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Does the light speed Barrier exist?Posts: Joined: 2003-02-18
According to the theory.... any particle you continuously accelerate requires more and more energy to accelerate so that as you approach relativistic velocities you need more energy to continue accelerateing up to light speed then is available in the entire Universe.
It is taken as a given that the same law, for reasons I'm not sure anyone understands, also applies to forces, which have no mass.
We know there is a finite limit on the speed of forces such as Radio waves, Radar wouldn't work otherwise.
But what about Gravity?
I'm not qualified to discuss Orbital mechanics in any depth and certainly can't calculate the orbits of planets, planets etc.
But I'm assured by those that can and do that the calculations they use make a fundamental assumption, that Gravity is an instantaneous force.
For example... it takes light eight minutes to travel from the sun to the earth but the calculations used to describe the Earths Orbit work ONLY when it takes in to account the Suns position to the earth right now, not where it was eight minutes ago.
And if you tried to work out earths orbit assuming that it's gravitational pull traveled at the same speed as light... the earth would spiral out twice it's current distance from the sun in one thousand years.
Furthermore, a black hole is something that is said to be so dense with such a strong gravitational field that nothing, including the fastest thing we know of.. Light itself.... has the velocity to escape it's event horizon.
So how come gravity does?
DaveGood
Submitted on Tue, 2007-10-30 18:20
Rooting around the Minus ONe
Dave
I have been waiting for a physicist to come along and sort things out, but in the absence of such, I think we need to start with categories. Gravity is one of the four fundamental forces of nature along with electromagnetic (EM), and the weak and strong nuclear forces. Each of the 4 has its mediating particle: photons for EM, gluons for strong and bosons for weak; Gravity has gravitons, but they remain elusive to detection. as indeed they would be if they move at infinite speed, because when anything exceeds the speed of light, its mass becomes the square root of minus 1, which is an imaginary number, or so I was told years ago. So gravitons have to be imaginary. Er... that's it. I get off here. C'mon Englishman, you're a physicist, give us a hand. Richard
Submitted on Thu, 2007-11-01 21:00
reply Ahem! Cough, cough.
I will do my best. I am a bit rusty on such matters. I think we are in the realms of mixing the concepts of quantum mechanics and General relativity. There are several theories but none fully accepted. This is my way of saying I am not going to go too deep because I will get lost. To address Dave's comments: you are right that according to Relativity theory (special and general) it would take infinite energy to accelerate a mass to the speed of light. There are a number of ways to view this but relativity, like quantum mechanics, needs mathematics to explain the behaviour. This can seem bizarre because it is not what we would experience in our everyday life. From special relativity the mass 'm' of an object moving at a velocity 'v' relative to an observer will increase as 'v' increases: m* = m/(1-v^2/c^2)^0.5 where 'c' is the velocity of light As v approaches c, m* approaches infinity so it takes an infinite amount of energy to accelerate it further. I assume you know this, or can read up on it, along with the effects of time dilation and Lorentz contraction. An interesting point, though nothing to do with what you ask, is that from the perspective of someone on an accelerating spacecraft, the time it takes him (on his clocks) to get from A to B would be exactly the same as he would calculate from Newtonian mechanics. It is just that although he does not see the speed of the planets zipping past him at the Newtonian calculated rate, the distance he travels gets Lorentz contracted such that the two relativistic effects cancel out. Of course when he returns to earth he will find that time will have passed more than for him; much more is if he got close to the speed of light. But to get to your point, a finite mass moving at the speed of light would have infinite mass (from the equation above) but that does not mean that a particle with "zero rest mass" can't have a finite mass at the speed of light. Photons are sometimes referred to in this way; not that you can ever stop a photon and weigh it. It is rather that you can consider the energy transport of an electromagnetic wave as a particle in some cases i.e. in quantum mechanics. As a wave it moves (by definition) at the speed of light, but when considered as a particle, and can behave as a particle and is affected by gravity as would a particle (in some ways), it is convenient to treat it as such. Forces and fields are really somewhat intangible concepts. The acceleration of an electron produces an electromagnetic wave that will radiate away at the speed of light. Any other charged particle will not notice the effect of the acceleration until the wave reaches it. However the static field of the electron and the field of any reacting particles seem mutually linked. This can also be thought of with masses and gravity. You can try to think what it means that a mass has inertia. I know this is a bit like saying why does mass have mass. It has been postulated that mass only has mass because of all the other mass in the universe. Richard Feynman put forward a theory that when an electron was accelerated it radiated out em waves both forwards and backwards in time. The universe reponded with due respect to the speed of light and it turns out that this can create the effect of the static field. As you can imagine, the maths for checking this out on various models of the universe is a daunting task and one that I believe he never completed. Richard Feynman is a hero of mine and on the list of people I would have most liked to meet. Gravity fields can be considered in the same way, but people have yet to experimentally prove the existance of gravitational waves. But I also think you can just look at gravity from a general relativistic view where you can dispose of ethereal fields and consider gravity as an effect of distorted space-time. It is then not a force as such. The force is what you have to exert to stop objects moving as they would naturally do. It seems like two objects are being drawn to each other, but actually they are moving freely in curved space-time. It seems like there is a force pulling them together, but actually this illusion is because you have to apply an equal and opposite force to keep them apart. The objects are really in free fall but in curved space-time. To complicate matters further there are issues of quantum entanglement which take action at a distance to new depths of complexity and wonderment. I don't think this will help much as I am ignorant as to recent thinking on these subjects. For sure there are no definitive answers although quite a few theories, mostly unintelligible except to those with a good grasp of some sophisticated maths. It is certainly an interesting subject to ponder and there are many questions. As Feynman would say "Nobody knows", which is why physics is an interesting field.
Submitted on Fri, 2007-11-02 10:14
reply pysics is a difficult subject
1- really i want to understand physics, but it is so much difficult for me, i have to read it well to understand, since school i find it difficult , i think it is better for me only to participate in conflicts not science but why you want the light speed to be barried if i understand? may be if their would be a barrier to it so we will have all nights and not days .
Submitted on Fri, 2007-11-02 01:54
reply understanding physics
Abdulksaida, physics is about how the universe works and what are the underlying rules and patterns. By the middle of the 19th century it all looked quite easy, but the discovery of quantum mechanics and relativity had made everything extremely complex. Physics is now a very big subject and so complex that most physicists have to specialise. There are not many (if any) who can understand the whole subject to any great depth. Fortunately even a meagre knowledge is useful in the world. On another subject, I noticed that I forgot the square root in the formula when I typed late last night so I edited in ^0.5 this morning. The order of the posts gets rearranged when you do this so that an edited post becomes the most recent. This is not how it used to work. I have noticed this happening with other people's posts too. It may seem like a good idea to some but it can make a thread very confusing. Clearly it doesn't matter in this case.
Submitted on Fri, 2007-11-02 10:32
reply Interesting:)
Interesting:)
I did not expect any replies at all since this forum was long dormant, apparently my post was the first in three or four years.
Abdulksaida..... the speed of light in a vacuum has been measured at something like 300, 000 kiliometres per second.... and nothing, aboslutely nothing, is believed to move faster then this speed. This is supposed to be true of "Information" or "data" as well as "Physical" things like say space ships.
That's what's known as the "Light speed Barrier".
The problem is that the Earth responds to the gravitational pull, of the sun instantaneously, not at light speed.
The gravitational "Data" or "Information" on the Sun's position is transmitted to Earth Instantly, not with the eight minute time lag of Speed of light.
Englishman .... ok... I followed about two thirds of what you said, thanks for the effort in helping me by the way :)
I've not come across the term "Zero rest mass" before and I'm not sure I buy it.... Sounds like a theologians fudge rather then a theory. I know Light can be modeled as either a particle (Photon) or a wave. I also know that photons have discrete energy levels ( Which is why they can be regarded as particles) but light displays Diffraction properties which is something waves do. I also know that light is affected by gravity, which does tend to suggest it has some degree of mass.
I was not aware of Richard Feynmans ideas about accelerating electrons radiating opposing em signals ( or at least forces), both forward and back in time.
That immediately flagged up intrigueing possibilities in my mind, plus counter arguements such as if that was true then that would mean events in the future would be having an impact today, which at first glance, we don't observe.
Unless the em wave coming from the future was such that it could not interact with the present through some process akin to polarization. But then I recall the vast amounts of "Dark"" Energy and " Dark" matter" whose effects astronomers observe and affect our universe but cannot find. And I start to wonder if thee so-called " Dark" energy and "Dark" matter might be Heynmans backward radiating forces.
Einstiens analogy of Space-time as a rubber sheet with rolling wieghts on it creating dips and and depressions has always seemed weak to me.... Not his fault. It was a concept graspable to the man in the street but I doubt it was really close to what he actually thought of as space time.
And I'm not sure when you refer to a Static field" what you mean, though I do grasp that if an event such as an acceleration of an electron radiates equal forces in opposite directions the effect is "Nuetral" or static..... I just don't grasp how that might exlain Gravities apparent FTL propogation
And it would not, does not explain Gravities apparent ability to transfer "Information " across the Universe instantaneously.
And where I brought up one example\possibility of something that should be impossible, something that moves faster then light, you've seen that and raised me with the possibility that "Information\data" can move back, as well as forwards in time!
I was really intrigued by Richards implied suggestion that if "Gravitons" exist as actual "Particles", we wouldn't detect them because we have no technology capable of capturing anything that moves FTL.
I started running across terms such as "Quantum Entanglement" maybe twenty years ago. Basically it looked like a bunch of theoretical physicists were\are sure that if two particles that were in some sense "Entangled", were then seperated, and moved apart with the whole universe between them. Whatever was done to one particle, would be instantly detected by the behaviour of the other.
I think there's been some experiments that "show" this.
But the explanations as to what and how this comes about is beyond me.
Thanks for the discussion, given me something to mull over.
Richard, I'll be back in the fight over the weekend, if my beloved grants me KB access this weekend. :)
DaveGood
Submitted on Fri, 2007-11-02 22:15
reply pysics again
DaveGood
1- what is the black hole you mention about it in your post, and its influence upon our universe?
Englishman
As you are pysicist, so it seems it is easy for you to understand rules of the universe and how it is going. I hate many equations, i like to know the conclusions without going to calculations. thanks for clarification
Submitted on Sat, 2007-11-03 10:35
reply Good you are interested
Dave, there is lots of good stuff on the web that explains stuff better than I can. It's hard to get ideas presented at the right level though; it's either fairly trivial or extremely mathematical. There are sites that are quite good though. I have little time for a while but I will sort some URLs out for you in the coming weeks. I'm not sure the rubber sheet and balls was Einstein's idea though it's often used to illustrate his general theory. All these illustrations fall far from being the whole story but the human brain cannot visualise 4-space too well. The maths gets hard quite quickly with any real scenario so analogies help with the visualisation.
Submitted on Fri, 2007-11-02 22:48
reply Understood Englishman
Understood Englishman :) I live with a brain evolved for use in a 3d world with an optional, add on, 4th dimension (Time). In fact the Universe may have far more dimensions then that, that my senses cannot see, as in I can't sense UV or EM. And perhaps only a grasp of higher maths can allow you to glimpse them, I know this. But then I have never seen or directly sensed Ulan Bator, or the centre of Kyoto, but can get a grasp on what they are like from descriptions of those that have. If you come across any interesting web-sites , post them here by all means, but keep in mind , for now, ny starting point. Why does gravity appear to act as speeds faster the FTL?
And thanks :)
DaveGood
Submitted on Sat, 2007-11-03 00:26
reply Action at a distance
Dave, gravity does not behave differently from other "forces" in terms of "action at a distance". If a black hole were to accrete more positive charges than negative charges it would remain as a positively charged black hole, as far as I know. The action at a distance issue you refer to applies to both. It does not, strictly, violate relativity in that it is not practically possible to use this effect to transmit information faster than light, but is still a mental puzzle. Other dimensions are thought to exist (according to string theory) but most of these are thought to be only important for calculations to see what happened in the first instance of the big bang or in the behaviour of some subatomic particles. I think the number of dimensions depends on the version of string theory but, in some theories, is up to 26. Abduksaida, a black hole is thought to be created when a large star collapses. To form a black hole the star must be much bigger than our sun. Eventually the huge amount of energy emitted by a star diminishes as its nuclear fuel runs out. It is this outpouring of energy that stops the huge gravitational forces caausing the star to collapse. There are several stages to the collapse of a star but, if the star is big enough, it can, in theory, collapse to a point (called a singularity). Because the gravity field at a point (containing a large mass) would be infinite, nothing can escape. There is a area around this point where it is not possible for anything to escape (actually to be correct, to escape to an infinite distance). In the case of a non-rotating black hole this is a sphere called the eveny horizon. This makes it difficult to observe black holes directly although their presence can be deduced by many other observations. I was trained as a physicist and use physics in my specialist area of work but I would not say it makes it easy to understand the universe and how it works. The more you know the more you realise how little you know.
Submitted on Sun, 2007-11-04 15:48
reply Hi Abdul
Englishman describes a black hole well, but I'll try a simpler version. Picture this.... You have a ball.. you throw it straight up, but the effect of gravity pulls it back down again.
So you throw it faster, it goes higher, for longer, but still falls down.
So you stick a rocket under it, to give it lot's of speed, and if it has enough it will escape the earth completely and not fall back ever. That speed is known as the "Escape Velocity" and every planet, sun, star etc has one. How fast that speed is depends on how heavy, how dense, the sun or planet or moon is. For example the "Escape velocity" of the moon is much less then the Earth because it has less mass, it wieghs less. Now, let's take a star, like our sun, but way bigger. After it's burned it's way through the nuclear fuel available, and cannot stay "On fire".. If it's still big enough, it all collapses inward. What you end up with is a tiny tiny dot that wieghs more then five times our sun.
And the Escape Velocity from something like that is so high that there is supposed to be nothing fast enough in the Universe capable of doing it. If you could stand on such a thing with a ball, even if you had all the energy of the entire universe, you could not put enough speed behind that ball to send it out into space.
The fastest thing we know of is Light... but if you stood on the surface and shone it up into the sky, it would fall back onto the surface.
It's called a black hole because whatever falls into it can never, ever come out. The centre of our own, and nearby galaxies are thought to contain huge black holes.
You can't see them directly (Because light cannot escape from them), but you can work out they are there by the way nearby suns etc are being pulled towards them. My point is.... that gravity appears too. I say "Appears", because it seems to be a force that reaches out from the singularity at the centre, through the event horizon to impact on the outside Universe.
Incidentally, Englishman? I've always been intrigued by the theoretical possibilty of the "Kugelblitz" , and if there is is any way of distuingishing that from a Black Hole.
DaveGood
Submitted on Sun, 2007-11-04 18:31
reply new knowledge for me
DaveGood
1- thanks for the simple clarification of the black hole which i admit that i enjoy reading it and i'd like to go back to it and read about it as it needs more understanding and execuse me when i hear anything about universe i relate to what i read in my faith and remember that Quran in one verse called star say in the first as God swear by the star when it will fall down, so may be the falling of star one day will change all our universe and may be that is the black hole? dont laugh that is my limit of thinking.
2- Also i remember another suran called moon sura in the first it mentioned that the day of judjment will be close then the moon fracture or i dont know the correct term in english but as breakdown . thank you englishman for your explanation and i know that you dont beleive in any faith , but if you were in my place and you are as a physicst , so you will try to relate all what you learned together, that is the point ony .
3- The universe which we are living under neath it really amazing .
Submitted on Mon, 2007-11-05 03:23
reply Kugelblitz
Dave, you had me there. I'd never heard of Kugleblitz. I guess you mean the theoretical physics kugelblitz rather than the WWII gun. I'd not heard of that either. From what I would guess, a kugelblitz would be a black hole but created in a different way. Once it has formed I would guess that you cannot distinguish it from one formed by accretion of matter. It is a theoretical construct and it may be that no such creation exists. It would seem a risky thing to make deliberately even if it could be practically done. By the way I notice I said "eveny horizon" when I meant "event horizon". This come from careless typing! A word of correction BTW. The escape velocity, for instance of an object from the earth, does not depend on the mass or density of the object. It is the same for any object (neglecting the air resistance of course). It is about 11.2km/s or about 25000mph at the earth's surface.
Submitted on Sun, 2007-11-04 19:48
reply Kugelblitz...
Kugelblitz... Yep, I as referring the theoretical Astrophysics version Einstien predicted that a concentration of matter would produce what we think of as "Black Hole".... but he also predicted that a concentration of Energy would do the same thing. Produce a singularity with an event horizon, and that, since Energy and matter are interchangeable in the equations, it would be impossible to tell the difference. How can we tell\know that the black holes we now currently believe we can indirectly observe were formed from one process (Matter collapse) and not the other route ( Immense densities of energy) Because knowing that would make a difference too our understanding of the evolution of the Universe. We appear to be assuming that any Black hole we think we observe were all formed via one route when Einstien postulated two.
I was refering to the the escape velocity of the earth as a function of the mass\density ( Gravitional effect at the surface) of the earth, not the object being launched, should have made that clearer.
sorry about that :)
Submitted on Sun, 2007-11-04 20:31
reply Einstein and black holes
The idea of a black hole predates Einstein and relativity as it can be a consequence of gravitational collapse in a Newtonian world. It was predicted in theory before Einstein although the more correct version needs to use the correct maths. As a matter of interest Einstein never really believed in black holes even though it is a consequence derivable from his relativity theory. But then he was uncomfortable with much of quantum mechanics too! Because of mass-energy equivalence, an event horizon can be formed about a sufficient concentration of electromagnetic energy as well as matter, hence the concept of a black hole starting off as light. I don't think Einstein was involved in such a development of his theory though. The best reference I can find is some work by Prof John Wheeler in the 1950s. There is also some discussion on the web but it's of variable quality.
Submitted on Sun, 2007-11-04 23:52
reply Good catch Englishman :)
I
Good catch Englishman :)
I was aware Einstien was uncomfortable with the consequences of some of his work .I did not know that a theoretical understanding of a black hole as a consequence of gravitational collapse predates him though!
I find t interesting that there is no discussion anywhere I know of that a "Kugelblitz" might account for phenomena we routinely assign to "Black Holes".
thank you Englishman :)
DaveGood
Submitted on Mon, 2007-11-05 00:25
reply Abdulksaida :)
Abdulksaida :) Think about this..... Almost all of Astrophysics ( The science of studying the Universe and all it contains)... is founded on work down by Arab\muslim scholars during the west's dark ages. and because of the fine work down by Muslim scholars long ago. when I look up into the sky at night at this star or that one, chances are it has an Arab name. Like the star Aldebaran.
DaveGood
Submitted on Mon, 2007-11-05 22:56
reply The universe which we are living under neath it really amazing .
AbdulKsaida, we can all agree to what you have said, whether we are people of religion or people of no religion. I remember the day that it was reported some scientists had picked up traces of microwave radiation in the far reaches of space which are the echoes of the Big Bang, and as I was falling asleep, I imagined the universe going back in space and time to the point when everything becomes just that, a singular point of infinite mass and infinite energy, but without time or space, that cannot be described as anything except the purest form of Being, just existence in and of itself, an existence that is co-extensive with everything that is since there is no non-being, only Being at that point. And then the thought struck me: <i>"But there was Existence, when there could so easily have been Nothing"</i>. For us to be truly conscious of that Existence is enough to make us all react with the same kind of feeling that Mohammed (peace be upon him) felt in the cave, and Jesus (peace be upon him) felt in the desert, and Moses (peace be upon him) felt on the top of the mountain, and the same feeling that any of us (peace be upon us all) may feel at any time when we feel compassion for another fellow creature. Salaam and Shalom Richard
Submitted on Mon, 2007-11-05 22:13
reply Bad thoughts about imaginary particles.
Am I right in thinking that nothing can escape from the event horizon of a black hole except gravity? If so, gravitons either have no mass, or are capable of infinite speed. In either case, they are imaginary, in the first case on account of having no mass, and in the second case, on account of their mass being a function of the square root of minus one, which is an imaginary number. If they are imaginary, that surely must mean they do not exist?(Although it must be said that even the concept of one squared is a bit dubious, because for a number to be multiplied, it has got to change, and anything multiplied by one does not change). So, physical naif that I am, I dare to question whether every force has to have its associated particle? It reminds me of every god had their attribute, Zeus his thunderbolt, Shiva his conch &c. Do we have to have gravitons, messy and dubious as they are? What is wrong with the idea of mutual attraction? If we have to think in terms of particles, why not call them Loveons, or Loveins rather than Gravitons? Maybe the larger body emits Gravitons and the smaller body in the system responds with Loveins. All of which reminds me of Guy Dauncey, another non-physicist, who has a critique of the mystery of the Heienburger principle. He holds that is is all perfectly obvious: "...if something is moving, it NEVER has any position, and so any attempt to locate its position is doomed to failure. Imagine something extremely small, and imagine it moving. Now take a tiny moment of time, and consider where the particle is. The 'moment 'of time must have a dimension, to be meaningful - ie it must be 1/10th of a second, or 1/1000th of a second. However small you make the 'moment' of time, it will always have dimension, and during that dimension, the particle will always be moving. You can take the moment of time and shrink it a billionfold, but it will still have dimension, and a moving particle will always cross a certain amount of space during that time. However small the space, you can always magnify it a billionfold to look at it more closely, to observe that it is a distance, and not a 'point'.Conversely, if you want the particle to have position at a certain 'point' which you can identify, that point too will always have dimension, and the particle will therefore need time to cross it. To prove this, you only have to take the smallest possible point you can ever imagine, and then magnify it a billionfold to discover that it is not a point at all, but a distance, which has dimension. My interpretation of this (which may be wrong) tells me there is nothing "new" in this at all : the fact that you can never know both the position and the momentum of a particle at the same time is not an enigma, or anything to do with uncertainty at all : it is simply a fact of nature, which needs no explaining." http://www.earthfuture.com/lit/uncertainty.asp In other words, the paradox arises from reducing movement to increments of space. An illusion that would come easily to someone who is used to using the calculus. Guy is not combative about this; his physicist friends tell him why he is wrong in mathematical terms that he cannot understand, and he is quite happy to bow to their greater expertise, but ... Sometimes I wonder if particles appear in cloud chambers just because the observing physicist believes they must be there somewhere. Like faries. I know it is very wrong and bad of me to think these thoughts.
Submitted on Mon, 2007-11-05 22:56
reply Richard, you are obviously a bad man :-)
According to Hawking mass can escape from a black hole and eventually black holes can "evaporate". In practice this happens to only small black holes. This is, of course, a theory, albeit one worked out very carefully. The reasons are to do with particle - antiantiparticle creation (that may occur spontaneously anywhere) near the event horizon then one particle being lucky enough to escape but the othe not so lucky. I don't remember the details but it is along these lines. The concept of gravity escaping is not quite right. The gravity field exists (what I was referring to as a static field and action at a distance). If there was more positive charges than negative ones accreted by the black hole the black hole would have a positive charge. The electric field would exist but electromagnetic radiation would not escape. When you alluded to forces being represented as an exchange of particles, this is one of Feynman's ideas that shows that the transfer of energy of the exertion of a force by one particle on another can be represented by the exchange of another particle. This is particularly useful in particle physics but may not be the best way to think about black holes. The problem is that we are trying to build models, both mathematical and, sometimes, ones we can visualise, of a reality we that our senses are not designed to experience. These model can help understanding and give some intuition on behaviour but for most of us they are not very helpful. More and more the mathematical models that represent reality do not give any visualisation at all, but going through the maths does enable prediction of the behaviour. The models are then used until someone shows they are inconsistant with reality and a new theory is needed. Unsatisfactory in many ways but fascinating nonetheless. Heisenberg's uncertainty principle is rather more complicated than was expressed in the couple of paragraphs. It represents something much more alien than can be expressed in such prosaic terms. Also because sqrt(-1) is called an "imaginary" number and other numbers "real" you should not think of these words as meaning the same as the everyday meanings. In other applications an imaginary number can refer to another "orthogonal" dimension. Imaginary numbers appear a lot in quantum mechanics and be part of a "probability amplitude" for an event, position etc.
Submitted on Tue, 2007-11-06 19:32
reply Ah....
Englishman, I thank you. I believe now. Words cannot capture particles accurately, but equations can. Does that mean that everything balances, because the equation is a balancing act? If so,I am glad that everything is in equilibrium. If not, I am intrigued that everything is not in equilibrium. Tichard
Submitted on Tue, 2007-11-06 23:01
reply For Dave Good, on modern physics...
Dave, I said I would give some reading recommendations when I had some time. Regrettably, I find I don't have the time to trawl the net, where I know there is interesting stuff to be had, but which is hard to get at the right level. Instead I would recommend, as a generally good read on modern physics but with undemanding maths, the books by Roger Penrose: The Emperors New Mind The Nature of Space and Time The Road to Reality: A Complete Guide to The Laws of the Universe. He has some ideas about quantum mechanics which are considered contraversial. He has, in particular, a theory that the human brain uses quantum computing, which is a bit odd (in my view) and not a necessary conclusion. But he is a very knowledgable guy and communicates very well. These books are very good the best written works on the subject I have seen.
Submitted on Sun, 2007-12-02 21:27
reply Dave Good
Regarding your comments: <>"The problem is that the Earth responds to the gravitational pull, of the sun instantaneously, not at light speed.
The gravitational "Data" or "Information" on the Sun's position is <> Maybe Englishman could correct me if I am wrong, but, as I
Submitted on Wed, 2008-03-26 18:57
reply I thought this subject had disappeared
Alan, you are right that gravitational waves are thought to travel at light speed. The difficulty with the question about what happens if the sun disappears is that it physically can't happen, as you say. You could imagine it exploding, for example, but then its centre of gravity would remain in the same position and its gravitation pull would remain until it could cease to be regarded as a point gravitational source. But in any case, we wouldn't know about it for 8 minutes. Action at a distance is still a "spooky" subject though and may need to invoke propagation of "advanced" waves (i.e. going backwards in time) as well as the usual retarded waves, according to the late Prof Feynman. He never completed his theory though but thought "someone" should do it. Unfortunately there are very few people with his ability.
Submitted on Sat, 2008-03-29 10:35
reply Action at a distance
Ah, now you are getting into the quantum world of Schrodinger's Cat. Fun thought experiment. Maybe the solution is: there is no "action at a distance" but, instead, there are parallel universes. So whatever choice is made and observered, simply creates two distant choices, one in this universe, and another in a parallel universe.
Submitted on Mon, 2008-03-31 17:05
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