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Author Topic: Are these the 8 reasons why people from the future have not come back in time?  (Read 5997 times)

Offline memoryerase1

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.... to visit us. Can you think of more than these 8 reasons.?

After thinking about time travel, and the grandfather paradox for a long time its just impossible to get around the causality problem, like in this quick experiment.
Say you have a time machine, and you moved a grain of sand out of place on a beach 5000 years from now, even a atom in the grain of sand, or even a quark, and everything in human history from that point changes instantly.
With the grandfather paradox you would not even have time to point the gun at your grandfather, because as soon as you tear the fabric of space and time time the past you would just vanish, this is how fast causality would affect you.
So if people in the future have achieved time travel why are they not here.
Here is my eight reasons why, can you think of more:
1. They never did it, they could not even do it with a googolplex years from now, with the amount of human progress in technology.
2. They have done it but they put some kind of causality lock on the time period they come from, keeping them safe from causality changes through time.
3. They create another dimension to go to the past in, exactly like our own in every way, so there is no causality effects on them.
4. They can just view the past but not interact with it, as they travel through time backwards, or even view it on a television monitor.
5. They have achieved time travel but are not interested in visiting our time period.
6. they can only go back in time short term like a few seconds, and they cannot go back in time before the time machine was built, or before they were born.
7.They can only send information back in time, and again short term or there is going to be causality problems.
8. Even short term maybe they cannot send people, or information back because they instantly get thrust somewhere else, or either killed, or even create a infinite paradox loop that they can never escape.
Can you think of a 9th reason.
Thank you for your help with this question.
« Last Edit: 11/01/2016 09:06:49 by chris »


 

Offline Space Flow

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Can you think of a 9th reason.
They created time travel lots of different times in the future, but no one ever got back to tell them it worked.
even if you go back to yesterday you would find yourself in empty space as yesterday the Earth was in a different set of cosmic coordinates than it is today. Even if they tried to return within one second of arriving in the past, by the time you account for all the relative movements through space, that is exactly what would meet them. This planet when all is said and done has a phenomenal combined orbital speed around the "Great Attractor".
 
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Offline chiralSPO

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10. The whole universe reverts to the state of the time the machine is set to (every particle travels back in time to the "same" point in time)
 
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Offline Bill S

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1. They never did it, they could not even do it with a googolplex years from now, with the amount of human progress in technology.

Considering the rate at which technology progresses, that may be a rash prediction.  My own feeling is that something more fundamental than technology will prevent past directed time travel.
 
2. They have done it but they put some kind of causality lock on the time period they come from, keeping them safe from causality changes through time.

Even J Richard Gott, who argues for the possibility of past directed time travel, points out the difficulty and expense.  Would it not seem pointless to go to that trouble and do nothing with the results?

3. They create another dimension to go to the past in, exactly like our own in every way, so there is no causality effects on them.

That’s a lot more complicated than it sounds.  There have been many attempts to use the multiverse idea to achieve PDTT, some of them seem to work, but, I suspect, only because they are not thought through completely.

4. They can just view the past but not interact with it, as they travel through time backwards, or even view it on a television monitor.

Is that really TT, or just retro-viewing?

5. They have achieved time travel but are not interested in visiting our time period.

I’ll pass on that one, as we have no way of knowing, unless they change their minds. :)

6. they can only go back in time short term like a few seconds, and they cannot go back in time before the time machine was built, or before they were born.

Going back just a few seconds would lead to all the problems of “full scale” PDTT.  Some of those might be averted if it were not possible to go back beyond the invention of the machine, but it would be only temporary.

7.They can only send information back in time, and again short term or there is going to be causality problems.

Who would receive the information?

8. Even short term maybe they cannot send people, or information back because they instantly get thrust somewhere else, or either killed, or even create a infinite paradox loop that they can never escape.

Lots of problems here. The biggest, I think, is the inescapable loop.

3, 6 and 8, especially, need more comment/explanation, but on the principle that the length of a post is inversely proportional to the number of people likely to read it, I will leave out those comments unless someone wants them.
 
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Offline jeffreyH

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You would actually decrease the entropy of the universe which would violate the second law of thermodynamics. If you could send one particle then in principle you could send a whole solar system back. If you could send a whole solar system back then in theory you could send the whole universe back. Thus you could decrease entropy indefinitely.
 

Offline Bill S

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Quote from:  SF
They created time travel lots of different times in the future, but no one ever got back to tell them it worked.


To justify that, you would first have to show how PDTT could be achieved.
 
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even if you go back to yesterday you would find yourself in empty space as yesterday the Earth was in a different set of cosmic coordinates than it is today. Even if they tried to return within one second of arriving in the past, by the time you account for all the relative movements through space, that is exactly what would meet them. This planet when all is said and done has a phenomenal combined orbital speed around the "Great Attractor".

That’s a bit like arguing against predestination by saying: “If I am predestined to be run over by a bus this evening, what happens if I don’t go out?” 
It misses the point.
 

Offline Bill S

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Quote from: Chiral
10. The whole universe reverts to the state of the time the machine is set to (every particle travels back in time to the "same" point in time)

I assume that if this were the case, no one would be aware that anything out of the ordinary had happened. 
There is still another problem though, isn’t there?  Point A ( the departure point) and B, (the point to which the Universe returns) are unique spacetime events.  B cannot happen, first without, then with the “return” of the Universe.
 

Offline Bill S

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Quote from: Jeffrey
You would actually decrease the entropy of the universe which would violate the second law of thermodynamics. If you could send one particle then in principle you could send a whole solar system back. If you could send a whole solar system back then in theory you could send the whole universe back. Thus you could decrease entropy indefinitely.

One of the great things about this sort of discussion is that someone often thinks of an angle you have overlooked.  I hadn’t thought about PDTT decreasing entropy. Thanks Jeffery.

My initial (poorly considered) response is that entropy would not be decreased beyond the level it was at the point to which you return.  Using points A and B, as above: the entropy at B will never decrease beyond its original  level.
 

Offline Bill S

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Reason 11: (anthropic reason); we are here, so the Universe must be a place in which rational beings can survive.  PDTT would make it impossible for rational beings to make any sense of life in the Universe.  We could not survive in such a universe, so PDTT cannot be possible.
 

Offline jeffreyH

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Quote from: Jeffrey
You would actually decrease the entropy of the universe which would violate the second law of thermodynamics. If you could send one particle then in principle you could send a whole solar system back. If you could send a whole solar system back then in theory you could send the whole universe back. Thus you could decrease entropy indefinitely.

One of the great things about this sort of discussion is that someone often thinks of an angle you have overlooked.  I hadn’t thought about PDTT decreasing entropy. Thanks Jeffery.

My initial (poorly considered) response is that entropy would not be decreased beyond the level it was at the point to which you return.  Using points A and B, as above: the entropy at B will never decrease beyond its original  level.

OK. Say we take the sun back 100 million years. We now have two suns at different stages in the life cycle. Each having produced its own amount of entropy. Past sun p has entropy generation S_p, while the future sun f has entropy generation S_f. It has to follow that S_f > S_p. If the life expectancy of the sun at time t in the past is t * n and the point at which the sun was sent back is t * m then we find that m < n so that the sun sent back to the past will still exists at time t * m. The resulting life cycle of this sun, although shortened due to travel through time, will contribute less to increase in entropy in its new future than would have originally occurred. The original sun now no longer exists in this time-line. What actual effect this will have on the universal entropy I don't know.
 

Offline Bill S

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Jeffrey, we are probably thinking of different interpretations of PDTT.

Consider: 1, in which you go back and meet a younger self.
2, in which you go back and are your younger self, but with “memories” of the future.

Both bring serious problems. 
In interpretation 1, if you take back the entire universe, you have, in effect, doubled the mass/energy of the universe, which is, sort of, frowned on.  You also run into a major problem involving the inescapable cycles of reason 8, above.
In interpretation 2 you are at the point to which you return, first without, then with memories of the future.
I think interpretation 2 should avoid the entropy problems, though. 
 

Offline jeffreyH

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But interpretation 2 adds information to the system. Since information itself is an ordered sequence, although not physical, it can still be considered a lowering of entropy. Especially if we are considering a holographic nature for the universe where information IS the universe.
 

Offline Bill S

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Point taken, but can we argue that information has lower entropy than no information, in any specific scenario?
 

Offline jeffreyH

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I was stretching a point a bit there.
 

Offline Thebox

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 ''Are these the 8 reasons why people from the future have not come back in time ?''


There is one reason only , the future does not exist, the past does not exist , only the now exists and the now is always the now and the past is a memory of the now which is now the future.

 
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Offline Bill S

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Quote from: Thebox
There is one reason only , the future does not exist, the past does not exist , only the now exists and the now is always the now and the past is a memory of the now which is now the future.

That seems OK as an intuition-based belief, but unless you can come up with a well defined supporting theory, it is probably a bit dogmatic for a science discussion.

Are you, for example, saying that time does not exist?

Do you equate the present with some concept of infinity/eternity?
 

Offline dlorde

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... the future does not exist, the past does not exist , only the now exists and the now is always the now and the past is a memory of the now which is now the future.
One wonders how - if the past or future don't exist, but only an instantaneous now - there can be causality and change.

Just asking...
 

Offline Thebox

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... the future does not exist, the past does not exist , only the now exists and the now is always the now and the past is a memory of the now which is now the future.
One wonders how - if the past or future don't exist, but only an instantaneous now - there can be causality and change.

Just asking...

Because the next moment is a new moment of now.
 

Offline Thebox

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Quote from: Thebox
There is one reason only , the future does not exist, the past does not exist , only the now exists and the now is always the now and the past is a memory of the now which is now the future.

That seems OK as an intuition-based belief, but unless you can come up with a well defined supporting theory, it is probably a bit dogmatic for a science discussion.

Are you, for example, saying that time does not exist?

Do you equate the present with some concept of infinity/eternity?

A theory? why would I need a theory to observe that the next ten minutes are not written until our moment of now, gets there.  Tomorrow is only there if your moment gets to tomorrow, where today becomes a memory of a past moment.  There is no future moment , only moments and memories.
« Last Edit: 05/01/2016 17:28:13 by Thebox »
 

Offline Bill S

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A theory? why would I need a theory to observe that the next ten minutes are not written until our moment of now, gets there.

You don't need a theory to make that observation.  St Augustine made some very astute comments along these lines, without a mention of mathematical proof.  In those days, it was philosophy, today it becomes science, so different kinds/levels of proof are needed if you are to move beyond personal belief, without slipping into solipsism.

You didn't address the questions in my last post.
 

Offline Bill S

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Offline Thebox

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Are you, for example, saying that time does not exist?
''Are you, for example, saying that time does not exist?''


I am saying time only exists in the moment.


''Do you equate the present with some concept of infinity/eternity?''


I equate the present to the now, infinity could only be immortal like space.



''The earliest reference we have to the moment is from the 8th century writings of the Venerable Bede.[2] Bede describes the system as 1 hour = 4 points = 10 minutes = 15 parts = 40 moments. Bede was referenced four centuries later by Bartholomeus Anglicus in his early encyclopedia De Proprietatibus Rerum (On the Properties of Things).[3] Centuries after Bede's description, the moment was further divided into 60 ostents, although no such divisions could ever have been used in observation with equipment in use at the time.[2]''


Our moments of time write a past, there is no future only  the now moment writing the past.

 

Offline Bill S

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We could continue to bandy conflicting quotes from Bede, Augustine and other historical greats, but interesting as that might be, I doubt it is what the OP was looking for. 

Quote
I am saying time only exists in the moment.

Are you defining a moment as 1/40 of an hour, or do you have another definition?

Quote
Our moments of time write a past, there is no future only  the now moment writing the past.

Where do these moments come from?
 

Offline Thebox

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1.Are you defining a moment as 1/40 of an hour, or do you have another definition?

2.Where do these moments come from?

1. No, I am defining a moment as precisely ''how fast the brain works'', consciousness ''moving on''

2. The work in the brain, neurological moments, a rock is not conscious so time is negligible to a rock, 


2.
« Last Edit: 05/01/2016 21:00:10 by Thebox »
 

Offline Bill S

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1. No, I am defining a moment as precisely ''how fast the brain works'', consciousness ''moving on''

Can you be more precise? 

Are you saying all brains work at the same speed, or that a moment is purely subjective?

 

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