Starship Asterisk*

geckzilla wrote:I thought there was a thread specifically relating to this picture already but I couldn't find it.

oldnewideas wrote:Is it ethical to discuss a topic which has been declared impossible by a couple of the seemingly most influential participants on this fourm?

Guest wrote:

oldnewideas wrote:Is it ethical to discuss a topic which has been declared impossible by a couple of the seemingly most influential participants on this fourm?

it's like discussing penrose triangle in math forum - we can discuss how would it look like were it actually possible.

oldnewideas wrote:

Guest wrote:

oldnewideas wrote:Is it ethical to discuss a topic which has been declared impossible by a couple of the seemingly most influential participants on this fourm?

it's like discussing penrose triangle in math forum - we can discuss how would it look like were it actually possible.

And who is considered authoritative enough to state with 100 percent certain proof that time travel is impossible?

oldnewideas wrote:And who is considered authoritative enough to state with 100 percent certain proof that time travel is impossible?

bystander wrote:

geckzilla wrote:I thought there was a thread specifically relating to this picture already but I couldn't find it.

Maybe this, or this.

Guest wrote:they almost got him once. he blamed it on his own generals.

swainy (tc) wrote:As for Time Travel, It is possible, if we could get past our physical limitations.

Chris Peterson wrote:What isn't possible if you can get past physical limitations? I'd say that the only thing that is truly impossible, however, is getting past physical limitations!

swainy (tc) wrote:When A physical limitation is well understood, A physical solution will be forth coming.

Chris Peterson wrote:What isn't possible if you can get past physical limitations?

Guest wrote:

Chris Peterson wrote:What isn't possible if you can get past physical limitations?

To get past mathematical limitations. Like, to find A such that A & !A = true. Or to divide by zero.

Chris Peterson wrote:In a sense, you can always "get around" mathematical limitations by simply redefining the axioms upon which you base your mathematical system. That's a little tricky with physics, though <g>.

Guest wrote:not at all, see Feynman electon theory for example - there you have legit time travelling.

http://en.wikipedia.org/wiki/Arrow_of_time wrote:
1) The thermodynamic arrow of time

The thermodynamic arrow of time is provided by the Second Law of Thermodynamics, which says that in an isolated system, entropy tends to increase with time. Entropy can be thought of as a measure of microscopic disorder; thus the Second Law implies that time is asymmetrical with respect to the amount of order in an isolated system: as a system advances through time, it will statistically become more disordered. This asymmetry can be used empirically to distinguish between future and past though measuring entropy does not accurately measure time. Also in an open system entropy can locally decrease with time: living systems decrease their entropy by expenditure of energy at the expense of environmental entropy increase.

While Naturalistic Evolutionists claim that the Second Law is statistical, physicists assert otherwise. British Physicist Sir Alfred Brian Pippard wrote, "There is thus no justification for the view, often glibly repeated, that the Second Law of Thermodynamics is only statistically true, in the sense that microscopic violations repeatedly occur, but never violations of any serious magnitude. On the contrary, no evidence has ever been presented that the Second Law breaks down under any circumstances." The Second Law is universal and seems to accurately describe the overall trend in real systems toward higher entropy.

This arrow of time seems to be related to all other arrows of time and
arguably underlies some of them, with the exception of the weak arrow of time.
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2) The cosmological arrow of time

The cosmological arrow of time points in the direction of the universe's expansion. It may be linked to the thermodynamic arrow, with the universe heading towards a heat death (Big Chill) as the amount of usable energy becomes negligible. Alternatively, it may be an artifact of our place in the universe's evolution (see the Anthropic bias), with this arrow reversing as gravity pulls everything back into a Big Crunch.

If this arrow of time is related to the other arrows of time, then the future is by definition the direction towards which the universe becomes bigger. Thus, the universe expands - rather than shrinks - by definition.

The thermodynamic arrow of time and the Second law of thermodynamics are thought to be a consequence of the initial conditions in the early universe. Therefore they ultimately result from the cosmological set-up.
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3) The radiative arrow of time

Waves, from radio waves to sound waves to those on a pond from throwing a stone, expand outward from their source, even though the wave equations allow for solutions of convergent waves as well as radiative ones. This arrow has been reversed in carefully worked experiments which have created convergent waves, so this arrow probably follows from the thermodynamic arrow in that meeting the conditions to produce a convergent wave requires more order than the conditions for a radiative wave. Put differently, the probability for initial conditions that produce a convergent wave is much lower than the probability for initial conditions that produce a radiative wave. In fact, normally a radiative wave increases entropy, while a convergent wave decreases it, making the latter contradictory to the Second Law of Thermodynamics in usual circumstances.
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4) The causal arrow of time

A cause precedes its effect: the causal event occurs before the event it affects. Birth, for example, follows a successful conception and not vice versa. Thus causality is intimately bound up with time's arrow.

An epistemological problem with using causality as an arrow of time is that, as David Hume pointed out, the causal relation per se cannot be perceived; one only perceives sequences of events. Furthermore it is surprisingly difficult to provide a clear explanation of what the terms "cause" and "effect" really mean, or to define the events to which they refer. It does seem evident, however, that dropping the plate is the cause while the plate shattering is the effect.

Physically speaking, this is another manifestation of the thermodynamic arrow of time, and is a consequence of the Second law of thermodynamics. Controlling the future, or causing something to happen, creates correlations between the doer and the effect, and these can only be created as we move forwards in time, not backwards.
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5) The particle physics (weak) arrow of time

Certain subatomic interactions involving the weak nuclear force violate the conservation of both parity and charge conjugation, but only very rarely. An example is the kaon decay. According to the CPT Theorem, this means they should also be time irreversible, and so establish an arrow of time. Such processes should be responsible for matter creation in the early universe.

This arrow is not linked to any other arrow by any proposed mechanism, and if it would have pointed to the opposite time direction, the only difference would have been that our universe would be made of anti-matter rather than from matter. More accurately, the definitions of matter and anti-matter would just be reversed.

That the combination of parity and charge conjugation is broken so rarely means that this arrow only "barely" points in one direction, setting it apart from the other arrows whose direction is much more obvious.
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6) The quantum arrow of time

According to the Copenhagen interpretation of quantum mechanics, quantum evolution is governed by the Schrödinger equation, which is time-symmetric, and by wave function collapse, which is time irreversible. As the mechanism of wave function collapse is philosophically obscure, it is not completely clear how this arrow links to the others. Despite the post-measurement state being entirely stochastic in formulations of quantum mechanics, a link to the thermodynamic arrow has been proposed, noting that the second law of thermodynamics amounts to an observation that nature shows a bias for collapsing wave functions into higher entropy states versus lower ones, and the claim that this is merely due to more possible states being high entropy runs afoul of Loschmidt's paradox. According to the modern physical view of wave function collapse, the theory of quantum decoherence, the quantum arrow of time is a consequence of the thermodynamic arrow of time.
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7) The psychological/perceptual arrow of time

Psychological time is, in part, the cataloguing of ever increasing items of memory from continuous changes in perception. In other words, things we remember make up the past, while the future consists of those events that cannot be remembered. The ancient method of comparing unique events to generalized repeating events such as the apparent movement of the sun, moon, and stars provided a convenient grid work to accomplish this. The consistent increase in memory volume creates one mental arrow of time. Another arises because one has the sense that one's perception is a continuous movement from the known (Past) to the unknown (Future). Anticipating the unknown forms the psychological future which always seems to be something one is moving towards, but, like a projection in a mirror, it makes what is actually already a part of memory, such as desires, dreams, and hopes, seem ahead of the observer.

The association of "behind = past" and "ahead = future" is itself culturally determined. For example, the Chinese and the Aymara people both associate "ahead = past" and "behind = future". In Chinese, for instance, the term "the day after tomorrow" literally means "behind day" while "the day before yesterday" is referred to as "front day".

The other side of the psychological passage of time is in the realm of volition and action. We plan and often execute actions intended to affect the course of events in the future. Hardly anyone tries to change past events. Indeed, in the Rubaiyat it is written (sic):

• The Moving Finger writes; and, having writ,
  Moves on: nor all thy Piety nor Wit
  Shall lure it back to cancel half a Line,
  Nor all thy Tears wash out a Word of it.
  - Omar Khayyám (Fitzgerald translation)

The psychological arrow of time is thought to be reducible to the thermodynamic arrow: it has deep connections with Maxwell's demon and the physics of information; In fact, it is easy to understand its link to the Second Law of Thermodynamics if we view memory as correlation between brain cells (or computer bits) and the outer world. Since the Second Law of Thermodynamics is equivalent to the growth with time of such correlations, then it states that memory will be created as we move towards the future (rather than towards the past).

Chris Peterson wrote:

swainy (tc) wrote:When A physical limitation is well understood, A physical solution will be forth coming.

No, when a physical limitation is well understood, people stop looking for ways around it. That is, once it is truly understood as a limitation.

swainy (tc) wrote:I could go on, and on, and on, The world is full of, has been physical limitations. But we beat them all.

Chris Peterson wrote:I guess it depends on how you define a "physical limitation".

swainy (tc) wrote:The Romans once thought, the end of the world, was just across the English channel. Hows that for a physical limitation?

Chris Peterson wrote:

swainy (tc) wrote:The Romans once thought, the end of the world, was just across the English channel. Hows that for a physical limitation?

In my opinion, it isn't.

swainy (tc) wrote:But Ok, hows this for a physical limitation?