I was going to write a lengthy comment, but accidently clicked another link researching for it when it was almost finished. Here's the condensed
1. A satellite with a webcam that would fit the entire planet in frame (like
, thanks AmoebaSized) would be a long way
away. In fact if you have a look at that image, you'll note that it shows a view from roughly 35,750km above earth. To put even a small satellite
into geostationary orbit at that altitude would cost a LOT of money. Would it be possible? For sure, but NASA or any other organisation are never
going to do it because...
2. It would be incredibly boring. You know when you're on a long haul flight and they have an image of a map displayed, with your plane tracing a
route over it as it flies? And how it hardly ever seems to move? Well that'd be a lot more exciting than looking at Earth. You do remember that it
takes a full 24 hours for the Earth to complete a full rotation. You would have to watch it for a long time before you would be able to tell it has
moved, and even then, you wouldn't have noticed because it would be so gradual.
3. Satellites whizzing past? Watch it 24/7 for months, maybe years and it might happen once or twice. Think about the scale of this... the diameter of
earth is about 12,750km. Halve that to get the radius (6,375). Add that to the altitude of the satellite (6,375 + 35,750) and you have 42,125km. Do
you remember doing Pi at school? Well to work out a circumference of a circle you first multiply the radius by 2, then multiply by Pi,
3.14159265358979323846 and on and on and on.
To save you scratching your head too much, here is the answer: The satellite would be on an stationary orbit in a circumference 264,679km long.
That's a lot of space it's not covering. And that's only on a two dimensional plane.
3D (looking at a sphere, not the edge of a circle) would make the area the satellite can see appear miniscule. It would only see maybe 1m2 of a total
sphere surface area of 22,299,221,004km2. (Here
is the site I used to calculate this, try it
I can't actually find something that will calculate that as a percentage, someone who is better at maths than me, please step in. Also check me on
the rest of my maths, I'm a bit out of practice.
Sorry, but I have to throw a little more maths at you. Probability. Probability of some object of interest entering that relatively miniscule area of
coverage, and close enough to actually see it... Well you get the picture.
And lastly, please, please, please don't take this as me being nasty. I just wanted to highlight the truly immense distances and show that the cost
of putting such a satellite would never be justified.
[edit on 23/1/2006 by 4for4]