Pentcho Valev
2015-10-16 08:43:07 UTC
http://www.palais-decouverte.fr/fr/au-programme/activites/conferences/thema-fabuleuses-mutations/cycle-1915-2015-lodyssee-de-lespace-temps/
Jeudi 12 novembre 2015 à 19h. Les physiciens disposent de deux grandes théories, la relativité générale et le modèle standard des particules, issu de la physique quantique. Mais ils butent sur l'origine de l'Univers, la matière noire et l'énergie sombre. Jusqu'à quel point devront-ils contester leurs théories pour lever ces mystères ? Jean-Michel Alimi, directeur de recherche au CNRS, laboratoire Univers et théories de l'Observatoire de Paris, chercheur associé à l'Institut d'astrophysique de Paris ; Aurélien Barrau, professeur à l'université Joseph-Fourrier de Grenoble, chercheur au laboratoire de physique subatomique et de cosmologie du CNRS ; Philippe Brax, directeur de recherche à l'Institut de physique théorique du CEA, à Saclay, chercheur associé à l'Institut d’astrophysique de Paris ; Pier Stefano Corasaniti, chargé de recherche au CNRS, laboratoire Univers et théories de l’Observatoire de Paris. Modérateur : Jean-Pierre Martin, physicien nucléaire, président de la commission de cosmologie de la Société astronomique de France (SAF).
La relativité d'Einstein et la physique quantique butent fondamentalement sur la notion du temps :
E. Klein (1:06:45) : "Est-ce que l'avenir existe déjà dans le futur ? C'est une question fondamentale ... Les relativistes disent oui - le futur est déjà là mais nous on n'y est pas encore ... Les physiciens quantiques, les présentistes disent non - le futur est un néant ... Les voyages dans le futur sont impossibles pour les présentistes alors qu'ils sont possibles pour les relativistes."
http://www.sciencemag.org/content/early/2015/08/05/science.aac6498
"In Einstein's general theory of relativity, time depends locally on gravity; in standard quantum theory, time is global - all clocks "tick" uniformly."
http://www.pbs.org/wgbh/nova/blogs/physics/2012/11/whos-on-first-relativity-time-and-quantum-theory/
Frank Wilczek: "Einstein's special theory of relativity calls for radical renovation of common-sense ideas about time. Different observers, moving at constant velocity relative to one another, require different notions of time, since their clocks run differently. Yet each such observer can use his "time" to describe what he sees, and every description will give valid results, using the same laws of physics. In short: According to special relativity, there are many quite different but equally valid ways of assigning times to events. Einstein himself understood the importance of breaking free from the idea that there is an objective, universal "now." Yet, paradoxically, today's standard formulation of quantum mechanics makes heavy use of that discredited "now."
Il faut abandonner la relativité d'Einstein avec son espace-temps idiot :
https://www.newscientist.com/article/mg22730370-600-why-do-we-move-forwards-in-time/
"[George] Ellis is up against one of the most successful theories in physics: special relativity. It revealed that there's no such thing as objective simultaneity. Although you might have seen three things happen in a particular order – A, then B, then C – someone moving at a different velocity could have seen it a different way – C, then B, then A. In other words, without simultaneity there is no way of specifying what things happened "now". And if not "now", what is moving through time? Rescuing an objective "now" is a daunting task. But Lee Smolin of the Perimeter Institute for TPs in Waterloo, Canada, has given it a go by tweaking relativity. He argues that we can rewrite physics in a way that includes "now" if we sacrifice some of our objective notions of space."
http://discovermagazine.com/2015/june/18-tomorrow-never-was
"Is the Future Already Written? A conscientious cosmologist rejects Einstein's notion that time is an illusion and the future is set. George Ellis is not afraid to rock the establishment. In his youth in South Africa, his target was a recognizably corrupt and racist government. Now a cosmologist at the University of Cape Town, Ellis has set his sights on something more abstract: the flow of time itself. First developed by Albert Einstein early in the 20th century, the orthodox view holds that the passage of time is an illusion. There is no difference between the past and the future - both are set in stone. Yet for Ellis, the philosophical implications of this mainstream theory do not simply run counter to our intuitions; he considers them dangerous..."
http://www.guardian.co.uk/books/2013/jun/10/time-reborn-farewell-reality-review
"And by making the clock's tick relative - what happens simultaneously for one observer might seem sequential to another - Einstein's theory of special relativity not only destroyed any notion of absolute time but made time equivalent to a dimension in space: the future is already out there waiting for us; we just can't see it until we get there. This view is a logical and metaphysical dead end, says Smolin."
http://www.bookdepository.com/Time-Reborn-Professor-Physics-Lee-Smolin/9780547511726
"Was Einstein wrong? At least in his understanding of time, Smolin argues, the great theorist of relativity was dead wrong. What is worse, by firmly enshrining his error in scientific orthodoxy, Einstein trapped his successors in insoluble dilemmas..."
https://edge.org/response-detail/25477
What scientific idea is ready for retirement? Steve Giddings: "Spacetime. Physics has always been regarded as playing out on an underlying stage of space and time. Special relativity joined these into spacetime... (...) The apparent need to retire classical spacetime as a fundamental concept is profound..."
Nima Arkani-Hamed (06:11): "Almost all of us believe that space-time doesn't really exist, space-time is doomed and has to be replaced by some more primitive building blocks."
http://www.space.com/29859-the-illusion-of-time.html
"Fotini Markopoulou-Kalamara, a theoretical physicist at the Perimeter Institute, said, "I have the distressing experience of physicists telling me that time is not real. ... It confuses me, because time seems to be real. Things happen. When I clap my hands, it happened. ... I would prefer to say that general relativity is not the final theory than to say that time does not exist." Time is a prime conflict between relativity and quantum mechanics, measured and malleable in relativity while assumed as background (and not an observable) in quantum mechanics."
http://www.newscientist.com/article/mg20727721.200-rethinking-einstein-the-end-of-spacetime.html
"Rethinking Einstein: The end of space-time (...) The stumbling block lies with their conflicting views of space and time. As seen by quantum theory, space and time are a static backdrop against which particles move. In Einstein's theories, by contrast, not only are space and time inextricably linked, but the resulting space-time is moulded by the bodies within it. (...) Something has to give in this tussle between general relativity and quantum mechanics, and the smart money says that it's relativity that will be the loser."
http://www.newscientist.com/article/mg20026831.500-what-makes-the-universe-tick.html
"...says John Norton, a philosopher based at the University of Pittsburgh, Pennsylvania. Norton is hesitant to express it, but his instinct - and the consensus in physics - seems to be that space and time exist on their own. The trouble with this idea, though, is that it doesn't sit well with relativity, which describes space-time as a malleable fabric whose geometry can be changed by the gravity of stars, planets and matter."
http://www.homevalley.co.za/index.php?option=com_content&view=article&id=135:its-likely-that-times-are-changing
"Einstein introduced a new notion of time, more radical than even he at first realized. In fact, the view of time that Einstein adopted was first articulated by his onetime math teacher in a famous lecture delivered one century ago. That lecture, by the German mathematician Hermann Minkowski, established a new arena for the presentation of physics, a new vision of the nature of reality redefining the mathematics of existence. The lecture was titled Space and Time, and it introduced to the world the marriage of the two, now known as spacetime. It was a good marriage, but lately physicists passion for spacetime has begun to diminish. And some are starting to whisper about possible grounds for divorce. (...) Einstein's famous insistence that the velocity of light is a cosmic speed limit made sense, Minkowski saw, only if space and time were intertwined. (...) Physicists of the 21st century therefore face the task of finding the true reality obscured by the spacetime mirage. (...) Andreas Albrecht, a cosmologist at the University of California, Davis, has thought deeply about choosing clocks, leading him to some troubling realizations. (...) "It seems to me like it's a time in the development of physics," says Albrecht, "where it's time to look at how we think about space and time very differently."
http://www.huffingtonpost.com/dr-sten-odenwald/happy-birthday-einstein-1_b_8219432.html
Sten Odenwald: "It all comes down to one thing: If we don't know what spacetime really is as a physical agency, how can we possibly understand gravity or try to manipulate it artificially to, among other things, create 'warp drive'? Now THAT is a mind-numbing question. When general relativity turns 200, we may well find its answer....or not!"
Pentcho Valev
Jeudi 12 novembre 2015 à 19h. Les physiciens disposent de deux grandes théories, la relativité générale et le modèle standard des particules, issu de la physique quantique. Mais ils butent sur l'origine de l'Univers, la matière noire et l'énergie sombre. Jusqu'à quel point devront-ils contester leurs théories pour lever ces mystères ? Jean-Michel Alimi, directeur de recherche au CNRS, laboratoire Univers et théories de l'Observatoire de Paris, chercheur associé à l'Institut d'astrophysique de Paris ; Aurélien Barrau, professeur à l'université Joseph-Fourrier de Grenoble, chercheur au laboratoire de physique subatomique et de cosmologie du CNRS ; Philippe Brax, directeur de recherche à l'Institut de physique théorique du CEA, à Saclay, chercheur associé à l'Institut d’astrophysique de Paris ; Pier Stefano Corasaniti, chargé de recherche au CNRS, laboratoire Univers et théories de l’Observatoire de Paris. Modérateur : Jean-Pierre Martin, physicien nucléaire, président de la commission de cosmologie de la Société astronomique de France (SAF).
La relativité d'Einstein et la physique quantique butent fondamentalement sur la notion du temps :
E. Klein (1:06:45) : "Est-ce que l'avenir existe déjà dans le futur ? C'est une question fondamentale ... Les relativistes disent oui - le futur est déjà là mais nous on n'y est pas encore ... Les physiciens quantiques, les présentistes disent non - le futur est un néant ... Les voyages dans le futur sont impossibles pour les présentistes alors qu'ils sont possibles pour les relativistes."
http://www.sciencemag.org/content/early/2015/08/05/science.aac6498
"In Einstein's general theory of relativity, time depends locally on gravity; in standard quantum theory, time is global - all clocks "tick" uniformly."
http://www.pbs.org/wgbh/nova/blogs/physics/2012/11/whos-on-first-relativity-time-and-quantum-theory/
Frank Wilczek: "Einstein's special theory of relativity calls for radical renovation of common-sense ideas about time. Different observers, moving at constant velocity relative to one another, require different notions of time, since their clocks run differently. Yet each such observer can use his "time" to describe what he sees, and every description will give valid results, using the same laws of physics. In short: According to special relativity, there are many quite different but equally valid ways of assigning times to events. Einstein himself understood the importance of breaking free from the idea that there is an objective, universal "now." Yet, paradoxically, today's standard formulation of quantum mechanics makes heavy use of that discredited "now."
Il faut abandonner la relativité d'Einstein avec son espace-temps idiot :
https://www.newscientist.com/article/mg22730370-600-why-do-we-move-forwards-in-time/
"[George] Ellis is up against one of the most successful theories in physics: special relativity. It revealed that there's no such thing as objective simultaneity. Although you might have seen three things happen in a particular order – A, then B, then C – someone moving at a different velocity could have seen it a different way – C, then B, then A. In other words, without simultaneity there is no way of specifying what things happened "now". And if not "now", what is moving through time? Rescuing an objective "now" is a daunting task. But Lee Smolin of the Perimeter Institute for TPs in Waterloo, Canada, has given it a go by tweaking relativity. He argues that we can rewrite physics in a way that includes "now" if we sacrifice some of our objective notions of space."
http://discovermagazine.com/2015/june/18-tomorrow-never-was
"Is the Future Already Written? A conscientious cosmologist rejects Einstein's notion that time is an illusion and the future is set. George Ellis is not afraid to rock the establishment. In his youth in South Africa, his target was a recognizably corrupt and racist government. Now a cosmologist at the University of Cape Town, Ellis has set his sights on something more abstract: the flow of time itself. First developed by Albert Einstein early in the 20th century, the orthodox view holds that the passage of time is an illusion. There is no difference between the past and the future - both are set in stone. Yet for Ellis, the philosophical implications of this mainstream theory do not simply run counter to our intuitions; he considers them dangerous..."
http://www.guardian.co.uk/books/2013/jun/10/time-reborn-farewell-reality-review
"And by making the clock's tick relative - what happens simultaneously for one observer might seem sequential to another - Einstein's theory of special relativity not only destroyed any notion of absolute time but made time equivalent to a dimension in space: the future is already out there waiting for us; we just can't see it until we get there. This view is a logical and metaphysical dead end, says Smolin."
http://www.bookdepository.com/Time-Reborn-Professor-Physics-Lee-Smolin/9780547511726
"Was Einstein wrong? At least in his understanding of time, Smolin argues, the great theorist of relativity was dead wrong. What is worse, by firmly enshrining his error in scientific orthodoxy, Einstein trapped his successors in insoluble dilemmas..."
https://edge.org/response-detail/25477
What scientific idea is ready for retirement? Steve Giddings: "Spacetime. Physics has always been regarded as playing out on an underlying stage of space and time. Special relativity joined these into spacetime... (...) The apparent need to retire classical spacetime as a fundamental concept is profound..."
Nima Arkani-Hamed (06:11): "Almost all of us believe that space-time doesn't really exist, space-time is doomed and has to be replaced by some more primitive building blocks."
http://www.space.com/29859-the-illusion-of-time.html
"Fotini Markopoulou-Kalamara, a theoretical physicist at the Perimeter Institute, said, "I have the distressing experience of physicists telling me that time is not real. ... It confuses me, because time seems to be real. Things happen. When I clap my hands, it happened. ... I would prefer to say that general relativity is not the final theory than to say that time does not exist." Time is a prime conflict between relativity and quantum mechanics, measured and malleable in relativity while assumed as background (and not an observable) in quantum mechanics."
http://www.newscientist.com/article/mg20727721.200-rethinking-einstein-the-end-of-spacetime.html
"Rethinking Einstein: The end of space-time (...) The stumbling block lies with their conflicting views of space and time. As seen by quantum theory, space and time are a static backdrop against which particles move. In Einstein's theories, by contrast, not only are space and time inextricably linked, but the resulting space-time is moulded by the bodies within it. (...) Something has to give in this tussle between general relativity and quantum mechanics, and the smart money says that it's relativity that will be the loser."
http://www.newscientist.com/article/mg20026831.500-what-makes-the-universe-tick.html
"...says John Norton, a philosopher based at the University of Pittsburgh, Pennsylvania. Norton is hesitant to express it, but his instinct - and the consensus in physics - seems to be that space and time exist on their own. The trouble with this idea, though, is that it doesn't sit well with relativity, which describes space-time as a malleable fabric whose geometry can be changed by the gravity of stars, planets and matter."
http://www.homevalley.co.za/index.php?option=com_content&view=article&id=135:its-likely-that-times-are-changing
"Einstein introduced a new notion of time, more radical than even he at first realized. In fact, the view of time that Einstein adopted was first articulated by his onetime math teacher in a famous lecture delivered one century ago. That lecture, by the German mathematician Hermann Minkowski, established a new arena for the presentation of physics, a new vision of the nature of reality redefining the mathematics of existence. The lecture was titled Space and Time, and it introduced to the world the marriage of the two, now known as spacetime. It was a good marriage, but lately physicists passion for spacetime has begun to diminish. And some are starting to whisper about possible grounds for divorce. (...) Einstein's famous insistence that the velocity of light is a cosmic speed limit made sense, Minkowski saw, only if space and time were intertwined. (...) Physicists of the 21st century therefore face the task of finding the true reality obscured by the spacetime mirage. (...) Andreas Albrecht, a cosmologist at the University of California, Davis, has thought deeply about choosing clocks, leading him to some troubling realizations. (...) "It seems to me like it's a time in the development of physics," says Albrecht, "where it's time to look at how we think about space and time very differently."
http://www.huffingtonpost.com/dr-sten-odenwald/happy-birthday-einstein-1_b_8219432.html
Sten Odenwald: "It all comes down to one thing: If we don't know what spacetime really is as a physical agency, how can we possibly understand gravity or try to manipulate it artificially to, among other things, create 'warp drive'? Now THAT is a mind-numbing question. When general relativity turns 200, we may well find its answer....or not!"
Pentcho Valev
