Discussion on: TIME TRAVEL

[sgreger1]

Over the years there have been several theories on what would happen if someone traveled back in time (or forward into the future), with a big emphasis on all the possible paradoxes that may arise from such a journey.

If I opened a time portal to 1 minute ago, would it act like a microphone and a large sound system, causing an endless loop of feedback between the two portals which destroys the earth? Would I die if I killed my grandfather? Does free will exist? What if I went back in time and met myself walking into the portal, who is then going back in time to meet himself going into the portal, only to find two of me standing there, watching a third me go into the portal etc etc into infinity, until at one point the entire universe is populated with multiple versions of me? And if I travel back to the past, technically I am traveling into my future, as it is something I would do in the course of my life (traveling back in time), so even in the past, my future includes traveling back tot he past, but then how does that work? And what if I step on a butterfly and chaos theory was right, what if it changes the entire course of history?



You will be glad to know that scientists have figured it out using quantum theory, and it's safe to say that time travel is 100% safe and paradox free. Here's the science:




Due to quantum physics and the concepts of superposition of multiple possibilities at once, and the fact that everything is quantumly entangled, completely eluding the normal rules of space/time/speed of light, it is impossible to change the past because it has already happened, it has already been observed and therefore is now unchangeable. However, if you were to go back in time, which scientist still believe is theoretically possible, could you walk around and do what you want, would you have free will? Yes and no. The old sci-fi concept of "the universe doesn't allow paradoxes to happen" seems to have been the right answer.

Imagine holding a rubber band in-between your two fingers, then pulling the middle off it waaaay back and letting it go. The middle part will sit there vibrating up and down for a while. The middle of the band is vibrating while the ends are stationary. According to this new science, if that rubber band is time, and I start on one end of the rubber band and traverse it's vibrating center towards the other end, that is like what time travel is. The rubber band is moving up and down, existing in many places at once and, when i travel across it, there is a certain probability factor that determines where in that vibration I will be at any given time. So while I can change little things with my free will, I can never go outside of the vibrating probability wave. In other words, I can travel across the rubber band, and use my free will to take a thousand routes, each which will appear different to the observer, but at the end of the day I am still traversing that vibrating rubber band and I cannot go further than the rubber band’s boundaries allow.

So I have free will to change things, but the changes will not make any real change, it is just an expression (for the observer) of one of an infinite number of possibilities that could have occurred, but nothing changes in the long run. Is that free will? Kind of. It's "limited" free will. You only have free will to operate within a certain set of existing parameters, just like someone who is not time-traveling does. So me traveling back in time would allow for free will, but only within the parameters that are allowed for me, only parameters which could not lead to a paradox. It's like regular free will, I can punch someone or I can choose to eat a sandwich, but can I jump to the moon? can I bring the dead back to life? no because my free will is limited to a certain set of parameters, and the universe restricts me to them. I can change a million things and go about my day making conscious decisions with my limited free will, but what I am allowed to do with my will is limited to the rules of the system. I cannot will myself to defy gravity and I cannot will myself to teleport somewhere. In time travel, I can make changes with my free will, but the rules are already in place to avoid a paradox, so I cannot will myself to create a paradox anymore than I can will myself to be able to fly. So for now, Grandpa is safe from time-traveling axe-murderers.



Hope that makes sense, but it's actually a pretty simple concept, just hard to write down.



Kind of complicated but it's referred to as postselection, which essentially means if you have a math problem and your solving for a variable, the answer to the variable is selected at the end. That variable is what the outcome of history would be, so since that variable has been solved, the equation must match the variable, the past must stay in line with what the present is, and cannot be significantly changed via a time travelers free will. The variable, now observed, cannot be anything different no matter what.

x=y

x= decisions people made in the past
y= what the future is like.

Since the future has already occurred, y is already solved, we already know what the current world is like. Therefore, x, being all the decisions people made in the past, must forever fall in line with what occurs in the future, not the other way around like has been traditionally assumed for time. You cannot go back in time and change the future, because the real variable in this equation is actually x, y is already solved. The future already exists and therefore going back and changing x will have no effect on y, x will =y (our current "future" relative to x) no matter what decisions you make to change x.

Imagine this simple equation: x+x=y , or decisions+decisions=future outcome.

If we know y=5, than we can change x to 4+1, or go back in time and change x to 3+2, but no matter what, x+x will always = y because Y is already known and is not a variable at all, x is. So past changes to x must be two numbers that, when added, = y no matter what. To come to a different conclusion than y (5) would be a paradox and paradoxes cannot occur in the math of the universe. We can use our free will to change x to anything, but we are limited only to numbers that add up to y (5).

If I travel back in time and make different decisions (affecting x), no matter how hard I try it will never change the outcome of the future (y), my decisions are limited to outcomes that will =y no matter what. The universe likes to make sure it math always works, therefore no paradox is possible.

[lxskllr]

I like the multiple universe theories better. You can travel through time, but only by utilizing different universes. You can change history(say kill your grandfather), but it won't cause a paradox because it doesn't affect the universe you're from.

[MGX]

From the study of books on the subject it would also be worthy of note to be aware that if one were to go back in time one would not also go back in SPACE.

I.e. if one were to transport 1 year in the past/future the position would not change so the timing would need to be near perfect to not find yourself lost in space (the planet Earth would need to be in the right place at the right time). Screw it up and find yourself 1,000 ft. above the surface/ on the moon etc.

Setting up the machine to be so precise...that's an engineering problem! Hawking remarks that time travel doesn't exist since we do not have 'time tourists' from the future; maybe our future children haven't perfected the technology yet and only send dogs and monkeys.

[lxskllr]

maybe our future children haven't perfected the technology yet and only send dogs and monkeys.

That explains our politicians....

[tom502]

It sems to be theoretically possible, and the idea is appealing, and I usually believe about anything can happen, though I find myself most sceptical about time travel. I'm not really believing it can be done.

[sgreger1]

I like the multiple universe theories better. You can travel through time, but only by utilizing different universes. You can change history(say kill your grandfather), but it won't cause a paradox because it doesn't affect the universe you're from.

That's possible, but the math would have to be much more difficult for that to exist. If every time someone makes a deicsion it spins off an alternate universe, where does the mass/energy come from to create that new universe?

If I decide to eat a turkey sandwich for lunch, that is in one universe. But if I go back in time and eat a ham sandwich, according to the mutliverse theory it would spin off an entirely new universe that contains all the outcomes of the world based on that single action of me eating ham instead of turkey. And in theory, an alternate universe would have to exist for every possible outcome for every decision ever made by anyone ever, including all of the decisions made by people in all of the infinite number of alternate universes. But where did the mass/energy for these many universes come from? How can it exist given the alleged finite amount of mass/energy available in any given system. It would involve rewritting the entire theory of our universes origins, the nature of the universe as a whole, as well as completely scrapping the entire concept of "mass cannot be created nor destroyed". (Not that those things aren't entirely possible to change.)



Anyone else have a unique theory on time travel or possible paradoxes?

[MGX]

You can search youtube for '10 dimensions'. Find the black and white video. It uses spatial relationships to work their way through all the dimensions. That is the easiest explanation to understand.

Years ago a math professor tried to explain things to yours truly using equations but my training is certainly not on that level.

[sgreger1]

From the study of books on the subject it would also be worthy of note to be aware that if one were to go back in time one would not also go back in SPACE.

I.e. if one were to transport 1 year in the past/future the position would not change so the timing would need to be near perfect to not find yourself lost in space (the planet Earth would need to be in the right place at the right time). Screw it up and find yourself 1,000 ft. above the surface/ on the moon etc.

Setting up the machine to be so precise...that's an engineering problem! Hawking remarks that time travel doesn't exist since we do not have 'time tourists' from the future; maybe our future children haven't perfected the technology yet and only send dogs and monkeys.

Well there are two different mindsets on how to solve the time /= space problem.

1. Like you said, if I travel back to 100 years ago, the position of the earth relative to the sun will be different than the point of origin I am departing from, therefore if I literally traveled back in time (and not space), I will likely end up somewhere in space. This is easy to fix because even modern day computers can solve simple equations like this. This is how we launch space shuttles and the like, we can say where everything is going to be at any given time based on computer algorhythms. Since the earth always revolves around the sun once a year, and rotates on it's axis once a day, these are constants and can therefore be easily predicted by simple computers, thus solving any problems that may arrise from traveling through time but not space.

2. As posited in the book "The Time Machine" by H.G. Wells, when traveling through time, the observer would be able to see everything as it passed, and could therefore stop the machine only at a point where the machine would land on firm ground and not in space. Since he can finely tune at what speed he travels through space (in both directions), this would be very easy. If you see space, keep going, once the earth rotates back towards you, slow down and fine tune it untill the earth is directly under you, so that when you stop time traveling, you will fall safely to the earth and not find your atoms bonded with any other atoms or find yourself lost in space. This however limits where one can travel, as you pretty much must arrive at relitavely the same point on earth as you departed from. You could not travel to china in the past or future if you left from the united states, unless you could somehow also design the time machine to move through space as well as time.


Stephen Hawking has mixed feelings on time travel, he believes there are too many paradoxes and that (while possible), it is unlikely that time travel exist, because at some point in the future time travel would have been created if it was possible to create, and therefore we would see people traveling back in time.

There are also multiple theories on this:

1. You cannot travel to a point in time PRIOR to the first time machine being created
2. Time travelers HAVE come back to our time or the time of our past but we didn't notice them
3. There is some technology that makes for this all to be possible without creating any paradox or us noticing it's existence. Perhaps the book "The end of eternity" was correct, and time travelers of the future do exist and actually travel back in time and make alterations (in a calculated manner) in order to positively effect the outcome of future generations without our knowledge.

[sgreger1]

[QUOTE=MGX;316188]You can search youtube for '10 dimensions'. Find the black and white video. It uses spatial relationships to work their way through all the dimensions. That is the easiest explanation to understand.

When trying to explain the universe around us, scientists have developed many theories on what the nature of the unvierse actually is. Much of the math doesn't work without creation theoretical conditions. For example, we can't explain the expansion of the universe without assuming that 75% of the universe is dark matter that is somehow undetectable. We don't know if that's right or not, but to make the math work there must be at least that much matter existing in secret somewhere within space/time. Many of these theories also revolve around the existence of extra dimensions, folded within our observable 4 dimensions. There is a debate as to what the correct number of dimensions is, for string theory to work it is perhaps 10 dimensions, for m-theory to work it may be 13 dimensions, etc etc (those are not real numbers btw).

But at the end of the day, we have to remember what words we are using to describe things. Dimensions does not mean alternate universes like in a sci-fi movie, the dimensions referred to in these theories are literally dimensions (as in measurements). 1st dimension is length, second dimension is width, 3rd dimension is dept etc etc. They are theorizing that multiple other dimensions must exist for some of our standing theories to work. But again, these dimensions are describing measurements and not necessarily "alternate universes" where everything is the same as it is in our universe.

A deer can observe only in 2d, everything appears like a cartoon to them. When they see the world they observe only two dimensions so it looks similar to what a TV screen looks to us when we are observing it. Humans on the other hand have the ability to observe 3 dimensions; we can see depth and things are "3d" to us, not "2d" like for deer. The difference between looking at a 2d picture (a photograph for example) and looking at a spherical beach ball is just the fact that with the beach ball, we are observing it with an additional dimension. It doesn’t mean some alternate universe exists or that the two objects are any different, only that the beach ball includes one extra dimension than the 2d photograph does. It is in this way that scientists use the term "dimension" when theorizing on things such as string theory, they are not referring to alternate universes with people and events.

[Snarfblat]

I like to ponder the idea of infinite multiple universes as well. I'm not sure about traveling into the past, but time travel into the future has already been done right here in this universe:

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

Now if we could put a human into a capsule, and fire him around the Large Hadron Collider at 99% the speed of light, what would we observe from the outside looking in? I think as he accelerates and time slows down (relatively) he would appear to stop moving? I think that we would need a plan to keep the machine going for a thousand years, and when we stopped it, the barely-aged passenger could step out into the future.

Of course there would be the problem of G-Forces to overcome... Nevertheless it looks like we've already built our first time machine with the LHC.

[sgreger1]

I like to ponder the idea of infinite multiple universes as well. I'm not sure about traveling into the past, but time travel into the future has already been done right here in this universe:

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

Now if we could put a human into a capsule, and fire him around the Large Hadron Collider at 99% the speed of light, what would we observe from the outside looking in? I think as he accelerates and time slows down (relatively) he would appear to stop moving? I think that we would need a plan to keep the machine going for a thousand years, and when we stopped it, the barely-aged passenger could step out into the future.

Of course there would be the problem of G-Forces to overcome... Nevertheless it looks like we've already built our first time machine with the LHC.

Incorrect. You are confusing time travel with relativity.


Imagine I, the observer am standing on earth with a telescope, and you are traveling at light speed in a space ship. Because of relativity, if I were to look through the window of your space ship from my telescope on earth, you would appear stationary. However, you are not stationary, for you time (physiological time) is moving at the same constant as always. You are aging and going about your day in the spaceship traveling at light speed in the same way that I am moving and going about my day traveling on planet earth which is spinning around the sun at thousands of miles per second.

It’s a question of time relative to the observer. No one has gone forward or backwards in time, and time has stopped for neither party. Instead, if I look at you while your traveling light speed, time APPEARS to be frozen in your ship, relative to me the observer, and vice versa. But in reality, we are both moving through time at the same pace, and we will both age in exactly the same way, just not relative to each other.

[tom502]

It's fantasy.

[sgreger1]

It's fantasy.

Lol, I never thought i'd see the day Tom tells me my ideas are fantasy lol. Technically, the possibility of time travel is infinitely more possible than nibiru or some other rogue planet striking the earth in 2012, a galactic alginment in 2012, or a polar shift occuring all at once in 2012. Infact, time travel is more theoretically possible than a hollow earth.

[tom502]

I just can't see time travel as possible, as we see it in movies and stories. One thing is, you are a culmination of time, and you can't go back. Or forward. I just don't see it possible, even though in theory it might be, such as going beyond the speed of light. These things might help us understand how things are put together, but to build a Tardis, I don't see it possible.

[sgreger1]

I just can't see time travel as possible, as we see it in movies and stories. One thing is, you are a culmination of time, and you can't go back. Or forward. I just don't see it possible, even though in theory it might be, such as going beyond the speed of light. These things might help us understand how things are put together, but to build a Tardis, I don't see it possible.

It's pretty simple really,a ll you need to do is move along the axis of 1 of the many dimensions (the 4th dimension of time). I can fly from point a to point b in an airplane, and all i'm doing is traveling along the axis of one dimension (the length between those two points). It should be possible to travel across time as well, since time isn't something we all made up, but rather a part of space/time, traveling through time should be just like traveling through space in theory. Now how we would go about making a machine to do that I have no idea and at a minimum I think that is millenia away at best, if ever.


And furthermore, nature may not even allow for the possibility of time travel, in the same way that nature may not allow us to reach the speed of light. Even if we could build a machine to accelerate us to the speed of light, nature puts us in check by making all of our atoms into light, rending the trip useless to a human since he couldn't reach his destination in physical form. Same might be true with time travel, we may be able to do it, but nature may have some check in place to make sure we never reach our destination.


I, however, think traveling faster than light will be a reality in the future. It just involves us getting over a few hurdles, but the scientists of a few centuries ago didn't believe we could ever fly or go faster than 35mph without our bodies breaking down either, and look at us now!