1 of 12
1
Is time travel possible?
Posted: 02 November 2011 09:06 AM   [ Ignore ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  3255
Joined  2011-08-15

This is a subject that has always fascinated me since I saw the original movie (1960) based on the H.G. Wells book The Time Machine (1894). It was my inspiration for studying history in order to mentally create my own time machine. Anyone have any thoughts on the subject?

http://www.angelfire.com/realm3/time_machine/

Cap’t Jack

 Signature 

One good schoolmaster is of more use than a hundred priests.

Thomas Paine

Profile
 
 
Posted: 02 November 2011 09:22 AM   [ Ignore ]   [ # 1 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  731
Joined  2007-06-20

It depends on which theory of time one is operating under.

http://plato.stanford.edu/entries/time/#TimTra

The nature of time does not appear to be a settled question.

 Signature 

PC

Profile
 
 
Posted: 02 November 2011 09:24 AM   [ Ignore ]   [ # 2 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  2425
Joined  2007-07-05

The past does not exist to go back to.  Time is just our conceptualization of the changes in reality.

NOW is the position and vector of every atomic particle.  Some “time” in the past consists of all of the positions and vectors of all of those particles then.  But there is no point in the past to go back to because all of those particles are where they are now.  Every atom in your body is millions of years old.  They existed 1000 years ago.  So if all of the atoms in your body went back to where they were 200 years ago then you would cease to exist.

psik

[ Edited: 02 November 2011 10:04 AM by psikeyhackr ]
 Signature 

Fiziks is Fundamental

Profile
 
 
Posted: 02 November 2011 10:20 AM   [ Ignore ]   [ # 3 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1201
Joined  2009-05-10
thevillageathiest - 02 November 2011 09:06 AM

http://www.angelfire.com/realm3/time_machine/

lolwut?

 Signature 

“What people do is they confuse cynicism with skepticism. Cynicism is ‘you can’t change anything, everything sucks, there’s no point to anything.’ Skepticism is, ‘well, I’m not so sure.’” -Bill Nye

Profile
 
 
Posted: 02 November 2011 10:44 AM   [ Ignore ]   [ # 4 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  4574
Joined  2007-08-31

I have a link too:

Time Travel to the Past – a discussion with Bradley Dowden, November 1993

But I must confess that I did not read it myself.

 Signature 

GdB

“The light is on, but there is nobody at home”

Profile
 
 
Posted: 02 November 2011 12:36 PM   [ Ignore ]   [ # 5 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  6195
Joined  2006-12-20
GdB - 02 November 2011 10:44 AM

I have a link too:

Time Travel to the Past – a discussion with Bradley Dowden, November 1993

But I must confess that I did not read it myself.

Thanks for posting Gdb, it seems to be a simple and correct solution to the grandfather paradox, wow.


Stephen

Profile
 
 
Posted: 02 November 2011 02:08 PM   [ Ignore ]   [ # 6 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  6162
Joined  2009-02-26

IMO, it is wholly impossible to visit the future. It simply has not yet happened and there are no spacetime reference points (coordinates) of any kind.

Perhaps it is possible to visit the past, but only as an observer, not a participant. There are reference points in the past but it is physically impossible to be in two places at the same time, i.e. now AND in the past.

Were we to visit the past, to us it would be a holographic representation of what it used to be. To the people in the past we would be holographic ghosts.

Actually, the whole concept of time travel ignores the fact that time is inextricably connected with space and we would have to invent spacetime travel which could place the atoms in your body (before it was formed) in the center of a star which has not yet gone nova…. cheese

[ Edited: 02 November 2011 02:24 PM by Write4U ]
 Signature 

Art is the creation of that which evokes an emotional response, leading to thoughts of the noblest kind.
W4U

Profile
 
 
Posted: 02 November 2011 02:51 PM   [ Ignore ]   [ # 7 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1201
Joined  2009-05-10
StephenLawrence - 02 November 2011 12:36 PM
GdB - 02 November 2011 10:44 AM

I have a link too:

Time Travel to the Past – a discussion with Bradley Dowden, November 1993

But I must confess that I did not read it myself.

Thanks for posting Gdb, it seems to be a simple and correct solution to the grandfather paradox, wow.


Stephen

I think there are still problems. For one, you cannot travel to the past as a disembodied observer because the act of observing affects the state of the universe. The only way this would be possible is through a simulation of the past, which could not rightly be called “travel”.

But what Norman is arguing for is if we travel into the past and interact with it, it would be the same past that exists in our timeline and technically nothing would change:

Suppose a visitor were to arrive here and now from the year 2045. He shakes my hand, and then sits and chats with me about what is in store during the next 52 years. I take notes and record them in my diary. A year (1994) from now, I even publish some of these notes. The visitor from the future (year 2045) has not changed the past (i.e. the past relative to the year 2045): he has contributed to making the past just the way it was. By traveling back to the year 1993, he caused certain events to occur in 1993 and in 1994. Nothing was changed from the way it was; but the past was changed from the way it would have been if he had not traveled back from 2045 to 1993. Nothing true is made false; there is no logical contradiction.

There is a weird infinite regress here. I think you run into the same problems as the grandfather paradox. When the visitor from 2045 first traveled back in time, did his timeline already have the event of him arriving in the past? Why? What started it?

Also, knowing that he traveled back in time, couldn’t he decide not to travel back in time, or to do things differently when he got there? Essentially, in each iteration, the next “him” may know more information than the previous “him”, so he isn’t technically the same person and may make different decisions.

 Signature 

“What people do is they confuse cynicism with skepticism. Cynicism is ‘you can’t change anything, everything sucks, there’s no point to anything.’ Skepticism is, ‘well, I’m not so sure.’” -Bill Nye

Profile
 
 
Posted: 02 November 2011 05:02 PM   [ Ignore ]   [ # 8 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  2229
Joined  2007-04-26
Write4U - 02 November 2011 02:08 PM

IMO, it is wholly impossible to visit the future. It simply has not yet happened and there are no spacetime reference points (coordinates) of any kind.

Perhaps it is possible to visit the past, but only as an observer, not a participant. There are reference points in the past but it is physically impossible to be in two places at the same time, i.e. now AND in the past.

Were we to visit the past, to us it would be a holographic representation of what it used to be. To the people in the past we would be holographic ghosts.

Actually, the whole concept of time travel ignores the fact that time is inextricably connected with space and we would have to invent spacetime travel which could place the atoms in your body (before it was formed) in the center of a star which has not yet gone nova…. cheese

Well this isnt really true. In fact you cant help but visit the future. We do it every moment of our lives. Times arrow forces us to and Einsteins Theories tell us that traveling into the future on a much more dramatic level is possible. When the crew of a ship traveling at relativistic speeds returns home they may find they have traveled years or centuries into the future during their months long absence. That much is really beyond dispute and in fact some of our own astronauts have traveled into the future by living aboard the ISS. Of course it was barely detectable but verifiable. A similar effect occurs when you spend time in a very strong gravity well like a black hole. Time slows down for you but from your perspective it speeds up in the universe around you so its like hitting the fast forward on your Tivo and traveling into the distant future.

Travel to the past is a whole different story. Most likely its not possible, but its premature to say its impossible.

[ Edited: 02 November 2011 05:05 PM by macgyver ]
 Signature 

For every complex problem there is a solution that is simple, obvious,.... and just plain wrong

Profile
 
 
Posted: 02 November 2011 05:04 PM   [ Ignore ]   [ # 9 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  6195
Joined  2006-12-20
domokato - 02 November 2011 02:51 PM
StephenLawrence - 02 November 2011 12:36 PM

Thanks for posting Gdb, it seems to be a simple and correct solution to the grandfather paradox, wow.


Stephen

I think there are still problems.

My reaction was due to the simple idea that although going back in time and killing your grandfather is a logical contradiction, going back in time and, say, introducing your grandfather to your grandmother isn’t.

But p’raps there are problems further down the line.

Suppose a visitor were to arrive here and now from the year 2045. He shakes my hand, and then sits and chats with me about what is in store during the next 52 years. I take notes and record them in my diary. A year (1994) from now, I even publish some of these notes. The visitor from the future (year 2045) has not changed the past (i.e. the past relative to the year 2045): he has contributed to making the past just the way it was. By traveling back to the year 1993, he caused certain events to occur in 1993 and in 1994. Nothing was changed from the way it was; but the past was changed from the way it would have been if he had not traveled back from 2045 to 1993. Nothing true is made false; there is no logical contradiction.

There is a weird infinite regress here. I think you run into the same problems as the grandfather paradox. When the visitor from 2045 first traveled back in time, did his timeline already have the event of him arriving in the past? Why? What started it?

What started it is him time traveling to the past, does that answer the question?

Also, knowing that he traveled back in time, couldn’t he decide not to travel back in time,

I don’t think he does know. But no need to get bogged down there. What he cannot do is decide not to travel back in time, act upon the decision successfully and travel back in time. But again that doesn’t mean he can’t travel back in time.

or to do things differently when he got there?

Let’s say he goes back and introduces his grandfather to his grandmother. Now, could he do things differently? Well he couldn’t kill his grandfather so there is one thing he couldn’t do and I’m quite sure there are plenty more.

I suppose what you are getting at is are there any things he could do differently with the year 2045 being the same?

But lets forget time travel for a mo. Isn’t this just the same issue as could I do differently now and my future be the same?  Or could I do differently now and my past be the same? If so it isn’t a problem for time travel as what ever the answer to these other questions is, the answer is the same.

Essentially, in each iteration, the next “him” may know more information than the previous “him”, so he isn’t technically the same person and may make different decisions.

Nope I don’t get what these next hims are I’m afraid.

Stephen

Profile
 
 
Posted: 02 November 2011 05:04 PM   [ Ignore ]   [ # 10 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  3255
Joined  2011-08-15

Ok, I think that everyone, including Einstein and Hawking agree that time travel into the past is impossible at least for now (i’m an optimist). However, and this was the premise of Well’s story and the two movies based on it, it is theoretically possible to travel into the future. I know what happened in the past anyway, but would like to see what happens when the population reaches critical mass, say in about 50 years? Read what Hawking says about creating a time machine:

http://www.dailymail.co.uk/home/moslive/article-1269288/STEPHEN-HAWKING-How-build-time-machine.html

 Signature 

One good schoolmaster is of more use than a hundred priests.

Thomas Paine

Profile
 
 
Posted: 02 November 2011 05:11 PM   [ Ignore ]   [ # 11 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  4860
Joined  2007-10-05
psikeyhackr - 02 November 2011 09:24 AM

The past does not exist to go back to. Time is just our conceptualization of the changes in reality.

That is as good a definition of time as I have seen anywhere. Because entropy always tends to increase in a closed system, time (or changes in reality) always moves forward. You cannot put the cooked egg back into the shell as a liquid, and neither can you travel back to when the universe was younger.

NOW is the position and vector of every atomic particle. Some “time” in the past consists of all of the positions and vectors of all of those particles then. But there is no point in the past to go back to because all of those particles are where they are now.

I agree 100 percent. Entropy always wins. That supernova we see in M31 exploded two million years ago, and there is no way we can travel the intervening distance to observe it just before it explodes. As for HG Wells, The Time Machine is an entertaining work of fiction, but it remains fiction. We cannot move backward in time: we can only travel forward at the same rate the rest of the universe changes.

 Signature 

You cannot have a rational conversation with someone who holds irrational beliefs.

Profile
 
 
Posted: 02 November 2011 05:35 PM   [ Ignore ]   [ # 12 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1805
Joined  2005-07-20

Sure I can travel through time, see:

7:39:30
7:39:31
7:39:32
7:39:33
7:39:34
7:39:35

LOL

And speaking as an electrical engineer, there are hardly any electrical devices without a capacitor inside, a capacitor accumulates electric flux, therefore you have some flux capacitors in your home, and so you’re almost ready for time travel, both forwards and backwards!  grin

I loved that 1960’s Time Machine and 20,000 Leagues Under the Sea, Jules Verne was a good fiction writer who also had a good grasp on science and technology.

Control over time travel, and extra dimensions sounds very far out to me.

 Signature 

I saw a happy rainbow recently.

Profile
 
 
Posted: 02 November 2011 05:42 PM   [ Ignore ]   [ # 13 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  4860
Joined  2007-10-05
jump_in_the_pit - 02 November 2011 05:35 PM

...there are hardly any electrical devices without a capacitor inside, a capacitor accumulates electric flux, therefore you have some flux capacitors in your home, and so you’re almost ready for time travel, both forwards and backwards!  grin

Now all I need are some ZPEs to power my flux capacitors.

Is there an app for that? cheese

 Signature 

You cannot have a rational conversation with someone who holds irrational beliefs.

Profile
 
 
Posted: 02 November 2011 05:44 PM   [ Ignore ]   [ # 14 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  6195
Joined  2006-12-20
psikeyhackr - 02 November 2011 09:24 AM

So if all of the atoms in your body went back to where they were 200 years ago then you would cease to exist.

psik

If they went back to where they were yes because they were all over the shop.  grin  But we’re talking about going back to when they were, not where they were.

So, if my body were to go back in time 200 years, let’s say in a machine that took three minutes to get there, then two hundred years ago what would have existed is my body containing all my atoms and all the same atoms 200 years younger scattered about the place.

Stephen

Profile
 
 
Posted: 02 November 2011 05:47 PM   [ Ignore ]   [ # 15 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1201
Joined  2009-05-10
StephenLawrence - 02 November 2011 05:04 PM

Suppose a visitor were to arrive here and now from the year 2045. He shakes my hand, and then sits and chats with me about what is in store during the next 52 years. I take notes and record them in my diary. A year (1994) from now, I even publish some of these notes. The visitor from the future (year 2045) has not changed the past (i.e. the past relative to the year 2045): he has contributed to making the past just the way it was. By traveling back to the year 1993, he caused certain events to occur in 1993 and in 1994. Nothing was changed from the way it was; but the past was changed from the way it would have been if he had not traveled back from 2045 to 1993. Nothing true is made false; there is no logical contradiction.

There is a weird infinite regress here. I think you run into the same problems as the grandfather paradox. When the visitor from 2045 first traveled back in time, did his timeline already have the event of him arriving in the past? Why? What started it?

What started it is him time traveling to the past, does that answer the question?

Not really. Let’s say he travels back in time to introduce his grandparents to each other. If he didn’t do this, he wouldn’t exist. So a pre-condition for him existing is him travelling back in time. If he doesn’t travel back in time he wouldn’t exist. And conversely, if he didn’t exist he couldn’t travel back in time. It’s kind of like a circular argument - a chicken and egg scenario. So, what started it?

Also, knowing that he traveled back in time, couldn’t he decide not to travel back in time,

I don’t think he does know.

But why should he not know? There is nothing in this theory that states that he cannot know that he traveled back in time. That seems like an arbitrary restriction anyway, not a physical one.

But no need to get bogged down there. What he cannot do is decide not to travel back in time, act upon the decision successfully and travel back in time.

But if he knew he traveled back in time, he could conceivably decide not to. Or does fate somehow push him in the right direction? That would be magical.

 Signature 

“What people do is they confuse cynicism with skepticism. Cynicism is ‘you can’t change anything, everything sucks, there’s no point to anything.’ Skepticism is, ‘well, I’m not so sure.’” -Bill Nye

Profile
 
 
   
1 of 12
1