Time Travel

[hariharan]

What is your concept about time travel? Just post your thoughts. Here mine, no proof.

I assume we humans as a radio receiver, we are tuned to a particular frequency. What ever we are seeing, feeling, happening is all related only to that particular frequency. At any point of time there will be “n” number off frequencies available. If we can change our frequency then we will be able to do the time travel. (my concept worth thinking?? Just childish?? ). Post your replies.

Dexter your comments pls.

 

[lone wolf]

I can think of an ass I'd like to go back and kick.... My own.

Woof!

 

[darkbeaver]

It's hard to think of how you would avoid changing your own past. But maybe the past is fixed in time somehow. And if you want to go forward where would you go the future isn't there yet. I think we're stuck in the present, at least I think I am.

 

[Andem]

The laws of physics and some popular theories state that travel to the future is theoretically possible but the idea of backwards time travel hasn't yet been sorted. The last episode of Lost had me thinking about it a few days ago.

 

[lone wolf]

Theoretically, it is possible - but you can't go back before the date the machine started working. So much for some really cool old TV shows....

Woof!

 

[darkbeaver]

Theoretically, it is possible - but you can't go back before the date the machine started working. So much for some really cool old TV shows....

Woof!

Ya haha that would sort of limit the trip wouldn't it.

 

[RomSpaceKnight]

The arrow of time moves in one direction. This is exhibited by how entrophy always increases. Eventually the universe may slow it's expansion and begin to contract. Perhaps then the arrow of time will reverse.

Then there are the philosophical paradoxes.

 

[darkbeaver]

The arrow of time moves in one direction. This is exhibited by how entrophy always increases. Eventually the universe may slow it's expansion and begin to contract. Perhaps then the arrow of time will reverse.

Then there are the philosophical paradoxes.

There's some recent papers on the steady state universe where entrophy ain't a big deal and time isn't either.

 

[Dexter Sinister]

What a fortuitous coincidence; I was reading about such things just this afternoon.

The equations of general relativity do allow for things like time machines, based on what's called a traversable wormhole. A wormhole is a shortcut through space-time caused by the curvature of the universe, but there's a catch: gravity crushes the throat of the hole, destroying anybody trying to go through it. To stabilize it requires a repulsive force based on negative mass and energy, which so far are purely speculative. Note that that's not the dark matter and energy postulated by cosmologists, neither is it antimatter, which we know exists, it's something different. Nobody has as clue whether it actually exists or not, but it's possible to work the equations with it. Assuming we could get around that little technical difficulty, you build a time machine by making a traversable wormhole with both ends initially close together, then flinging one end of it off into space at near light speed. Time slows down at that end compared to the stationary end, so a traveler going back and forth along the wormhole moves back and forth in time. But the Woofer's right, you can't go back in time beyond the point when the machine was built, which might be why travelers from the future haven't arrived yet: we haven't built the machine.

You can read all about it the same place I did this afternoon. The March 2008 issue of Discover magazine is a special issue about Einstein, $6.50 at better magazine racks everywhere in Canada. Probably cheaper in the United States, but the !#$!@#$!@#$ publishers no longer put both Canadian and American prices on things, to hide the fact that they're still gouging us in Canada.

 

[hariharan]

What ever happened is happened. We cannot change it. Traveling to the past just as a viewer, (i.e) we can see what is happening in the past time and they cannot sense us at all?? That’s why we are not able to sense any time traveler from the future. Just a thought Dexter.

 

[Lester]

time

It's hard to think of how you would avoid changing your own past. But maybe the past is fixed in time somehow. And if you want to go forward where would you go the future isn't there yet. I think we're stuck in the present, at least I think I am.

Hugh Everette was a theoretical quantum physisist who wrote an essay regarding the many worlds theory -
In 1957, Hugh Everett III proposed a radical new way of dealing with some of the more perplexing aspects of quantum mechanics. It became known as the Many-Worlds Interpretation.
According to this interpretation, whenever numerous viable possibilities exist, the world splits into many worlds, one world for each different possibility (in this context, the term "worlds" refers to what most people call "universes"). In each of these worlds, everything is identical, except for that one different choice; from that point on, they develop independently, and no communication is possible between them, so the people living in those worlds (and splitting along with them) may have no idea that this is going on.
In this way, the world branches endlessly. What is "the present" to us, lies in the pasts of an uncountably huge number of different futures. Everything that can happen, does, somewhere.more herehttp://frombob.to/many.html

Lester

 

[Dexter Sinister]

There are at least 8 interpretations around of what quantum theory "really means," which a physicist named Nick Herbert in a wonderful and informative little book called Quantum Reality (highly recommended) summarized this way:

1. the Copenhagen interpretation, part 1, due mostly to Niels Bohr and Werner Heisenberg: there is no deep reality. This is where most physicists go when you ask them what quantum theory means. They'll tell you that when something isn't being measured, it has no definite attributes.
2. the Copenhagen interpretation, part 2: reality is created by observation.
3. Reality is an undivided whole, an idea from David Bohm. Quantum attributes are not localized in quantum objects but are part of the entire experimental arrangement.
4. The many-worlds interpretation: This is Everett's idea that Lester described.
5. Quantum Logic: reality follows a non-human kind of reasoning, an idea due to John von Neumann and Garrett Birkhoff.
6. Neo-realism: the world is made of ordinary objects. This idea is usually treated as heresy.
7. Consciousness creates reality. Another of John von Neumann's ideas.
8. The duplex world, another idea of Werner Heisenberg's: the results of measurements are truly real, but the act of measurement transforms what's "really there" into a form compatible with ordinary experience.

Take your pick or invent your own, nobody really knows what quantum theory means, and no less an authority than the Nobel Prize winner Richard Feynman, described by his colleagues as the smartest man in the world, said so. All we really know is that it works spectacularly well.

 

[Niflmir]

I vote for the Quantum logic. The wave function gives you more information than classical trajectories. In the vanishing Planck constant approximation you can retrieve the classical equations of motion. In any case, you can't get information about time travel from quantum mechanics, unless you are talking about quantum gravity - also you would need to be an atom.

Well, we aren't atoms. We are fairly large, massive, complicated objects; we aren't suddenly going to tunnel into the past. We follow classical equations of motions. So you genuinely need general relativity and not quantum relativity to help you here. This idea is not new at all, the first person that I know of who looked at this problem in GR (general relativity) was an engineer named Kurt Gödel, who wanted a way to cheat death.

The Gödel universe contains closed timelike loops. We all travel through time along timelike curves, so following these curves means that you can arrive to the past without doing anything special, but you aren't really turning back time since you are constantly moving in a forward timelike direction.

In any case all these universes with closed timelike curves require exotic matter and/or highly tuned cosmological constants. All the matter that we know about follows energy conditions which ensure conventional causality: no backwards time travel.

However, as I said. We all travel through time. Its a one way highway and the only interesting fact is that some vehicles move `faster' along this highway than others. That is the joy of relativity.

 

[Dexter Sinister]

I vote for the Quantum logic.

So do I. I've never liked either version of the Copenhagen interpretation, though admittedly that's more for aesthetic than logical reasons, and I dislike the "consciousness creates reality" school for similar reasons. They provide the opening for fools like Deepak Chopra to invent all kinds of mystic nonsense and grotesquely misrepresent, at great personal profit, one of humanity's greatest intellectual achievements. Besides, Quantum Logic seems to explicitly recognize a fundamental fact in a way the others don't: quantum objects observably *don't* behave in ways that make intuitive sense to us. I never did investigate David Bohm's formulation of it, and it seems there are still some people around who think he was on to something, but I think the old brain's too ossified and out of practice to deal with that level of mathematics anymore. I'd have to go back to my textbooks and spend a year studying up... Not gonna do it, I'm retired.

 

[Niflmir]

Bohm basically believed the same thing Einstein did. That there was a hidden local variable that would explain everything using classical logic if we could only discover it. Bohm really pushed this point of view. Recently (1-2 years ago) someone from Canada (Joy Christian) seemed to have constructed a local hidden variable using Clifford algebras that reconstruct the quantum values obtained from Bell's theorem. If you understand Clifford algebras (I don't) you can read his papers by following the links at his homepage.

But seriously, if nature is described by Clifford algebras, that is even stranger than operators in Hilbert space.

 

[eanassir]

The past and the future​

Concerning the past:
According to the light speed, we may be able to see some events that happened in the past on some distant objects in the universe, on condition we have the advanced means of viewing such objects precisely from faraway distances and we are on Earth.

Moreover, all acts, works and words will leave some influence on the surroundings, like the influence on the video-tape; which may be possible to display by some or other means.
This is in the Quran 41: 20-21 ​

حَتَّى إِذَا مَا جَاؤُوهَا شَهِدَ عَلَيْهِمْ سَمْعُهُمْ وَأَبْصَارُهُمْ وَجُلُودُهُمْ بِمَا كَانُوا يَعْمَلُونَ . وَقَالُوا لِجُلُودِهِمْ لِمَ شَهِدتُّمْ عَلَيْنَا قَالُوا أَنطَقَنَا اللَّهُ الَّذِي أَنطَقَ كُلَّ شَيْءٍ وَهُوَ خَلَقَكُمْ أَوَّلَ مَرَّةٍ وَإِلَيْهِ تُرْجَعُونَ​

The explanation: (Until when they [shall] come to it [: the fire], their hearing, their eye-sights and their skins shall bear witness against them of what they did.
And they [shall] say to their skins: "Why have you borne witness against us?" They [shall] say: "God let us speak Who let everything speak." [Gabriel will say:] "He did create you [naked] at first, and to Him [shall] you be [after death] returned [naked.]")

Concerning the future:
None in the heavens and the earth knows, but only God does know the forefuture; then how about traveling to the future; this is not logical and not reasonable; although some novelists like H.G. Wells wrote fiction stories about that.

This is in the Quran 27: 65​

قُل لَّا يَعْلَمُ مَن فِي السَّمَاوَاتِ وَالْأَرْضِ الْغَيْبَ إِلَّا اللَّهُ وَمَا يَشْعُرُونَ أَيَّانَ يُبْعَثُونَ​

The explanation: (Say [O Mohammed]: "None in the heavens and the earth knows the forefuture except God; and they perceive not [about] when they shall [die and] be sent forth [from their bodies to the Hereafter.]")​

 

[darkbeaver]

If we ignore the speed of light we should be able to leave home ten minutes late for work and arrive five minutes early. I have always found being limited by the speed of light inconvienient.

 

[MikeyDB]

Time travel is only "interesting" to those unprepared and unhappy with the "now". The song goes that if we could travel backward we could "right some wrongs"...for whom and on the basis of what...?

If you travel forward you'd have an opportunity to learn the winning lottery ticket numbers or see how little Johnny did at Yale......and to whom would this make an iota of difference?

Short-lived sentient species throughout the multiverse have travelled through time forever and found that like solar cycles and life cycles and growth cycles etc. the challenge is in finding comfort in the now. Breaking the temporal event wave is like a mythic panacea for a species disenchanted with itself.

 

[darkbeaver]

today becomes yesterday as it becomes tomorrow

 

[dancing-loon]

I think time exists only for us humans. Everything else is "Eternity", is unmeasurable.

The concept of time has evolved along with the human, I think. Time is now the ruler of our lives.
Did time matter to the cave man?