Time Travel Discussion

[Linguz]

Is time travel possible? And if it is possible, can it change anything?

Here are my thoughts:

I believe that time travel, while possible, cannot change anything that
happens. Why? You already did the thing you go back in time to do. I'll
use an example: You're 25 and you go back 20 years. At that point, there
are two of you in that time, a 5 year old and a 25 year old. When you
were 5, your 25 year old self went back in time and did what he was
going to do. Therefore, before you even time travel, what you are going
to do in the past has already happened. If you choose not to go back in
time, then what you did in the past didn't occur and has already been
factored into the equation of life.

What are your thoughts?

[Apple Crumble]

For me time travel is not even possible, though I like to travel back in time. As for time paradoxes and changing the course of the future, if you change the past then your future will be changed too but you won't even notice it because you already ran that course in your life (I don't know if I'm making it clear or I can't explain it right :P). I don't think if there are 2 of you in that time frame I guess its not gonna blow up the world or disrupt the time continuum or something since the time traveling part is already inputted in your history.

Well I guess pinkie pie can answer that question since she can even defy the laws of physics

[Derpy Hooves]

Is time travel possible? And if it is possible, can it change anything?

Here are my thoughts:

I believe that time travel, while possible, cannot change anything that
happens. Why? You already did the thing you go back in time to do. I'll
use an example: You're 25 and you go back 20 years. At that point, there
are two of you in that time, a 5 year old and a 25 year old. When you
were 5, your 25 year old self went back in time and did what he was
going to do. Therefore, before you even time travel, what you are going
to do in the past has already happened. If you choose not to go back in
time, then what you did in the past didn't occur and has already been
factored into the equation of life.

What are your thoughts?

There is a name for this theory of time travel and it is what jk Rowling studied when writing The Prisoner of Azkaban.

I personally don't follow this, because though I can understand it, and it's a feasible theory, the way I believe time travel works being nearly 100% mechanical doesn't actually allow for this theory to work. Not that I'm saying you are wrong, but my thoughts more closely follow the butterfly effect theory.

[Linguz]

There is no right or wrong answer to this question. It is impossible to know whether one would be right or wrong until we actually try it out.

I also came up with the theory myself. I never once looked at anything online or printed or anything else other than myself. If it is similar or exactly like some theory, it is a coincidence.

Do you mind explaining the butterfly effect theory when you have time?

[Ferrous_Oxide]

Is simply the act of choosing to create a time machine enough to alter the time stream?

[Elipsilon]

Do you mind explaining the butterfly effect theory when you have time?

The Butterfly Effect is when a small change occurs and starts a chain reaction leading to larger and more significant changes.

[Spitfire]

IE: step on a butterfly in the past, humans never exist in the future

[Twilight Sparkle]

Time travel is impossible, and it's our faulty human intuition about time that can make us think otherwise. We imagine time as a "flow," where there are past, present, and future events. In philosophy this is called the A-theory of time.

We know from physics, however, that this is not the case. Time is merely one more dimension of a mathematical structure; spacetime. All events, past, present, and future, would appear as points in a space all "existing" at once, to an outside observer. These are the basics of general relativity.

Our perception of a "passage" of time comes from the fact that our brains, and therefore minds, and physical phenomena, subject to the same laws of physics as any other system. The second law of thermodynamics is the reason for this. While some people understand this to mean "increasing randomness," a more technical definition would be that the amount of energy available to do work in any system decreases. The effect this has is making physical processes irreversible, and this "preferred direction" is what gives us the perception of a "passage" of time.

Of course, the non-fundamental nature of time means that if we could bend or fold spacetime, we could "skip into" the future, but it would have to be accompanied by a similar movement in space. In fact, we experience different subjective times when we orbit the Earth, the difference is just FAR too small to make a difference. When moving at or near the speed of light, and/or when great distances are involved, this effect becomes very strong.

While the theoretical potential of bending spacetime to move to other points in spacetime faster than the limit imposed by the speed of light on convention motion through spacetime (the idea is called an Alcubierre drive), the idea of time travel in the conventional sense - of having timestreams, keeping your subjective time, travelling to different times in the same place, affecting events, etc. - is preposterous to any physicist.

[Linguz]

Time travel is impossible, and it's our faulty human intuition about time that can make us think otherwise. We imagine time as a "flow," where there are past, present, and future events. In philosophy this is called the A-theory of time.

We know from physics, however, that this is not the case. Time is merely one more dimension of a mathematical structure; spacetime. All events, past, present, and future, would appear as points in a space all "existing" at once, to an outside observer. These are the basics of general relativity.

Our perception of a "passage" of time comes from the fact that our brains, and therefore minds, and physical phenomena, subject to the same laws of physics as any other system. The second law of thermodynamics is the reason for this. While some people understand this to mean "increasing randomness," a more technical definition would be that the amount of energy available to do work in any system decreases. The effect this has is making physical processes irreversible, and this "preferred direction" is what gives us the perception of a "passage" of time.

Of course, the non-fundamental nature of time means that if we could bend or fold spacetime, we could "skip into" the future, but it would have to be accompanied by a similar movement in space. In fact, we experience different subjective times when we orbit the Earth, the difference is just FAR too small to make a difference. When moving at or near the speed of light, and/or when great distances are involved, this effect becomes very strong.

While the theoretical potential of bending spacetime to move to other points in spacetime faster than the limit imposed by the speed of light on convention motion through spacetime (the idea is called an Alcubierre drive), the idea of time travel in the conventional sense - of having timestreams, keeping your subjective time, travelling to different times in the same place, affecting events, etc. - is preposterous to any physicist.

And someday, someone will create a time machine and then you'll feel stupid for doubting it.

Just wait, you'll see.

[Spitfire]

With the rate of advanced, as long as a great threat to humanity does not kill us, it will happen. I'm I'm right in the perfect age bracket to do it

[Twilight Sparkle]

And someday, someone will create a time machine and then you'll feel stupid for doubting it.

Just wait, you'll see.

But there's no physical principle by which it could work. As I said, time isn't even the sort of thing that can be traveled "through" independently of travelling through space.

Not that the latter isn't possible. Suppose we wanted to go to some point in spacetime (x1,y1,z1,t1). Normally, we'd have to cover so much space and time to get there. But we if we could fold spacetime, we could violate this. Imagine spacetime as a tablecloth, and then imagine dragging your finger along it. To get from one point to another, far across the tablecloth, you have to drag a certain distance. But if you folded the tablecloth between the points, you'd only have to drag a short distance to get to the place you wanted. Hell, you could "put" the points right next to each other if you folded right.

These ways of getting around the light speed limit are the closest thing to time travel that are possible.

[Derpy Hooves]

Time travel is impossible, and it's our faulty human intuition about time that can make us think otherwise. We imagine time as a "flow," where there are past, present, and future events. In philosophy this is called the A-theory of time.

We know from physics, however, that this is not the case. Time is merely one more dimension of a mathematical structure; spacetime. All events, past, present, and future, would appear as points in a space all "existing" at once, to an outside observer. These are the basics of general relativity........
...

I honestly understand that you don't believe that its possible, but the highlighted sentence of this quote leads me to the simple question of, if time is just another dimension, and we can move freely in the 3 dimensions we perceive naturally, then why is it impossible to move within that dimension?

also, stating that one theory of time is a theory, then saying "We know from physics, however, that this instead is true, makes your statement seem a little less believable, as if claiming that the "instead" theory you propose is now a law.

I personally, don't believe that time is a dimension being moved along, it just doesn't seem like something I can believe. I also HATE when people say the 4th dimension is time (which I know you didn't claim, but its a commonly stated theory that I dislike greatly) rather than just another spacial dimension.

I think that time isn't a dimension per se, but simply something that is there, the passage by which actions we can perceive happen, and it is weaved into timespace, but timespace in this case is a different timespace theory than the one that you mentioned. Where instead of a dimension being moved upon, it is just there and can be affected by the other dimensions and the forces within them, waves in the timespace.

@Twilight, please don't get mad at my criticism above my claims, I'm not trying to start a fight or anything, its just my personal view on your reply. Talking about things we can't be sure of is always a sensitive thing and I don't want a nerd fight to arise.

ALSO EVERYONE REMEMBER! Twilight has set for his body to be cryogenically frozen when he dies, so if any one of us will learn the truth about time travel in the future, he has the best chance.

[Twilight Sparkle]

I honestly understand that you don't believe that its possible, but the highlighted sentence of this quote leads me to the simple question of, if time is just another dimension, and we can move freely in the 3 dimensions we perceive naturally, then why is it impossible to move within that dimension?

Well depends what you mean by "move" and "freely." Events are static points in spacetime. You are already "moving" along t, right now, but you aren't literally "moving." Rather, there are different events (points) which correspond to each moment in time. The idea is that time and space are not separable. You cannot "travel" backwards in time for two reasons. One is, as I said, physical irreversibility. The other is that backwards time travel would require closed timelike curves. A timelike curve is a type of worldline in spacetime, a worldline being the unique path of an object as it moves through four-or-more-dimensional (higher dimensional) spacetime, and a closed one is one that loops back on itself, so an event can be simultaneous with its own cause. The problem is that there are no globally unobjectionable solutions to the Einstein field equations which allow for them, which are a set of equations in relativity which describe the fundamental interaction of gravitation.

Furthermore, my preferred theory of quantum gravity, Loop quantum gravity (quantum gravity is the "fundamental" theory which will unify relativity and quantum mechanics, which we know are incomplete), leads me to accept the so-called chronology protection conjecture, which also doesn't allow for time travel. Unlike what I described in the last paragraph, however, this is speculated and is not a scientific consensus, so approach this more skeptically.

also, stating that one theory of time is a theory, then saying "We know from physics, however, that this instead is true, makes your statement seem a little less believable, as if claiming that the "instead" theory you propose is now a law.

This is the same theory/law confusion that creationists get tripped up on. If it were uncertain, it would be a conjecture or a hypothesis. In science, a theory is just a collection of statements about reality. The term "law" has not been used since the 19th century for new discoveries, as it implies that there is a sort of "law" being "imposed." It's an archaic term; theories like evolution, relativity, quantum mechanics, etc. are as certain as any "law."

I personally, don't believe that time is a dimension being moved along, it just doesn't seem like something I can believe. I also HATE when people say the 4th dimension is time (which I know you didn't claim, but its a commonly stated theory that I dislike greatly) rather than just another spacial dimension.

Unfortunately you're going against the understanding of the global scientific community. The classic model of spacetime is called Minkowski spacetime, which is exactly what you described - time as the fourth dimension. In contemporary physics there are other speculative theories; higher-dimensional spacetimes with MORE than four dimensions (one is still time though), and there is also an idea called "timelessness" which things that time doesn't exist at all (this is difficult to explain). Either way though, if time exists at all, it's a dimension.

I think that time isn't a dimension per se, but simply something that is there, the passage by which actions we can perceive happen, and it is weaved into timespace, but timespace in this case is a different timespace theory than the one that you mentioned. Where instead of a dimension being moved upon, it is just there and can be affected by the other dimensions and the forces within them, waves in the timespace.

This simply flies in the face of the understanding of the scientific community.

Anyway, I will again point out that a sort of time travel into the FUTURE is possible, it just isn't what we usually imagine. This is due to an effect called time dilation. If we have two observers, and one is moving very close to the speed of light (or is deep in a gravity well), the slow observer will observe time as passing very slowly for the fast moving observer, where time will appear to be passing "normally" from the fast observers perspective. These different perspectives of subjective time could be said to be a sort of time travel.

please don't get mad at my criticism above my claims, I'm not trying to start a fight or anything, its just my personal view on your reply. Talking about things we can't be sure of is always a sensitive thing and I don't want a nerd fight to arise.

Oh, don't worry about me getting mad. It isn't personal. We're just debating with the goal of reaching greater understanding. Don't mistake forceful debating on my part for unfriendliness.

[Derpy Hooves]

This is the same theory/law confusion that creationists get tripped up on. If it were uncertain, it would be a conjecture or a hypothesis. In science, a theory is just a collection of statements about reality. The term "law" has not been used since the 19th century for new discoveries, as it implies that there is a sort of "law" being "imposed." It's an archaic term; theories like evolution, relativity, quantum mechanics, etc. are as certain as any "law."

I'm not trying to demote theory to a guess, I got that mentality beat out of me by my science teacher. But a "Law" is something that is known to not have any possible alternatives, whereas theories are made to be as true as possible, while allowing for expansion as new information is discovered.

Like the laws of physics, are recognised to be correct to the preciseness we can achieve, whereas gravitational theory (often mis-appropriated as a law) as been shown to have flaws in practice, and is open to expansion.

That is my understanding of these, but as this isn't a "scientifical" term thread (c wut i did thar?), and I don't want one of them, i return to time travel.

Time isn't necessarily understood under any umbrella of theories by a (strict)majority of the scientific community, which is why I see all the ideas proposed here as perfectly feasible.

[Twilight Sparkle]

I'm not trying to demote theory to a guess, I got that mentality beat out of me by my science teacher. But a "Law" is something that is known to not have any possible alternatives, whereas theories are made to be as true as possible, while allowing for expansion as new information is discovered.

Like the laws of physics, are recognised to be correct to the preciseness we can achieve, whereas gravitational theory (often mis-appropriated as a law) as been shown to have flaws in practice, and is open to expansion.

You're just getting hung up on terminology. There is, in the scientific community, no difference between a highly-confirmed theory and a law. "Law" is just an old-fashioned term. Only in philosophy is there a difference. In philosophy, the laws of nature refer to the regularities in nature, whereas theories are the things that describe them.

Time isn't necessarily understood under any umbrella of theories by a (strict)majority of the scientific community, which is why I see all the ideas proposed here as perfectly feasible.

Just because we don't know exactly what time is doesn't mean we don't know a lot of things that it isn't. Time is either a dimension or doesn't exist at all; these are the only views in the physics community.

[Derpy Hooves]

I'm not simply getting hung up on terminology for fun, I'm getting hung up on it because I have written a 9 page paper for school about the difference between a scientific law and theory's of any sort, as with any research I may not be 100% correct, but that is my understanding, and it's how I use the terms.

Time isn't necessarily understood under any umbrella of theories by a (strict)majority of the scientific community, which is why I see all the ideas proposed here as perfectly feasible.

Just because we don't know exactly what time is doesn't mean we don't know a lot of things that it isn't. Time is either a dimension or doesn't exist at all; these are the only views in the physics community.

This is where I draw the line at the appropriateness of stating the science as fact, science is a collection of observations, and there is science based on direct and indirect observation. The science behind time theories is obviously based on indirect observation, which is where I decide to draw the line against math as sheer fact and place it in the category of "what we know from information we can obtain." This is just my way of understanding it so I don't end up that one person throwing Hawking's original black hole theory in people's faces as if it's sure and concrete fact, only to have major holes discovered later.

I should also let you know, that I was taught to view science with a personal eye, where only what you know yourself is what you know, and what others claim cannot be true to you unless you see undoubtable proof, or can understand the proposed proof with enough confidence to truly believe what you've been told. This is why you see what I say as something being randomly thrown information that contradicts all scientific understanding in your point of view.

Same goes for language, if a person knows from being told that saying strawberry is a greeting, then they will say strawberry, and they meaning to them is a greeting. This is the same logic between my use of law and theory. I was taught that laws and theories are two separate, but related things and that's how I use them.

I hope this helps you to understand my previous posts.

[Moonlight]

If time travel is possible, then all of our memories are made up of the ultimate paradox of when people stop time traveling. As an abstract theory, it would then collapse in on itself. So I say, yes, time travel is possible, but nobody has any way of knowing because if something crossed within its own time stream, it would nullify itself and be rendered nonexistant.

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