Snerk
Smeghead
I've been served a Chai Latte on a few occasions. They are pretty tasty!
TIL: Today I Learned
- Thread starter Cutlass
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Broken_Erika
Play with me.
I like my sugar with coffee and cream.
TIL why spacecraft orbits look like sine waves on a map.
https://twitter.com/fermatslibrary/status/916327081662857219
I guess there's no upside to orbiting over the north or south pole.
And because the Earth rotates, you eventually get satellite coverage like this
https://goo.gl/images/Mgo1QU
https://twitter.com/fermatslibrary/status/916327081662857219
I guess there's no upside to orbiting over the north or south pole.
And because the Earth rotates, you eventually get satellite coverage like this
https://goo.gl/images/Mgo1QU
Also, today I broke my shoelace and learned there are actually 3 ways to deal with it.
In the past I'd just tuck it in and have a loose shoe all day.
1) Tie the broken shoelace back together with a square knot.
http://www.animatedknots.com/reef/
2) Take the remaining shoelace completely out of the shoe, center it, and then lace up the shoe again skipping the top eyelet since the shoelace is now too short.
This is my favorite.
3) If the break is very severe, lace up every other eyelet.
Should still be enough to get a sorta tight shoe.
In the past I'd just tuck it in and have a loose shoe all day.
1) Tie the broken shoelace back together with a square knot.
http://www.animatedknots.com/reef/
2) Take the remaining shoelace completely out of the shoe, center it, and then lace up the shoe again skipping the top eyelet since the shoelace is now too short.
This is my favorite.
3) If the break is very severe, lace up every other eyelet.
Should still be enough to get a sorta tight shoe.
hobbsyoyo
Deity
- Joined
- Jul 13, 2012
- Messages
- 26,575
There are several upsides to orbiting over the pole. You can't get good coverage of the polar areas without going over them or very close to them. Another benefit is that orbiting over the poles in a certain way allows you to have the same light conditions over a specific ground area every time you pass over it. This is useful for say, spy satellites, which need specific light conditions to take optimal photos.TIL why spacecraft orbits look like sine waves on a map.
https://twitter.com/fermatslibrary/status/916327081662857219
I guess there's no upside to orbiting over the north or south pole.
And because the Earth rotates, you eventually get satellite coverage like this
https://goo.gl/images/Mgo1QU
Gori the Grey
The Poster
- Joined
- Jan 5, 2009
- Messages
- 13,351
TIL there's a legal principle, estoppel, that prevents one from adopting contradictory positions:
That must be the reason Canadians are so much nicer than everyone else. They have no satellite coverage so they can't watch all the violent, reality, cable news, etc., crap TV that the rest of the world doesTIL why spacecraft orbits look like sine waves on a map.
https://twitter.com/fermatslibrary/status/916327081662857219
I guess there's no upside to orbiting over the north or south pole.
And because the Earth rotates, you eventually get satellite coverage like this
https://goo.gl/images/Mgo1QU
Oh no, we get all that crap from your piped in TV networks. We just don't take it seriously.
OMG, we're either surrounded by a gigantic string art project, or the Tholians have found us!TIL why spacecraft orbits look like sine waves on a map.
https://twitter.com/fermatslibrary/status/916327081662857219
I guess there's no upside to orbiting over the north or south pole.
And because the Earth rotates, you eventually get satellite coverage like this
https://goo.gl/images/Mgo1QU
Take another look. That coverage covers the most heavily populated areas of our country. Only the people in the Yukon, Northwest Territories, and Nunavut are safe.That must be the reason Canadians are so much nicer than everyone else. They have no satellite coverage so they can't watch all the violent, reality, cable news, etc., crap TV that the rest of the world does
And your theory doesn't explain people like Sarah Palin, since Alaska isn't covered and she is not a nice person.
Some of the Reformacons seem to.Oh no, we get all that crap from your piped in TV networks. We just don't take it seriously.
I was going to add exactly that to my post... the fact that the "meanest" Canadians are in the close-to-the-US parts that have the coverage makes the correlation even clearer... but I thought I had laid it on thick enough already and I didn't want to offend you Canadian guys/gals too badly
Don't you think that "theory" is a rather generous term for it Valka? I mean, I put a tongue smiley and everything
hobbsyoyo
Deity
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- Jul 13, 2012
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- 26,575
The orbital paths of low-earth orbiting (LEO - the kind in @Kaitzilla's post) satellites don't matter so much for broadcast coverage because they are not typically used for broadcasting television services. For that, you need to look at geostationary (GEO) satellites. These guys orbit an altitude such that their orbital speed takes them through one orbit in 24 hours. What this means is that they appear to 'hover' over a single spot on the Earth. From this vantage point they can steer their beams to cover specific spots under them continuously. Those coverage maps look like this one for the communications satellite Intelsat 33e:
Notice that they do cover a lot of the polar regions with some of their beams (each shape overlaid on the map is a specific spot beam coverage area). However, reception towards the poles is pretty bad as the beams have to pass through a lot more atmosphere towards the poles since the beams intersect the Earth at an oblique angle at the poles. Another challenge for these systems is the fact that in the far north the beams are not coming from directly overhead but from near the horizon (that oblique angle) and as such they tend to be easily blocked by tall buildings.
This is one reason why satellite radio services do tend to use satellites with non-GEO orbits as 'backups' to their GEO birds to better service the cities that are farther north in North America and Europe. However, television broadcasters do not tend to use these types of satellites very much. This is mostly because of how much more expensive the big GEO comm satellites are compared to simple(ish) radio broadcasting satellites - since they are so expensive they can only build a few and they put them where they can cover the most territory.
By placing a satellite in GEO, you can provide continuous coverage of a huge portion of the Earth. Once you move down into LEO you can only cover a small part of the Earth at a given time (and the areas being covered are continually changing as the satellite whips around the Earth) and so you need a large fleet to cover the same amount of ground continually from LEO. In GEO you can cover the same amount of ground continuously with just one bird.
One big problem with GEO satellites is their altitude. Because they are so high up, the travel time for light to and from them is actually noticeable. For a satellite that is simply broadcasting TV, this lag doesn't really matter. However, for companies that are trying to provide satellite internet services from GEO this causes noticeable lag. This is one of the reasons why satellite internet is mostly a niche service for those who cannot access traditional, land-based internet services.
SpaceX and a few other companies are trying to change this, however. They want to build a satellite internet network that utilizes low or medium Earth orbiting satellites that have very little lag in hopes that they can upend the ISP market. The downside is that this approach requires many, many more satellites to offer global coverage than a GEO network would require. From GEO, you could cover almost the entire Earth with just 3-6 satellites. From LEO/MEO, you need hundreds or thousands. SpaceX hopes that their reusable booster technology will bring down launch costs so much that they can afford to orbit 4,000 satellites for their constellation. Time will tell if this approach is viable.
As always, The Thread for Space Cadets is a welcoming place for more science and space related discussions.
Spoiler :
Notice that they do cover a lot of the polar regions with some of their beams (each shape overlaid on the map is a specific spot beam coverage area). However, reception towards the poles is pretty bad as the beams have to pass through a lot more atmosphere towards the poles since the beams intersect the Earth at an oblique angle at the poles. Another challenge for these systems is the fact that in the far north the beams are not coming from directly overhead but from near the horizon (that oblique angle) and as such they tend to be easily blocked by tall buildings.
This is one reason why satellite radio services do tend to use satellites with non-GEO orbits as 'backups' to their GEO birds to better service the cities that are farther north in North America and Europe. However, television broadcasters do not tend to use these types of satellites very much. This is mostly because of how much more expensive the big GEO comm satellites are compared to simple(ish) radio broadcasting satellites - since they are so expensive they can only build a few and they put them where they can cover the most territory.
By placing a satellite in GEO, you can provide continuous coverage of a huge portion of the Earth. Once you move down into LEO you can only cover a small part of the Earth at a given time (and the areas being covered are continually changing as the satellite whips around the Earth) and so you need a large fleet to cover the same amount of ground continually from LEO. In GEO you can cover the same amount of ground continuously with just one bird.
One big problem with GEO satellites is their altitude. Because they are so high up, the travel time for light to and from them is actually noticeable. For a satellite that is simply broadcasting TV, this lag doesn't really matter. However, for companies that are trying to provide satellite internet services from GEO this causes noticeable lag. This is one of the reasons why satellite internet is mostly a niche service for those who cannot access traditional, land-based internet services.
SpaceX and a few other companies are trying to change this, however. They want to build a satellite internet network that utilizes low or medium Earth orbiting satellites that have very little lag in hopes that they can upend the ISP market. The downside is that this approach requires many, many more satellites to offer global coverage than a GEO network would require. From GEO, you could cover almost the entire Earth with just 3-6 satellites. From LEO/MEO, you need hundreds or thousands. SpaceX hopes that their reusable booster technology will bring down launch costs so much that they can afford to orbit 4,000 satellites for their constellation. Time will tell if this approach is viable.
As always, The Thread for Space Cadets is a welcoming place for more science and space related discussions.
Last edited:
Lexicus
Deity
TIL there is a very odd website called Civfanatics Wiki
I'm merely pointing out that most of us aren't safe from the corrupting influence of American media. It tends to make a lot of us cranky.I was going to add exactly that to my post... the fact that the "meanest" Canadians are in the close-to-the-US parts that have the coverage makes the correlation even clearer... but I thought I had laid it on thick enough already and I didn't want to offend you Canadian guys/gals too badly
I don't mean "theory" in the scientific sense. Maybe the words "notion" or "idea" would have been better?Don't you think that "theory" is a rather generous term for it Valka? I mean, I put a tongue smiley and everything
Broken_Erika
Play with me.
It has like one actual page, the rest are templates and welcome pages.
The Civ2 Scenario League Wiki on the other hand...
http://sleague.civfanatics.com/index.php?title=Main_Page
Lohrenswald
世界的 bottom ranked physicist
have you never heard the saga of oldschool88
Lexicus
Deity
No, apparently it's not a story the Jedi would tell me
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