one eye and that adding the second eye actually only extends my field of few by another 10 degrees so that using binocular vision I reckon that I only get 60 degrees of visual coverage and that both this monitor and that space craft would actually fill half of my binocular field of view.