18-07-2002 17:27									#211
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quote: Originally posted by Solver Kingpin, that's just sick... people somehow have the tendency to fear discoveries... rubbish... you see, humans do already easily have the ability to destroy ALL the humankind, should there be a nuclear war.

Now we'll just have a more gruesome way of doing it.
Teleport 1 enemy POW into another... that'll stop an advance...

Still though, I'd never want to do such a thing... who's to say 'your' consciousness wouldn't be destroyed and re-created into a new being? And either way you'd never know, because the 'new' copy will have the exact same memory.

What a way to go.

	18-07-2002 17:42									#212
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I have just got back from holiday, and there is no way I am going to read this entire post. I have skimmed it, and I have a few comments...

First of all, I think it is unfair to call this 'teleportation' as this implies moving something instantaneously, and that is not what is happenning here. They are using qunatum entanglement, triggering a quantum collapse to a state with the object in the final position. By triggering this collapse from far away, it looks like 'teleportation'.
However, such a quantum collapse clearly needs a wavefunction which has spread out as far as the destination in the first place, which takes a finite time. One could consider the object as being really already at the destination before the 'teleportation' occurs.

The main advantage then is in completely reproducing the object at the destination without having to disassemble it - record its exact state - transmit it across space - and reconstruct it at the other end (the traditional 'Star-Trek' way). It is actually the same object - quantum mechanics takes care of that for you.

This should calm Stefu's fears, because I agree that there is no way I would stand in a 'traditional teleporter'. The question there would be: is the gathering of information good enough to reproduce 'me', or in other words 'my soul'. If you are able to record and transmit the information, multiple copies can be created, so which one is really you? (Ever read the book 'Altered Carbon'?)

But in this case, it wouldn't be like that. Everything is 'transported' automatically and nothing can be left behind, so it would most certainly be 'you'.

I suspect though that this technology will be useless in practical terms, until we understand the method of collapsing the wavefunction more completely. Macroscopic objects like us don't seem to exist in quantum states - somehow the macroscopic nature already collapses the wavefunction. It is not clear whether this is due to our complexity, our consciousness, or whatever. Since our very presence collapses our own wavefunction it would be impossible to set up this experiment with a complex/conscious/whatever subject. I can't see any way round this - no matter what the cause of the collapse is, it is most certainly inherent to us, precluding us from 'teleportation'.

It doesn't even get round the speed of light barrier for interstellar distances, because the wavefunction can only spread out at the speed of light. So to set the experiment up for teleporting an object from here to Alpha Centauri (4 light years away) would take more than four years.

It would be useful for trade purposes though. Imagine that you lived on Alpha Centauri and wanted a new toaster delivered from a company on Earth. If the company on Earth was far sighted enough, they could have set up this pseudo-teleportation thing in advance, so that they could deliver the toaster from their site on Earth to a collection site on AC should it be required there. You would have to be happy with a four year old model though. (This would still be very useful form delivery of goods on Earth, where delivery at the speed of light isn't such a problem.)

Trip has a good point - this would also be useful for 'delivering' nuclear warheads to a target!

Last edited by Rogan Josh on 18-07-2002 at 17:59

	18-07-2002 17:43									#213
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Solver,

The sick thing is what people have done with technology to kill other people over the centuries.

Explosives, for example, are tremendous tools in the construction industry. And Aircraft for travel. Yet how many people have died when someone decides to take a useful tool, and kill hundreds, if not thousands, of people with it.

Teleportation, in the hands of terrorists, madmen, rogue states or oppressive regimes is too terrifying to contemplate. It is a bad idea. Scientists spend too much time trying to discover things and not enough time considering the consequences.

	18-07-2002 17:46									#214
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Work of scientists is to discover. Completely anything might be used both to harm and to develop. Are you offering that the humanking stops researching of some things?

	18-07-2002 17:53									#215
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The work of scientists cannot be seperated from ethics.

	18-07-2002 17:56									#216
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Are you a ludite? Your beliefs seem to tell so...

	18-07-2002 18:15									#217
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LOL

No, I'm not a Ludite. But perhaps I do have a different world-view than most people.

By the way, I'm not really advocating killing scientists involved with teleportation. I just think we need to consider whether the possible costs will outweigh the possible benefits before we charge ahead with research.

And there are numerous technologies I feel this way about: Stem-Cell Research, Genetically Modifying Organisms, Engineered Viruses, Nano-technology and Cloning to name a few. I think they're bad ideas that will cause more harm to human-kind than they solve. They're beneficial in the right hands, but sooner or later, they end up in the wrong hands...

	18-07-2002 18:27									#218
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Anything might end up in the wrong hands, in fact.

I'm a believer that research must be conducted - that's what the humankind is doing currently. And I can't understand those people who are so terribly against human cloning, either.

	18-07-2002 19:06									#219
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The insurmountable fact remains that all human progress always comes at a cost. That's just how it is, and nothing will change, we must simply deal with it.

	18-07-2002 19:09									#220
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Exactly, and if we stopped research, we would no longer be humans as we are.

	19-07-2002 03:05									#221
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Kingpin... terrorists can use the internet to communicate without being monitored... Get out, now! Run away!

Would you rather live ten thousand years ago, before agriculture and such, or now?

Sorry, back on topic.

I like science, a lot. Sadly the most advanced science class I have taken is Physics in high school. That will change once I get into college.

Anyway, can someone briefly explain to me what the quantum state of an object is and what wave functions have to do with all of this? I have only a very vague understanding.

	19-07-2002 15:02									#222
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quote: Originally posted by Lorizael Anyway, can someone briefly explain to me what the quantum state of an object is and what wave functions have to do with all of this? I have only a very vague understanding.

I will give this a go.

Very small objects obey quantum mechanics rather than classical mechanics. Every object has a 'wave-function' which is a little bit like a probability distribution. When a measurement or observation of the object's position (for example) is made the object is in a definite position. Then, while not being watched, rather than being in one place, the wave-function spreads out to all possible places the object could be within the given time. Making another position measurement, the wavefunction will 'collapse', making a specific choice of position, so you will observe the object in one place rather than all spread out. The probability of picking one particular position choice is proportional to the size (squared) of the wave-function at that point.

Now, this sounds like nonsense because if the wave-function collapses when you look at it, how can you say it was ever spread out like that. Well, the wavefunction itself behaves exactly like a light wave (in fact this is what a light wave is) so you can observe things like interference patterns.

The point here is that the collapse of the wavefunction is instantaneous. So, if you have a wavefunction which is spread out enough, you can affect things on the other side of the room (or universe!) by collaping the wavefunction on our side of the room.

How the collapse happens - why the affect of a measurement collapses the wavefunction - is unknown. The old thought experiment of schroedinger's cat was supposed to show how silly this is: would the cat be able to collapse its own wavefunction or not?

Hope this helps a little.

	19-07-2002 15:10									#223
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Rogan,

Are they fixing the Standard Model to deal with neutrinos?

	19-07-2002 19:24									#224
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quote: You would have to be happy with a four year old model though. (This would still be very useful form delivery of goods on Earth, where delivery at the speed of light isn't such a problem.)

Eight years. The information has to make a two-way trip.

	19-07-2002 19:29									#225
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Well at least nicely it's a 4 second cycle for moon, IIRC.

	19-07-2002 19:46									#226
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quote: Originally posted by Urban Ranger Rogan, Are they fixing the Standard Model to deal with neutrinos?

Yes, they are. It is fairly straightforward to do in principle (although rather aesthetically unpleasing imho), but more experimental details are required to get all the parameters for the oscillations right. There are some snazzy new satellites going up soon to check the Solar neutrino emissions (and their subsequent oscillations) more accurately. (I forget the names.)

There is still a disagreement between the experiments though. LSND seem to disagree with everyone. There have been some attempts to explain this theoretically, but I think the general feeling here is that they are just full of ****.

	19-07-2002 19:47									#227
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Don't they just have to adjust a few parameters?

Any how, I hope the Standard Model gets broken beyond repair...

	19-07-2002 19:54									#228
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quote: Originally posted by Frogger Don't they just have to adjust a few parameters?

No. The Standard Model has no neutrino mass terms in the Lagrangian (although I suppose you could say that you are adjusting the masses away from zero ). The question is whether or not the mass terms should be Dirac mass terms or Majoranna mass terms - or in other words, is the right handed neutrino the anti-particle of the left handed one, or not?

Since they also mix, you need some mixing angles too (which weren't there before).

quote: Any how, I hope the Standard Model gets broken beyond repair...

That is what we are all hoping for. Roll on Supersymmetry....

	20-07-2002 09:47									#229
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...and the Standard Model would be??

Reading science magazines only does so much good if you don't have background information. *sigh*

	20-07-2002 09:52									#230
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Standard model is the current best approximation of everything we know about the fundamental particles and their interactions.

Don't worry; half of what Rogan just said is gibberish to me too, and I've got a Bachelor's degree in physics. I've only taken one particle physics course, and it was sort of bobo...I can sort of draw Feynman dagrams, but that's about it...

	20-07-2002 09:55									#231
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On the plus side, I've done an unholy amount of quantum mechanics and abstract math courses...

	20-07-2002 09:58									#232
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Thanks anyway, KH. I didn't even know Feynman could draw.

And you Rogan Josh, what are your qualifications?

I read most of A Brief History of Time.

Oh and I also read The Physics of Star Trek.

	20-07-2002 10:08									#233
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Rogan's a Ph.D. in high energy physics, IIRC. And I think that he's currently working at CERN. Feynman diagrams are a graphical way of depicting the possible paths a reaction can take. A might go straight to B, or it might take an intermediate step or two (A->C->D->B). With each step is associated a probability (coupling coefficient) so to get the total probability (known as cross-section) for a reaction you need to theoretically add up all the probabilities from the infinite number of possible reaction paths. Luckily, the importance of each possible path drops as the number of steps in it increases (usually), so you can get away with only looking at the relatively simple paths (say 1-4 steps, depending on reaction)...

	20-07-2002 17:17									#234
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Damn KH you and Rogan are clever.

	20-07-2002 22:37									#235
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quote: Originally posted by Frogger Rogan's a Ph.D. in high energy physics, IIRC. And I think that he's currently working at CERN.

That's right

quote: Feynman diagrams are a graphical way of depicting the possible paths a reaction can take. A might go straight to B, or it might take an intermediate step or two (A->C->D->B). With each step is associated a probability (coupling coefficient) so to get the total probability (known as cross-section) for a reaction you need to theoretically add up all the probabilities from the infinite number of possible reaction paths. Luckily, the importance of each possible path drops as the number of steps in it increases (usually), so you can get away with only looking at the relatively simple paths (say 1-4 steps, depending on reaction)...

I spend my PhD calculating lots of these little buggers - the especially hard ones with loops in them. For a little while, after I had finished it, I held the record for the most advanced one-loop Feynman diagram calculation ever

Didn't take long before someone did an even harder one though

I try to steer well clear of the little buggers these days.....

	20-07-2002 22:38									#236
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It sounds like a great deal of pain...

	20-07-2002 22:39									#237
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quote: Originally posted by Lorizael I read most of A Brief History of Time.

I met Hawking once at a conference. He wheeled his wheelchair right next to my seat during a seminar. When the talk got boring (they usually do) I was very temped to tweek his little joystick control thing and spin him round in circles.

	20-07-2002 22:42									#238
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I know someone at Cambridge that Hawking knocked down with his wheelchair. He claims it was on purpose...

	21-07-2002 01:57									#239
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Wow... you know Stephen Hawking. The closest I've come to him is seeing him on the Simpsons.

Oh, and you're a horrible horrible person for wanting to harass one of our greatest geniuses...

Why didn't you?

	21-07-2002 02:34									#240
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I didn't say I knew him. I only sat next to him.

Anyway, Hawking isn't so great. I have had dinner with much brighter geniuses. I used to be the seminar organiser, so I got to invite lots of big name physicists and take them out to dinner on expenses.

A couple of months ago, I was at a conference with lots of big names at it. One evening I was having dinner with a friend at a small table for three, when Ed Witten came up to us. Ed Witten is pretty much the acknowledged greatest genius alive (ask any particle physicist). Much cleverer than Hawking...

Anyway, he recognises me from somewhere (I think a previous conference the year before where I asked him a stupid question), and so asks if he can join us. My friend, who has never met him before and didn't recognise him replies "Sorry, we are saving that seat for a friend"!

I could have throttled him....