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AUDIENCE COMMENTS |
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An opportunity for the audience to have their say on In Our Time. |
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THE GRAVITON
Cornelius Kavanagh - Graviton vs Higgs Boson
Did this week's programme on the Graviton, conveyor particle of gravitational fields, exist on a parellel dimension to your equally excellent programme on the Higgs Boson, conveyor particle of gravitational fields? Are they alternative theories or parts of the same mechanism? There seemed an unspoken taboo against mentioning the other term in either programme. I remember being taught about Gravitons at A level, and when I heard the Higgs programme last year I thought it was just that the name of the partivle had changed. I had an option of English or Physics at University, and chose English; I am writing this in the genuine hope that someone who has kept up with their Physics can explain it to what's left of the brain I had 20 years ago.
Roger Jones - the Graviton
Should Mostyn Kearle still be wondering, the point Roger Cashmore was making was that gravity is *only* attractive and not repulsive (or more to the point, there are masses but no negative masses), while the strong interaction (and you may as well have mentioned electromagetism and the weak interaction) can be either attractive or repulsive. They are all mediated by spin-1 bosons (the gluon, the photon and the W and Z respectively); gravity is believed to be mediated by the spin-2 graviton. Hope that helps.
Jim Russell
In response to Philip Morgan, his indignation is as misplaced as the professor's. Both meanings are correct - in their appropriate context. And I am not sure that Melvyn's PS comment in his letter is entirely fair. There is at least a discernable reality behind the search for the graviton. I have to admit, however that when I made the same comparison when referring to mathematicians discussing 'proof' - the subject was 'mathematically proven' software - I drew from my boss the remark 'Typical b****y chemist'. In amy case a great thought provoking programme.
Anthony Ariss
Poscasts Would it be possible for the podcasts to include 'bonus' material' such as further discussions at the end of the program - which I'm certain there must be? The mp3's /podcasts are a tremendous idea. I have been collecting them since they first appeared and its great to go back and listen to other relevent programs ( higgs boson / dark matter / graviton . Although listeners can go to the archive to listen to other programs, why not make the entire back catalogue available in mp3 format?
Jim Grozier - gravitons
James Baring said: "A being within the sheet with only 2-dimensional sensibility would find everything drawn towards a significant mass without being able to see the curve in the sheet. The curve represents a changing in value in a dimension they cannot perceive". But what is doing the drawing? Just being in a 2D sheet which is "curved" in another dimension would not make things move. To do that you need to have a uniform force field at right angles to the sheet - because the rubber sheet model will only work in such a field. I repeat - this is not really a very useful model. What, in terms of the scenario the sheet is being used to model, is doing the job of the earth's gravitational field, which makes the masses distort the sheet?
Jim Grozier - Quantum Leap
I agree with Philip Morgan but for a different reason. Many physicists seem to get confused about why we use the word quantum; it isn't because a quantum is very small, it's because it's very big - at least, when compared with the alternative, which is a continuum. If you have a continuum, all energies are possible and so you can change energy by as small an amount as you like. The revolutionary thing about quantum theory was that it said such small changes were NOT possible - that you have to change energy by a discrete step, nothing less will do. So a quantum is indeed a big thing, and the term "quantum leap" when applied to non-physics contexts, is being used correctly. The fact that quanta are very small compared to the human scale is irrelevant.
Wyn Pugh - Graviton
underground for about twenty-seven miles and spans Switzerland, France and Germany" The CERN ring between Geneva and Ferney-Voltaire is a long way from Germany... We lived in Meyrin, Geneva and used to walk across the fields and meadows under which the previous CERN ring was firing away. A great programme - I loved the explanation of the distortion of space-time using a rubber mat!
Jim Grozier - The Graviton
No comments on the graviton, anyone? Or is everyone else (like me) waiting to see what everyone else says? What do people think about the rubber sheet analogy? I hope this won't sound arrogant, but I don't believe that simplistic pictures like this are very useful as they tend to oversimplify what they are trying to convey and paint a false picture. Can anyone honestly say that they understand what "curved space" (or to be more precise, curved spacetime) really means? What is the third dimension in the rubber sheet model? It isn't time, and it isn't space. So what is the sheet being curved into? I think I'm with Jim Al-Khalili and his "Shut Up & Calculate" interpretation of quantum mechanics. Subjects like QM and general relativity are, unfortunately, simply too far away from everyday experience to be described using everyday models. We have to rely on the maths for an accurate (if abstract) picture.
Philip Morgan - 'a quantum leap'
Prof. Al-Khalili's indignation with regard to the use of this expression is misplaced. In Latin quantum is used as an adverb meaning 'how much' or 'as much as', or as an adjective meaning 'how great'. Physicists should not have adopted the word as a noun to mean something extremely small. WThe expression 'quantum leap' simply means a great leap forward - it is the leap that is great, quantum being used as an adjective. The use of the word as an adjective is perfectly correct; it is its use as a noun that is incorrect.
Terence Walls - Graviton
Lots of us will be familiar with the Rubber Sheet as an illustration of the gravitational distortion of space, but what struck me was that Gravity Waves were meant to be generated by resonance, or oscillation of the central mass. If a mass is dropped into a rubber sheet we can imagine ripples of distortion spreading out from that mass, but these will be a consequence of the kinetic energy derived from the dropped mass. As the mass settles, the potential energy will be dissipated and the generation of any waves will cease. Is it proposed that there is some kind of gravity-energy source within all matter that would propagate Gravity Waves in perpetuity? If so could someone explain where the 'E' come from?
Euan Smith - Graviton newsletter
This is really a comment on the issue of physics teaching brought up in the newsletter, an issue close to my heart as I am also another extremely concerned physicist. The issue of salary was raised, but I do not believe that is the whole story. I know of physicists in teaching who, along with the other subject specialists, have to teach the other scientists. This will never produce passionate lessons. There is also, I believe, misconceptions in career advice - Physics, along with Maths, opens more career doors than any other subject I can think of, but few teenagers are told this. How about a programme (probably not in our time, but an investigative programme) to find out the reasons behind the current decline and debate the salary (and other) issues. This debate desparately needs to be started somewherer.
Anthony Briginshaw: Search for the Graviton
I was intrigued with the speculation that space-time might occur in packets. The implication is that the universe arose from an irreducible initial state. Packet number 1. What does that imply for the Big Bang? That the first space-time quantum suddenly arrived? From this side of the Big Bang that looks like an act of creation by some agency. But then one quantum would not be enough, would it? The process of creation would have to continue until, what? Until there was a "critical 'mass'", and a process of interaction and regeneration by which the observable universe continued to develop?
John Booth - the graviton
The Unification of Relativity and Quantum Physics 1. Einstein stated that acceleration and gravity are 'equivalent'. What exactly is meant by this? Most people, it would seem, think that this means that they both produce the same result i.e. curved space-time. Then, an accelerating particle bends space-time just as would a gravitational field. 2. This however is not strictly what is meant in my opinion, nor is it sensible, as an accelerating particle creates gravity by causing space-time to bend and therefore gravity created by a body such as the Earth is caused by its acceleration through space-time. 3. Hence the meaning of 'equivalence' is that gravity and the curving of space-time by an accelerating body are the same. The Earth causes gravity by its acceleration in space-time not by its presence alone. That is, if the Earth were still it would have no gravity. 4. I doubt if even Einstein realized or wanted to accept the consequence of this as it puts space-time back to being some kind of ether, but one that reacts with the matter within it. 5. What then are the consequences for the unification of Relativity and Quantum Theory, and the graviton? A particle's trajectory is bent by space-time because it follows the curvature of space-time. Similarly the Earth bends the space-time around it. Hence the interaction is between body and space-time, not between body and body. A graviton would have to react between space-time and a particle. This would put the graviton as being of a different character than the three quantum forces of electro-magnetism, strong and weak nuclear. 6. Since space-time is probably a form of energy like everything else the graviton should exist, but whereas the other forces are seen against a back drop of space-time the graviton would have characteristics of space-time. It could therefore be seen as a continuous ripple in space-time emanating to and from a particle. Of course since we cannot even detect gravity waves its detection would be practically impossible. No doubt however its value could be calculated and in fact would be gravity per unit mass divided by the number of radians in a sphere. Hence the graviton would be a function of h2(h bar squared). The expanding Universe 1. What is or what caused the Big Bang? A photon travels at the speed of light. Therefore for a photon time is stopped and distance infinitely small. A photon would be everywhere in the line of its trajectory throughout the Universe. In other words taking all the photons in the Universe, the Universe is a timeless dot. 2. The Big Bang was the Big Slowdown. As the particles of matter began to slow down space and time was created. 3. This would explain the so called Dark Energy. Matter on the outer reaches of the Universe as observed today would still have the speed nearer to the start of the Big Bang, therefore time for them would be running slower than for us now. What would be a second to them would be less than a second to us thus causing them to be moving even faster by our standards and causing the red shift observed.
Eva Zurron
I always listen to your program with great attention and this time I want to comment on the state of science teaching. My personal experience can back up the fact that biology teachers with little knowledge of physics are teaching physics, and chemistry for that matter. In fact, they have to teach themselves before they teach their pupils. This is just terrible but it is a fact! I must admit that my time as a trainee teacher in a big comprehensive was one of the most awful times in my life, because of the lack of support. I agree that science teachers probably deserve a better pay, but also more support for teachers in general is needed. The state of education in this country will not change till the work of teachers, and not only science teachers, is payed better. In my personal experience I've never met so many demoralised a demotivated workmates that the people I've met at the staff room of this comprehensive school. That can put anyone off teaching!
Bernard - Gravition Musings
Some mischievous thoughts prompted by the Graviton newsletter. As every politician knows, and most physicists, the answer lies in putting a spin on it. All other particles (sic) in the world of physics have spin. Yes, do abandon thoughts of 'volume' (as suggested in the newsletter). The deeper one looks into a politics, philosophy, physics topic the less substance is found. It is only 'movements' (in any sense) that sustain them. Meanwhile I hold to the mathematical, philosophical, all discipline perspective that 'nothing is true' (taken in its positive sense, of course). And, that for any 'rule', 'axiom', 'truism' to hold then it should do so across the disciplines. The 'nothing is true' movement has only gained small momentum in the decades since the 70's, and certainly has not yet had any mainstream impact. It lacks having a spin with sufficient momentum Coincidentally IOT is also how one of the main groups exploring this chaotic view names itself. Similarly, for the Graviton, once both its proponents and their theories gain sufficient spin then a proper understanding of this mysterious force can be gained. These words can be taken lightly as even truth can be injested.
Anthony Wood - Graviton - Dirac
I was surprised and disappointed that whilst the program discussed the unificaion of quantum mechanics and relativity, no mention was made of Paul Dirac's work. This brilliant British (born & bred in Bristol) physicist unified the two for electrons in his 'Beautifully' simple and elegant Dirac equation in the 1920's (if I remember the date correcly). From his equation antimatter and spin (discussed in the program) are directly predicted. It is only by considering the relativistic effects of electrons that gold appears gold rather than silver. I just do not understand why Dirac does not have a higher profile in his native Britain. For instance Stephen Hawking said (in 1995) "Dirac has done more than anyone this century, with the exception of Einstein, to advance physics and change our picture of the universe". The Danes do not seem to have this block and even have a football team F.C.Dirac!
James Baring - GRAVITONS
The graviton debate set out some current theoretical positions and coming experiments and as usual admitted that even the hypotheses are disputed. The word carefully omitted from the discussion was inertia, the property of mass that is critical to our understanding of gravity. Energy normally either travels at the velocity of light or it is manifested in part by what we call mass. It was when the geometry of space in the neighbourhood of a very large mass was seen to deflect massless photons that the case for the nonlinearity of space-time (space-time of a sort was a concept originating in Special Relativity) was proven So let us admit that the 'rubber sheet' analogy for the geometric approach is useful. A being within the sheet with only 2-dimensional sensibility would find everything drawn towards a significant mass without being able to see the curve in the sheet. The curve represents a changing in value in a dimension they cannot perceive. A magical force of attraction with no interceptable tractor beam. In fact there is no force, of attraction at all. How should we visualise this in 3-D space? Simple, just as in the 2-D model, there is a change in value in an invisible dimension as we approach a large mass. We can't perceive the dimension in which this value changes but the 3-D effect is the space has less 'existential' (to make up or borrow a phrase). The inertial frame of reference for any point in space-time is affected by the energy of the space time in every direction. So forget about forces of attraction - there are none. The experiment to detect gravitational waves would be better understood if these were called inertial waves. First we need to clear up a common misunderstanding of the Michelson-Morley experiment. This was taken by some to prove there is no 'fabric of space-time' or 'aether' as it was called then. Not so. It it just showed that you cannot detect it by that means, and Special Rel. explains why. The new experiment using an updated Michelson-Moreley technique over a huge distance is not to measure the motion of the earth but to measure distortion of the space-time fabric by inertial waves generated by occasional huge accelerations of masses long ago and far away. It might work! As for a graviton, it was rightly explained as a value, not a particle (there are no particles in the sense that we normally visualise things anyway), a value which as the team said might be detected as missing in an extreme collision of what we call particles and their resulting fragments. The reason we detect packets and particles is because all the energy in the universe which in the form of phenomena which oscillate or vibrate in what we call 'time' to manifest their existence. An unplucked violin string makes no sound. We are observing the equivalent of sound, not silence, when we observe what we call a THING. But when we get to inertial frames of reference we are getting near to dealing with the violin strings. It is only when people get a better idea of the how the other dimensions relate to the world we have to live in that any of this can bring results. It is knowledge we don't understand because we don't yet need it.
Louise Hancock - The Graviton
Cor blimey! I'm off to the garden shed to make a particle accelerator - I can feel exhilerating waves of gravitons passing through me as I write! I'm enthused about this. What I really like is the way it links up to other 'stuff' I've heard about on this programme or Horizon - like dark matter, string theory and quantum mechanics....... I feel about 12 again. I wish I'd listened more during physics lessons! The only disappointment was that no one referred to shagging (as in the Cynics programme)- but I suppose it was too hard to work it into the context. Any chance of making it a pre-requisite for appearing on the programme? ;-)
Graham Gynn gravitons and levitation
the question I would like discussed in relation to the fascinating programme on gravity is how, in the light of gravitons, is it possible for the human body to levitate? (Assuming such a thing is possible) Does this theory of gravitational particles make it easier to understand how something we can do with our consciousness can overcome this very weak force?
Robin "The graviton or no graviton"
I have been contemplating a conundrum for years. Why are atoms are solid to us and now I realise that the only two logical solutions to me fall into the two different camps of physics. The "quantum mechanics" with gravitons were atoms are made from energy waves/ particles that are traped interacting by flinging graviton particles back and forth to each other or the "relativity camp" with no graviton were i invisage the world of atoms to be made of particles and sub-atomic particles that are "nodes", points in space time were two or more energy waves are flowing through that given node continually. If they were then one energy wave could pass through more than one particle, and the nodes resembeling beads vibrating on a sting or energy wave, bonded together by the energy wave a sort of gravitational froce of its own! Fasinating program I must do some more reading! Could I ask has anyone ever suggested
Mostyn Kearle -Graviton
In the progamme it was stated the graviton was unique in having spin 2 and this must be so because it only exerts an attractive force. But as I understand it the strong nuclear force (the 'glue' that hold a nucleus together) is also only anattractive force. So should not the Bosons that mediate this force also have spin 2?
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