Time travel; is it really possible, or doesn't it go much further than the stories about time machines in comic books? In brief I wrote down a few facts, accompanied by a few of my own theories.
Time travel; it would seem impossible, yet we're constantly traveling through time. This is because gravity has a pull effect on the time dimension. If you're close to a massive object let's say a pyramid time will go by slower near you. The time difference however is so imperceptible that you might as well neglect it.
For a relevant time difference, you would have to fly around the most massive object known in the universe (or multiverse); a supermassive black hole. You would have to fly around it for a longer period of time, and with enough speed to ignore the gravitational pull, thus avoiding lapsing over the event horizon and getting sucked into the black hole and become an infinitely small point which we call the singularity.
Another theoretical way to travel through time is by traveling at the speed of light (or rather, 99.9999% of the speed of light). If you get in some sort of transportation that travels near the speed of light, double the Earth time (assuming the experiment takes place on Earth) will have passed relative to the time passed in your hyper-transportation. But why wouldn't this hyper-transportation travel at 100% of the speed of light, or even faster that that? According to Einstein's theory of relativity, no physical object, message or field line can go faster than the speed of light*, because the maximum speed of light is finite, and an absolute value. The speed of light in a vacuum is the same for all observers, regardless of their relative motion or of the motion of the source of the light. What this means is that no form of transportation can reach or exceed the speed of light; not even by cumulative speeds. Now let's assume our hyper-transportation is a long form of transportation. Let's call it a hyper-train. If this hyper-train travels at 99,99% of the speed of light, and you drive from the back to the front of the train with a small yet fast form of transportation, you would still not reach or exceed the speed of light because the speeds are not cumulative. This is because at such high speeds, time slows down just enough to prevent you from ever reaching 100%. Still, the time difference you experience by going close to the speed of light can already count as time travel, even if the travel is not instant.
Every material even a seemingly solid and smooth material is everything but flat on a micro level. The material consists of a robust construction with gaps and holes. The time dimension is no different. There are tiny holes in the very fabric of time. These tiny holes are very, very tiny black holes through which you can travel through time. They're just too tiny for humans to be relevant. But what if that isn't necessarily true? What if it's because of these black holes that we can constantly travel forwards in time (though gradually as opposed to controlling the time's speed and direction [meaning backwards or forwards])? What if this is the very reason that we perceive time as being linear? What if this is the only reason that everything is dynamic as opposed to static and lifeless? I guess you could see it as a link from this moment to the next one.
Also, as you might know we are constructed of matter, which is the residue of the big bang. During the big bang matter and anti-matter collided and formed a violent reaction infinitely more powerful than a nuclear explosion or even a supernova. The matter and anti-matter off-set each other, but there was one in a billion particles more matter than anti-matter, which is why we are made of matter. What if anti-matter has its own time dimension which has an opposite effect of "our" time dimension? Just some thoughts.
It may be easier than we first thought (as space phenomena can tell us), but any effects of time travel would most likely not be visible to us due to the fact that we would be affecting the past of another parallel universe.
Btw, thought you might be interested in this journal I wrote too: On-the-Feasibility-of-Time-Travel
Now that would be fascinating to study to say the least!
In order to "time travel" you only need to get close to the barrier. Time will slow down by half relative to the "outside". You would be 5 years older while everyone not in the hypertrain would be 10 years older. Of course this is not really time traveling in the conventional sense, in which you actually go ahead or back in time in a flash. This is theoretically possible with a wormhole. A wormhole is a connection between two supermassive black holes (one in an other dimension) which have such a gravitational mass that they create a tunnel connected with the other dimension. It's a controversial subject however because you could never survive getting sucked into a supermassive black hole. And even if you could create a non-violent controlled portal to travel back into time, there are several paradoxes. For one there is the fact that in the past there wouldn't have been a time travel machine to time-travel through, so you can only go back to the point where the time travel machine would have been invented. So if it were invented today, in 2050 people would only be able to travel as far back in time as today in 2010. Besides that there is the probability that you will meet yourself back in time which could be troublesome. This is due to the butterfly effect, which could potentially bring many problematic results to the future; perhaps on a global scale or of a more domestic nature. There is the 'grandfather paradox' which describes that if you kill your grandfather, you wouldn't even be born, so you practically can't exist now.
Another thing I wanted to bring up is the possibility of travelling faster than the speed of light. It could be possible given the right circumstances. In particular, consider that the velocity of light is 3.00E+08 m/s. If travel through wormholes is possible then it would occur in a dimension that currently is inperceptable to us. Thus, if we enter the wormhole at point A (x=0 m), and exit at point B (x=5.00E+08 m) less than one second later, then theoretically, we travelled faster than the speed of light.
As for your statement about a wormhole, if we assume a wormhole can exist then why would it occur in a dimension imperceptible to us? Also, why do you assume that you've traveled through the wormhole faster than light? I know the physics inside a black hole would break down but I thought strange effects in space and time would still account for what seems to be a violation of the absolute maximum speed which can be achieved in the universe. And are you not confusing light with ordinary matter? I know a wormhole is a theoretical object conceived in math, so do you perhaps know a source which explains what you just told me? I'm little good with math but I would still like to explore this if indeed what you say is true.
How is that an argument though? I think you will have to elaborate because you seem to imply that the speed of light is defined based on the distance it travels in a certain time in our space, as opposed to something else in a wormhole. I would want to know what that "something else" is, and even so, I don't think I would accept it as an argument for a violation of the maximum speed of light.
I won't say a second dimension of time can't exist because frankly I'm not well versed in math so I couldn't prove or disprove it even in theory, however I've never heard of a secondary time dimension. I must admit though it might not be that crazy; not crazier than 10 spatial dimensions, anyway. Isn't time an universal thing linked to the spatial dimensions though? Can you link to a source which talks about a secondary time dimension?
Why do you invoke a 5th dimension which isn't linked to either space or time? That's just crazy.
"Now, if it is a dimension of space that we do not currently perceive, then the rate of velocity would still only apply to movement through the currently understood dimensions of space."
You seem to imply that the rate of velocity would only apply to movement through "our" dimension because we can't perceive it in the other dimension. I see no logic in that.
"If it is a dimension of time, then by allowing movement say maybe a couple of seconds earlier, it could cause the impression that an object just moved a vast distance in no time at all."
Perhaps I'm confusing a time dimension with a spatial dimension but as I understand it, you said it right: it can cause the impression; that doesn't mean the object actually did go faster than the speed of light. I suppose I'm misunderstanding something fundamental here, so perhaps I would indeed have to see some kind of visualization.
"But, if it is neither space nor time, then velocity through space and time does not apply to movement through the wormhole."
You're basically talking about instant teleportation, right? To go from one place to the other without going through either space or time. If that's true then I guess you could both argue that the object did and didn't travel faster than light. On the one hand, it did travel from point A to point B in no time, but on the other hand it didn't travel through either space or time to get from point A to point B so it's not fair to compare that to something which does. In fact, speed and velocity seem to be empty concepts in this dimension, and presumably mass too. That's just too weird to be true, right? Why even think of such a possibility if it seems to violate everything we know?
But to go back to the premise, as I said I don't have the math to support this claim, but I think a black hole is an object with a two-dimensional surface. Inside the physics break down and there is no concept of either time or space. I don't know in which way this 4th dimension would be relevant and as for that timeless and spaceless dimension you speak of... can you even call that a dimension? I guess what you're saying is basically true, however I don't quite understand how you can theorize about an object traveling through it. We've been assuming wormholes exist, but I actually don't think they do anyway. A question which remains to me however is indeed what a black hole would tunnel into, if it does. Is it an object within our dimensions with an intra-dimensional surface or is it like a hole in our dimensions which tunnels into a higher dimension? I think that's a fair question, but you're loosing me when you talk about objects going through a wormhole and how they would go faster than the speed of light. I might be wrong but it seems to be pure speculation rather than well-reasoned possibilities.
"Why even think of such a possibility if it seems to violate everything we know?"
Good question, and to answer I ask, what do we know? Even as far as we have come in the field of science, most of our knowledge of how the Universe works, are just theories, not laws, but theories. Even Einstein's theories as brilliant as they are, have numerous gaps where we simply just cannot find the answer. And Stephen Hawking's theories are far from answering the ultimate questions. So, even with all that we 'know,' about the Universe, I keep an open mind, because so far we have done everything, but rule out the farfetched and 'impossible.'
About the black holes, believe it or not, I was just answering my brother's question about this just a few hours earlier. From what I've read, and I'll have to dig out my Science and National Geographic magazines to find this, The object of the Black Hole (the singularity) is actually 3-dimensional. Even though the singularity is well the mass of a Super Giant in the space of an atom, remember that atoms also take up 3 dimensional space. The part of the black hole that people are most familiar with, the black disc, is actually the event horizon, and it is also 3-dimensional. Basically the event horizon begins at the radius where the black hole's escape velocity exceeds the speed of light. Where the singularity is the center point, the event horizon would extend out in all three dimensions. It does appear to be 2-dimensional because the event horizon itself is not an object. By the way, I was thinking about this when I read that last paragraph, but it might be possible that black holes are the wormholes themselves. You just have to figure out how to miss the singularity.
"Well, I can't explain it, but I can at least tell you that I learned of this concept from String theory."
Can I ask what your education is? I'm obsessed with these subjects but I don't have the education — and most likely lack intelligence — to grasp such subjects as String Theory. I've seen several documentaries and even a fantastic lecture on string theory but regarding the documentary, it was probably The Universe or a similar program so they dumbed it down a lot, and as for the lectures, a few hours were on geometry but other than that they left most of the math out.
"Good question, and to answer I ask, what do we know?"
To some extent that's a good answer but I don't completely accept it. I have to admit there is a lot left to learn about the universe, and we may never actually understand black holes and the universe/multiverse itself. Although I'm skeptical in nature I don't have the knowledge or authority to disregard a theory, however although I'm pretty certain concepts like the theory of relativity are incomplete, accumulated evidence supports the notion that the laws of these theories are not violated — or at least many of these theories seem to fit the observed evidence. I don't disregard the possibilities you postulate but I think they do need to replace or supplement existing theories. I'm aware you don't present these possibilities a something near truths but I do like to oppose it with skepticism — or quite possibly just stubbornness. A good example of this would be the Higgs boson. I would never deny the possibility that the Higgs boson does not exist, however if it didn't exist we would have to re-think the whole standard model. I was waiting for the scientists to tell me one way or another but I was very skeptical about the notion that it didn't exist. The same counts for those faster-than-light neutrinos. I can't contribute the math or even the conception of something to oppose or disprove, but I would be stubborn until the scientists come with peer-reviewed observations and solutions. Having said that, I very much live by the scientific protocol and science always has to be open to other possibilities; even if it's something as farfetched and improbable as the notion of a God.
"About the black holes, believe it or not, I was just answering my brother's question about this just a few hours earlier."
I believe it. I suppose this could turn into a whole new debate about reality and cosmology, however although I don't believe in faith, I do believe in chance and too many things just occur at too perfect moments to be absolutely random. Maybe I'm just seeing patterns while they're not actually there but I've experienced too many of this moments to really consider total randomness. I don't like to say everything happens for a reason because at least on the surface that doesn't appear to be true, but I keep thinking about it as a strange characteristic of reality.
As for the singularities of black holes, I'm convinced it's 3-dimensional but the surface of the black hole (not the singularity) as far as I understand Susskind and 't Hooft's hypothesis is 2-dimensional with the information of the three dimensions embedded in it. If this is true then I don't think wormholes can actually exist, and as far as I understand it indeed a wormhole could never be stable. What's that about the black disc though? I think most people misunderstand a black hole for a two-dimensional hole in the fabric of the universe, but as you say it's a 3-dimensional hole or object. By the way, a while ago I read an article about the hypothesis that there is actually no point as a singularity but that the singularity is essentially spread out in a "hair ball". Strangely enough I can't find any mention of this hair ball black hole on the Internet, which makes me wonder if the hypothesis was even peer-reviewed.
What do you mean with the black hole being the wormhole itself? Are you suggesting that an object going in could somehow get out if it misses the singularity? Even if that were possible, wouldn't the object only have moved through time and not through space? I would accept it as a one-way time machine but not as a wormhole.