Mystery111

Real physical events only happen within the sphere of the present moment: that would be in your abstraction, the black horizontal line.

Because I said the first part was agreed with, and not confirmed the second part, that was my fault I guess. I was not disagreeing, I was adding to the different interpretations of tachyons. Nowhere in that reference you made of me: ''Non-highlighted part: A timelike tachyon does, not a spacelike tachyon which was the point I was raising earlier. Some models go back as far as the 60's which try to circumvent the problem of a faster than light particle which would oscillate throughout time and the causality problems which closely asist it.'' Contains anywhere that I disagreed with your post. You brought up causality, which is what is implied by that model you speak of. That is why my reference to the non-highlighted part was in nature of the problem of causality offerring other solutions, which I gave.

I didn't qoute that, so you are misrepresenting the facts. My post qouted you talking about knowing very little on tachyons, then asking me what a spacelike condition has to do for a tachyon. I explained to you that was one solution I referenced before and if you wanted those references you would need to go back. Secondly I explored a further option. So qouting me like you did is disingenuous.

It's the only time ever happening. And the past is only a record because our psychology dictates this so. There is no real past, only memories of past events.

Change means motion, Einstein's field equations generate motion in time that is a symmetry of the theory, not true time evolution. So there is a problem with believing the definition of time is change.

There are in fact many models which attempt to deal with the causal nature. For the timelike-spacelike references, I noted them before go back and check. ''It has been argued that we can avoid the notion of tachyons traveling into the past using the Feinberg reinterpretation principle[3] which states that a negative-energy tachyon sent back in time in an attempt to challenge forward temporal causality can always be reinterpreted as a positive-energy tachyon traveling forward in time. This is because observers cannot distinguish between the emission and absorption of tachyons. For a tachyon, there is no distinction between the processes of emission and absorption, because there always exists a sub-light speed reference frame shift that alters the temporal direction of the tachyon's world-line, which is not true for bradyons or luxons. The attempt to detect a tachyon from the future (and challenge forward causality) can actually create the same tachyon and sends it forward in time (which is itself a causal event).'' I actually know a bit about negative energy tachyons. Two negative energy states in the form of two negative energy bispiners are: [math]\psi_3 = \psi_{-} = N \begin{pmatrix} 1 \\ 0 \\ -a \\ 0 \end{pmatrix}[/math] [math]\psi_4 = \psi_{-}' = N \begin{pmatrix} 0 \\ -a \\ 0 \\ 1 \end{pmatrix}[/math] There are two positive energy bispiners as well. The four component bispiner [math]\psi_{\sigma}[/math] comes from the desription for a free particle plane wave with momentum [math]\vec{p}[/math]. Using the wiki article, this would mean that there no way we can destinguish temporal causality between the negative tachyonic description sent back in time as it can be reinterpreted as a postive energy tachyon moving forward in time.

Highlighted part: agreed. Non-highlighted part: A timelike tachyon does, not a spacelike tachyon which was the point I was raising earlier. Some models go back as far as the 60's which try to circumvent the problem of a faster than light particle which would oscillate throughout time and the causality problems which closely asist it.

I think what he is saying is it still ''takes time'' for a luminal signal to be taken from one point to another. A slightly faster process would be a new ''communication limit'' in his words. In that sense, it could be possible we are just dealing with a new species of particle which moves slightly faster than light, but does not physically oscillate in time. Such models have been constructed for superluminal particles.

The present is a record of the past, with an intuitive mind present.

Causation in itself is correct. Though the state vector of a system determines in the probabilistic sense of why you don't suddenly show up in other places. Remember this is strictly the weird yet wonderful nature of quantum mechanics; somehow subatomic objects can be in more than one place at one time, they can also show up great distances away from where they are due to potential vacuum tunnelling. These things aint so apparant on our level, in fact that is an understatement; it is more or less non-existent at our level. So the wave function would be dictating that this behaviour would be improbable for large macroscopic objects, which are themselves modelled causally, as you say.

I know what you mean. You could be right.

Some might come to think this. I've often seen definitions where ''time is equated to the ability to change'', and ''time is a measurement of a change of space.'' I suppose you could. I probably wouldn't though, I don't like the idea of equating time to the ability to change because of the quantum mechanics principle of veiwing time as short beginnings and stops. Motion requires a linear notion of time when you measure events next to each other like that. But motion in General Relativity arises as a symmetry of the equations, so perhaps it can be faulty veiwing it directly like this if not careful.

A reinterpretation of tachyons moving back in time was speculated all the way back in the 60's O. M. P. Bilaniuk, V. K. Deshpande, and E. C. G. Sudarshan, Am.J.Phys. 30 (1962) 718. G. Feinberg, Phys. Rev. 159 (1967) 1089. The other way to avoid causality problems is to introduce a kinematic time under a non-standard form of Lorentz Transformations R. Tangherlini, Nuov. Cim Suppl., 20 (1961) 1. P. Caban and J. Rembielinski, Phys. Rev., A 59 (1999) 4187. Here are the first two http://prola.aps.org/abstract/PR/v159/i5/p1089_1 http://wildcard.ph.utexas.edu/~sudarshan/pub/1962_006.pdf

I'll get back to this. Defining time is hard, many different cases to consider than I have free at the moment. Right now I have enough time... lol... mind the pun. Let's start with Relativity. I've already spoken about timelessness arising as the time problem of uniting General Relativity with quantum mechanics in another thread, so time might not even exsit according to this theory. Special relativity is a little more mundane; this theory allows clocks to be moving in a flat spacetime. Essentially relativistic theories treat time as a ''dimension'' of space. Time actually has two very loose meanings in this context. One is a true real time description Real Time (or also known as imaginary space) or it can be called Real Space (which is imaginary time). Describing your universe or system in either context can be rewarding in physics when viewing the physical world. For instance timelike and spacelike movements are pivotal to understanding how a Bradyon and a Luxon and a Tachyon are all defined as speeds. Bradyons (''brady'' root word meaning slow, also known as tardyons) are spacelike whereas a tachyon (''tachy'' from the root word ''fast'' as in tachycardia) is timelike in nature (though not all tachyons require to be timelike according to some work). Time in quantum mechanics has many descriptions, some of which are outdated. Newtonian physicists and a few quantum thinkers today still believe that time has a flow. This has been demonstrated in quantum mechanics to be false, there does not seem to be an arrow of time nor does there seem to be a flow associated to events. Instead time in quantum mechanics is more like a set of starts and stops. Tiny momentary fleeting flashing of physical existence which is not tied to any fundamental flow. Time is non-linear, and has a geometry. Time is not an arrow directly drawn from any center in space either because space does not contain your normal definition of ''up'', ''down'' ''left or right''. Nor did the big bang happen in one place alone, in fact big bang happened in all places at once. So if you are looking for a nice, clean definition of time that is simple, you would certainly be leaving out a lot of details which may provide a clearer definition. A nice easy one would be ''Time is an instantaneous moment or short duration of an instantaneous moment.'' That would be the definition from physics. From Relativity, time may have two descriptions, actually one is a non-description: 1) Time does not exist 2) Time is a measurement of moving clocks Of course, Relativity may permit a third 3) Time is an instrinsic degree of freedom Where here ''degree of freedom'' is by definition a dimension.

The thing that stops you from suddenly ending up on the moon is more or less due to your wave function which peaks wherever you are right now. My wave function extends far out past our local galaxy, but chance of finding me there is very very very slim.

This is quite funny.

I'll see if I can find the relevent papers.

Yes maybe in his opinion he would like to have seen gravitons. We are all under the idea though it was to find the Higgs Boson. Which is still elusive... if it even exists. A lot of people are questioning it now.

Yes but experimentation clearly shows there is a ''cut-off'' between the micro-world and the macro-world. This may be no larger than let us say a semi-macro object - we've managed to observe quantum wave oscillations to a certain degree without direct observation, but after a certain point the usual quantum weirdness we might associate at the level of electrons and protons begins to dissipate with the larger object you deal with. The Schrodinger Cat experiment can easily be determined not to be the product of two outcomes because we initially believed that the quantum weirdness extends even to our level of every day macroscopic objects, which just isn't the case.

It turns out you can avoid causality problems for tachyons if you model them spacelike instead of timelike, which is possible.

Nothing is the meaning of something devoid of description and existence. So how can a universe really be expanding in nothing? It is a useless statement in itself.

It's an anecdote acting as a thought experiment. As for what he was proving, just as was said. It was to highlight the descrepency of understanding how quantum systems behave differently to larger masses and how two different outcome can exist due to a wave function. His experiment has been answered through decoherence. The cat won't be alive and dead at the same time.

I have said it in plain English.

You have been speculating the recent news that a nuetrino could violate causality. That would mean the neutron would be a tachyon. I apologize, would mean the neutrino would be a tachyon! See am getting mixed up now!

Curious, I don't think I said anything about imaginary time dilation. I said it was able to oscillate in the time dimension. That is to say, it freely able to move into the past and the future, obviously many causality problems arise. Imaginary time is real space. Real time is imaginary space. Travelling at different speeds lets to travel through these descriptions of time. No because a tachyon would find the lowest amount of energy available for it at the speed of light. It's the effects of the speed which does not linearly move through the time. This is why when you send a tachyon off on it's journey, it could end up arriving at place before it had been fired.