Do you know the rational behind having override-overrides from the cockpit? For me, this only makes sense under the assumption that Prob(malicious agent who knows emergency codes in cockpit and good agents knowing codes outside ) is much smaller Prob(good agent knowing codes in cockpit and malicious agents knowing codes outside). How is this assumption justified? Under current regulations, the latter is becoming more and more unlikely. Or this could be fixed by letting the protocol to lock the door from inside the cockpit depend on an exchange with a trusted third party like air controllers.
[edit: language]
In post-9/11 world a good agent would not open the door even at the threat of his life, because were the attackers gain control of the cockpit, he would die anyway, and a lot of other people too.
I think that's the only possible counterpoint, really. But the override should be constructed so that it can only put the plane onto a "safe" autopilot route. And even then, I'm not really sure if that's actually safe without giving the plane collision avoidance, because it's entirely conceivable that in some urban airports just reverting to straight and level could cause a crash.
If you're descending into an airport near NYC it's possible that you need to fly towards the city, turn and then continue descending to land. If you hit the autopilot external override at the right time you could be lower than the tallest buildings and get locked into flying into them without enough time to react.
The real solution would seem to be what other people in the thread are suggesting; you must always have two people in the cockpit. At least one pilot and possibly another crew member.
The autopilot on modern aircraft is more than capable of landing the plane. I have a friend who flies for Air Canada who tells me that Air Canada requires pilots to be in manual control of the aircraft from takeoff to 500 feet, but after that the pilot can put the plane in autopilot and not touch anything until they're on the ground if she wants to. The plane will even apply breaking thrust after touchdown and bring the plane to a stop.
At this point, pilots are really there to take care of unusual situations that the computer can't (which do happen from time to time.)
The idea that a pilot could put a plane on autopilot soon after takeoff and then "not touch anything" and end up landed on the ground again is patently ludicrous. There are certainly things that automatic controls can do to make flying and landing a plane easier but they don't resemble your description at all.
1. When you tell me the result 6296, my brain becomes only classically correlated with it, not entangled. The source of randomness (whether you got it through a quantum experiment or not) does not matter here, as I am only receiving the classical information.
2. After I forget it completely, all I can say is that I (my current body) am not correlated with the event --- but there is no reason to think of the event as being in my future. It's simply not correlated to me any longer. The process of forgetting means dumping all correlations with an event in the environment. For instance, neurons interact with blood stream that interacts with lungs, passing along those correlations to some air particles. So for my current body, the event never happened, although you might have written the number down and will always remember it. In other words, the past is relative.
> So for my current body, the event never happened, although you might have written the number down and will always remember it. In other words, the past is relative.
So where this event would be for you? In the future? Again?
Yes. Past is definitely relative. Special relativity is very specific about that ;)
The event is neither in my causal past (it has no influence over the current state of my body) nor in my causal future (I have no influence on it). It's simply uncorrelated with me. If now you remind me of the number again, it becomes part of the causal past of my (new) body. Analogy: if a dwarf dies in a fortress far far away and you don't hear about it, her death is neither in your past nor in your future. You know nothing about her state: in QM, you would say that your brain and her are in an uncorrelated, product state, something like |dunno><dunno| x (|dead><dead| + |alive><alive|)/2 .
The x stands for \otimes, tensor product.
When you say you receive classical information as the outcome of that experiment, what's an example situation in real life when you receive quantum information and do indeed get entangled with it (I mean if at all such a situation ever arises)?
"real life" as in "they can do it for real in a lab": Alice has two photons, applies a quantum operation to them so that they become entangled, and gives one to Bob. Bob received "quantum information" from Alice. They can use this resource (entanglement between the photons they own) to perform several tasks now, like "teleportation" of the state of a particle, or secure key distribution.
Good answers. Just a small comment: quantum entropy is a generalization of classical entropy. In particular, if A and B are classically correlated, then S(A|B) has all the properties of a classical entropy (Shannon's, in this case), for instance, it is non-negative.
Performance aside, here is what I hate about Skype compared to MSN / WLM: privacy.
(1) Skype logs you in to your last known status / on MSN you could choose before login (for example, "appear offline"/"invisible"). If I just want to check if a contact is online without my aunt start chatting, I can't.
(2) There is no easy way to block whole contact groups temporarily. When I'm at work, I don't want my friends to see me online; when I'm at home, I don't want to be contacted by co-workers.
(3) Say I'm chatting with Bob, and he goes offline just before I send him a last IM. This IM will be delivered the next time that we are both online. Even if one of us is "appearing offline"/"invisible". So we have a way of knowing when someone is hiding: just send someone a message when they are offline. Bah.
(4) Not related, but the delivery of old messages is awful across platforms.
What annoys me the most about these bugs (1-3) is that they seem so easy to fix, and yet nothing is done. Meh. Do you have similar frustrations?
Skype doesn't make it easy to use two accounts. There is no "multiple accounts" feature where you can be logged in as one or both; instead, you have to log out and log back in again as the other. Sometimes, you might be on-call, so chatting with friends is OK, but you still need to be available to coworkers.
The problem with Skype is that it's totally closed. I use a multi-protocol IM client, with multiple accounts, so I can chat with people over AIM, FB, Google Chat, my work chat, and so on. Sadly, despite the fact that my work has Google Apps, which includes chat, they have standardized on Skype instead, so I need to have an entirely separate client, and log out and log back in when switching between work and personal accounts.
