We've got exactly the same thing happening here in the U.K. British Telecom has been told by our telecomms regulator (OFTEL) to open up the local loop to competitors, but it's dragging it's heels. And since OFTEL doesn't exactly have a huge amount of power, the situation isn't changing too quickly.
Add to that rumours and allegations of stuff like BT giving it's own (not particularly big) ISP the lion's share of DSL connections while the two biggest ISPs in the country get a pathetic fraction of the broadband lines (AOL and Freeserve), and I guess a lot of people are going to be waiting a long time for broadband on this side of the Atlantic too. And seeing as I live in a fairly rural area (as rural as anywhere in the West Yorkshire conurbation gets anyway), I guess I'm not going to see any high speeds at a reasonable price for my home machine for several months yet.
Awww, I mixed up geosynchronous and geostationary. Doh!
But surely the altitude of the satellite is arbitrary. If it's higher then it needs to travel faster (speed proportional to height) to still orbit the planet once each day. See my other posts for the maths.
Orbit at exactly this altitude? Why? Let's see now:
Using your figures of a 23 hour, 56 minute day and 35785 km the speed (note; not the same as velocity) of the satellite =
2 x pi x (35785km + radius of Earth) / 23.933 h
The radius of the Earth is about 6370 km (see here for info), so the speed of the satellite is:
2 x pi x 42115 km / 23.933 h = 11067 km/h
Now, suppose we put a satellite at, let's say, 43630 km from the surface. Gravity still works at this height. So you can still put an object in orbit. And suppose we set it moving in an orbit parallel to the lower satellite at a speed of, ooooh, about, 13127 km/h. What then?
Geosynchronous orbit is simply keeping the satellite over a particular point on the ground (as I'm sure you're aware). Or in this case we simply need to see if we can keep pace with the lower satellite (using your figures).
Let's think of an analogy - two runners going round a circular circuit. One runner gets an inside lane, and the other gets the outside lane. But the outside lane is longer (the radius is bigger) than the inside lane, so if the outside runner wants to keep pace with the inside runner he has to run faster. The speed he has to run depends on the circumference of his track - the ratio of his speed to the inner runner must be the same as the ratio of his track length to the inner track length. And because it's a circle, we can simplify that ratio to Radius(outer):Radius(inner).
Now, let's return to our satellites - suppose yours and mine start above the same point on the Earth, and we know that yours is geostationary. If mine manages to travel faster than yours around it's larger orbit then it will keep pace with yours and stay geostationary.
The ratio of distances from the centre of mass of the Earth is (43630km + radiusEarth):(35785km + radiusEarth) = 50000:42115 = 1.187:1
So my satellite needs to be moving 1.187 times faster than yours - 11067km/h x 1.187 = 13136km/h, which is pretty damn close to the speed I specified above (accounting for rounding errors). Why, it's almost like I cheated.
Essentially, a geosynchronous orbit can be achieved at any altitude, but it must be over the Equator (as I already explained to someone else) and the speed that the satellite must move is directly proportional to the altitude.
Please don't believe everything you find on Google - try doing the maths yourself first.
Ahhh, talking at cross-purposes; don't you just love it? I figured that it was implied that the satellite needed to be over a single line of logitude, but my point was that the only place where this is possible is over the Equator.
[Start poorly worded explanation] Y'see, a satellite's orbit has to be the centre of mass of the object it's orbiting - that's just how gravity works and I'm not really enough of a Physics expert to start explaining why.
So you couldn't, for example, have a satellite orbiting directly above the Tropic of Cancer, because the tropic is off to the North of the centre of the Earth. You could have one that orbited between the tropics, because then it'd be orbiting the centre of mass of the Earth again.
However, this isn't a geosynchronous orbit. Obviously there's the North-South variation in relative position. But this wouldn't stay over the same line of longitude either. The satellite would have a constant speed. But the surface of the Earth at the Equator would be moving at a different speed (relative to the satellite) than it would be at one of the Tropics. It works like this:
Circumference @ tropic = 2 pi Rt
Circumference @ Equator = 2 pi Re
where Re ~= 1.5 Rt (ratio of 1.5 just plucked off the top of my head to make the sums easier, but it should be clear that the radius of the Equator is larger than the radius of a tropic).
therefore Circ @ Equator = 2 pi (1.5 * Rt)
Now, each rotation of the Earth takes 1 day. For a line of longitude (say, the Greenwich Meridian) to move through this arc in a day it has to move at 2 pi R / 24 m.p.h.
Since the circumference at the Equator is bigger (1.5 times in our example) the Greenwich Meridian moves 1.5 times faster at the Equator than it does at the Tropic.
Still with me? OK, now remember that our satellite has a constant speed. To make sure that the satellite's average position is geosynchronous, it's average speed needs to be equal to the average of the speeds at the tropics and Equator (and adjusted for it's greater distance from the centre of mass, but this is a secondary issue that I'm going to ignore for the sake of clarity). Which would leave the satellite tracing a vertical figure eight over the surface of the Earth, with the crossover point over the Equator, the top and bottom over the Tropics, and the bulges equidistant from the tropics and the Equator.
And that's obviously not truly geosynchronous, even if the average position of the satellite is. The further away from the Equator you start, the more distinct this figure of eight becomes. In theory, even satellites that are considered to be geosynchronous are actually tracing tiny 8s.
The Equator is the only division between any two hemispheres that's truly parallel to the rotation of the Earth (or orthogonal to the rotational axis, depending on how you think about it). And that's why geosychronous satellites have to be placed directly above it.
[End poorly worded explanation]
Thats all well and good. But these measurements mean nothing to me since they are in imperial. Most of the world uses metric, most science projects use metric. Why not this?
There's no particular altitude that needs to be used for geosynchronous orbit. The only limit is that the satellite must be over the equator. You could, in theory, have a satellite orbiting the Earth further out than The Moon. The only problem is that the speed that the satellite needs to be moving at increases proportionally to distance from Earth (i.e. double the altitude, and you need to double the speed - 2 pi R t^-1).
However, there's various vague orbits that are typically used for practical reasons (cost to launch, power, inverse square law etc.). Generally, you'll hear about:
Low altitude orbits - these don't require as much broadcast power or cost as much to launch, but are close to the top of the atmosphere (particularly when it expands in summer) and can slowly get dragged back down to Earth.
High altitude orbits - cost more to put up and the inverse square law means they need more power (include Tim Allen grunt here), but they're less likely to come crashing back down onto Fiji (or wherever) in a few years.
And yes, you're right, there's a lot of satellites already up there because it's so much more convenient to have your satellite in a fixed position in the sky (relative to the ground). Of course, IANANASAE(ngineer), but that's the basic issue with orbit altitude.
Um, wait a sec, the flakes would contain DNA wouldn't they. Um, but, uh.....
[/me cautiously backs towards the door] ....Y'see, the sugar-frosting DNA would, uh, mix with the corn DNA, and....
SLAM! [sound of/me running to car, starting engine and peeling away at speed]
I think curling should still count among the more traditional sports - it relies on physical skill just like sprinting, weight-lifting, cycling etc. Only difference is the type of skill it requires, but there's plenty of non-endurance/strength based categories e.g. figure-skating, acrobatics (applies more to the womens side of the sport), synchronised swimming. I know that you've got to be way fitter than, say, me to do these sports, but they're more down to co-ordination than brute strength.
Of course, curling is kinda a minority sport, and one of the weirder ones they've included.
Chess, on the other hand, is in a totally different league - it's solely reliant on mental ability. A quadraplegic could play it as well as someone with full use of their limbs. This isn't true of any of the other sports (AFAIK). Quake would still require fairly physical skills, so I wouldn't count it as the same sort of game. I'd still love to see it as an Olympic sport though:)
I dunno. I mean, that's gonna take an awful lot of batteries, and AFAIK Lego don't make any launch kits. And I wouldn't have thought the little connector-bumps (do they have a technical name?) would be all that aerodynamic. And what if you want it back - re-entry's going to be a bitch on the plastic.
So you're suggesting they put up the old box and make it viewable again.
And then maybe post the news as a story on the main page.
And include a link so that we can all go look at what it used to look like when the number of visitors was in the order of about 10^2.
Hmmmmm......
I'd also like to suggest that they set up a webcam pointing at the old box, so that we can all watch it burst into flames and be totally beyond repair thanks to a heavy slashdotting starting moments after the link to it is posted, as it tries to handle thousands more hits than it was ever designed to take.
Kinda like a viking funeral, only without the boat.
Dude, it's going to be years into the future. I'm not going to plant them - I'm going to clone them.
Or, rather, I'm going to sell them to someone else (Kelloggs, whoever makes cornflour, Green Giant etc.) for a vast profit and let them bother with the cloning. I'll just pop in occasionally to make unhelpful comments - "Maybe you should try repairing the freezer damage to the chromosones with frog DNA..."
Ooooh, or now I think about it, I could just buy tinned corn and then I wouldn't have to worry about keeping the freezer running.
Awwww, damnit, I really need to stop telling everyone my ideas...
Valuable advice from the future
on
Windows in 2020
·
· Score: 3, Funny
I'm going out today to buy various samples of corn and freeze them. Then when the blight hits I'll be the only person who still has corn. Kelloggs will pay $billions!!!!
Perhaps I'm off the mark a little way, but I thought what the original poster was saying was that Red Hat is comparable in terms of user-friendliness to Windows (this was in response to someone asking what'd be a good starter distro after all). I'm sure no-one here could equate Red Hat's business policies with those of the Redmond monster.
Similarly, Mandrake (my personal choice, because although I'm not afraid of the command line I'm too lazy to get to know it beyond occasional use of gcc, ls, ps aux and kill -9) is comparable in terms of GUI to Mac (at least compared to other Linux distros). Etc. etc.
The problem with the internet is that where you're located isn't necessarily anywhere near the same jurisdiction as the site that you're visiting. Physical borders become considerably more tenuous when it's as easy (pretty much) to view a site hosted a mile away as it is to view one on the other side of the world.
For an example I don't have to look very far; my site has a.uk domain, but it's actually hosted in Norway (even though I'm actually based in the U.K.). Now suppose I slander someone from China on my site - which legislation does it fall under? It's time to face up to the fact that the internet is a global system, and is difficult to regulate nationally.
Well I, for one, am glad at this. I just hate it when a large predator attacks me, bites down on a limb, and I'm unable to shed it and grow a new one.
This (or possibly having several extra limbs grafted on so I've got more to spare) looks like the most promising research to facilitate this defence mechanism. Hooray for George W!
Let's see now..... the parent said [/me cracks open economy-size BLOCKQUOTE tag box]:
It showed its characters embracing violence (Amidala), deceit (Qui-Gon) and anger (Obi-Wan) in order to do what they considered to be the right thing.
and:
All three contingents are effectively "disarmed" (sometimes forcibly) before they achieve victory. And the moment they give up their weaponry -- they win.
Heh, tell that to Qui-Gon : )
But aside from Qui-Gon becoming a double-ended shish-kebab (and forgetting to become one with The Force), Obi-Wan was only briefly disarmed, before picking up Qui-Gon's sabre and finishing the job. And I recall Amidala fighting her way into the throne-room where she could point a gun at the Trade Federation guys. Neither really gave up their weapons. And the whole battle was eventually resolved when Anakin fluked the destruction of the control ship (man, they had light-speed travel, but didn't know about redundancy) using a Naboo ship he'd borrowed.
I suspect that you're reading just a little bit too much intentional sub-plot into the movie.
The way I heard it, GL went into the studio a short while before the movie was complete and said he was changing the name to "Return...".
When questioned why, he said that "Revenge is not a Jedi Concept".
IIRC, this little factoid was revealed on the "The Making Of...." preview at the start of the Special Edition video tape (3-tape widescreen collection, U.K. version, though it's probably present on all the SE Ep III tapes).
However, I'm posting from work, so I'm unable to verify this source right now. It could all be a figment of my diseased imagination. Or it could be marketing spin to make Lucas sound more like Buddha and less like a merchandising-cash-hungry dog.
Hey; Easy on Hamil. Don't stick him in with Jar-Jar and Jake Lloyd (BTW, would a quick IMDB search to check names have killed you? : )! He's infinitely prefereable to either of those two losers (he also appeared in some of the Wing Commander games, an episode of The Outer Limits, and I hear he does a few of the voices on the Batman animated series - a much classier resumé).
Anyway, if Jar-Jar and Jake had been involved the title would have been more like "Itsa De Cloneys Attacking. Yippeee!".
Slashdot Mirror
Add to that rumours and allegations of stuff like BT giving it's own (not particularly big) ISP the lion's share of DSL connections while the two biggest ISPs in the country get a pathetic fraction of the broadband lines (AOL and Freeserve), and I guess a lot of people are going to be waiting a long time for broadband on this side of the Atlantic too. And seeing as I live in a fairly rural area (as rural as anywhere in the West Yorkshire conurbation gets anyway), I guess I'm not going to see any high speeds at a reasonable price for my home machine for several months yet.
I got my words backwards, but otherwise I think I'm right.
Do the swap in the title for the parent. I got my words mixed up, but otherwise I think I'm right.
But surely the altitude of the satellite is arbitrary. If it's higher then it needs to travel faster (speed proportional to height) to still orbit the planet once each day. See my other posts for the maths.
Using your figures of a 23 hour, 56 minute day and 35785 km the speed (note; not the same as velocity) of the satellite =
2 x pi x (35785km + radius of Earth) / 23.933 h
The radius of the Earth is about 6370 km (see here for info), so the speed of the satellite is:
2 x pi x 42115 km / 23.933 h = 11067 km/h
Now, suppose we put a satellite at, let's say, 43630 km from the surface. Gravity still works at this height. So you can still put an object in orbit. And suppose we set it moving in an orbit parallel to the lower satellite at a speed of, ooooh, about, 13127 km/h. What then?
Geosynchronous orbit is simply keeping the satellite over a particular point on the ground (as I'm sure you're aware). Or in this case we simply need to see if we can keep pace with the lower satellite (using your figures).
Let's think of an analogy - two runners going round a circular circuit. One runner gets an inside lane, and the other gets the outside lane. But the outside lane is longer (the radius is bigger) than the inside lane, so if the outside runner wants to keep pace with the inside runner he has to run faster. The speed he has to run depends on the circumference of his track - the ratio of his speed to the inner runner must be the same as the ratio of his track length to the inner track length. And because it's a circle, we can simplify that ratio to Radius(outer):Radius(inner).
Now, let's return to our satellites - suppose yours and mine start above the same point on the Earth, and we know that yours is geostationary. If mine manages to travel faster than yours around it's larger orbit then it will keep pace with yours and stay geostationary.
The ratio of distances from the centre of mass of the Earth is (43630km + radiusEarth):(35785km + radiusEarth) = 50000:42115 = 1.187:1
So my satellite needs to be moving 1.187 times faster than yours - 11067km/h x 1.187 = 13136km/h, which is pretty damn close to the speed I specified above (accounting for rounding errors). Why, it's almost like I cheated.
Essentially, a geosynchronous orbit can be achieved at any altitude, but it must be over the Equator (as I already explained to someone else) and the speed that the satellite must move is directly proportional to the altitude.
Please don't believe everything you find on Google - try doing the maths yourself first.
[Start poorly worded explanation]
Y'see, a satellite's orbit has to be the centre of mass of the object it's orbiting - that's just how gravity works and I'm not really enough of a Physics expert to start explaining why.
So you couldn't, for example, have a satellite orbiting directly above the Tropic of Cancer, because the tropic is off to the North of the centre of the Earth. You could have one that orbited between the tropics, because then it'd be orbiting the centre of mass of the Earth again.
However, this isn't a geosynchronous orbit. Obviously there's the North-South variation in relative position. But this wouldn't stay over the same line of longitude either. The satellite would have a constant speed. But the surface of the Earth at the Equator would be moving at a different speed (relative to the satellite) than it would be at one of the Tropics. It works like this:
Circumference @ tropic = 2 pi Rt
Circumference @ Equator = 2 pi Re
where Re ~= 1.5 Rt (ratio of 1.5 just plucked off the top of my head to make the sums easier, but it should be clear that the radius of the Equator is larger than the radius of a tropic).
therefore Circ @ Equator = 2 pi (1.5 * Rt)
Now, each rotation of the Earth takes 1 day. For a line of longitude (say, the Greenwich Meridian) to move through this arc in a day it has to move at 2 pi R / 24 m.p.h.
Since the circumference at the Equator is bigger (1.5 times in our example) the Greenwich Meridian moves 1.5 times faster at the Equator than it does at the Tropic.
Still with me? OK, now remember that our satellite has a constant speed. To make sure that the satellite's average position is geosynchronous, it's average speed needs to be equal to the average of the speeds at the tropics and Equator (and adjusted for it's greater distance from the centre of mass, but this is a secondary issue that I'm going to ignore for the sake of clarity). Which would leave the satellite tracing a vertical figure eight over the surface of the Earth, with the crossover point over the Equator, the top and bottom over the Tropics, and the bulges equidistant from the tropics and the Equator.
And that's obviously not truly geosynchronous, even if the average position of the satellite is. The further away from the Equator you start, the more distinct this figure of eight becomes. In theory, even satellites that are considered to be geosynchronous are actually tracing tiny 8s.
The Equator is the only division between any two hemispheres that's truly parallel to the rotation of the Earth (or orthogonal to the rotational axis, depending on how you think about it). And that's why geosychronous satellites have to be placed directly above it.
[End poorly worded explanation]
Phew. So much for my lunch break.
Caffeine please!
However, there's various vague orbits that are typically used for practical reasons (cost to launch, power, inverse square law etc.). Generally, you'll hear about:
- Low altitude orbits - these don't require as much broadcast power or cost as much to launch, but are close to the top of the atmosphere (particularly when it expands in summer) and can slowly get dragged back down to Earth.
- High altitude orbits - cost more to put up and the inverse square law means they need more power (include Tim Allen grunt here), but they're less likely to come crashing back down onto Fiji (or wherever) in a few years.
And yes, you're right, there's a lot of satellites already up there because it's so much more convenient to have your satellite in a fixed position in the sky (relative to the ground). Of course, IANANASAE(ngineer), but that's the basic issue with orbit altitude.BTW, I'm an expert on Slashdotters.
Sooo, all I need to do now is figure out how to incorporate this research in my Lego Mindstorms robot, to help me get up to the ISS. Fantastic!
Um, wait a sec, the flakes would contain DNA wouldn't they. Um, but, uh..... /me running to car, starting engine and peeling away at speed]
[/me cautiously backs towards the door]
....Y'see, the sugar-frosting DNA would, uh, mix with the corn DNA, and....
SLAM!
[sound of
Of course, curling is kinda a minority sport, and one of the weirder ones they've included.
Chess, on the other hand, is in a totally different league - it's solely reliant on mental ability. A quadraplegic could play it as well as someone with full use of their limbs. This isn't true of any of the other sports (AFAIK). Quake would still require fairly physical skills, so I wouldn't count it as the same sort of game. I'd still love to see it as an Olympic sport though :)
I dunno. I mean, that's gonna take an awful lot of batteries, and AFAIK Lego don't make any launch kits. And I wouldn't have thought the little connector-bumps (do they have a technical name?) would be all that aerodynamic. And what if you want it back - re-entry's going to be a bitch on the plastic.
And then maybe post the news as a story on the main page.
And include a link so that we can all go look at what it used to look like when the number of visitors was in the order of about 10^2.
Hmmmmm......
I'd also like to suggest that they set up a webcam pointing at the old box, so that we can all watch it burst into flames and be totally beyond repair thanks to a heavy slashdotting starting moments after the link to it is posted, as it tries to handle thousands more hits than it was ever designed to take.
Kinda like a viking funeral, only without the boat.
Or, rather, I'm going to sell them to someone else (Kelloggs, whoever makes cornflour, Green Giant etc.) for a vast profit and let them bother with the cloning. I'll just pop in occasionally to make unhelpful comments - "Maybe you should try repairing the freezer damage to the chromosones with frog DNA..."
Ooooh, or now I think about it, I could just buy tinned corn and then I wouldn't have to worry about keeping the freezer running.
Awwww, damnit, I really need to stop telling everyone my ideas...
Um, but don't anyone else do it, OK?
Similarly, Mandrake (my personal choice, because although I'm not afraid of the command line I'm too lazy to get to know it beyond occasional use of gcc, ls, ps aux and kill -9) is comparable in terms of GUI to Mac (at least compared to other Linux distros). Etc. etc.
Mmmmmmm, beeeeer.....
Oh, just to clarify, I'm geniunely not being sarcastic here (I would have used more italics and the SARCASM tag).
Wow.....
For an example I don't have to look very far; my site has a .uk domain, but it's actually hosted in Norway (even though I'm actually based in the U.K.). Now suppose I slander someone from China on my site - which legislation does it fall under? It's time to face up to the fact that the internet is a global system, and is difficult to regulate nationally.
This (or possibly having several extra limbs grafted on so I've got more to spare) looks like the most promising research to facilitate this defence mechanism. Hooray for George W!
But aside from Qui-Gon becoming a double-ended shish-kebab (and forgetting to become one with The Force), Obi-Wan was only briefly disarmed, before picking up Qui-Gon's sabre and finishing the job. And I recall Amidala fighting her way into the throne-room where she could point a gun at the Trade Federation guys. Neither really gave up their weapons. And the whole battle was eventually resolved when Anakin fluked the destruction of the control ship (man, they had light-speed travel, but didn't know about redundancy) using a Naboo ship he'd borrowed.
I suspect that you're reading just a little bit too much intentional sub-plot into the movie.
When questioned why, he said that "Revenge is not a Jedi Concept".
IIRC, this little factoid was revealed on the "The Making Of...." preview at the start of the Special Edition video tape (3-tape widescreen collection, U.K. version, though it's probably present on all the SE Ep III tapes).
However, I'm posting from work, so I'm unable to verify this source right now. It could all be a figment of my diseased imagination. Or it could be marketing spin to make Lucas sound more like Buddha and less like a merchandising-cash-hungry dog.
Anyway, if Jar-Jar and Jake had been involved the title would have been more like "Itsa De Cloneys Attacking. Yippeee!".