Applying Fermi's Paradox To Time Travel

[Twighlight]

Applying Fermi\'s Paradox To Time Travel

Enrico Fermi is once quoted to have said something along the lines of " If the galaxy is so full of advanced civilizations - where are they ?" The paradox between the estimated number of extraterrestrial civilisations ( Carl Sagan estimated a million ) and the total lack of ET passing by...is called Fermi's Paradox.

A somewhat similar paradox exists with time travel. If time travel is invented let's say in the near future, and our civilization lasts even let's say 1000 years more......that's 1000 years worth of time travellers. Obviously, the longer our civilization lasts, the more time travellers there will be.

So, unless we seriously screw up prior to time travel coming along, there really OUGHT to be a whole bunch of time travellers popping up all over the place. Not just one or two...but hundreds or even thousands of them.

And Fermi's question arises yet again.....where are they ?

'If'...and it's a big if....there are multiple timelines, one possibility is that there are vastly more timelines than time travellers.....and that OUR chance of receiving a time traveller is very small. This is somewhat equivalent to a possible answer to Fermi's original paradox......that there are indeed other civilizations but they are spread so far apart ( maybe the nearest one is in the next galaxy ) that we would simply never receive a signal.

Another possibility...once again with the big 'if' of timelines existing.....is that not being able to return to one's original timeline is pretty damned good incentive not to take a trip back to 2009 in the first place. In other words, there would be no 'package holiday' time travel trips for the masses. It would be reserved just for a foolhardy few who would never be seen again.

Well, the list of answers to 'Where are they ?' could expand. Feel free to add more possible reasons. Of course....one has to include the possibility also that time travel simply never happens. But..let's be optimistic, and assume it does....

Where are they ?

 

[aerohead]

Re: Applying Fermi\'s Paradox To Time Travel

One soppy little planet with enough ego to boil the sun. It's like someone living in the ghetto that wonders why rich people don't visit. Really, why bother? A rich person goes to the ghetto, gets robbed etc. Same with a time traveler visiting this era. I've met lots of time travelers but they are a cautious lot. Instead of wishing someone will visit, why not spend some time improving your neighborhood? Make the time more attractive to tourists.

 

[dimaggio]

Re: Applying Fermi\'s Paradox To Time Travel

From all the millions of alien races that could exist, it isn't a guarantee that many of them invent the means to leave their planet.
And from all these who HAVE the possibility to leave the planet, it isn't a guarantee either that some of them have space travel exceeding ours.
And from THESE it't not a guarantee that a few will have the means to cross millions of lightyears in a short time.

And even if there are some aliens with this capability, who's to say they would even find us in the vast space that is the universe? Maybe after many hundred years, they finally found another civilisation, but it wasn't ours.

Even if something is 99.999% probably, we could still be the 0.0001% (yeah, life's not fair)


An about time travel:
Well, maybe there are time travellers arriving all over the place, but covert, without telling anyone. Or maybe some are arriving a few years in the future, and some a few years in the past, but without their changes ever propagating to us, because it could very well be that since their changes start five years ago, they maybe need five years to reach the moment we call the here-and-now. But since our feeling of here-and-now will have moved five years forward as well, the changes never catch up. For that they would have either have to accelerate (which doesn't make sense IMO), or every change was already in the timeline, without the need of propagation time.

What I want to say with this is not that this is the way it works. Just that IF it works this way, then it would be very plausible that we didn't yet see any time traveller.

EDIT:
Ok, I just realised that what Twighlight said about the multiple timelines is essentially what I meant. But as usual, my mind couldn't find the right words. Thanks Twighlight. /ttiforum/images/graemlins/smile.gif

 

[Monkeybat]

Re: Applying Fermi\'s Paradox To Time Travel

Because the first person to travel back in time rewrites history overwriting the future world that produced him so there can be only one visitor from the future at a time and first we have to go through the boring timeline where there are no visitors from the future.

 

[EricCarr1]

Re: Applying Fermi\'s Paradox To Time Travel

The time line could of been changed 1000s of times and we would never know it. What if there are time travellers that change time to protect our very existence?

 

[Darby]

Re: Applying Fermi\'s Paradox To Time Travel

Because the first person to travel back in time rewrites history overwriting the future world that produced him so there can be only one visitor from the future at a time and first we have to go through the boring timeline where there are no visitors from the future.

Not that it has anything to do with actual physics, your statement is logically inconsistent. What boring timeline where there are no time travelers is any different than any other timeline? According to your statement the time traveler erases all traces of time travel with the possible except for his personal one-time-only experience and no other time travelers are allowed.

And only one time traveler at a "time"? One at a time where? What do you mean by one at a time? So a time traveler from planet Buru in the Andromeda Galaxy lands in Buru's past and the entire universe is prevented from time traveling due to the One At A Time Conjecture?

 

[Twighlight]

Re: Applying Fermi\'s Paradox To Time Travel

Ok, I just realised that what Twighlight said about the multiple timelines is essentially what I meant. But as usual, my mind couldn't find the right words. Thanks Twighlight.

There's a real problem if one conjectures an infinite number of timelines.....as then there ought to be an infinite number of time travellers visiting us.

 

[TimeNot_0]

Re: Applying Fermi\'s Paradox To Time Travel

There are an infinite line of time-travellers. How many humans have been on this planet and are on this planet and will be on this planet?

Making sure the humans understand their contract.
Sacred Heart of Jesus.
Eastern Orthodox Catholic Church.

Now, out of the human thinking process, I guess, where time and so-called- reality shifting may actually occur.

 

[qbicle]

Re: Applying Fermi\'s Paradox To Time Travel

Hi,

To answer the timetravel question:
1)Let's say that some huge institute made an installation that is capable of warping space-time,
and that this machine has only one on/off button. When that button is turned/switched to the on
position, it would most probably cause total chaos in the machine, because of all the people coming
out of it, so in that case, the button is switched immediately to "off" to cause no further harm.

2) let's assume that the machine causes no such effect, and that the time on which it is turned on, is
01 januari 10000AD 00AM 00minutes and 00seconds and 00 00 00 00 00 00(you know what I mean).
Timetravel happens in our universe so it must obey some sort of cause and effect laws.
That would mean that timetravel would only be possible from that time on. And only possible to that
time, because before the initial "flicking the switch-time" there is no way of going back in
time(there is no working machine). That is why no travellers are yet to be seen.

3)Lets say that it's the kind of machine you see in the "back to the future" -movies, a Delorian or
a single spaceship or something like this with a yet to be invented name,
FACT=> these things eat energy(of some sort).
And suppose the traveller would run out of energy. If this could happen, then this project would
immediately be classified to the garbage bin.
________

So in these 3 hypothetical scenario's timetravel would be or very risky and never be attempted, or
not that risky but not happening right away.
________

The most plausible manner of traveling back/forward in time is the following:
Humans(or it's descendants) build a ultra-super-mega-giga computational devise that is capaple to
hold a perfect and completely precise realtime rendering of the complete universe. In
such a "virtual" universe everything is exactly like it should and would be. Then it would be
possible to visit another time than the time in which the traveller is born.

An interresting thing about these virtual universes is that the occupants of it would be you, your
family, your friends, me and everybody that has ever existed and will exist and there would be no
way of telling that this perfect universe would "not" be real, and the people in it could say
strange things like:
there must be a God who made it for us otherwise we wouldn't be here and this universe wouldn't be
possible...(x-files theme starts playing now)

 

[Darby]

Re: Applying Fermi\'s Paradox To Time Travel

A somewhat similar paradox exists with time travel.

Twilight,

I answered another member last year but never responded to your post.

The apparent paradox isn't the same between sub-light travelers from other galaxies and time travel. That we don't see travelers from other star systems, assuming that time travel doesn't exist, isn't a paradox. The chances of seeing someone from another star system - people restricted to subliminal travel - is consistent with what we should expect. Our planet has only advanced enough to even recognize protons, neutrons and electrons for the past 80 years. We have only been sending signals without wires since the 1880's. As far as we can tell there is no star system with a Terran planet within at least 100 light years. In fact we have, to date, discovered none anywhere. Any off planet society that could have received our 19th Century signals would still be enroute no matter how fast they traveled at sub-light velocity.

That we don't see time travelers is another issue. No matter where they are when they receive signals from earth; light, radio, television, whatever; they are seeing the past. It has already occured. For them to make a decision to travel through time and arrive here at the same time that the signals were emitted is the real paradox. They could alter the history of our world by doing so without also altering their own history (in the sense of what they have already experienced). Singals from here are already enroute to their planet that could determine their future in some way - signals that have not been received - and they travel to their past and make a change. How that alters the signals already emitted and which are enroute to their planet is the paradox. So far there is no theory that even suggests that singals lready emitted and received by intervening entities, i.e. planets between Here and There, can be altered and come out differently There even if a time traveler intervenes. Its a situation of it either is or isn't.

I hope that you get the gist of what I'm suggesting here. If not then I'll restate it. A signal is transmitted Now. Sometime later a time traveler comes to the time when the signal was transmitted and changes the situation. A new signal is transmitted based on the change. You now have two simultaneous signals transmitted from the same event but each has different information. Expand that to an infinite number of time travelers coming to the same event (neglecting the absurd situation of infiinite mass vs. finite volume) how, given the state of our knowledge, does this not become a huge paradox? If, on the other hand, you assume that the time traveler prevents the original signal from being transmitted and instead transmits the new altered signal how do we square this with what the planet between Here and There received? Again, that's the real paradox.

 

[Twighlight]

Re: Applying Fermi\'s Paradox To Time Travel

Expand that to an infinite number of time travelers coming to the same event (neglecting the absurd situation of infiinite mass vs. finite volume) how, given the state of our knowledge, does this not become a huge paradox? If, on the other hand, you assume that the time traveler prevents the original signal from being transmitted and instead transmits the new altered signal how do we square this with what the planet between Here and There received? Again, that's the real paradox.

Hmm....I don't see what difference it makes. A time traveller from another planet would still be 'alien'....and it would make little difference to us whether he was 100 or 1000 years ahead in his own future as we'd have no idea what his past was. That he was a time traveller would be purely incidental to him being ET.

So to all extents and purposes, time travel is only really meaningful in the context of our own planet. My primary point was, if all those zillions of timelines exist, then by pure numbers alone we ought to be getting time travellers regularly. It's an argument not unlike the one in which in an infinite universe there's a zillion of 'you' out there who are President of the US.

But even if we leave out the zillion timelines.....if mankind survives another 100,000 or million years, then if time travel to the past is ever a reality I'd expect time travellers to be popping up with some regularity.

That they are not, can only mean one of two things. Eiether mankind simply doesn't last that long......or time travel to the past is impossible.

 

[Darby]

Re: Applying Fermi\'s Paradox To Time Travel

Hmm....I don't see what difference it makes. A time traveller from another planet would still be 'alien'....and it would make little difference to us whether he was 100 or 1000 years ahead in his own future as we'd have no idea what his past was. That he was a time traveller would be purely incidental to him being ET.

The paradox is one of conflicting information. The time traveler decides to go into the past and visit some event. His memory says to him, "Never been there. Never done that." He looks at the physical evidence. It apparently also says, "You never been there - never done that."

It sounds good so far but this is his affective past that he's pondering. It's already happened - the event, that is. He has evidence to support that it already occured - and he wasn't there according to the evidence.

So he goes there comes back and now he has a memory of the event that includes himself and he apparently now has the ability to gather new evidence supporiting his new position, "Been there - done that." How did this paradox happen? If this occured in his affective past why was there no evidence of his involvement the first time that he looked?

Someone will step up and say - Oh, oh ... it's another universe. Good. Wonderful. Well, not really. An ad hoc solution pulled from a hat (actually they are generally pulled from a position somewhat south of the hat rack) for the sole purpose of solving the paradox without taking into consideration everything else implied by the conjecture is about as likely correct as Stevie Wonder's chance of getting a commercial pilot's license from the FAA.

It's a paradox. There is of course a chance that it is just the way the world works and that it actually isn't a paradox. I'm not betting on that position without a lot of convincin' going on.

 

[thantifaxathbeta]

Re: Applying Fermi\'s Paradox To Time Travel

Consider the possibility that any civilization capable of creating wormholes and time machines and FTL travel will also have cloaking technology as well. Remember that space-time can be considered a type of metamaterial, and, if one has the appropriate technology, can be re-engineered to suit. Physicists now speak of electromagnetic wormholes (see arXiv: math-ph/0703059 and arXiv:0704.0914 [math.AP]("Electromagnetic wormholes via handlebody constructions")), which, I believe can be reproduced in space-time and can be used to 'cloak'. Consider also the possibility of chronology protection by creating trapped surfaces (see "Levi-Civita effect in the polarizable vacuum (PV) representation of general relativity" by Puthoff, Davis, and Maccone for an example)in which time travelers might stay when traveling to the past. These, I think, show that the Fermi Paradox can be easily avoided.