Why haven't alternate-stream time travellers begun appearing?

Ah, but they could be hiding among us in plain sight.

You’re asking if I’m reading this right…. That assuming the theory of time machines being constructable based using the gravity/wormhole trick, combined with the theory of multiple realities…. why haven’t we seen people or signals of some kind from people in the future, of alternate realities?

Well the answer would basically be that there are WAYYYY too many variables and theories in there, and somewhere along the way one or more of them must be wrong.

To clear up time travel for you. The only “known” or “proven” method of time travel (and it was discovered by Einstein), is this…. Basically we KNOW that time travels slower in areas of higher gravity. So what may be 100 years in an area of no gravity, could be a day in an area of heavy gravity.

So the theory goes that if you made a worm hole and placed one end of it at something of very high gravity (in particular a black hole), and then took the other end out into the middle of nowhere.. and then traveled through it, you would travel back in time to the moment you placed the worm hole at the black hole. Now this theory comes with a lot of simple problems For instance how do you keep your black hole from eating your worm hole, or your space ship, and you need a space ship capable of interstellar travel. And it also means (as you pointed out) that you can only go back as far as the moment you placed the wormhole at the black hole.

But to clarify for you, you will never see people randomly start showing up at a lab, because that lab would have to be holding a black hole, and our planet would be swallowed in sometime probably less than a second.

The key is “bending light” not matter. (just expressing my thoughts)

Move faster then the speed of light look back and watch the past, or bend light back at yourself and watch the past.

We have done that already. I send a video transmission to the other side of the world or to the moon. What you are seeing at the other end is what already has occurred.

Perhaps it has something to do with once a traveler has landed in a different branch- that branch then turns into a different branch than if they hadn’t traveled. Two branches, one goes between- now there are four branches. (One- traveler moves from; two- traveler moves to; three-traveler didn’t move from; four traveler didn’t go to). So for every traveler there would be four worlds to start with- then add another traveler and we’ve created even more- exponentially.

On a basic level- how would one map a journey? If you leave a world, could you go back to the same world you left- or would you end up in a fifth world? (Fifth world being created from a successful trip) How would you get home? If one didn’t care to return home- that’s fine but how would they be able to plan to get to the right dimension?

God I hope that made sense at all. Good brain-stretching material, this.

@gemiwing I believe thats the entire plot to the television series Sliders lol

Although it doesn’t lead to good stories, I personally think the Chronology protection conjecture is likely true.
As for inter-universe travel, it may be that it would require something other than simply trying to time travel to accomplish. (In Sliders, there wasn’t time travel, just branches that developed at different rates)
And even if both of those are false, there is still “Does the bent-light time machine have to have a terminus in our specific branch?” – I think it certainly would, so until we try to build one we just won’t know (And I think pretty much all proposed time machines need more energy to make than humanity can produce)

Maybe the answer is as simple as: ‘It can’t be done.”

I question the entire premise of the question. How would we know if we they aren’t here? Wouldn’t they look and behave pretty much like us? Or are you thinking that because they are from the future they would look or behave differently enough to be identified?

If you were from the future, you’d probably have some technology that was more advanced than that of the time you travel to. You’d probably develop some aspect of the technology that was just advanced enough to be a big deal, so you could make a lot of money. Slowly you let more technology out, so you could stay just ahead. Eventually you might let that lead lag so as to not generate too much suspicion.

Who fits that description? Perhaps Bill Gates? Maybe you should try to interview him to see if he’s really from an alternate future—one that this past will not develop into? How about Sergey Brin? Larry Page? Paul Allen?

Even Jesus.

I think when it comes to time travel, from what I understand it is according to physics, possible.

However to travel forward in time you simply need to travel faster. Time moves slower the faster you travel. For example, if we could achieve the ability to travel at light speed, traveling 1 year at light speed, 100 years would go by on earth (approximately, If I remember correctly) You can read about the theory of relativity on wiki, and this has been proven true.

http://en.wikipedia.org/wiki/Theory_of_relativity

Moving backwards in time however is the hard part. To go “back in time” one would need to create a machine, however travelers could only go back to the point that machine was turned on. To go further back we would need to find a natural means of doing so, many theorize that a worm hole could make this possible, but nothing has been proven.

There is also the theory of parallel universes, something that potentially overcomes the grandfather paradox. Some theorize that if you could go back, you essentially could be visiting a parallel universe which would not effect the future you had come from. Because simply telling someone you were from the future could alter your past entirely.

Assuming that time travel is possible, and that is assuming a lot, perhaps the early 21st century is not a preferred time travel destination. The people of the future may have far more interesting, pleasant and desirable “pasts” to travel back to. Maybe future time travelers say things like “Why on earth would anyone want to travel back to the early 21st century? There’s constant warfare, rampant poverty, the air is barely breathable and their medicine is primitive.” We could seem very brutish and primitive to the people of the future, if people have a future. Maybe we annihilate ourselves in some nuclear, environmental, biological or other type of holocaust and there’s no one left to travel back in time.

It appears there is a traffic COP who enforces a speed limit in the universe. Large masses cannot exceed the speed of light because the Causal Ordering Postulate or COP won’t let them. If it were not so, travelers from some distant future should be popping into our time every now and then. Postulating an alternate universe for them doesn’t seem to me to be intellectual honest.

Why don’t you see spies lurking on the streets all the time?
You know, the thing is, people who really want to keep their identity secret, usually are quite capable of doing so.
Essentially that means if time travellers are here, they are probably concealing their identity. They might even have cloaking technology.

@ragingloli If time travelers arrive here, they would materialize from nothing. That would tend to make them stand out in ways spies in the street do not come close to. :-)

@ETpro
”If time travelers arrive here, they would materialize from nothing.”...
... in deserted places where there is no one to observe them. (could be a dark forest, a back street, a deserted house, etc.)
You know a time travelling agency could very well have the technology to monitor the target time frame and location before they send anyone through. Or they could just look at old records to see which places were deserted at what time and plan their temporal insertions accordingly.

or
... already cloaked

“Or they could just look at old records to see which places were deserted at what time and plan their temporal insertions accordingly.”

Which would cause that record information to be false, since they are going there. They were there already.

@ragingloli You are grasping at straws. How does somebody 10,000 years in the future know what spaces on Earth are deserted 10,000 years in their past before they make the jump?

@ETpro How did they know? They checked the 21st century Google maps archives, of course. :-) All that stuff is probably on a biochip in their brains.

@ETpro
I am not grasping at straws at all.
It is not a far leap to assume that a civilisation that has the ability to physically send someone back through time would also have the ability to simply monitor the target time frame. In fact, I would expect the monitoring technology to emerge way before the capability of sending someone through time.

Yea, tell that to the guys of Apollo 13. :-)

@ChazMaz
Case in point. We had telescopes (the technology to monitor the moon) centuries before we invented the means to physically go there (rockets).

But, did we have the right monitoring system in place to prevent what almost turned out to be a deadly and non returnable situation?

What’s sticking me about this is that for all the new technology we now have, the original designs were close but not quite right. Like cell phones and airplanes, the original designs were close but forgot to count for something small, that in the end, changes a lot of the design.

Planes, when first dreamed up, look remotely (in some cases) like what we have now. Except they were open air, no jets etc. So they were close…but little things are off. They never saw the airline peanut packaging that can withstand a twenty minute assault.

I guess what I’m trying to say is that we’re probably on the right track, but horribly wrong at the same time. For reasons like airline peanuts. In the future, someone will find this and laugh; saying something like ‘the silly fudders, don’t they know you have to use sea bass jelly?’ or ‘well, they were close, but they forgot the quantum-casings’.

Because I blend in well.

The real problem is that when the time travel machine was invented, they used it and found out they materialized in the middle of space, where the earth once was, but had long ago moved along it’s path through the cosmos.

Ok here’s the deal, nothing can be conclusively proven or disproven.
The universe we are in might be number ????? or any other ????? so even order in our universe might just be a product of coincidence and our superdelusional minds. Time travel is trapped in the realm of fiction for now. But it’s not because we know it doesn’t happen, it’s because we can’t conceive of it happening.

@YARNLADY There are no absolute locations in the Universe. Everything can only be located relative to other things. The Earth has “moved on” relative to what? The Sun? The Moon? Jupiter? Proxima Centauri? Galactic centre? The terminus of the time machine would be the place where it was switched on, and that remains the same relative to the Earth.

Maybe we haven’t seen them because the past really isn’t that interesting.

Moreover, were such technology available, it might just not be worth the energy – as I understand the proposals for wormhole technology, it requires truly massive amnounts of energy to accomplish. Maybe those future would-be time travellers realised that it’s all about people, and it’s about now, rather than then.

@ragingloli & @lillycoyote Ha! I am unaware of any resource, even on Google Maps, that will give me a moment-by-moment view of all points on Earth. These visitors would somehow need to poof into adult existence here without ever being noticed by any of us as an odd man out. People suddenly showing up with no friends or relatives or connections to anyone are likely to attract notice.

But most telling, they would have to be exceedingly careful while here. Say a time traveler came back to 2010 and happened to bump into someone who grew angry and drew a weapon. The time traveler, being very technically advanced, pulls out a zubba ray and evaporates the boorish character, only to find himself suddenly dematerializing. Too late he realizes he has just killed the man who was going to be his great, great, great grandfather; and so he no longer can exist in the future to have come back into the past and done the dastardly deed.

As soon as I posit time travel, I am faced with logical paradoxes out the yin-yang. Generally, when a postulate leads to paradoxes, that is a clue it’s wrong. I would love to find proof time travel is possible, because I would welcome a chance to go back and correct a few of the dumbest things I have done in my long life. But my educated guess is that if I live another 10,000 years that isn’t going to happen.

I am of the opinion that a time traveller can never alter history, no matter how hard he tried. He can only help history fulfill itself by becoming part of it. A time traveller can not kill his own grandfather because he exists, therefore any attempt to kill the grandfather failed and will fail.
Also, a time traveller could simply make up his own history, tell people that he just moved here from someplace far away. He can manipulate official records while he is at it too. Someone from the future would not have much difficulty hacking our primitive computer systems or overcoming our primitive locks on our doors. Would not be too problematic, considering how oblivious and disinterested most people are toward their neighbours. Works for witness protection programmes all the time. Making up a new identity and all.

@ETpro & @ragingloli My understanding is that time travel (into the past, never into the future) is only mathematically possible with the many-worlds model, such that you never step into the same river twice. Each time you travel, you’re stepping into an alternate version (which may well be completely indistinguishable except for, say, the position of a single grain of sand somewhere on the surface of Mars) of the set of probabilities you recognize as “your” Earth. You can’t kill your own grandfather, you can kill the grandfather of someone who, if you hadn’t changed things, would eventually have been someone indistinguishable from you (and who would otherwise have gone on to kill someone else’s grandfather in yet still another alternate version of probabilities).

Who says they have not appeared to some people !?
If you meet someone who seems befuddled check their watch :-)
Seriously, generally folks believe almost anything so time travelers would have minimal problems if they are prepared when they arrive. If they are so undeveloped socially that we discover them but so superior scientifically that they can arrive I would think their society would fail before it becomes a problem to us.
I see no reason why they could not have been here or are here now.

Haven’t read other posts, so might be repeating but:
1) As far as I know, if you build a time machine at time t, you can’t travel back before time t.
2) I don’t see a reason why we would expect such travelers to appear on Earth. At least not yet.
3) Maybe I’m one of them…

I consider myself fairly astute, but my brain is spinning from trying to follow this thread. I can read works by Stephen Hawking without difficulty. Either I am really tired (too many late nights) or much of what I reading does not make sense to me.

I will check back tomorrow.

According to a hypothesis I read about the multiverse theory is that there may be alternative dimensions in time so if you time traveled you could alter events in that dimension of time but not another. You could go back in time by breaking the light barrier or you could slow your own time down by moving closer to light speed or traveling in an area of increased gravity but you never actually alter the events in that dimension. I guess we will learn more when we learn more about cosmic strings. Perhaps everything in the universe does vibrate through different dimensions of time to keep itself from collapsing on itself.

Because physicists haven’t succeeded in sending rays of time travelers through a double slit. Anyone interested in being a particle and a wave at the same time? Yes? Well, enjoy the ride.

@mattbrowne No thank you! I get seasick just thinking about being a particle on a wave.

I produce a particle wave every time get up in the morning.

@mattbrowne Well, if string theory is correct, we’re all just vibrations anyway (as per my extremely limited understanding).