# Archives de la catégorie: Physique

Physique a été mon premier amour. Cette catégorie contient les messages les plus proches de mon coeur. Vingt ans à partir de maintenant, si ce blog survit, cette catégorie sera probablement tenir mes idées les plus durables. Et deux cents ans, si je me souvenais de tout, ce sera pour ces idées; pas le genre de personne que je suis, l'argent que je gagne, ni rien d'autre. Only for my first and last love…

# Perception, Physique et le rôle de la lumière dans la philosophie

Réalité, comme nous le sentons, est pas tout à fait réel. Les étoiles que nous voyons dans le ciel de nuit, par exemple, ne sont pas vraiment là. Ils ont déménagé ou sont même morts au moment où nous arrivons à les voir. Cette irréalité est dû au temps que met la lumière des étoiles et des galaxies lointaines nous rejoindre. Nous savons de ce retard.

Même le soleil que nous connaissons si bien, c'est déjà huit minutes vieux au moment où nous voyons. Ce fait ne semble pas présenter de problèmes épistémologiques particulièrement graves – si nous voulons savoir ce qui se passe sur le soleil maintenant, tout ce que nous avons à faire est d'attendre huit minutes. Nous n'avons qu'à «correcte’ les distorsions dans notre perception en raison de la vitesse finie de la lumière avant que nous pouvons faire confiance à ce que nous voyons. Le même phénomène en voyant a une manifestation moins connu dans la façon dont nous percevons les objets en mouvement. Certains corps célestes apparaissent comme si elles se déplacent plusieurs fois la vitesse de la lumière, alors que leur «vrai’ vitesse doit être beaucoup moins que ce que.

Ce qui est surprenant (et rarement mis en évidence) est que quand il s'agit de détecter le mouvement, nous ne pouvons pas rétro-calculer dans le même genre de façon que nous pouvons pour corriger le retard dans l'observation du soleil. Si nous voyons un corps céleste se déplaçant à une vitesse incroyablement élevée, nous ne pouvons pas calculer à quelle vitesse ou même dans quelle direction il est «vraiment’ déplacer sans avoir à apporter certaines autres hypothèses.

Einstein a choisi de résoudre le problème en traitant perception déformée et inventer de nouvelles propriétés fondamentales dans le domaine de la physique – dans la description de l'espace et du temps. Une idée de base de la théorie de la relativité est que la notion humaine d'une séquence ordonnée d'événements dans le temps doit être abandonné. En fait, car il faut du temps pour la lumière d'un événement à un endroit éloigné de nous rejoindre, et pour nous de prendre conscience de ce, le concept de 'maintenant’ pas plus de sens, par exemple, lorsque nous parlons d'une tache solaire apparaissant à la surface du soleil juste au moment où l'astronome essayait de photographier. Simultanéité est relative.

Einstein a redéfini la place simultanéité en utilisant les instants dans le temps nous détectons l'événement. Détection, comme il l'a défini, implique un aller-retour Voyage de lumière semblable à la détection radar. Nous envoyons un signal voyageant à la vitesse de la lumière, et attendre pour la réflexion. Si l'impulsion réfléchie par deux événements nous parvient au même instant, puis ils sont simultanés. Mais une autre façon de voir les choses est tout simplement d'appeler deux événements «simultanée’ si leur lumière nous parvient au même instant. En d'autres termes, nous pouvons utiliser la lumière générée par les objets sous observation plutôt que d'envoyer des signaux à eux et à la recherche à la réflexion.

Cette différence peut sembler un détail technique arguties, mais cela fait une énorme différence pour les prévisions que nous pouvons faire. Le choix d'Einstein en résulte une image mathématique qui possède de nombreuses propriétés souhaitables, y compris celui de faire le développement théorique plus élégant. Mais alors, Einstein croyait, comme une question de foi, il semblerait, que les règles qui régissent l'univers doivent être «élégant.’ Cependant, l'autre approche a un avantage quand il s'agit de décrire les objets en mouvement. Parce que, bien sûr, nous n'utilisons pas de radar pour voir les étoiles en mouvement; nous sentons simplement la lumière (ou un autre rayonnement) provenant de leur. Pourtant, l'utilisation de ce type de paradigme sensorielle, plutôt que de «détection de type radar,’ pour décrire les résultats de l'univers dans une image mathématique plus laid. Einstein ne serait pas approuver!

La différence mathématique engendre différentes positions philosophiques, qui à son tour percoler à la compréhension de notre image physique de la réalité. A titre d'illustration, supposons que nous observons, à travers un télescope radio, deux objets dans le ciel, avec à peu près la même forme, la taille et les propriétés. La seule chose que nous savons avec certitude, c'est que les ondes radio à partir de ces deux points différents dans le ciel nous parviennent au même instant dans le temps. Nous ne pouvons que deviner quand les vagues ont commencé leurs voyages.

Si nous supposons (comme nous le faisons régulièrement) que les vagues ont commencé le voyage à peu près au même moment dans le temps, nous nous retrouvons avec une photo de deux «réel’ lobes symétriques plus ou moins la façon dont les voir. Mais il est un autre, possibilité qui est différent et que les ondes proviennent d'un même objet (qui est en mouvement) à deux instants différents dans le temps, atteindre le télescope, au même instant. Cette possibilité serait en outre expliquer certaines propriétés spectrales et temporelles de ces sources radio symétriques. Alors laquelle de ces deux images devrions nous considérer comme réel? Deux objets symétriques telles que nous les voyons ou un objet se déplaçant dans une manière de nous donner cette impression? Est-ce vraiment important que l'on est «réel»? Le réel ne de’ quoi que ce soit dans ce contexte signifie?

Relativité restreinte donne une réponse sans ambiguïté à cette question. Les mathématiques exclut la possibilité d'un seul objet en mouvement dans une telle façon que pour imiter deux objets. Essentiellement, ce que nous voyons est ce qui existe. Encore, si nous définissons les événements par ce que nous percevons, la seule position philosophique qui fait sens est celle qui se déconnecte de la réalité détecté des causes se trouvent derrière ce qui est détectée.

Ce décalage n'est pas rare dans les écoles philosophiques de la pensée. Phénoménalisme, par exemple, Considère que l'espace et le temps ne sont pas des réalités objectives. Ils ne sont que le support de notre perception. Tous les phénomènes qui se produisent dans l'espace et le temps sont regroupe simplement de notre perception. En d'autres termes, espace et le temps sont des constructions cognitives découlant de la perception. Ainsi, toutes les propriétés physiques que nous attribuons à l'espace et le temps ne peuvent s'appliquer à la réalité phénoménale (la réalité des «choses-dans-le-monde’ comme nous le sentons. La réalité sous-jacente (qui détient les causes physiques de notre perception), en revanche, reste hors de notre portée cognitive.

Pourtant, il ya un gouffre entre les points de vue de la philosophie et de la physique moderne. Pas pour rien que le physicien prix Nobel, Steven Weinberg, se demander, dans ses rêves de livres d'une théorie finale, pourquoi la contribution de la philosophie à la physique avait été si étonnamment faible. C'est peut-être parce que la physique n'a pas encore de se réconcilier avec le fait que quand il s'agit de voir l'univers, il n'y a pas une telle chose comme une illusion d'optique – qui est probablement ce que Goethe a voulu dire quand il a dit, 'Illusion optique est la vérité optique.’

La distinction (ou l'absence de) entre illusion d'optique et de la vérité est une des plus anciennes débats en philosophie. Après tout, il s'agit de la distinction entre la connaissance et la réalité. La connaissance est considérée comme notre point de vue à propos de quelque chose qui, en réalité, est «effectivement le cas.’ En d'autres termes, la connaissance est une réflexion, ou une image mentale de quelque chose d'extérieur, comme représenté sur la figure ci-dessous.

Dans cette image, la flèche noire représente le processus de création de connaissances, qui comprend la perception, activités cognitives, et l'exercice de la raison pure. Telle est l'image que la physique a fini par accepter. Tout en reconnaissant que notre perception peut être imparfaite, physique suppose que nous pouvons nous rapprocher et plus proche de la réalité extérieure à travers l'expérimentation de plus en plus fine, et, plus important encore, grâce à une meilleure théorisation. Les théories spéciales et de la relativité générale sont des exemples d'applications brillantes de ce point de vue de la réalité où les principes physiques simples sont poursuivis sans relâche à l'aide formidable machine de la raison pure de leurs conclusions logiquement inévitables.

Mais il est un autre, autre point de vue de la connaissance et de la réalité qui a été autour depuis longtemps. C'est le point de vue que ce qui concerne la réalité perçue comme une représentation cognitive interne de nos entrées sensorielles, comme cela est illustré ci-dessous.

Dans ce point de vue, connaissance et la réalité perçue sont deux constructions cognitives internes, bien que nous en sommes venus à les considérer comme séparé. Ce qui est externe n'est pas la réalité telle que nous la percevons, mais une entité inconnaissable donnant lieu à des causes physiques à l'origine des entrées sensorielles. Dans l'illustration, la première flèche représente le processus de détection, et la seconde flèche représente les étapes cognitives et logiques de raisonnement. Afin d'appliquer cette vision de la réalité et de la connaissance, nous devons deviner la nature de la réalité absolue, inconnaissable comme il est. Un candidat possible à la réalité absolue est la mécanique newtonienne, qui donne une prévision raisonnable pour notre réalité perçue.

Pour résumer, quand nous essayons de traiter les distorsions dues à la perception, nous avons deux options, ou deux positions philosophiques possibles. La première consiste à accepter les distorsions dans le cadre de notre espace et le temps, comme la relativité restreinte ne. L'autre option consiste à supposer qu'il existe un «supérieur’ réalité distincte de notre réalité détectée, dont les propriétés nous ne pouvons conjecture. En d'autres termes, une option est de vivre avec la distorsion, tandis que l'autre est de proposer des suppositions éclairées pour la réalité supérieure. Aucun de ces choix est particulièrement attrayant. Mais le chemin est similaire à deviner le point de vue accepté dans phénoménalisme. Elle conduit aussi naturellement à la façon dont la réalité est perçue en neurosciences cognitives, qui étudie les mécanismes biologiques à l'origine de la cognition.

La torsion de cette histoire de la lumière et la réalité est que nous semblons avoir connu tout cela pendant une longue période. Le rôle de la lumière dans la création de notre réalité ou l'univers est au cœur de la pensée religieuse occidentale. Un univers dépourvu de lumière n'est pas simplement un monde où vous avez éteint les lumières. Il est en effet un univers dépourvu de lui-même, un univers qui n'existe pas. C'est dans ce contexte que nous devons comprendre la sagesse derrière l'affirmation que «la terre était sans forme, et non avenu’ jusqu'à ce que Dieu a fait la lumière soit, en disant: «Que la lumière soit.’

Le Coran dit aussi, «Allah est la lumière des cieux et de la terre,’ qui se reflète dans l'un des anciens écrits hindous: «Conduis-moi de l'obscurité à la lumière, Conduis-moi de l'irréel au réel.’ Le rôle de la lumière en nous tenant du vide irréel (le néant) à une réalité a été bien compris depuis longtemps, longtemps. Est-il possible que les saints et les prophètes anciens savaient des choses que nous commençons seulement maintenant à découvrir avec tous nos progrès supposés de connaissances?

Il ya des parallèles entre la distinction noumène-phénoménale de Kant et les phénoménistes plus tard, et la distinction Brahman-Maya en Advaita. Sagesse de la nature de la réalité du répertoire de la spiritualité se réinvente en neurosciences modernes, qui traite la réalité comme une représentation cognitive créée par le cerveau. Le cerveau utilise les entrées sensorielles, mémoire, conscience, et même langue comme ingrédients dans concocter notre sens de la réalité. Ce point de vue de la réalité, cependant, est quelque chose de physique est toujours incapable de venir à bout. Mais dans la mesure où son arène (l'espace et le temps) est une partie de la réalité, la physique n'est pas à l'abri de la philosophie.

En fait, comme nous poussons les limites de nos connaissances de plus en plus, nous découvrons interconnexions insoupçonnés et souvent surprenantes entre les différentes branches d'efforts humains. Encore, la façon dont les divers domaines de la connaissance peuvent être indépendants les uns des autres si toute connaissance est subjective? Si la connaissance est simplement la représentation cognitive de nos expériences? Mais alors, c'est le sophisme moderne de penser que la connaissance est notre représentation interne d'une réalité extérieure, et donc distincte de lui. Plutôt, reconnaissant et en utilisant des interconnexions entre les différents domaines de l'activité humaine peut être la condition sine qua non pour la prochaine étape dans le développement de notre sagesse collective.

 Boîte: Train d'EinsteinL'un des célèbres expériences de pensée d'Einstein illustre la nécessité de repenser ce que nous entendons par des événements simultanés. Il décrit un train à grande vitesse se précipitant le long d'une voie rectiligne passé une petite station comme un homme se tient sur le quai de la gare regarder accélérer par. À son grand étonnement, que le train lui passe, deux éclairs frappent la piste suivante à chaque extrémité du train! (Idéalement, pour les enquêteurs plus tard, ils laissent des traces de brûlure à la fois dans le train et sur le terrain.) Pour l'homme, il semble que les deux boulons de foudre, exactement au même moment,. Plus tard, les marques sur le terrain par la voie ferrée révèlent que les endroits où la foudre a frappé étaient exactement à égale distance de l'. Depuis lors, les éclairs se sont rendus à la même distance vers lui, et depuis leur apparition à l'homme pour arriver exactement au même moment,, il n'a aucune raison de ne pas conclure que les éclairs ont frappé exactement au même moment,. Ils étaient simultanée. Cependant, suppose un peu plus tard, l'homme rencontre une passagère, qui se trouvait assis dans la voiture-bar, exactement au centre du train, et la recherche par la fenêtre au moment où les éclairs ont frappé. Ce passager lui dit qu'elle a vu le premier boulon de foudre a frappé le sol près du moteur à l'avant du train peu avant de savoir quand le second a touché le sol à côté de la voiture de bagages à l'arrière du train. L'effet n'a rien à voir avec la distance la lumière a dû voyager, à la fois la femme et l'homme sont à égale distance entre les deux points que le coup de foudre. Pourtant, ils ont observé le déroulement des événements tout à fait différemment. Ce désaccord de la chronologie des événements est inévitable, Einstein dit, que la femme est en effet le déplacement vers le point où le flash de foudre a frappé près du moteur -et à partir du point où le flash d'alléger frapper à côté de la voiture de bagages. Dans la petite quantité de temps qu'il faut pour les rayons lumineux d'atteindre la dame, parce que le train se déplace, la distance du premier flash doit se rendre à ses psys, et la distance que le second flash doit voyager grandit. Ce fait ne peut être remarqué dans le cas des trains et des avions, mais quand il s'agit de distances cosmologiques, simultanéité n'a vraiment pas de sens. Par exemple, l'explosion de deux supernovae lointaines, considérée comme simultanée de notre point sur la terre de vue, apparaîtra à se produire dans des combinaisons différentes de temps d'autres perspectives. Dans la relativité: Le spécial et Théorie (1920), Einstein a mis de cette façon: «Toute référence au corps (coordonner système) a son propre temps particulier; sauf si on nous dit la référence du corps à laquelle la déclaration de temps se réfère, il n'y a pas de sens dans une déclaration de l'heure de l'événement.’

# Tsunami

The Asian Tsunami two and a half years ago unleashed tremendous amount energy on the coastal regions around the Indian ocean. What do you think would’ve have happened to this energy if there had been no water to carry it away from the earthquake? I mean, if the earthquake (of the same kind and magnitude) had taken place on land instead of the sea-bed as it did, presumably this energy would’ve been present. How would it have manifested? As a more violent earthquake? Or a longer one?

I picture the earthquake (in cross-section) as a cantilever spring being held down and then released. The spring then transfers the energy to the tsunami in the form of potential energy, as an increase in the water level. As the tsunami radiates out, it is only the potential energy that is transferred; the water doesn’t move laterally, only vertically. As it hits the coast, the potential energy is transferred into the kinetic energy of the waves hitting the coast (water moving laterally then).

Given the magnitude of the energy transferred from the epicenter, I am speculating what would’ve happened if there was no mechanism for the transfer. Any thoughts?

# Universe – Size and Age

I posted this question that was bothering me when I read that they found a galaxy at about 13 billion light years away. My understanding of that statement is: At distance of 13 billion light years, there was a galaxy 13 billion years ago, so that we can see the light from it now. Wouldn’t that mean that the universe is at least 26 billion years old? It must have taken the galaxy about 13 billion years to reach where it appears to be, and the light from it must take another 13 billion years to reach us.

In answering my question, Martin and Swansont (who I assume are academic phycisists) point out my misconceptions and essentially ask me to learn more. All shall be answered when I’m assimilated, it would appear! 🙂

This debate is published as a prelude to my post on the Big Bang theory, coming up in a day or two.

 Mowgli 03-26-2007 10:14 PM

Universe – Size and Age
I was reading a post in http://www.space.com/ stating that they found a galaxy at about 13 billion light years away. I am trying to figure out what that statement means. To me, it means that 13 billion years ago, this galaxy was where we see it now. Isn’t that what 13b LY away means? If so, wouldn’t that mean that the universe has to be at least 26 billion years old? I mean, the whole universe started from one singular point; how could this galaxy be where it was 13 billion years ago unless it had at least 13 billion years to get there? (Ignoring the inflationary phase for the moment…) I have heard people explain that the space itself is expanding. What the heck does that mean? Isn’t it just a fancier way of saying that the speed of light was smaller some time ago?
 swansont 03-27-2007 09:10 AM

Quote:
 Originally Posted by Mowgli (Post 329204) I mean, the whole universe started from one singular point; how could this galaxy be where it was 13 billion years ago unless it had at least 13 billion years to get there? (Ignoring the inflationary phase for the moment…)

Ignoring all the rest, how would this mean the universe is 26 billion years old?

Quote:
 Originally Posted by Mowgli (Post 329204) I have heard people explain that the space itself is expanding. What the heck does that mean? Isn’t it just a fancier way of saying that the speed of light was smaller some time ago?

The speed of light is an inherent part of atomic structure, in the fine structure constant (alpha). If c was changing, then the patterns of atomic spectra would have to change. There hasn’t been any confirmed data that shows that alpha has changed (there has been the occasional paper claiming it, but you need someone to repeat the measurements), and the rest is all consistent with no change.

 Martin 03-27-2007 11:25 AM

To confirm or reinforce what swansont said, there are speculation and some fringe or nonstandard cosmologies that involve c changing over time (or alpha changing over time), but the changing constants thing just gets more and more ruled out.I’ve been watching for over 5 years and the more people look and study evidence the LESS likely it seems that there is any change. They rule it out more and more accurately with their data.So it is probably best to ignore the “varying speed of light” cosmologies until one is thoroughly familiar with standard mainstream cosmology.You have misconceptions Mowgli

• General Relativity (the 1915 theory) trumps Special Rel (1905)
• They don’t actually contradict if you understand them correctly, because SR has only a very limited local applicability, like to the spaceship passing by:-)
• Wherever GR and SR SEEM to contradict, believe GR. It is the more comprehensive theory.
• GR does not have a speed limit on the rate that very great distances can increase. the only speed limit is on LOCAL stuff (you can’t catch up with and pass a photon)
• So we can and DO observe stuff that is receding from us faster than c. (It’s far away, SR does not apply.)
• This was explained in a Sci Am article I think last year
• Google the author’s name Charles Lineweaver and Tamara Davis.
• We know about plenty of stuff that is presently more than 14 billion LY away.
• You need to learn some cosmology so you wont be confused by these things.
• Also a “singularity” does not mean a single point. that is a popular mistake because the words SOUND the same.
• A singularity can occur over an entire region, even an infinite region.

Also the “big bang” model doesn’t look like an explosion of matter whizzing away from some point. It shouldn’t be imagined like that. The best article explaining common mistakes people have is this Lineweaver and Davis thing in Sci Am. I think it was Jan or Feb 2005 but I could be a year off. Google it. Get it from your local library or find it online. Best advice I can give.

 Mowgli 03-28-2007 01:30 AM

To swansont on why I thought 13 b LY implied an age of 26 b years:When you say that there is a galaxy at 13 b LY away, I understand it to mean that 13 billion years ago my time, the galaxy was at the point where I see it now (which is 13 b LY away from me). Knowing that everything started from the same point, it must have taken the galaxy at least 13 b years to get where it was 13 b years ago. So 13+13. I’m sure I must be wrong.To Martin: You are right, I need to learn quite a bit more about cosmology. But a couple of things you mentioned surprise me — how do we observe stuff that is receding from as FTL? I mean, wouldn’t the relativistic Doppler shift formula give imaginary 1+z? And the stuff beyond 14 b LY away – are they “outside” the universe?I will certainly look up and read the authors you mentioned. Thanks.
 swansont 03-28-2007 03:13 AM

Quote:
 Originally Posted by Mowgli (Post 329393) To swansont on why I thought 13 b LY implied an age of 26 b years:When you say that there is a galaxy at 13 b LY away, I understand it to mean that 13 billion years ago my time, the galaxy was at the point where I see it now (which is 13 b LY away from me). Knowing that everything started from the same point, it must have taken the galaxy at least 13 b years to get where it was 13 b years ago. So 13+13. I’m sure I must be wrong.

That would depend on how you do your calibration. Looking only at a Doppler shift and ignoring all the other factors, if you know that speed correlates with distance, you get a certain redshift and you would probably calibrate that to mean 13b LY if that was the actual distance. That light would be 13b years old.

But as Martin has pointed out, space is expanding; the cosmological redshift is different from the Doppler shift. Because the intervening space has expanded, AFAIK the light that gets to us from a galaxy 13b LY away is not as old, because it was closer when the light was emitted. I would think that all of this is taken into account in the measurements, so that when a distance is given to the galaxy, it’s the actual distance.

 Martin 03-28-2007 08:54 AM

Quote:
 Originally Posted by Mowgli (Post 329393) I will certainly look up and read the authors you mentioned.

This post has 5 or 6 links to that Sci Am article by Lineweaver and Davis

http://scienceforums.net/forum/showt…965#post142965

It turns out the article was in the March 2005 issue.

I think it’s comparatively easy to read—well written. So it should help.

# Twin Paradox – Take 2

The Twin Paradox is usually explained away by arguing that the traveling twin feels the motion because of his acceleration/deceleration, and therefore ages slower.

But what will happen if the twins both accelerate symmetrically? That is, they start from rest from one space point with synchronized clocks, and get back to the same space point at rest by accelerating away from each other for some time and decelerating on the way back. By the symmetry of the problem, it seems that when the two clocks are together at the end of the journey, at the same point, and at rest with respect to each other, they have to agree.

Then again, during the whole journey, each clock is in motion (accelerated or not) with respect to the other one. In SR, every clock that is in motion with respect to an observer’s clock is supposed run slower. Or, the observer’s clock is always the fastest. So, for each twin, the other clock must be running slower. However, when they come back together at the end of the journey, they have to agree. This can happen only if each twin sees the other’s clock running faster at some point during the journey. What does SR say will happen in this imaginary journey?

(Note that the acceleration of each twin can be made constant. Have the twins cross each other at a high speed at a constant linear deceleration. They will cross again each other at the same speed after sometime. During the crossings, their clocks can be compared.)

# Unreal Time

Farsight wrote:Time is a velocity-dependent subjective measure of event succession rather than something fundamental – the events mark the time, the time doesn’t mark the events. This means the stuff out there is space rather than space-time, and is an “aether” veiled by subjective time.

I like your definition of time. It is close to my own view that time is “unreal.” It is possible to treat space as real and space-time as something different, as you do. This calls for some careful thought. I will outline my thinking in this post and illustrate it with an example, if my friends don’t pull me out for lunch before I can finish.

The first question we need to ask ourselves is why space and time seem coupled? The answer is actually too simple to spot, and it is in your definition of time. Space and time mix through our concept of velocity and our brain’s ability to sense motion. There is an even deeper connection, which is that space is a cognitive representation of the photons inputs to our eyes, but we will get to it later.

Let’s assume for a second that we had a sixth sense that operated at an infinite speed. That is, if star explodes at a million light years from us, we can sense it immediately. We will see it only after a million years, but we sense it instantly. I know, it is a violation of SR, cannot happen and all that, but stay with me for a second. Now, a little bit of thinking will convince you that the space that we sense using this hypothetical sixth sense is Newtonian. Here, space and time can be completely decoupled, absolute time can be defined etc. Starting from this space, we can actually work out how we will see it using light and our eyes, knowing that the speed of light is what it is. It will turn out, clearly, that we seen events with a delay. That is a first order (or static) effect. The second order effect is the way we perceive objects in motion. It turns out that we will see a time dilation and a length contraction (for objects receding from us.)

Let me illustrate it a little further using echolocation. Assume that you are a blind bat. You sense your space using sonar pings. Can you sense a supersonic object? If it is coming towards you, by the time the reflected ping reaches you, it has gone past you. If it is going away from you, your pings can never catch up. In other words, faster than sound travel is “forbidden.” If you make one more assumption – the speed of the pings is the same for all bats regardless of their state of motion – you derive a special relativity for bats where the speed of sound is the fundamental property of space and time!

We have to dig a little deeper and appreciate that space is no more real than time. Space is a cognitive construct created out of our sensory inputs. If the sense modality (light for us, sound for bats) has a finite speed, that speed will become a fundamental property of the resultant space. And space and time will be coupled through the speed of the sense modality.

This, of course, is only my own humble interpretation of SR. I wanted to post this on a new thread, but I get the feeling that people are a little too attached to their own views in this forum to be able to listen.

Leo wrote:Minkowski spacetime is one interpretation of the Lorentz transforms, but other interpretations, the original Lorentz-PoincarÃ© Relativity or modernized versions of it with a wave model of matter (LaFreniere or Close or many others), work in a perfectly euclidean 3D space.

So we end up with process slowdown and matter contraction, but NO time dilation or space contraction. The transforms are the same though. So why does one interpretation lead to tensor metric while the others don’t? Or do they all? I lack the theoretical background to answer the question.

Hi Leo,

If you define LT as a velocity dependent deformation of an object in motion, then you can make the transformation a function of time. There won’t be any warping and complications of metric tensors and stuff. Actually what I did in my book is something along those lines (though not quite), as you know.

The trouble arises when the transformation matrix is a function of the vector is transforming. So, if you define LT as a matrix operation in a 4-D space-time, you can no longer make it a function of time through acceleration any more than you can make it a function of position (as in a velocity field, for instance.) The space-time warping is a mathematical necessity. Because of it, you lose coordinates, and the tools that we learn in our undergraduate years are no longer powerful enough to handle the problem.

# Of Rotation, LT and Acceleration

In the “Philosophical Implications” forum, there was an attempt to incorporate acceleration into Lorentz transformation using some clever calculus or numerical techniques. Such an attempt will not work because of a rather interesting geometric reason. I thought I would post the geometric interpretation of Lorentz transformation (or how to go from SR to GR) here.

Let me start with a couple of disclaimers. First of, what follows is my understanding of LT/SR/GR. I post it here with the honest belief that it is right. Although I have enough academic credentials to convince myself of my infallibility, who knows? People much smarter than me get proven wrong every day. And, if we had our way, we would prove even Einstein himself wrong right here in this forum, wouldn’t we? Secondly, what I write may be too elementary for some of the readers, perhaps even insultingly so. I request them to bear with it, considering that some other readers may find it illuminating. Thirdly, this post is not a commentary on the rightness or wrongness of the theories; it is merely a description of what the theories say. Or rather, my version of what they say. With those disclaimers out of the way, let’s get started…

LT is a rotation in the 4-D space-time. Since it not easy to visualize 4-D space-time rotation, let’s start with a 2-D, pure space rotation. One fundamental property of a geometry (such as 2-D Euclidean space) is its metric tensor. The metric tensor defines the inner product between two vectors in the space. In normal (Euclidean or flat) spaces, it also defines the distance between two points (or the length of a vector).

Though the metric tensor has the dreaded “tensor” word in its name, once you define a coordinate system, it is only a matrix. For Euclidean 2-D space with x and y coordinates, it is the identity matrix (two 1’s along the diagonal). Let’s call it G. The inner product between vectors A and B is A.B = Trans(A) G B, which works out to be $a_1b_1+a_2b_2$. Distance (or length of A) can be defined as $\sqrt{A.A}$.

So far in the post, the metric tensor looks fairly useless, only because it is the identity matrix for Euclidean space. SR (or LT), on the other hand, uses Minkowski space, which has a metric that can be written with [-1, 1, 1, 1] along the diagonal with all other elements zero – assuming time t is the first component of the coordinate system. Let’s consider a 2-D Minkowski space for simplicity, with time (t) and distance (x) axes. (This is a bit of over-simplification because this space cannot handle circular motion, which is popular in some threads.) In units that make c = 1, you can easily see that the invariant distance using this metric tensor is $\sqrt{x^2 - t^2}$.

Continued…

# The Unreal Universe — Discussion with Gibran

Hi again,You raise a lot of interesting questions. Let me try to answer them one by one.

You’re saying that our observations of an object moving away from us would look identical in either an SR or Galilean context, and therefore this is not a good test for SR.

What I’m saying is slightly different. The coordinate transformation in SR is derived considering only receding objects and sensing it using radar-like round trip light travel time. It is then assumed that the transformation laws thus derived apply to all objects. Because the round trip light travel is used, the transformation works for approaching objects as well, but not for things moving in other directions. But SR assumes that the transformation is a property of space and time and asserts that it applies to all moving (inertial) frames of reference regardless of direction.

We have to go a little deeper and ask ourselves what that statement means, what it means to talk about the properties of space. We cannot think of a space independent of our perception. Physicists are typically not happy with this starting point of mine. They think of space as something that exists independent of our sensing it. And they insist that SR applies to this independently existing space. I beg to differ. I consider space as a cognitive construct based on our perceptual inputs. There is an underlying reality that is the cause of our perception of space. It may be nothing like space, but let’s assume, for the sake of argument, that the underlying reality is like Galilean space-time. How would be perceive it, given that we perceive it using light (one-way travel of light, not two-way as SR assumes)? It turns out that our perceptual space would have time dilation and length contraction and all other effect predicted by SR. So my thesis is that the underlying reality obeys Galilean space-time and our perceptual space obeys something like SR. (It is possible that if I assume that our perception uses two-way light travel, I may get SR-like transformation. I haven’t done it because it seems obvious to me that we perceive a star, for instance, by sensing the light from it rather than flashing a light at it.)

This thesis doesn’t sit well with physicists, and indeed with most people. They mistake “perceptual effects” to be something like optical illusions. My point is more like space itself is an illusion. If you look at the night sky, you know that the stars you see are not “real” in the sense that they are not there when you are looking at them. This is simply because the information carrier, namely light, has a finite speed. If the star under observation is in motion, our perception of its motion is distorted for the same reason. SR is an attempt to formalize our perception of motion. Since motion and speed are concepts that mix space and time, SR has to operate on “space-time continuum.” Since SR is based on perceptual effects, it requires an observer and describes motion as he perceives it.

But are you actually saying that not a single experiment has been done with objects moving in any other direction than farther away? And what about experiments on time dilation where astronauts go into space and return with clocks showing less elapsed time than ones that stayed on the ground? Doesn’t this support the ideas inherent in SR?

Experiments are always interpreted in the light of a theory. It is always a model based interpretation. I know that this is not a convincing argument for you, so let me give you an example. Scientists have observed superluminal motion in certain celestial objects. They measure the angular speed of the celestial object, and they have some estimate of its distance from us, so they can estimate the speed. If we didn’t have SR, there would be nothing remarkable about this observation of superluminality. Since we do have SR, one has to find an “explanation” for this. The explanation is this: when an object approaches us at a shallow angle, it can appear to come in quite a bit faster than its real speed. Thus the “real” speed is subluminal while the “apparent” speed may be superluminal. This interpretation of the observation, in my view, breaks the philosophical grounding of SR that it is a description of the motion as it appears to the observer.

Now, there are other observations of where almost symmetric ejecta are seen on opposing jets in symmetric celestial objects. The angular speeds may indicate superluminality in both the jets if the distance of the object is sufficiently large. Since the jets are assumed to be back-to-back, if one jet is approaching us (thereby giving us the illusion of superluminality), the other jet has bet receding and can never appear superluminal, unless, of course, the underlying motion is superluminal. The interpretation of this observation is that the distance of the object is limited by the “fact” that real motion cannot be superluminal. This is what I mean by experiments being open to theory or model based interpretations.

In the case of moving clocks being slower, it is never a pure SR experiment because you cannot find space without gravity. Besides, one clock has to be accelerated or decelerated and GR applies. Otherwise, the age-old twin paradox would apply.

I know there have been some experiments done to support Einstein’s theories, like the bending of light due to gravity, but are you saying that all of them can be consistently re-interpreted according to your theory? If this is so, it’s dam surprising! I mean, no offense to you – you’re obviously a very bright individual, and you know much more about this stuff than I do, but I’d have to question how something like this slipped right through physicists’ fingers for 100 years.

These are gravity related questions and fall under GR. My “theory” doesn’t try to reinterpret GR or gravity at all. I put theory in inverted quotes because, to me, it is a rather obvious observation that there is a distinction between what we see and the underlying causes of our perception. The algebra involved is fairly simple by physics standards.

Supposing you’re right in that space and time are actually Galilean, and that the effects of SR are artifacts of our perception. How then are the results of the Michelson-Morley experiments explained? I’m sorry if you did explain it in your book, but it must have flown right over my head. Or are we leaving this as a mystery, an anomaly for future theorists to figure out?

I haven’t completely explained MMX, more or less leaving it as a mystery. I think the explanation hinges on how light is reflected off a moving mirror, which I pointed out in the book. Suppose the mirror is moving away from the light source at a speed of v in our frame of reference. Light strikes it at a speed of c-v. What is the speed of the reflected light? If the laws of reflection should hold (it’s not immediately obvious that they should), then the reflected light has to have a speed of c-v as well. This may explain why MMX gives null result. I haven’t worked out the whole thing though. I will, once I quit my day job and dedicate my life to full-time thinking.

My idea is not a replacement theory for all of Einstein’s theories. It’s merely a reinterpretation of one part of SR. Since the rest of Einstein’s edifice is built on this coordinate transformation part, I’m sure there will be some reinterpretation of the rest of SR and GR also based on my idea. Again, this is a project for later. My reinterpretation is not an attempt to prove Einstein’s theories wrong; I merely want to point out that they apply to reality as we perceive it.

Overall, it was worth the \$5 I payed. Thanks for the good read. Don’t take my questions as an assault on your proposal – I’m honestly in the dark about these things and I absolutely crave light (he he). If you could kindly answer them in your spare time, I’d love to share more ideas with you. It’s good to find a fellow thinker to bounce cool ideas like this off of. I’ll PM you again once I’m fully done the book. Again, it was a very satisfying read.

Thanks! I’m glad that you like my ideas and my writing. I don’t mind criticism at all. Hope I have answered most of your questions. If not, or if you want to disagree with my answers, feel free to write back. Always a pleasure to chat about these things even if we don’t agree with each other.

– Best regards,
– Manoj

# Anti-relativity and Superluminality

Leo wrote:I have some problems with the introductory part though, when you confront light travel effects and relativistic transforms. You correctly state that all perceptual illusions have been cleared away in the conception of Special Relativity, but you also say that these perceptual illusions remained as a subconscious basis for the cognitive model of Special Relativity. Do I understand what you mean or do I get it wrong?

The perceptual effects are known in physics; they are called Light Travel Time effects (LTT, to cook up an acronym). These effects are considered an optical illusion on the motion of the object under observation. Once you take out the LTT effects, you get the “real” motion of the object . This real motion is supposed to obey SR. This is the current interpretation of SR.

My argument is that the LTT effects are so similar to SR that we should think of SR as just a formalization of LTT. (In fact, a slightly erroneous formalization.) Many reasons for this argument:
1. We cannot disentagle the “optical illusion” because many underlying configurations give rise to the same perception. In other words, going from what we see to what is causing our perception is a one to many problem.
2. SR coordinate transformation is partially based on LTT effects.
3. LTT effects are stronger than relativistic effects.

Probably for these reasons, what SR does is to say that what we see is what it is really like. It then tries to mathematically describe what we see. (This is what I meant by a formaliztion. ) Later on, when we figured out that LTT effects didn’t quite match with SR (as in the observation of “apparent” superluminal motion), we thought we had to “take out” the LTT effects and then say that the underlying motion (or space and time) obeyed SR. What I’m suggesting in my book and articles is that we should just guess what the underlying space and time are like and work out what our perception of it will be (because going the other way is an ill-posed one-to-many problem). My first guess, naturally, was Galilean space-time. This guess results in a rather neat and simple explantions of GRBs and DRAGNs as luminal booms and their aftermath.

# Discussion on the Daily Mail (UK)

On the Daily Mail forum, one participant (called “whats-in-a-name”) started talking about The Unreal Universe on July 15, 2006. It was attacked fairly viciously on the forum. I happened to see it during a Web search and decided to step in and defend it.

#### 15 July, 2006

##### Posted by: whats-in-a-name on 15/07/06 at 09:28 AM

Ah, Kek, you’ve given me a further reason to be distracted from what I should be doing- and I can tell you that this is more interesting at the moment.I’ve been trying to formulate some ideas and there’s one coming- but I’ll have to give it to you in bits.I don’t want to delve into pseudoscience or take the woo-ish road that says that you can explain everything with quantum theory, but try starting here: http://theunrealuniverse.com/phys.shtml

The “Journal Article” link at the bottom touches on some of the points that we discussed elsewhere. It goes slightly off-topic, but you might also find the “Philosophy” link at the top left interesting.

##### Posted by: patopreto on 15/07/06 at 06:17 PM

Regarding that web site wian.One does not need to ead past this sentence –

The theories of physics are a description of reality. Reality is created out of the readings from our senses. Knowing that our senses all work using light as an intermediary, is it a surprise that the speed of light is of fundamental importance in our reality?

to realise that tis web site is complete ignorant hokum. I stopped at that point.

#### 16 July, 2006

##### Posted by: whats-in-a-name on 16/07/06 at 09:04 AM

I’ve just been back to read that bit more carefully. I don’t know why the writer phrased it like that but surely what he meant was:(i) “Our perception of what is real is created out of the readings from our senses.” I think that most physicists wouldn’t argue with that would they? At the quantum level reality as we understand it doesn’t exist; you can only say that particles have more of a tendency to exist in one place or state than another.(ii) The information that we pick up from optical or radio telescopes, gamma-ray detectors and the like, shows the state of distant objects as they were in the past, owing to the transit time of the radiation. Delving deeper into space therefore enables us to look further back into the history of the universe.It’s an unusual way to express the point, I agree, but it doesn’t devalue the other information on there. In particular there are links to other papers that go into rather more detail, but I wanted to start with something that offered a more general view.

I get the impression that your study of physics is rather more advanced than mine- as I’ve said previously I’m only an amateur, though I’ve probably taken my interest a bit further than most. I’m happy to be corrected if any of my reasoning is flawed, though what I’ve said so far s quite basic stuff.

The ideas that I’m trying to express in response to Keka’s challenge are my own and again, I’m quite prepared to have you or anyone else knock them down. I’m still formulating my thoughts and I wanted to start by considering the model that physicists use of the nature of matter, going down to the grainy structure of spacetime at the Plank distance and quantum uncertainty.

I’ll have to come back to this in a day or two, but meanwhile if you or anyone else wants to offer an opposing view, please do.

##### Posted by: patopreto on 16/07/06 at 10:52 AM

I don’t know why the writer phrased it like that but surely what he meant was:

I think the write is quit clear! WIAN – you have re-written what he says to mean something different.

The writer is quite clear – “Once we accept that space and time are a part of the cognitive model created by the brain, and that special relativity applies to the cognitive model, we can ponder over the physical causes behind the model, the absolute reality itself.”

Blah Blah Blah!

The writer, Manoj Thulasidas, is an employee of OCBC bank in Singapore and self-described “amateur philosopher”. What is he writes appears to be nothing more than a religiously influenced solipsistic philosophy. Solipsism is interesting as a philosophical standpoint but quickly falls apart. If Manoj can start his arguments from such shaky grounds without explanation, then I really have no other course to take than to accept his descriptions of himself as “amateur”.

Maybe back to MEQUACK!

# Superluminal Laser Dots

A discussion in the Science Forums on the appearance of a laser dot on a ceiling. It is thought that if you pointed a laser dot on a ceiling and turned the laser gun fast enough, you could create superluminal laser dots. Could you, really?