GPS vs. Galileo; Where Are They Headed?

ben_ writes "This keynote speech from the recent European Navigation Conference talks about the history between the US military's GPS and the proposed EU Galileo system, as well as where they're both going. Interested in how you know where you are and what's going to happen to those satellites?"

Comments

Here's the big question:

[MtViewGuy]

Will the ESA Galileo satellite navigation system be sufficiently different that you'll need all-new receivers to pick up Galileo navigation information?

That could get VERY expensive as manufacturers of satellite navigation receivers will have to accommodate both systems for airplanes, automobiles, trucks, boats, etc.

Re:Essential to Ending US Dominance

[AKAImBatman]

The truly messed up part is that many European nations (*cough*Sweden*cough*) would need to rely on the US military in the case of a major assault. The EU has troops and weapon systems, but it's doubtful they would be sufficient to defend against a major superpower. While many Europeans are upset over Iraq, the US is unlikely to be the aggressor in any major European conflict. That leaves two other possibilities:

1. Someone more intelligent than Putin takes over Russia and uses Putin's communist-like infrastructure to once again impose a military state.
2. China decides that they have the most people in the world and that someone else should give up some land to support them.

While the second is more likely, either one would spell defeat for the European Union. Only the US currently has the necessary military power to stop another superpower. On the upside, China might be more inclined to take on the US first since we have more undeveloped land. It wouldn't be much of a war though. We'd fight until the Chinese start lobbing nukes. Once that happens, China can kiss their population goodbye when a few neutron bombs fall.

Re:Where are they going?

[-brazil-]

Talk about not knowing what you're talking about. Geostationary orbit is at 42,245km, can only be above the equator (so you wouldn't get a signal at the poles) and means (depending on how you define it) either one or no rotation per day. The GPS satellites are not in geostationary orbit.

Re:A Relativity Question

[blingbing]

I strongly recommend you read Brian Greene's "Fabrics of the Cosmos", the book explain in plain english the exact same question and much more.

What's to say that the spaceship is actually in geostationary orbit and not just STATIONARY if there is nothing else to measure their motion against? These two things are all that exist in this hypothetical universe and they are stationary relative to each other, so why aren't they 'absolutely' stationary, causing the spaceship just to fall? How do you know the moon is really even spinning?

I am no physics major, here's my amateurish understanding.

Newton pondered the same question, but he used a spinning water bucket as an example. suppose you are on the inner bucket wall, you know your are spinning because you can feel your back is pressed against the wall, even if you can see any motion relative to the wall or the center pole. but when the spinning stops, the force disappears. By the same token, we can deduce the spaceship is geostationary because it does't fall, a truly stationary spaceship will fall because of gravity.

The way I usually phrased this to physics professors was that if the spaceship, floating in space for all it knows, comes flying past the moon at near light speed, why do we assume the spaceship is moving at near lightspeed and therefore clocks on it run slower, rather than the moon is hurtling through space at near lightspeed past a stationary ship?

Einstein says you can see it either way, and both perspective are valid but they don't necessarily reconcile in a traditional sense. the distance and time measures differ depends on the observer's speed. In general, when you speed up and down, your space and time perspective dynamically changes. According to Einstein, it's perfectly valid for everyone on Earth to have a different time reading for the very same event, like exactly when Smarty Jones won the Kentucky Derby.