How is future time travel possible when the future has not happened yet? It's like going in a direction in a car for which there is no road. Your pretty much stuck! I am aware of John Titor, however, there is no way he is from the future. If someone could explain this in a logical way, I would apprecitate it.
How is future time travel possible?
- Thread starter vegasdude
- Start date
Darby
Epochal Historian
vegasdude,
That's correct. From your perspective the future has not happened yet therefore there's no future to quickly travel to, but...
From special relativity we discover that time is relative, not absolute. You can travel at a velocity near the speed of light relative to the Earth, for instance, and from the Earth's point of view time passes for you at a slower rate than there. That is called time dilation. This is not just a theory. It has been tested for 100 years and it is a physical fact.
Therefore, when you slow down, turn around and return to Earth maybe only a few months have passed inside your ship - but many years have passed on Earth. In effect you have found a shortcut through spacetime to arrive in the future.
The general theory of relativity has solutions that theoretically allow you to take shortcuts through spacetime to arrive at far distant places and times. Unlike time dilation, those solutions cannot be tested yet. We don't know if they are simply mathematical constructs with no validity in the real world or if they are actually viable solutions.
That's correct. From your perspective the future has not happened yet therefore there's no future to quickly travel to, but...
From special relativity we discover that time is relative, not absolute. You can travel at a velocity near the speed of light relative to the Earth, for instance, and from the Earth's point of view time passes for you at a slower rate than there. That is called time dilation. This is not just a theory. It has been tested for 100 years and it is a physical fact.
Therefore, when you slow down, turn around and return to Earth maybe only a few months have passed inside your ship - but many years have passed on Earth. In effect you have found a shortcut through spacetime to arrive in the future.
The general theory of relativity has solutions that theoretically allow you to take shortcuts through spacetime to arrive at far distant places and times. Unlike time dilation, those solutions cannot be tested yet. We don't know if they are simply mathematical constructs with no validity in the real world or if they are actually viable solutions.
Time_Traveller
Temporal Novice
but then will you be able to come back again? do you want go to the future when all your relatives are dead and no one knows you. this is actually related to the spacetravel and time dilation is its concomitant effect.
but what I wonder is whether the general theory of relativity or any other present day theory allows one to travel to the past or future and then come back to one's own time again. I think this has nothing to do with space travel. or does time travel always have to be space related as in what you said?
Darby
Epochal Historian
Time_Traveller,
There are literally hundreds of theoretical solutions to general relativity that suggest time travel to the past but they cannot presently be tested. So who knows for sure?
Yes. This goes to the very heart of space travel. We cannot travel to distant stars unless we find a way to take shortcuts through spacetime. The speed of light is an absolute limit, thus directly traveling at that velocity is out of the question (unless general relativity is completely wrong on that issue which is highly doubtful and supported by 75 years of experiment). Even traveling at 99.99999% C it takes a long time to make the trip and "back home" from the ships perspective time is advancing at a terrific rate.
But that doesn't mean that we can't take shortcuts through spacetime that avoid having people on earth age several generations while we are gone and which don't require FTL velocities..
That's why we, as people who are discussing time travel, have to remember that space and time are not seperate. It is spacetime. Traveling in space or time is a "simple" rotation of the system of 4 dimensional coordinates.
Sounds simple enough - but we aren't even close today. <sigh>
There are literally hundreds of theoretical solutions to general relativity that suggest time travel to the past but they cannot presently be tested. So who knows for sure?
Yes. This goes to the very heart of space travel. We cannot travel to distant stars unless we find a way to take shortcuts through spacetime. The speed of light is an absolute limit, thus directly traveling at that velocity is out of the question (unless general relativity is completely wrong on that issue which is highly doubtful and supported by 75 years of experiment). Even traveling at 99.99999% C it takes a long time to make the trip and "back home" from the ships perspective time is advancing at a terrific rate.
But that doesn't mean that we can't take shortcuts through spacetime that avoid having people on earth age several generations while we are gone and which don't require FTL velocities..
That's why we, as people who are discussing time travel, have to remember that space and time are not seperate. It is spacetime. Traveling in space or time is a "simple" rotation of the system of 4 dimensional coordinates.
Sounds simple enough - but we aren't even close today. <sigh>
Time_Traveller
Temporal Novice
well, wh,le reading Titor's writings I have always consired what he wrote to be specific to time travel. (assuming he were real) was he travelling in space too while going back and fort between years 2036-1975. then does 2036 exist somewhere physically? (again assuming time travel future is possible)
Darby
Epochal Historian
Time_Traveller,
This is one of the issues that point to Titor's not being what he said he was - a time traveler.
He was very specific, dating back to his 1998 faxes to Art Bell. He said that his gadget remained "stationary" in space but traveled through time. He even answered one member in the negative when asked if his society had managed to acquire advanced space travel. It was pointed out to him that space travel is assumed if time travel is possible via the "simple" rotation of 4D coordinates that I alluded to above. For a "time traveler" he wasn't too keen on the implications of what spacetime travel entails or allows.
Does 2036 exist "physically" somewhere? A spacetime diagram would say that it does. Again, the question remains as to whether this description is simply "the math" or does it have some real world validity. Who knows?
I often point this out: Math is not physics. Math is the language of physics. Spain doesn't exist because people there speak some dialect of Spanish. Spain is a geo-physical location on a planet called Earth irrespective of the language that is spoken.
This is one of the issues that point to Titor's not being what he said he was - a time traveler.
He was very specific, dating back to his 1998 faxes to Art Bell. He said that his gadget remained "stationary" in space but traveled through time. He even answered one member in the negative when asked if his society had managed to acquire advanced space travel. It was pointed out to him that space travel is assumed if time travel is possible via the "simple" rotation of 4D coordinates that I alluded to above. For a "time traveler" he wasn't too keen on the implications of what spacetime travel entails or allows.
Does 2036 exist "physically" somewhere? A spacetime diagram would say that it does. Again, the question remains as to whether this description is simply "the math" or does it have some real world validity. Who knows?
I often point this out: Math is not physics. Math is the language of physics. Spain doesn't exist because people there speak some dialect of Spanish. Spain is a geo-physical location on a planet called Earth irrespective of the language that is spoken.
RainmanTime
Super Moderator
Darby,
RMT
Very well put. This is an important distinction that is lost on many people without a solid grasp of science and how math is used therein.
RMT
At present there are many theories envoloped into a category known as VSL Theories. These have been around since the early 90's started by a physicist named Moffat. While empirical evidence is lacking, there have been findings from particle physicists that show variations in the speed of "light" with very very high frequencies. These extremely high frequencies have such short wavelengths that it is theorized they must "leap frog" through quanta gaps in space. I only bring this up because even though the current best approximation of our universe (relativity) states that C is constant (btw Special Relativity calls for a constant C), this is by no means the end of the discussion, espeically in light of recent theories.
As far as time travel goes....
Travel "into the future" is far more possible than into the past, ofcourse only because of a technicality. Travel near speed of light, go a long ways, come back...you haven't aged but everyone who was not traveling at that speed has.....This according to current theory is irreversible however, ie you can't travel back.
As far as time travel goes....
Travel "into the future" is far more possible than into the past, ofcourse only because of a technicality. Travel near speed of light, go a long ways, come back...you haven't aged but everyone who was not traveling at that speed has.....This according to current theory is irreversible however, ie you can't travel back.
Darby
Epochal Historian
Rainman,
Thanks for the reply and concurrence.
I'd add that the heart of modern science is experiment. No matter what the math tells us we endeavor to design an experiment based on the theory and see if it really works as predicted. Beyond that we then see if we can make predictions in the real world outside the lab based on the theory and math.
In your field it doesn't do an engineer any good if he/she designs a glider aircraft based on pure theory and by-pass the experimental design phase only to see the aircraft have the glide ratio of a brick. /ttiforum/images/graemlins/ooo.gif
Thanks for the reply and concurrence.
I'd add that the heart of modern science is experiment. No matter what the math tells us we endeavor to design an experiment based on the theory and see if it really works as predicted. Beyond that we then see if we can make predictions in the real world outside the lab based on the theory and math.
In your field it doesn't do an engineer any good if he/she designs a glider aircraft based on pure theory and by-pass the experimental design phase only to see the aircraft have the glide ratio of a brick. /ttiforum/images/graemlins/ooo.gif
Darby
Epochal Historian
CPE,
Corrrect. Its this sort of "shortcut" through spacetime that we have to be able to take advantage of. The speed of light in a vacuum (Galilean frame of reference) is fixed. The average speed of a photon through an electromagnetic field (or some other medium) is not C. It varies as a function of the Index of Refraction of the medium.
A good example of this situation is a photon emitted near the core of our sun. It should only take ~8 minutes from emission to arrive at Earth. However, on average, it takes approximately 1 million years for the photon the reach the solar surface.
Corrrect. Its this sort of "shortcut" through spacetime that we have to be able to take advantage of. The speed of light in a vacuum (Galilean frame of reference) is fixed. The average speed of a photon through an electromagnetic field (or some other medium) is not C. It varies as a function of the Index of Refraction of the medium.
A good example of this situation is a photon emitted near the core of our sun. It should only take ~8 minutes from emission to arrive at Earth. However, on average, it takes approximately 1 million years for the photon the reach the solar surface.
Darby
Epochal Historian
Time_Traveller,
Just a follow-up to my answer to your post that I made on the 11th.
One thing to keep in mind regarding spacetime diagrams (Penrose Diagrams) is this:
Yes, they all show five "singularities" and they all have one-way membranes leading to the past and to the future via spacelike, timelike and lightlike paths. But, and this is important, they all assume a black hole in an idealized universe where the only object occupying that universe is the black hole. No other mass, field or energy is in that universe. Even the "thing" that would traverse the black hole is idealized and has no mass, field or energy associated with it.
When any mass, field or energy exists in the universe the math blows up and safe passage across the event horizon is for one reason or another negated or it leads to a description of a universe other than the one that we live in..
This doesn't mean that safe passage in the real world (again, whatever that means) is not possible. At a minimum it means that the math and/or underlying knowledge base is incomplete.
But all of the Penrose Diagrams associated with each class of black hole does indicate a past and future singularity associated with the timelike, spacelike and lightlike areas and one way membranes into and out of that area. But they have no path that leads back to the original "world" where a traveler would start the journey. You can leave home, go to the future or past in another universe but you can never return home unless, by chance, one of the worlds that you visit has an exit to an absolute twin copy of your original home.
The exception to the one way membrane is a maximal Kerr-Newman BH. Like a Tipler cylinder it has no membrane and two way travel is theoretcally possible. But like all other GR solutions for black holes, if you add any external mass to the universe, and especially if you account for quantum effects, the solution blows up.
Just a follow-up to my answer to your post that I made on the 11th.
One thing to keep in mind regarding spacetime diagrams (Penrose Diagrams) is this:
Yes, they all show five "singularities" and they all have one-way membranes leading to the past and to the future via spacelike, timelike and lightlike paths. But, and this is important, they all assume a black hole in an idealized universe where the only object occupying that universe is the black hole. No other mass, field or energy is in that universe. Even the "thing" that would traverse the black hole is idealized and has no mass, field or energy associated with it.
When any mass, field or energy exists in the universe the math blows up and safe passage across the event horizon is for one reason or another negated or it leads to a description of a universe other than the one that we live in..
This doesn't mean that safe passage in the real world (again, whatever that means) is not possible. At a minimum it means that the math and/or underlying knowledge base is incomplete.
But all of the Penrose Diagrams associated with each class of black hole does indicate a past and future singularity associated with the timelike, spacelike and lightlike areas and one way membranes into and out of that area. But they have no path that leads back to the original "world" where a traveler would start the journey. You can leave home, go to the future or past in another universe but you can never return home unless, by chance, one of the worlds that you visit has an exit to an absolute twin copy of your original home.
The exception to the one way membrane is a maximal Kerr-Newman BH. Like a Tipler cylinder it has no membrane and two way travel is theoretcally possible. But like all other GR solutions for black holes, if you add any external mass to the universe, and especially if you account for quantum effects, the solution blows up.
