aommaster Posted October 17, 2005 Share Posted October 17, 2005 Hi guys! Sorry I haven't been participating a lot lately. This is because I just finished my As levels and movedo on to do A levels. AT the start of the year, the first physics topic we are doing is about waves and our universe. We watched quite a lot of videos on the string theory and quantum mechanics. The question about quantum mechanics is: From what I have understood, quantum mechanics states that if there is a probability of, let's say, 10 things happening, then ALL 10 things will happen. MY question: Where do they happen? Do they happen in parallel universes? Please make your language simple and have mercy on me I only just started doing this stuff, and we have only touched upon it very briefly, so my knowledge isn't really that high! Thanks! Link to comment Share on other sites More sharing options...
thorN Posted October 17, 2005 Share Posted October 17, 2005 It sounds like I'm in the same boat as you - but here's what I've gleaned on the subject up to know: Having a seperate universe for each possible result of a quantum mechanical phenomena is called the "Many Worlds Interpretation" (http://en.wikipedia.org/wiki/Many-worlds_interpretation). It basically says that there's an unimaginable (almost infinate) number of other universes where the dice landed slightly differently, and as a result (and because of Chaos theory) are completely different. All these universes are completely seperate, and grow in number - sort of "budding" off each other every time anything happens. But, this is just a hypothesis (unsubstantiated theory). I don't like the idea personally, if everything ultimately happens anyway then it nullifies the whole idea of choice and risk. Link to comment Share on other sites More sharing options...
Mart Posted October 17, 2005 Share Posted October 17, 2005 originally posted by thorNAll these universes are completely seperate, and grow in number - sort of "budding" off each other every time anything happens. If they do "bud" off each other then they can't be totally seperate. I don't like the idea personally, if everything ultimately happens anyway then it nullifies the whole idea of choice and risk. What if you could choose to "navigate" into another parallel universe? Link to comment Share on other sites More sharing options...
Severian Posted October 17, 2005 Share Posted October 17, 2005 The question about quantum mechanics is: From what I have understood' date=' quantum mechanics states that if there is a probability of, let's say, 10 things happening, then ALL 10 things will happen. [/quote'] That is not the accepted viewpoint. The standard viewpoint is the Copenhagen Interpretation, in which only one of the outcomes occurs (with the probability you already mentioned). Link to comment Share on other sites More sharing options...
thorN Posted October 17, 2005 Share Posted October 17, 2005 If they do "bud" off each other then they can't be totally seperate. What if you could choose to "navigate" into another parallel universe? You're making a good point here, I read somewhere that if Many Worlds is right, then it would be possible to 'time travel' by switching between one reality and another. But this is all pretty flimsy science I think, Severian is right that the Copenhagen view is far more accepted. Link to comment Share on other sites More sharing options...
thorN Posted October 17, 2005 Share Posted October 17, 2005 I've had a quick scan through The Fabric of the cosmos, it says here that the parallel universes are created as the quantum wave-functions collapse. This means there is an infinate number of parallel universes. In each universe, (for example,) the electron could be in any location, distributed asymtotically. Greene explains how the paradox of travelling backwards in time to kill your grandfather can be resolved if you're actually altering a different universe, and hence have travelled between parallel universes. Anyway, it still doesn't alter the fact that (with Many Worlds) no matter what horse I bet on, in an infinate number of places I win the bet, no matter what. Link to comment Share on other sites More sharing options...
Mart Posted October 17, 2005 Share Posted October 17, 2005 If you were living several centuries ago I bet there would be people around who would say that epicycles was the way to go. Challenge the Copenhagan convention. There are at least eight different interpretations of quantum theory as a physical theory (not as a computing device). Link to comment Share on other sites More sharing options...
Mart Posted October 17, 2005 Share Posted October 17, 2005 Read David Deutsch "The Fabric of Reality". He's much better at crazy ideas than Brian Greene. Link to comment Share on other sites More sharing options...
thorN Posted October 17, 2005 Share Posted October 17, 2005 lol, fair enough. Pretty much anything that is common knowledge is wrong I'll check out fabric of reality. Crazy ideas are awsome - what's fabric of reality about? Link to comment Share on other sites More sharing options...
Severian Posted October 17, 2005 Share Posted October 17, 2005 If you were living several centuries ago I bet there would be people around who would say that epicycles was the way to go. Challenge the Copenhagan convention. There are at least eight different interpretations of quantum theory as a physical theory (not as a computing device). If you can't tell the difference between them by experiment (and you can't) then it is not science. Please take non-scientific discussions elsewhere. Link to comment Share on other sites More sharing options...
Mobius Posted October 18, 2005 Share Posted October 18, 2005 Going back to the original post. The question about quantum mechanics is:From what I have understood, quantum mechanics states that if there is a probability of, let's say, 10 things happening, then ALL 10 things will happen. this is not quantum mechanics..... Quantum mechanics is based on probabilty... However if you think of an infinite universe or a universe that has infinite time... then if something has a non zero probability of happinning then it WILL happen (an infinite number of times). Crazy world we live in.... Many worlds inturpretation indulges in this..... Link to comment Share on other sites More sharing options...
Mart Posted October 18, 2005 Share Posted October 18, 2005 Originally Posted by SeverianIf you can't tell the difference between them by experiment (and you can't) then it is not science. I take it that the you in your quote is your way of saying that there is no possibility of decidiing by experiment that there is a difference. What experiment/experiments was/were performed to reach this result? Can I replicate it/them. Details please . . . Link to comment Share on other sites More sharing options...
aommaster Posted October 18, 2005 Author Share Posted October 18, 2005 Going back to the original post. this is not quantum mechanics..... Quantum mechanics is based on probabilty... However if you think of an infinite universe or a universe that has infinite time... then if something has a non zero probability of happinning then it WILL happen (an infinite number of times). Crazy world we live in.... Many worlds inturpretation indulges in this..... Sorry if I sound a little stupid, but you said that it was not quantum mechanics. Isn't it? Because there is a probability of something happening? I'm fairly new to the subject, so, please, simplify the explanations down to my level! Link to comment Share on other sites More sharing options...
Mart Posted October 18, 2005 Share Posted October 18, 2005 Quantum Mechanics is a computational strategy to predict the outcomes of certain types of event. Link to comment Share on other sites More sharing options...
aommaster Posted October 18, 2005 Author Share Posted October 18, 2005 So, isn't the event of what I have mentioned quantum mechanics, since there will be a probability of 10 things happening? Or is it just the science of probability? Link to comment Share on other sites More sharing options...
Mart Posted October 18, 2005 Share Posted October 18, 2005 Originally Posted by SeverianThat is not the accepted viewpoint. The standard viewpoint is the Copenhagen Interpretation, in which only one of the outcomes occurs (with the probability you already mentioned). Please take non-scientific discussions elsewhere. Link to comment Share on other sites More sharing options...
aommaster Posted October 18, 2005 Author Share Posted October 18, 2005 Is this related to my post? Link to comment Share on other sites More sharing options...
swansont Posted October 18, 2005 Share Posted October 18, 2005 From what I have understood' date=' quantum mechanics states that if there is a probability of, let's say, 10 things happening, then ALL 10 things will happen. MY question: Where do they happen? Do they happen in parallel universes? [/quote'] One problem here is that this is really not a well-defined statement. One interpretation has already been dealt with here, because of the parallel universes statement. But conceptually one could also interpret the statement to mean that a particle is in a superposition of states, and the answer to that is that yes, in that basis, the particle is in the different states, and only "collapses" into a single state when you make a measurement. Or, one could be looking at an ensemble of systems, and discover that all 10 outcomes happen (related to particle physics idea of "that which is not forbidden is required") It depends on the context. Link to comment Share on other sites More sharing options...
aommaster Posted October 18, 2005 Author Share Posted October 18, 2005 Sorry Swansont, but I cannot really understand what you mean by a "superposition of states". Could you please explain to me what that means? Link to comment Share on other sites More sharing options...
Severian Posted October 18, 2005 Share Posted October 18, 2005 I take it that the you in your quote is your way of saying that there is no possibility of decidiing by experiment that there is a difference. What experiment/experiments was/were performed to reach this result? Can I replicate it/them. Details please . . . This is not an experimental statement - it is a statement of principle. If different theories do not predict different outcomes then they cannot be distinguished. I do not need to verify this experimentally because I can prove it mathematically. Link to comment Share on other sites More sharing options...
swansont Posted October 18, 2005 Share Posted October 18, 2005 Sorry Swansont' date=' but I cannot really understand what you mean by a "superposition of states". Could you please explain to me what that means?[/quote'] Consider a spin 1/2 particle - the two states are "spin up" and "spin down." I can prepare that particle such that it is in both states, so that the wave function is a linear combination of the two. The particle is then said to be in a suerposition of the two states - the wave functions add together, following the principle of superposition. When I measure the particle's state, it can only be spin up or down, but it is not the case that it was in that one state all along. Link to comment Share on other sites More sharing options...
aommaster Posted October 18, 2005 Author Share Posted October 18, 2005 So basically, if there are 10 possible outcomes, the particle is in a superposition of all 10 outcomes? Link to comment Share on other sites More sharing options...
swansont Posted October 18, 2005 Share Posted October 18, 2005 So basically, if there are 10 possible outcomes, the particle is in a superposition of all 10 outcomes? That's one way of interpreting the original statement, yes. Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted October 19, 2005 Share Posted October 19, 2005 This is not an experimental statement - it is a statement of principle. If different theories do not predict different outcomes then they cannot be distinguished. I do not need to verify this experimentally because I can prove it mathematically. If they predict different outcomes, but present technology cannot differentiate them, is that science? Link to comment Share on other sites More sharing options...
aommaster Posted October 19, 2005 Author Share Posted October 19, 2005 I think this is the problem with quantum mechanics and string theory. Although I beleive that the String theory is correct, many people say that it cannot be proven (and may never will be) by experiment, and therefore, it is not a science, but a philosophy! Link to comment Share on other sites More sharing options...
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