I don't understand; if someone/something can know with certainty what I can do at a particular instant, then my choice does not exist. I am predestined to do exactly what I will do at that instant. I may not know what I will do, but that is immaterial; the mere fact that my future action is known makes it a a predestined action. It cannot be anything different.
OK, I guess one could postulate at the time of creation/big bang all events took place simultaneously unseparated by time as we understand it, and thus everything that will occur has already occurred which is why the outcome can be known, but we run into many problems with this theory, such as why time flows in one direction (at least in out perceptions) and how actions contingent on a prior action (such as shooting a person and then having him die) can occur simultaneously, but the nature of the pre-universe singularity could be so strange that I would not rule it as impossible. It also more or less rules out time travel in the conventional sense, since both the past and future should be immutable as they have already occurred (perhaps a time traveler could only observe but not interact?).
keld feldspar wrote:The speed of light just like everything else has to accelerate so realistically it's not a constant.
I'm not sure that's true. It is an interesting point but I don't think light particles start off with zero velocity and accelerate to the speed of light. I suspect that wave particle duality would treat light as waves for that purpose.
If a man speaks in the forest and there are no women around to hear is he still wrong?
keld feldspar wrote:The speed of light just like everything else has to accelerate so realistically it's not a constant.
I'm not sure that's true. It is an interesting point but I don't think light particles start off with zero velocity and accelerate to the speed of light. I suspect that wave particle duality would treat light as waves for that purpose.
I stand corrected, for light in a vacuum there is NO acceleration.
Since light has no mass...
Sometimes it seems as though one has to cross the line just to figger out where it is
I don't understand; if someone/something can know with certainty what I can do at a particular instant, then my choice does not exist.
The person has the ability to change at any point unless physically made to do a particular action.
The knowledge of that action does not make that action happen.
Refer to my "knew it" post...
But that's the point, isn't it? If the outcome is "known" (and here I mean known with certainty, not guessed at) it cannot be changed, and however many times that actor may change his/her mind, (s)he will always do the same thing. Now the entity which "knows" the outcome need not be the one which predestined it, but if the outcome can be known with a certainty before the decision is made, it cannot be the result of free will, it occurs because it must occur.
But if the outcome is inevitable, then it is by definition susceptilble to no one's "free will," regardless of who or what entity "knew" the outcome in advance.
Sue U wrote:But if the outcome is inevitable, then it is by definition susceptilble to no one's "free will," regardless of who or what entity "knew" the outcome in advance.
Then anyone that says "I knew that would happen" has caused "that" to happen.
As a lawyer I'm sure you can see the implications...
Sometimes it seems as though one has to cross the line just to figger out where it is
It's two different issues: if the outcome is inevitable, it doesn't matter if anyone "knew" it; there is simply no way to affect it.
Also, human "foreknowledge" -- to the extent one might "know" what will happen -- is not exactly the same thing as divine omniscience. Certainly, the closer we are in time to an event's occurrence, and the more we know about its relevant factors, the better we can say we "know" what will happen; but at the birth of my son I could not have predicted what he'd be doing today -- although if there is an omniscient deity, he/she/it certainly could. By the same token, I "know" the Sun will rise tomorrow, but when it does my foreknowledge is obviously not the cause; however, if God knows that it will not -- and knew so from the beginning of time -- there is nothing either I or the Sun can do to avert that result. Divine omniscience may or may not be the cause of any particular result (depending on what view of a deity's attributes you might hold), but it would certainly be an indication that there is no free will to change the course of events.
One cannot "know" with a certainty what will happen unless that event is predestined to happen. Now i agree the mere knowledge does not cause the event to happen, but if an event must occur, and this is the only way one can have absolute foreknowledge of that event, then it is predestined to occur and there can be no free will (at least with regard to that event); otherwise the entity claiming to know what will occur cannot know that with any certainty. As far as i can see, you cannot have both ways.
loCAtek wrote:Not necessarily, I didn't mean to ignore it, but clarify it with the current data
Your "current data" was "my point was that the limits of our universe are not because of lack of knowledge, but the limits of what the human mind can comprehend. " - which is wrong, as I pointed out when I addressed it by saying "The limits of our universe have nothing *whatsoever* to do with our lack of knowledge or comprehension. They have nothing to do with us. We have near as makes no odds no influence over the universe at all." ... which you ignored
If the limits have nothing to do with us, then how can we comprehend them?
thestoat wrote:
Back to time travel ...
Off the top of my head, the observations were around particles with a small half life - fractions of a second. Researchers found that if these were accelerated close to the speed of light, their lifespan increased dramatically - they were travelling forward in time. My physics study is over 20 years old not though - they didn't have a web thing back then.
Special Relativity also says that a surprising thing happens when you move through space-time, especially when your speed relative to other objects is close to the speed of light. Time goes slower for you than for the people you left behind. You won't notice this effect until you return to those stationary people.
Say you were 15 years old when you left Earth in a spacecraft traveling at about 99.5% of the speed of light (which is much faster than we can achieve now), and celebrated only five birthdays during your space voyage. When you get home at the age of 20, you would find that all your classmates were 65 years old, retired, and enjoying their grandchildren! Because time passed more slowly for you, you will have experienced only five years of life, while your classmates will have experienced a full 50 years.
The author goes on to say
I am confident time travel into the future is possible, but we would need to develop some very advanced technology to do it. We could travel 10,000 years into the future and age only 1 year during that journey. However, such a trip would consume an extraordinary amount of energy. Time travel to the past is more difficult. We do not understand the science as well.
General relativity is, from what I recall, simply special relativity but allowing for acceleartion of objects (the maths becomes exponentially harder).
I'm familiar with that, I'm a big SF buff...but that's conjecture and not observation; and not travel through time to the past or to the future of the individual; but the present progressing at different rates according to the speed of light (which reaching is Science Fiction, not fact). However, their 'now' is not reliving their past nor experiencing their future. That's time relativity, not time travel.
Last edited by loCAtek on Tue Jan 25, 2011 3:38 am, edited 1 time in total.
Some theories, most notably special and general relativity, suggest that suitable geometries of spacetime, or specific types of motion in space, might allow time travel into the past and future if these geometries or motions are possible.[16] In technical papers, physicists generally avoid the commonplace language of "moving" or "traveling" through time ('movement' normally refers only to a change in spatial position as the time coordinate is varied), and instead discuss the possibility of closed timelike curves, which are worldlines that form closed loops in spacetime, allowing objects to return to their own past. There are known to be solutions to the equations of general relativity that describe spacetimes which contain closed timelike curves (such as Gödel spacetime), but the physical plausibility of these solutions is uncertain.
[Stoat's theory]
Relativity states that if one were to move away from the Earth at relativistic velocities and return, more time would have passed on Earth than for the traveler, so in this sense it is accepted that relativity allows "travel into the future" (according to relativity there is no single objective answer to how much time has 'really' passed between the departure and the return, but there is an objective answer to how much proper time has been experienced by both the Earth and the traveler, i.e. how much each has aged; See twin paradox). On the other hand, many in the scientific community believe that backwards time travel is highly unlikely. Any theory which would allow time travel would require that problems of causality be resolved. The classic example of a problem involving causality is the "grandfather paradox": what if one were to go back in time and kill one's own grandfather before one's father was conceived? But some scientists believe that paradoxes can be avoided, either by appealing to the Novikov self-consistency principle or to the notion of branching parallel universes (see the 'Paradoxes' section below).
[edit] Tourism in time
Stephen Hawking once suggested that the absence of tourists from the future constitutes an argument against the existence of time travel—a variant of the Fermi paradox. Of course this would not prove that time travel is physically impossible, since it might be that time travel is physically possible but that it is never in fact developed (or is cautiously never used); and even if it is developed, Hawking notes elsewhere that time travel might only be possible in a region of spacetime that is warped in the right way, and that if we cannot create such a region until the future, then time travelers would not be able to travel back before that date, so "This picture would explain why we haven't been over run by tourists from the future."[17] Carl Sagan also once suggested the possibility that time travelers could be here, but are disguising their existence or are not recognized as time travelers.[18]
[edit] General relativity
However, the theory of general relativity does suggest scientific grounds for thinking backwards time travel could be possible in certain unusual scenarios, although arguments from semiclassical gravity suggest that when quantum effects are incorporated into general relativity, these loopholes may be closed.[19] These semiclassical arguments led Hawking to formulate the chronology protection conjecture, suggesting that the fundamental laws of nature prevent time travel,[20] but physicists cannot come to a definite judgment on the issue without a theory of quantum gravity to join quantum mechanics and general relativity into a completely unified theory.[21]
loCAtek wrote:If the limits have nothing to do with us, then how can we comprehend them?
Are you being serious? You think that the Universe must be understandable by us? Really?
As for the wiki, no Strawmen please. I am nowhere near clever enough to have my own theory. I merely state what has happened or refer to the theories of others.
loCAtek wrote:but that's conjecture and not observation; and not travel through time to the past or to the future of the individual
No, not conjecture - it has been observed!
I agree it is for particles and not people - if you look back over my posts you will see I have never said people have moved through time (at anything other than the standard 1 hour per hour).
loCAtek wrote:That's time relativity, not time travel.
You haven't grasped this. If I travel 10 years into the future in a space ship and it takes me an hour, then I have travelled into the future. I start off in 2011. I end up in 2021. I stay the same age. How is this not time travel?
If a man speaks in the forest and there are no women around to hear is he still wrong?
thestoat wrote:If I travel 10 years into the future in a space ship and it takes me an hour, then I have travelled into the future. I start off in 2011. I end up in 2021. I stay the same age. How is this not time travel?
Does this mean that I am a time traveller?
I left Heathrow and travelled for 24 hours. I arrived in Brisbane 34 hours after the time I left Heathrow... but only 24 hours older!
I think Stoat that the form of time travel you describe could only be considered such if you travelled only through time and not space.
Why is it that when Miley Cyrus gets naked and licks a hammer it's 'art' and 'edgy' but when I do it I'm 'drunk' and 'banned from the hardware store'?
Sean - I suppose we are all time travellers, though I envy your Oz trip - best place in the world, that.
Sean wrote:I think Stoat that the form of time travel you describe could only be considered such if you travelled only through time and not space.
I agree. You might have to travel through space to achieve the effect (maybe head out to the nearest star and then return). There are some excellent Sci Fi books that Lo might like (perhaps you have read them, lo?) about "Ender" by Orson Scott Card, which are largely based on travelling to far distant planets at near the speed of light. Upon returning, the travellers get to see their great great grandchildren.
If a man speaks in the forest and there are no women around to hear is he still wrong?
There is a way to convince your family that you are a time traveller:
Simply choose your most garish item of clothing... let's say a xmas reindeer sweater. Now, while the family are gathered in the living room, slip out, put on the sweater and burst in on them crying "What day is it?" When they answer, shout "Good God, it worked!" and then run out of the room. Remove the sweater, hide it and rejoin your family. They will undoubtedly ask about your actions, just deny everything.
Next day, dress in the reindeer sweater. In the afternoon you can casually mention that you think you may have discovered the secret of time travel and are going to attempt to travel back in time 24 hours.
Cue one astonished family!
Why is it that when Miley Cyrus gets naked and licks a hammer it's 'art' and 'edgy' but when I do it I'm 'drunk' and 'banned from the hardware store'?
