Dear Quan,

No, a "time machine" (I assume you mean by this a "time travel machine") is not feasible now, and never will be. For an explanation, please see my essay 'On the Impossibility of Time Travel,' which will be found at the following link: https://fqxi.org/data/essay-contest-files/Smith_IOTT6.cwk.pdf .

People who hold that time travel is possible fail to understand the fundamental nature of time. I hope you'll find my essay helpful in this regard.

Best,

J. C. N. Smith

Dear Quan Hoang Nguyan,

Theoretically it's possible but practically in this moment this is difficult to achieve, for more details and in formation about this subject, i suggest you to see links on topic.

Is Time Travel Possible? Scientists Explore the Past and Future | Space

https://www.space.com/40716-time-travel-science-fiction-reality.ht...

It should be possible to build a time machine ... - The Independent

https://www.independent.co.uk/.../time-travel-possible-time-machi...

Is time travel possible? | Human World | EarthSky

https://earthsky.org/.../is-time-travel-possible-simple-time-machine

Time Travel Is Possible: Scientists Have Already Built A Time Machine ...

https://www.techtimes.com › Home › Science › Material Science

How To Build A Time Machine | IFLScience

https://www.iflscience.com/physics/how-build-time-machine/

Best regards

Of course it's possible twenty years ago in Mexico it was a dream the internet and now

is a reality, has driven knowledge as the use of drones and robots in agriculture, and to be more concise 100 years ago was a dream to fly or go to the moon, the machine of time is possible because sooner or later someone will achieve perform it in this century, or maybe you will.

We can always speculate and dream how far, but the answer is a definite yes.

We know that time dilates, for a traveler whose vehicle is approaching the speed of light. Which means, with respect to what's transpiring outside the vehicle, that traveler is going into the future.

t = tr * sqr(1 - v^2/c^2)

where tr is time at rest, or time passage as perceived by the traveler inside the vehicle, as long as he does not look outside, and c is the speed of light. So, what does that equation tell us?

It says, if a traveler is moving at a speed v = 0.9c, the time elapsed outside his window is moving 2.3 times faster than his own watch shows. His watch says 1 hour has elapsed from the last time he peeked outside, but the clocks outside have moved ahead 2 hours and 18 minutes! So in fact, that traveler is going into the future. And at v = 0.95c, time outside moves 3.2 times faster than in the vehicle. The effect becomes ever more pronounced, as the vehicle gets closer to v = c.

Therefore, without a doubt, a time machine is feasible. Even if, at lower speeds, it's not so impressive. People are now speculating that travel at 0.2c may be feasible in the future (matter-antimatter engines). At that speed, the traveler's time is dilated by a factor of 1.02, which means that every hour in the vehicle, the traveler is going 1.2 minutes into the future. Or, if an astronaut spends two years traveling at v = 0.2c, when he gets back to earth, he will arrive 14.6 days into the future of where he would have been, had he stayed on earth during those two years.

That's pretty cool, and it's real.

Now an interesting question is, what about time travel to the past? Well, going by the "symmetry principle," assuming there is such a thing, we might speculate that traveling faster than v = c will make time go the other way around. Mathematically, that factor gamma becomes imaginary (which does not necessarily mean "make-believe").

Albert Manfredi Thanks for sharing. That sounds interesting.

Dear All, Mr. Albert Manfredi is a amazing person who justifies so clearly that it is possible. I hope soon the day comes. same to accept the truth that going back in time is still a dream and to make it possible - Right now - is impossible. Thanks Mr. Albert Manfredi.

Dear Manfredi,

It is theoretically feasible. Do we have anything that is close to it? Or when will there be? So if one goes around the globe, he will be able to go to the future or even back to the past.

As Dr Hameed correctly pointed out, heading into the past is only speculative, at this point. Physicists are searching for particles that travel faster than v = c, called tachyons, but for now, they are only an exercise in mathematics. If we could discover tachyons, we might possibly get to see what "imaginary time" is, and what "time dilation" means on the other side of c. Which, by the way, could also explain why we may never find tachyons. Because, they would have to exist in this very different time dimension, orthogonal to our own.

But heading into the future is something we do just about always, if only infinitesimally. The earth orbiting around the sun, and rotating on its axis, and ourselves traveling on the surface of the earth, and the earth traveling around the center of the Milky Way galaxy, are all speed vectors that can be summed, to see how fast we are moving compared with c. That v/c ratio is what determines how fast we are traveling into the future.

t = tr * sqr(1 - (v/c)2)

So, leaving aside the small numbers, the significant speed is the solar system as it travels around the Milky Way. Our movements on the earth's surface, and the earth's rotation about its axis, and the earth's orbital speed around the sun, will slightly add or subtract, depending on time of day and on our movements, to this speed of the solar system.

The speed of the solar system as it travels around the Milky Way is average 828,000 km/ hr, or 230,000 m/sec, or 2.3E5 m/sec. And c is 3E8 m/sec.

So, v/c is 7.667E-4, and time is dilated by a factor of 1.0000002939.

Anything approaching v = 0.2c, which is still very slow, and which would dilate time by a still small 1.0206, is not yet visible over the horizon.

Dear Manfredi,

Thanks for your valuable discussion. Would you think that if, tachyons were to be found, the constant c would simply be replaced by the speed on tachyons in the original equation?

Yes

Not necessarily, Quan. In fact, I would very much doubt that, and it would defeat the whole purpose of tachyons! The speed of light, by all appearances so far, remains a singularity. Tachyons would exist on the other side of that singularity. They are postulated specifically for this reason. Do particles exist on the other side of c? What does imaginary mass look like? So, c must stay where it is, or we'd have no reason to be looking for imaginary mass.

By the way, it turns out, if you really want to achieve speeds that approach c, the best way known to us so far would be to approach a black hole. It seems that every galaxy has a black hole at its center. So, if you go to the black hole's so-called "event horizon," a circle around the black holes where matter is spinning around the black hole very fast, and anything closer to the black hole falls in with no hope of escape, then on that event horizon, your speed would be about 0.5c. At that speed, you'd be traveling to the future by a factor of 1.155. Meaning, for every year you spin around the black hole, you would be going 1.5 months into the future.

And if you are unlucky enough to fall in, it's unknown what happens then. As things go beyond the event horizon, they are stretched by insurmountable gravitational attraction, enter into some bright place with huge energy content and tiny volume (as perceived from outside), and we can only speculate what happens then. Get beyond c? Go back in time?

Hey, here's my theory. Black holes create the equilibrium that makes the universe persistent.

We know that stars have a definite lifespan. As their H2 fuses into He, they eventually run low on H2, the energy from the nuclear fusion can no longer beat gravitational attraction, and the star implodes. The big stars implode and become black holes, drawing other stars and planets inside. So you'd think, eventually the galaxies collapse into nothing?

What if all the matter that enters black holes goes back to the past, to create gas, then stars and planets? I mean, we know that solar systems are being created all the time. Has this matter come from the future, as some galactic recycling mechanism?

Dear Manfredi,

Many thanks for the insights. Appreciate it.

Was there any experiment that a particle, atom or anything was carried to the future?

Tachyons appear to be imaginary. How will it really help us to achieve that goal? And how will blackholes help if one can't escape from it (i.e. it's not a travel). If one can travel around the global with a speed close to c, what will it imply?

Quan, on particles going into the future, which is in other words time dilation, yes. It is shown to happen:

http://alternativephysics.org/book/TimeDilationExperiments.htm

As to black holes, well, for now, it's speculation. To reach a speed of c should require a massive particle an infinite amount of energy. And black holes are just the type of singularity where such tremendous energies may exist. So this may be similar to how photons travel at v = c. Because they have no mass. And by the way, photons do not travel at any other speed, than v = c.

Sometimes, we have situations of "immovable objects encountering irresistible forces," where the results are astonishing.

“Is time machine feasible?”

- no. More see, for example, the SS post in

https://www.researchgate.net/post/Who_says_that_cauzation_backwards_in_time_is_impossible_Classical_mechanics_The_relativity_theory_Is_there_a_proof#view=5d217893661123b0ea4114e3 near a day ago now. Though the last SS post would be interesting also.

Cheers

Dear Sergey,

Thanks for the link. Can you give a brief summary what you want to share with the readers of this thread?

Dear Sergey Shevchenko,

The topic of that thread is interesting.

Dear Quan,

“…..Thanks for the link. Can you give a brief summary what you want to share with the readers of this thread?....”

The brief summary is: the SS posts in linked thread are directly relevant to this thread question and contain explanation of the answer in the SS post above here on this question.

Cheers

Hi Sergey Shevchenko ,

It'd be good if you can make a summary of what you want to share with the readers in this thread. For your discussions in the thread you referred, they appear to be not the interests of the readers of that thread. May you double-check with them?

Dear Quan,

No, a "time machine" (I assume you mean by this a "time travel machine") is not feasible now, and never will be. For an explanation, please see my essay 'On the Impossibility of Time Travel,' which will be found at the following link: https://fqxi.org/data/essay-contest-files/Smith_IOTT6.cwk.pdf .

People who hold that time travel is possible fail to understand the fundamental nature of time. I hope you'll find my essay helpful in this regard.

Best,

J. C. N. Smith

Hi, Quan Hoang Nguyen,

I answered on this question already: to answer on this thread question is evidently necessary before to understand – what is “time”?

The answer on the last question is possible only in the “The Information as Absolute” conception; and in the referred threads this question is rather essentially clarified – just therefore they are refereed in the SS posts here.

However, indeed, the conception, and the phenomenon “Time” aren’t trivial, and so require some education level, and ability to think logically and non-standardly; some example of corresponding discussion see posting SS-Will Harwood in the thread

https://www.researchgate.net/post/Can_we_mathematically_model_consciousness#view=5d230dfd36d23579fa749240

Cheers

Sorry, but philosophical arguments are unconvincing. Special relativity explains how time travel into the future occurs, and there are examples where this has been demonstrated very precisely. I've posted a link.

Time travel into the past is a different matter, and can at best be the subject of conjecture, as of now. Maybe, as we discover more about black holes, we will uncover facts not yet known to us, in this regard.

What makes practical time travel into the future impossible now is our inability to generate the required force. Because even at speeds of 0.5c, the effect is very minimal, and we aren't even close to achieving 0.2c. At 0.95c, travel into the future starts to become a little more impressive, but that's very far from anything we know, yet, how to achieve.

To claim this is impossible, with philosophical arguments, in spite of demonstrations that special relativity theory works, seems a little overly "deterministic," let's say.

The problem with philosophical arguments is that they are based on logic we have developed with today's experiences. Our intuition is often incorrect, when dealing with new discoveries. The cheap example is how objects fall to earth. We had been told for centuries that heavy objects fall faster than light ones, and why, and this was incorrectly proven with feathers and rocks. Then we discovered some more facts, and suddenly that philosophy was seen to be inadequate.

Thanks J. C. N. Smith and Sergey Shevchenko for your valuable discussions. I tend to agree with Albert Manfredi to distinguish the discussions into past and future travel. It seems it is still an open question. Readers are welcome to share your expertise and opinions.

JCN, let me respond to a couple of points here:

https://fqxi.org/data/essay-contest-files/Smith_IOTT6.cwk.pdf

"We are all time travelers in this latter sense, which, this essay will argue, is the only sense in which time travel is possible."

Here, you are close, but I think not going as far as special relativity theory has already demonstrated. We are indeed traveling in time, as you say, but we are constrained to only one pre-determined speed, along this 4th dimension. So our "time travel" is strictly determined. By sitting around for one year, sure enough, we'll end up one year into the future, compared with when we started our one year wait.

Exactly how would we demonstrate the reality of such a phenomenon?

Turns out, that part is easy. We wear a watch that gives time of day, month, and year, and we compare it to what time pieces are saying when we arrive at our destination. Time travel to the past is problematic, conceptually, but time travel to the future is simple enough to demonstrate. As I will do below.

"In order to travel to and experience the universe as it was in The Age of Dinosaurs, this person would need somehow to travel to and experience a universe in which all the various bits and pieces had been rearranged so that they exactly replicate the configuration 2 For additional details on the development and ramifications of this definition, see [4].

7 which they had when the earth had made roughly 200 million fewer revolutions around the sun."

How do you travel in 3D space? Do you rearrange anything, or do you simply move to a new location? There is no rearrangement involved, just because you traveled a distance, other than rearranging your own location. The rest remains as it was.

So, let's start on our journey. We go to the airport, climb onto our spaceship, and we plan to get into orbit, rotate around the earth for a period of time, and then land back at the same airport. Our plan calls for orbiting the earth at v = 0.99c, for exactly one year, by our watch on board.

We dial in 0.99c, hit the "go" button, and suddenly people on earth notice we have vanished. Inside the capsule, we're quite comfortable, carefully keeping track of time.

So, we left in July of 2019, and exactly one year later, July of 2020 by our watch on board the ship, we hit the brakes, we find the airport, and we glide to a safe landing. Then we look at the clocks in the airport. They say it is August of 2026!

Amazing. So instead, had we dialed in a speed of 0.999c, and stayed in orbit for that same year, we would return to earth in November of 2041!

Or work it the other way around. You want to end your journey on Christmas Day of 2055, for some reason. And you want to limit your travel time to one year. So, you want to go 36.4583 years to the future, in one year. For that, you have to travel at 0.9996238c. You picked the destination, now you need to watch your speed and time at that speed.

Needless to say, the people we left behind will have aged, and a lot of other things will have changed on earth. But, aside from the difficulty in reaching these high speeds, for massive objects like ourselves, the physics involved here has been demonstrated. This isn't Jules Verne. We can determine exactly where we end up, simply by keeping track of time inside the capsule.

When Marco Polo went on his 17 year trek to the Far East, and then returned to Venice, he was 17 years older upon his return. Many people didn't immediately recognize him. Instead in this case, the time traveler will look very much like he did on the day he left, even though he's returning perhaps over 22 years later. There is no philosophical conundrum here. No questions about whether the person can coexist at two different times, in the same location, no issues with the possibility of "changing history." None of what makes time travel to the past more mysterious.

No.

Dear Virgil Matthews ,

Do you have some insights to share with the readers?

No. Time is a conceptual perception about change. It is a great invention of human to measure change. Like other great inventions of human being, like language, paper monery, mathematics, it measures the value of changes. But it doesn't have any value of its own. It is not a physical existence in nature. A time duration defined as a segment from the past to future, is actually impossible to exist at the same time, and is not measurable. What we measure is, as stated by Einstein, 'the position of the small hand of my watch': "http://hermes.ffn.ub.es/luisnavarro/nuevo_maletin/Einstein_1905_relativity.pdf

Past and future are only psychological phenomena, and not real existence. What exists is the ever changing present.

Dear Ligen Yu,

Apart from your concern about the existence of time and time interval, what is your suggestion? If we have a sequence of actions (1. a ball is at A and is thrown from A to B; 2. the ball is moving in the air from A to B; 3. the ball is at B). If the present is at 1, then 2 and 3 are the future of 1. If the present is at 2, then 1 is the past and 3 is the future. If the present is at 3, then 1 and 2 are the past of 3. Ligen, so the question should be clear now.

No. Don't try to use logic and reasoning. They are all mind play, and are not natural existance. Only use your perception (or you can do the perception with the help of some tools like a clock) to feel the nature. If you cannot find it by any means, it do not exist.

Dear Ligen,

Without using logic and causality, what is your suggestion? Do you know the difference between time, clock and time interval?

Dear Quan

You may be interested in this:

https://www.google.com/amp/s/qz.com/1279371/this-physicists-ideas-of-time-will-blow-your-mind/amp/

Dear Ligen,

Thanks for sharing. Interesting article, but appears to be an extreme. It is somehow a mix of discussion about time, clock and time interval. Causality is also absent.

Albert Manfredi,

First, thank you for actually reading my essay about time travel and for your thoughtful reply to some of the points I raised in that essay. Much appreciated.

Now, it is clear to me, however, why we are not seeing eye to eye on this topic. You wrote:

"Turns out, that part is easy. We wear a watch that gives time of day, month, and year, and we compare it to what time pieces are saying when we arrive at our destination."

And therein lies the reason for our different views. You (like most people) implicitly are accepting and using the operational definition of time (i.e., time is that which is measured by clocks) as the starting point for your thinking on the topic. This is the same starting point Einstein used as the basis for his brilliant theories of relativity. Unfortunately, this starting point is flawed. In my opinion, Einstein's "greatest blunder" was not his thinking about the cosmological constant, but rather his failure to begin his investigations by asking "what is time?" Rather than beginning by asking this more fundamental question, however, he tacitly accepted and used the operational definition, which is the same definition used by Galileo and others as the basis for their pioneering work in physics.

The problem with the operational definition is that it leads to circular reasoning. If time is that which is measured by clocks, then it seems only fair to ask, what is a clock? The answer is, of course, that a clock is a device that measures time. Now, proponents of the operational definition will hasten to add that this does not lead to circular reasoning because a clock is a mechanical or electronic device that measures regular, recurring motions of things such as pendulums or oscillations of cesium atoms, etc. But how would one know whether such motions were in fact "regular" unless their motions were timed by yet another clock, etc., ad infinitum.

As Julian Barbour wrote in his book The End of Time, "Relativity is not about an abstract concept of time at all: it is about physical devices called clocks. Once we grasp that, many difficulties fall away." Relativity gives perfectly fine and internally consistent answers to many questions posed in physics, but only so long as we remain within the construct dictated by the operational definition of time. It is this same reliance on the operational definition that leads to the theoretical possibility of time travel. The unfortunate incompleteness and circularity of this construct, however, very well may account for deeper problems such as the persistent and seemingly irreconcilable disconnect between general relativity and quantum mechanics.

In his book The Trouble With Physics, physicist Lee Smolin wrote, "More and more, I have a feeling that quantum theory and general relativity are both deeply wrong about the nature of time. It is not enough to combine them. There is a deeper problem, perhaps going back to the beginning of physics." I agree with Smolin wholeheartedly.

I would like to suggest that there are other -- potentially more fruitful -- ways to think about the nature of time. Some of these are spelled out in other essays such as 'Time: Illusion and Reality' ( https://sites.google.com/site/smithjcn/time ) and 'Toward a Helpful Paradigm for the Nature of Time' ( https://sites.google.com/site/smithjcnparadigm/ ). Should you have an opportunity to read them, I'd welcome your thoughts on them. Thank you.

J. C. N. Smith

JCN,

The problem with the operational definition is that it leads to circular reasoning. If time is that which is measured by clocks, then it seems only fair to ask, what is a clock?

Actually, this is what makes the philosophical approach to scientific questions untenable, resulting in endless circular arguments.

Science looks at what is, verifying what is, by showing it to be quantifiable and independently repeatable. So, we think of time as being an orthogonal fourth axis, along which the 3D space we see with our eyes moves. If this model can be shown to work, through any number of experiments, to provide predictable and quantifiable results, it is a useful model.

People all over the world could build time pieces, which tracked the movement of our 3D space along this time axis. Using the sun and stars at first, then mechanical contraptions, all of these time pieces, anywhere in the world, were functioning in synchronism. Cool. That was enough to proceed.

Now came several scientists, Fizeau, Lorentz, Michelson and Morley, and Einstein, who discovered that mere philosophical arguments, while they may have demonstrated some manner of "internal consistency," were simply wrong. Again, the "cheap shot" example being how objects fall to earth. Not at all as the philosophers had been telling us. Physics requires people who can say "BS," to any unsubstantiated claim, no matter how familiar the claim. So, we came to discover that light travels at a specific speed, not carried by an "ether," light does not follow the simple Galilean transformation, its speed is instead constant in any moving frame of reference, and the speed of light is a singularity that affects also time and mass.

At first, these were mostly mathematical derivations, using the discoveries of Fizeau, and Michelson and Morley. But still subject to being completely false. Much like philosophical arguments can be completely false. Einstein himself acknowledged this possibility. Because until the effects could be verified, it was still speculation.

But as far as we can tell today, actual experiments have shown special relativity to be real. Time dilation, for one, is real. So, unlike philosophy, science is not based on a foundation of nothing more than a thinker's imagination. Instead, initial hypotheses have to be proven correct, repeatable, before science can proceed.

As Julian Barbour wrote in his book The End of Time, "Relativity is not about an abstract concept of time at all: it is about physical devices called clocks. Once we grasp that, many difficulties fall away."

Yes, and the fact is, the operation of clocks is not make-believe. Clocks are repeatable, verifiable, quantifiable, predictable. In contrast, when a philosopher claims that the "soul" consists of these three things, and then concludes a long list of "facts" from this hypothesis, everyone should be asking whether that initial hypothesis was even valid. "Soul," for example, and never mind the three aspects of this "soul." This was only a figment of his imagination. He could base any number of conclusions on that foundation, but the foundation was pure imagination. Time is not like that.

So, in this world that we live in, time works as physics has been demonstrating, including the more recent discoveries of how it dilates. As long as experimental results confirm this in a quantifiable manner, and they do, we can use that as a firm foundation, until some other scientist, with real verifiable results, not just imagination, proves otherwise.

And with this background, time travel to the future is indeed possible. To the past? We don't know yet. It might be.

Albert Manfredi

We seem to be two perfectly good ships passing in the night on this topic.

First, I totally agree with you when you say:

"So, in this world that we live in, time works as physics has been demonstrating, including the more recent discoveries of how it dilates. As long as experimental results confirm this in a quantifiable manner, and they do, we can use that as a firm foundation, until some other scientist, with real verifiable results, not just imagination, proves otherwise."

I'm not sure whether you're familiar with the work of physicist Lee Smolin. A well known, well respected theoretical physicist, Smolin has devoted a great deal of thought to the topic of time and the role of time in physics. Smolin draws a distinction between what he calls the "empirically validated" implications of relativity (e.g., time dilation, etc., for example) as distinguished from what he refers to as "metaphysical" implications such as the so-called "block universe" in which all times, past, present, and future are equally real. (See his book The Singular Universe and the Reality of Time: A Proposal in Natural Philosophy, for example.)

I fully accept and agree with all of the empirically validated aspects of relativity. Where our thinking apparently diverges, however, is in your apparent belief that "time dilation" is one and the same as "time travel." I hold that these are two totally different things. I infer from your comments that you have not read my relatively brief essay 'Time: Illusion and Reality' ( https://sites.google.com/site/smithjcn/time ), which, I hope, will shed further light on my thinking on this matter, should you care to pursue it further.

On one final note, however, I must take strong exception to your casually dismissive attitude toward the role of philosophical thinking in science. Contrary to your dismissive comment, sound philosophical thinking -- based solidly on logic -- need not lead to "endless circular arguments." Rather, it can be the starting point for brilliant, revolutionary scientific discovery, as in Einstein's brilliant thought experiments. So I hope that -- contrary to your comments -- you do not truly believe that there is no valid role for logical thought or thinking in science!

Cheers!

J. C. N. Smith

JCN,

I fully accept and agree with all of the empirically validated aspects of relativity. Where our thinking apparently diverges, however, is in your apparent belief that "time dilation" is one and the same as "time travel." I hold that these are two totally different things.

They are indeed the same thing. I submit to you, tell someone that he can climb into a vehicle, set the controls correctly, and in a matter of months, end up on Christmas Day of 2025, and he will tell you that this qualifies as time travel. The numbers I provided, for speed and time of travel, were not just fictitious. They were calculated, based on theories and equations which, so far, have been demonstrated to be valid, in real world experiments.

If you say this is incorrect, it is incumbent upon you to explain why, in detail. Time travel to the future, even now, is physically possible, although unimpressive as of today (due to difficulty in generating the needed power). Time travel to the past will most likely require a lot more knowledge about black holes. That's my guess, today.

Smolin draws a distinction between what he calls the "empirically validated" implications of relativity (e.g., time dilation, etc., for example) as distinguished from what he refers to as "metaphysical" implications such as the so-called "block universe" in which all times, past, present, and future are equally real

Not a problem! But this changes nothing, in our own existence and experience in this universe, nor of the time travel I explained previously. The 4D model of our space supports that. The only issue is, in order to be able to perceive the 4th dimension time line in its entirety, you most likely have to be in a higher dimensional space. So, we can't do that. We don't exist in that universe.

So, if we want to play such mind games, let's do so. In order to perceive a dot (0th dimension) in space, you have to at least be a line (one dimensional object). Along that line, you can appreciate the existence of individual points.

In order to perceive a line, you have to be a plain (2D object). The plain is determined by orthogonal lines.

In order to perceive a plane, you have to be an object in 3D. The 3D object consists of different planes.

In order to perceive a 3D object, you have to travel through time (4th dimension), or that 3D object is frozen. For example, you can't move around it, to see that it is a 3D object, without moving along that 4th orthogonal axis.

And, in order to perceive the entirety of a 4D object, such as the entire lifetime of that cube, in one fell swoop, you have to be up at the 5th or higher dimension.

Mind games, philosophical, which in no way contradict special relativity or time travel to the future, for 4D objects such as ourselves.

On one final note, however, I must take strong exception to your casually dismissive attitude toward the role of philosophical thinking in science.

Well, I get that reaction a lot from philosophers, who however are equally dismissive of hard science, as you were here. I do have issues with the philosophical approach, because it has a habit of building arguments upon tenuous or faulty foundations. For example:

Plato claims that the human "soul" is composed of three parts: the rational part, the spirit part, and the appetitive part. From this claim, he concludes any number of things. Including that the three parts of the soul must be in harmony, for strife or evil to be avoided.

So of course, a student of philosophy must be able to reconstruct these arguments, attributable to Plato, and maybe compare them with other models of "the soul," proposed by other philosophers.

Good so far. Now show me proof that this isn't all bunk. In science, that initial hypothesis, that a "soul" even exists, let alone that it is composed of three parts, has to be verified first, before you can generate that long list of conclusions. Conclusions based on faulty hypotheses are also going to be faulty. So for example, heavy objects do not fall to earth faster than light ones. Not because of their weight, at any rate. In spite of what philosophers claimed, for centuries. Or for that matter, another cheap shot, many religious people consider homosexuality to be evil. And yet today, we understand that some people are born homosexual, it has nothing to do with "three parts of the soul not being in harmony," and to boot, most people don't consider it evil anyway. So, what does that do to Plato's explanations?

In general, just because someone can make an argument that sounds logical, or seems to support what we experience around us, does not make it fact. It could be nonsense. And yes, Einstein made some such philosophical mind exercises, but he fully admitted they needed to be put to the test first, because they could be totally wrong. Indeed, his special relativity theory was one such, and indeed, many years later, actual experimentation show it to be quite valid, so far (even while there are many physicists bent on poking holes in it). That's the only reason I posted those quantified examples. Otherwise, I would have said, "Once upon a time," to begin the explanation.

Here's a pure mind game, to support space travel across extremely long distances, with the use of wormholes. This is philosophy and not science. What I posted previously was science, demonstrable by theories that have been validated.

So, assume you are a two dimensional being, living in a flat plane. The universe you perceive is this flat plane, with any number of objects in it.

Unbeknownst to you, because you live in 2D space, is that this flat plane you live in is actually a shower curtain. You know, with folds along its length.

Someone asks you how fast you can get to some location in that flat surface, and the best you can do is t = d/r, along the shower curtain, up and down along each fold.

And yet, a 3D object would say nonsense, I can do that a lot faster, and simply jump over all of the curves of the curtain, taking a shortcut to the destination point on the curtain.

Now, by extension, think of a way for us to jump across "folds in space-time," so that we can reach point B in much less time than it takes with our normal way of traveling, along the fourth dimension, through 3D space. That shortcut is a wormhole. And this explanation is pure conjecture, much like Plato's soul that consists of three parts.

Dear JCN

I like your quote of Schopenhauer: "The task is rather to think what no one yet has thought about that which everybody sees."

Yet, for time it is the opposite. No one can see time or prove its existence physically, but most of the people still hold the firm belief that they have time in hand.

Dear Ligen,

Although the existence of time is challenged by very few people as you mentioned, it's not necessarily the main stream. Those sound more philosophical than scientific.

Regarding your statement "No one can see time or prove its existence physically, but most of the people still hold the firm belief that they have time in hand", I guess the notion of time that you referred is different from the notion of time that people around the globe know and understand. For normal people with no advanced background, we all are happy to know that, the sun is at the highest (or almost) at noon time, and there is no sun at night time. That's the common notion of time. To travel from a place to another place, normal people know that it will take some time, it can be slow or fast depending on how to travel (foot, bus, train, car, plane).

Dear Quan

Thank you for reading my comment. In my understanding, time is a highly abstracted conceptualization of one feature of all the the physical existence, the change of physical existence, and leaving out other features of the physical existence like color, smell or hardness of the physical existence. time is so highly conceptualized that it even leave out the difference of the changes of each physical object (for example the change of a clock is not the same like that of the sun, and the change of both of them is not the same as the change of moon.

This high conceptualization is very useful, because it make the comparison possible, otherwise we don't have any method to compare the change of an apple to the change of an orange.

So time is a conceptualization of one feature of physical existence, and it is not physical existence by itself.

Albert Manfredi ,

Our different views here ultimately may be irreconcilable, but this need not be the case, in my opinion. I fully understand the concept of time dilation. Traveling clocks give readings that are different from the readings of stationary clocks. I have absolutely no problem with that; it has been amply demonstrated in endless tests to be true. We have no quarrel there.

On the other hand, I've seen no evidence that you've made any serious attempt to understand where I'm coming from or to understand the arguments I've made in the several essays to which I've referred you. All I seem to hear you saying is that it's a waste of time (yours or anybody else's) even to consider a logical argument that leads to a conclusion different from your own. After all, there is absolutely no way you could possibly be wrong, because your arguments are rooted firmly in well established, thoroughly tested and experimentally validated hard science rather than in fuzzy-headed wool gathering.

That certainly sounds convincing, I must admit, but I suspect it is not the full story. I fear that you (and many others) have been blinded by relativity's amazing and unquestioned success to the possibility that it is an incomplete theory and that it may not have all the answers that science ultimately needs. Look at the failure of science to reconcile general relativity and quantum mechanics, for example.

It is my view that time travel involves traveling from one particular time to another. Moreover, as I hope I've explained clearly and logically in my various essays, particular times are identically equivalent to, and are completely defined by, and only by, particular configurations of the universe, and, moreover, they have virtually nothing whatsoever to do with the readings of wristwatches, clocks, or calendars (aside from the fact that these things form parts of a configuration of the universe).

I hope you might entertain the notion that this view (which I arrived at after more than 50 years of study on the topic) could be worth a moment of your time to consider fairly and without prejudice.

Cheers,

J. C. N. Smith

@J.C.N. Smith

Why do U think Manfredi has ignored your arguments?

JCN,

Traveling clocks give readings that are different from the readings of stationary clocks. I have absolutely no problem with that; it has been amply demonstrated in endless tests to be true. We have no quarrel there.

And yet, even though I explained how this phenomenon creates time travel to the future, and quantified my points (as opposed to just generating more words), you responded that this is not what you consider to be time travel. Get in machine, set controls, and in months you are two decades in the future, most people would call that time travel. Explain why you don't.

It is my view that time travel involves traveling from one particular time to another.

Exactly as I described. In one of my examples, which I repeat here, in bold font, as you must have missed it. (This trip starts in July of 2019, but I ignored acceleration and decelerations times, in this quick example.)

Or work it the other way around. You want to end your journey on Christmas Day of 2055, for some reason. And you want to limit your travel time to one year. So, you want to go 36.4583 years to the future, in one year. For that, you have to travel at 0.9996238c. You picked the destination, now you need to watch your speed and time at that speed.

This responds to your questions of how you determine the time (or date) at which you journey is supposed to take you. No, there are no road signs, but there is the clock inside your vehicle. That's how you determine when you have arrived. Time travel, any way you want to define it.

@ Alfred Manfredi

Time travel to future or past is impossible. You are not going to be able to get in a machine (which doesn't exist), set controls to take U somewhere in future, and go there..

Virgil, impossible is overstated. It might be impossible to go to your local Walmart and buy a "time machine," I agree, but that doesn't make going to the future faster than other people "impossible."

I would only agree to the extent that significant time travel to the future is not currently possible, because we do not have the motive force available, to reach speeds close enough to c to make it impressive. But the equation for time dilation is this:

t = to / sqr(1 - v2 / c2)

First thing to notice is, any amount of v > 0 will dilate time. Unimpressive perhaps, but even astronauts who've been in space have gone some tiny amount to the future, compared with the rest of us. So all we are really talking about here is impressive vs barely noticeable. But not "impossible."

t/to is the expression that shows how far you want to travel to the future, in how much time. For example, if you want 1 year of travel to take you 25 years to the future, then t/to = 25. Or, if you want 6 months of travel to take you 25 years to the future, then t/to = 50.

Now use your high school algebra, and solve that equation for v/c. That expression, v/c, will indicate at what fraction of c you have to travel, for the year, or the 6 months, or whatever travel time you decide, in order to reach that date in the future.

Aside from the engineering problem of getting close enough to c to make this impressive, there's nothing impossible here. If I have a modest goal, like a few days to the future, even two weeks, after a couple year journey, that might be possible in a few decades. (You will discover that for impressive jumps, v/c ends up being a string of two or more 9s, as I showed previously. Oh, and not to forget, mass increases by the same factor as time dilates. Lots of mass to accelerate, as you approach c!)

The effect has been demonstrated, with clocks in orbit and with very short-lived subatomic particles, accelerated to ridiculous speeds through collisions, which allows them last longer than they otherwise would. So, that factor, so-called "gamma," is not make-believe, it's not just an ocean of words, it's not just a mind game, it's something which has been verified.

http://alternativephysics.org/book/TimeDilationExperiments.htm

I think the problem people are having is appreciating what time dilation does.

Dear J. C. N. Smith

Can you give a short summary of what you want to share with the readers of this thread? It would save time for all of us from long essays.

Nothing is impossible!

Dr Kamath Madhusudhana.

Albert Manfredi

Get in machine, set controls, and in months you are two decades in the future, most people would call that time travel. Explain why you don't.

While you are sitting in your time machine looking at your clocks, and while your friends are staying behind looking at their clocks, the rest of the universe is continuing to evolve just as it would if you and your friends weren't doing any of this. Your machine -- regardless of how cleverly crafted -- will not cause every other portion of the entire universe to evolve at a rate any differently than it would if you and your machine and your friends weren't doing any of the things you were doing. So at the end of your "journey" you may find that your clock and the clocks of your friends are not in agreement, but in the meantime, while you were "traveling" in your machine the earth will have continued to revolve around the sun at a rate of one revolution per year, and the Andromeda Galaxy will have continued steadily along on its collision course with our Milky Way Galaxy.

Is it your belief that "traveling" in your machine would somehow dramatically alter the evolution of all of these larger, infinitely vast portions of the universe? Unless that were indeed the case, you will not arrive at a "destination" in which the configuration of the universe at large will have evolved at a rate any different from the rate of one revolution of the earth around the sun per year. The only "clock" that really matters here in this regard is the universe at large.

What we perceive to be the flow of time is, in reality, nothing more and nothing less than the evolution of the physical universe, an evolution governed by rules that we strive to understand and which we refer to as the laws of physics. Much as we might like to believe otherwise, it's my view that we and our puny machines -- regardless of how cleverly crafted -- will not succeed in dramatically altering the evolution of the universe at large. That said, we certainly can (and inevitably do) influence the evolution of our immediate surroundings in purposeful ways, but only at a rate of one revolution of the earth around the sun per year.

J. C. N. Smith

Quan Hoang Nguyen

Can you give a short summary of what you want to share with the readers of this thread? It would save time for all of us from long essays.

With all due respect to you and to other readers of this thread, sir, it has taken me more than 50 years of reading, studying, and thinking to arrive at my current views on this topic. I believe that you could read my essay 'Time: Illusion and Reality,' ( https://sites.google.com/site/smithjcn/time ) and my essay 'On the Impossibility of Time Travel,' ( https://fqxi.org/data/essay-contest-files/Smith_IOTT6.cwk.pdf ) which -- together -- lay out the gist of my thinking, in a matter of only one or two hours or even less. I can understand your eagerness and desire for instant gratification on these points (it seems we never have enough time to do everything we want to do), but I must respectfully ask that you set aside the necessary time and do the reading.

Thank you!

J. C. N. Smith

The link with SS posts https://www.researchgate.net/post/Who_says_that_cauzation_backwards_in_time_is_impossible_Classical_mechanics_The_relativity_theory_Is_there_a_proof#view=5d217893661123b0ea4114e3 where the what is Time? problem is briefly, but substantively enough, is explained, now, after some animate posting of some members, who by some unknown reasons don’t like Time and so claim that poor Time doesn’t exist, is outside the visible page. However the posts in a few mouse clicks are accessible.

Besides some introduction in the Time problem see the SS post in https://www.researchgate.net/post/What_is_the_most_precise_definition_of_time_And_what_is_the_easiest_way_to_describe_time

Cheers

Thanks J. C. N. Smith and Sergey Shevchenko . Would appreciate if you could give a summary of the points you want to share in this thread.

Here is an useful article to have a basic idea that scientific conceptions, facts, hypothesis and theories are not natural reality:

Significance of a conceptualized and formulated hypothesis in thinking through Research:

http://www.abhijna-emuseum.com/articles/significance-of-a-conceptualized-and-formulated-hypothesis-in-thinking-through-research/

Both facts and concepts are abstractions and have meanings only within some frame of reference or theoretical system. 

JCN,

While you are sitting in your time machine looking at your clocks, and while your friends are staying behind looking at their clocks, the rest of the universe is continuing to evolve just as it would if you and your friends weren't doing any of this. Your machine -- regardless of how cleverly crafted -- will not cause every other portion of the entire universe to evolve at a rate any differently than it would if you and your machine and your friends weren't doing any of the things you were doing. So at the end of your "journey" you may find that your clock and the clocks of your friends are not in agreement, but in the meantime, while you were "traveling" in your machine the earth will have continued to revolve around the sun at a rate of one revolution per year, and the Andromeda Galaxy will have continued steadily along on its collision course with our Milky Way Galaxy.

And, while the rest of the universe did exactly as you describe, oblivious perhaps that you even exist in this space capsule, traveling at very high speeds, and generations of people went thought their entire life cycles perhaps, in your space capsule, only (say) 24 months passed. You slow down, land, and the entire world has changed.

Is it your belief that "traveling" in your machine would somehow dramatically alter the evolution of all of these larger, infinitely vast portions of the universe?

Not my belief. Yours, perhaps. Even in your essay, you had this notion that the universe had to "rearrange" itself. It does not. You are getting lost in thought, and draw conclusions that need not be valid. Simply, your own time, at speeds close to c, became dilated, compared with the rest of the universe. The rest of the universe does not care, and is not affected, and goes along as it always did.

Just like, you go on a trip away from home. It does not change the daily events at home. You are not there, and no one else needs to care.

The only "clock" that really matters here in this regard is the universe at large.

Not to you. To the rest of the universe, sure. To you, your own clock is incredibly important. In fact, you even asked yourself, how do you know where to go in this time machine, to get back to the dinosaurs. Well leaving aside that time travel to the past is not clearly feasible that we know, yet, you know where to end up by watching your own clock and your own speed (compared to c). And we know, thanks to Michelson and Morley's experiments, that your own speed compared with c is independent of how fast you are traveling in this capsule. This c is constant in any frame of reference.

What we perceive to be the flow of time is, in reality, nothing more and nothing less than the evolution of the physical universe, an evolution governed by rules that we strive to understand and which we refer to as the laws of physics.

What we call time is an appreciation of the natural cycles the ancients measured, for night and day, and for the seasons. Natural cycles that the ancients discovered were predictable. They divided these up into day/night cycles, subdivided those day/night cycles into hours and minutes and seconds, accumulated the seasonal cycles into years, subdivided these into months, weeks, and days. That measurement is what we call time. A "clock," since you did ask what it was, is merely a mechanical device that keeps track of the natural cycles the ancients quantified. (Obviously, had we evolved in a different planet, our time measurements would be different - dependent on the natural day/night and seasonal cycles of that world. No big deal. They would still be predictable.)

What you are missing here is that this definition and quantification, of the natural repetitive cycles, is distorted when the particle, or the space capsule with person in it, travels close to this weird speed called v = c.

No matter what words you might dream up, the duration of events in the universe outside remains the same. The duration of events apparent to the particle or person traveling at these high speeds also seems to remain the same, to that particle or person. He still shaves every 24 hours, by his clock, gets hungry at the same intervals and eats meals, and so on. The mechanical contraption called "clock" seems to say that everything is as it always was.

And yet, surprise surprise, everything outside this capsule, the rest of the universe moving at much lower speeds, has aged considerably during your trip.

No, it did not rearrange itself, or need to accommodate your trip. Not a bit. The time distortion affected only you, the traveler, not the rest of the universe!

Dear Quan Hoang Nguyen,

“…Thanks … Sergey Shevchenko . Would appreciate if you could give a summary of the points you want to share in this thread.……”

The summary of the points that relate to the phenomenon/notion “Time”, from which follows also that there cannot be any feasible time machine, is given in the SS posts in linked in the SS post above [22 hours ago now] threads; besides it would be useful to read at least the last SS post in the thread

https://www.researchgate.net/post/Why_is_the_notion_of_Big_Bang_inconvenient_inappropriate_for_you_question_for_physicists_chemists_and_researchers_working_in_related_sciences#view=5d2a417ca4714b7d635a8cbf

Cheers

@ Alfred Manfredi

Your last post to JCN Smith shows that you don't understand his arguments. Read his article about time travel being impossible. He never claimed that traveling thru time would change the Universe., but that the configuration of the Universe was different at particular times and it is impossible to go from one configuration to another. He never said that the time machine would change the configuration.

@ Alfred Manfredi

Your last post to JCN Smith shows that you don't understand his arguments. Read his article about time travel being impossible. He never claimed that traveling thru time would change the Universe., but that the configuration of the Universe was different at particular times and it is impossible to go from one configuration to another. He never said that the time machine would change the configuration.

Virgil,

Your last post to JCN Smith shows that you don't understand his arguments. Read his article about time travel being impossible. He never claimed that traveling thru time would change the Universe., but that the configuration of the Universe was different at particular times and it is impossible to go from one configuration to another.

This is what JCN claimed in the recent post:

Is it your belief that "traveling" in your machine would somehow dramatically alter the evolution of all of these larger, infinitely vast portions of the universe?

The answer is no, it is absolutely not my belief that if time is dilated inside my super-fast space capsule, that anything in the vastness of the universe has to be "altered."

This is what JCN wrote previously:

Your machine -- regardless of how cleverly crafted -- will not cause every other portion of the entire universe to evolve at a rate any differently than it would if you and your machine and your friends weren't doing any of the things you were doing. So at the end of your "journey" you may find that your clock and the clocks of your friends are not in agreement, but in the meantime, while you were "traveling" in your machine the earth will have continued to revolve around the sun at a rate of one revolution per year, and the Andromeda Galaxy will have continued steadily along on its collision course with our Milky Way Galaxy.

Correct, and I never claimed otherwise, even though JCN thinks he's found some logical impasse in my points. He didn't. The clock inside my capsule, as well as the clocks inside other moving vehicles, are the only ones that are getting out of synch with the clocks which are "at rest."

This is what JCN claims in his essay (link provided in a previous post):

If then, as we have proposed, a particular time is identically equivalent to, and is completely defined by, and only by, a particular configuration of the universe, it follows logically that time changes if, and only if, the configuration of the universe changes.

No, inside the space capsule, time is defined by its internal clock, not the clock which defines passage of time for objects at rest, or clocks in vehicles traveling at other speeds, elsewhere in the universe. Throughout the universe, the clocks in all moving platforms will get slowly out of synch with the clocks "at rest," depending how fast these other bodies are moving. All depends how close these moving bodies are to v = c. And by the way, the "other" bodies can be entire galaxies, themselves moving at very high speeds compared to our own. (Note that JCN has also dismissed the importance of the clock inside the moving platform, saying that clock doesn't matter. And I replied, not to the rest of the universe maybe, but it sure matters to the traveler.)

This argument about a "requirement" that the rest of the universe must be "altered," is an argument JCN makes to dispute the possibility of time travel. That's why it keeps recurring. Yet, I never made any such claims, nor are they required. I've been trying to disabuse him of this obstacle.

Hey, it's not like I'm inventing this, just throwing out words with no justification. This is not a mind game. These effects have been demonstrated in actual experimentation, long after Einstein had passed away. Only to confirm, so far, what his special relativity theory claimed. Which theory, by the way, was not just a figment of Einstein's imagination either. Instead, it followed logically from Fizeau's measurement of c, Michelson and Morley's determination that c is a constant in different reference frames, and Lorentz's transformation, an algebraic exercise that provides what we need to deal with moving particles which approach c, as opposed to Galileo's transformation, the more obvious one everyone can understand, for objects traveling at v

I did not see where JCN ever said the Universe had to be altered. He said it was already altered because configuration is different at different times. One thing he did not say, which I say, is that nobody will ever be able to construct a machine which can travel at v.= 0.9999c

I did not see where JCN ever said the Universe had to be altered. He said it was already altered because configuration is different at different times. One thing he did not say, which I say, is that nobody will ever be able to construct a machine which can travel at v.= 0.9999c

Time-travel to the future is what everyone in this discussion does with a speed of 24 hours per day. Speeding this up by moving close to the speed of light has nothing with time-travel to do... because for the "traveler" alone time is going slower... seen from the outside time is running as it has to... it's an illusion for the traveler, because his time was running slower for a while... traveling to the past is "not even nonsense" and not worth discussing...

Seriously discussing time travel is for dreamer only... and a terrible waste of time. We will never be able to reach velocities that produces time dilation great enough to produce a serious illusion of time-travel... it is very doubtful that living creatures can live at a speed close to the speed of light.

Dear Berndt,

Thanks for your valuable discussions. If a traveler (say, an astronaut) moves at a high speed, will the traveller's bio clock will move slower? Do you know any convincing arguments that is or is not feasible?

Time as it is will run slower, that includes your biological clock, apart from that are the spatial dimensions shrinking, the density of mass is increasing... not the mass. At the speed of light mass is transformed to pure electromagnetic energy, how will you reverse that process ? So at a certain speed living creatures will die.

Think about this:

1. The distance in time between two dead persons is forever constant ! Right ?

2. The distance between a living and a dead person is increasing with 24 hours per day ! Also right ?

3. When you reach the speed of light you move compared to a dead person with constant time difference ! ! ...and 1. tells you what that means to you. Still true ?

When you think about this for a while, looking at the light you are reflecting into space... compared to the light a dead person once reflected to space... you will find that 1. 2. and 3. are unavoidable for you...

So... what do you now think about time machines ?

Albert Manfredi

First, thank you for your very well thought out and clearly stated reply to my previous comment. Much appreciated! Simply, your own time, at speeds close to c, became dilated, compared with the rest of the universe. The rest of the universe does not care, and is not affected, and goes along as it always did. Thank you; this helps. I agree that the clocks and other physical and biological processes (which are also a form of clock) of the traveler near the speed of light will slow relative to the processes of the non-traveling portions of the universe, which, as you said, will go along as they always do.

I'm becoming cautiously optimistic that we may be converging -- albeit gradually -- on an understanding of one another's points of view on this topic. For example, I think we both agree that the "future" arrives one day at a time, for the traveler as well as for the non-traveling ("at rest") portions of the universe. And I think we agree that the "days" of the traveler proceed at a rate different from the "days" of the non-travelers. And, I believe (you may disagree here), it is this difference that creates the "illusion" of time travel.

Let us look at a specific "twins" example to put some flesh on these ideas. Let us say hypothetically that an aspiring time traveler gets into his marvelous machine at some arbitrary "Time A," which, I maintain is defined by, and only by, some particular configuration of the universe. Present at the auspicious occasion of the traveler's sendoff is his incredibly healthy identical twin who decides to stay behind. The traveler blasts off and (let's skip the details of how he does it) accelerates to a velocity closely approaching the velocity of light. The traveler and his machine and his twin are all small portions of the evolving universe. As you said, "The rest of the universe does not care, and is not affected, and goes along as it always did."

Now, at some point in his journey, the traveler decelerates and returns to the point on the earth from which he departed on his journey. He arrives there at some particular "Time B," which, I maintain is defined by, and only by, a configuration of the universe that will necessarily be different from that at the Time A of his departure. Fortunately, the stay-behind twin is there to greet the traveler upon his return, and they have a joyous reunion and compare notes. The stay-behind twin says that the earth has revolved around the sun 75 times since his twin began his journey. The traveling twin looks at his clocks and says that he has been away for only some small fraction of that time. He looks like a much younger man than his stay-behind twin, because his biological functions, like his clock, have slowed relative to those of the non-traveling twin.

But did the traveling twin actually accomplish the illusive feat of "time travel"? Did he travel into the "future"? Yes, of course, but -- and here is the crux of the matter -- he traveled in time only to the same extent as his non-traveling twin. They both have ended up celebrating together at the same Time B, a configuration of the universe in which the earth has revolved around the sun 75 times (among countless other changes) since the traveler departed on his journey.

In essence, the "time machine" might be described more accurately as an "anti-aging machine." Space adventurers whose goal is to travel to distant parts of the universe could use the machine to retard their aging during their long (from the standpoint of stay-behinds) journey. They conceivably could arrive at some particular future Time C configuration of the universe long after their stay-behind colleagues had passed away due to old age. If this is what one chooses to define and describe as "time travel," then so be it.

This same reasoning further explains why "time travel" to the past is absolutely not possible. The configurations of the universe that define particular times in the past have evolved -- courtesy of the laws of physics -- into subsequent configurations. Previous configurations such as those that included dinosaurs on our planet, for example, simply no longer exist. Anywhere. Period. We simply cannot "travel" to something (i.e., to a configuration of the universe) that no longer exists.

I hope this helps clarify my view, and I look forward to reading your thoughts on why I'm wrong. :-)

Cheers,

J. C. N. Smith

Not feasible

Two SS posts in the thread https://www.researchgate.net/post/Why_is_the_notion_of_Big_Bang_inconvenient_inappropriate_for_you_question_for_physicists_chemists_and_researchers_working_in_related_sciences#view=5d2a417ca4714b7d635a8cbf

are relevant to this thread’s question.

Cheers

Many persons travel in Time and are not aware of that because ... Modern Science do not allow such understanding as well Einstein Theory consider is not possible.

... I will not give you too much now ... but some persons can watch the Entire neighbor Galaxy in all its beauty and this means you travel many Light years ... now this do not means you use a ship or a machine ... but was only your consciousness ...

Virgil,

I did not see where JCN ever said the Universe had to be altered.

Again, quoting JCN:

If then, as we have proposed, a particular time is identically equivalent to, and is completely defined by, and only by, a particular configuration of the universe, it follows logically that time changes if, and only if, the configuration of the universe changes.

This is used as proof that time travel, therefore, cannot happen. It is a form of reductio ad absurdum, used in philosophy.

nobody will ever be able to construct a machine which can travel at v.= 0.9999c

"Never say never" comes to mind. But more importantly, as I already pointed out, any v > 0 causes time dilation, and hence, travel to the future, according to special relativity theory. Doesn't have to be a string of 9s. A few weeks is possible at 0.2c, for instance.

The only way to dispute any of this, credibly, without just claiming "it's impossible," is to discredit special relativity entirely. Which people keep trying to do, don't get me wrong. So go ahead and dispute that, and then explain away all of the experimental evidence.

JCN,

And I think we agree that the "days" of the traveler proceed at a rate different from the "days" of the non-travelers. And, I believe (you may disagree here), it is this difference that creates the "illusion" of time travel

Okay on this, other than, as you already guessed, the use of the word "illusion." I do think we are converging, though. Yay!

He looks like a much younger man than his stay-behind twin, because his biological functions, like his clock, have slowed relative to those of the non-traveling twin.

Yes, and this is demonstrated when those subatomic particles, mentioned previously, last six or seven times longer that they otherwise would have, had they not been accelerated to such high speeds.

and here is the crux of the matter -- he traveled in time only to the same extent as his non-traveling twin. They both have ended up celebrating together at the same Time B, a configuration of the universe in which the earth has revolved around the sun 75 times (among countless other changes) since the traveler departed on his journey.

Let me put it this way. The twin on the fast space capsule celebrated, say, two birthdays, following his calendar and clock on board, and his natural aging process, while the twin at rest celebrated 75 birthdays.

In essence, the "time machine" might be described more accurately as an "anti-aging machine."

Absolutely, yes. How else to describe time travel to the future? But let's be careful. We aren't just talking about skin care lotions here. We are talking about actual aging process. The traveler perceives normal time passage, but it is totally out of sync with what's going on outside.

This same reasoning further explains why "time travel" to the past is absolutely not possible.

The problem here is "reasoning." Our "reasoning" alone did not determine that time dilation was possible, or Isaac Newton, and never mind ancient philosophers, would have mentioned it. But at least, we can agree that time travel to the future (aka "anti-aging") was demonstrated, and it does not pose any particular logical obstacles, after we accept that special relativity seems to be real. (Some people don't, of course, and that's what's wonderful about science. Always someone out there saying "BS," to anything assumed true by anyone else.)

Time travel to the past would require discoveries not yet made, and would result in an update to our "intuition." Which happens all the time, with gaining knowledge. Hence, the continuing search for tachyons. And adjusting your words previously, time travel to the past can otherwise be called "anti-rejuvinating process?" Travel through time without becoming younger. But that's pure speculation.

People used to proclaim all sorts of nonsensical things, about topics no one even questions today. As I mentioned previously, the speed at which object fall to earth is a cheap example.

Dear @Ar .Saravanakumar,

Thanks for your discussion. It'd be appreciated if you can add more details.

Dear Berndt,

Please see recent discussions by Albert for some examples of speed. We don't need to travel at the speed of light. The question is also not restricted to humans. Can we place any physical items into the past or future?

Albert, agree with you. That's the question about bio clock I'm asking Berndt Barkholz.

--- you wrote --

"Yes, and this is demonstrated when those subatomic particles, mentioned previously, last six or seven times longer that they otherwise would have, had they not been accelerated to such high speeds. ....

The twin on the fast space capsule celebrated, say, two birthdays, following his calendar and clock on board, and his natural aging process, while the twin at rest celebrated 75 birthdays."

Following..discussion....

Dear Friends ... I will tell you something more ...

The Universe is NOT a Space ... to be traveled with a rocket using Liquid Nitrogen and the NASA or ESA begin a countdown ... 9, 8,7 ... 0 ... Engine! ... No!

The Universe is a Time ... and still an Exta (an infinitesimal or millionth bit of the Electron) ... Now also the Electron has consciousness ... as well the Atom and all life.

An Electron that travel from Saturn to the Moon or Venus ... has performed a Time Travel ... and not necessarily at small speeds or the speed of light (c=300,000 km/s) ... may be at 10,000 c ... or less ... or higher 1,000,000 times c ...

Therefore the answer "Is Time travel possible?" ... is an excellent question its answer affirmative but the frames ... around the question are distorted by an Empirical Physics ... tailored by an Empirical Math ...

Take care,

Giovanni.

Albert Manfredi,

The problem here is "reasoning." Our "reasoning" alone did not determine that time dilation was possible, or Isaac Newton, and never mind ancient philosophers, would have mentioned it. But at least, we can agree that time travel to the future (aka "anti-aging") was demonstrated, and it does not pose any particular logical obstacles, after we accept that special relativity seems to be real. (Some people don't, of course, and that's what's wonderful about science. Always someone out there saying "BS," to anything assumed true by anyone else.)

Ah, Mr. Manfredi, my friend, (and I am beginning to think of you as a friend and fellow seeker of truth, fwiw), I fear that you dramatically and unjustly underestimate the amazing power of our "reasoning"! Contrary to what you have said, it is exactly our reasoning alone that determined that time dilation is possible! Are you suggesting that this knowledge was magically handed to us on a platter? To be a bit more accurate, it is an ongoing, ever growing chain of reasoning that has allowed us to arrive at the notion of time dilation, along with many other amazing modern concepts that never would have occurred to Isaac Newton. Galileo and Newton and other pioneers of science forged some of the early links in this amazing chain of reasoning, and Einstein, through a stroke of brilliant, creative insight and genius forged yet another noteworthy link in the chain. In other words, he used his reasoning to determine that time dilation is possible!

In essence, the "time machine" might be described more accurately as an "anti-aging machine."

Absolutely, yes. How else to describe time travel to the future?

Here is how I would describe meaningful time travel: you or I or anyone else somehow would be able to experience valid configurations of the universe (i.e., configurations that represent a part of the natural evolution of our universe) that are dramatically removed (either prior to or subsequent to) the configuration in which we currently find ourselves, and then (and here's the kicker) be able to return to our starting point (our Time A or very close to -- within a few years of -- our Time A) and describe to our contemporaries what we had experienced in some arbitrary Time X, Y, or Z that would be perhaps thousands of years (i.e., revolutions of the earth around the sun) removed from our Time A. After all, if it's not "Buck Rogers," science fiction style time travel, what's the point? But then one gets into all sorts of paradoxes about killing one's grandfather, etc., which, I agree, quickly become philosophical nonsense and give all of philosophy and all of time travel (at least to the past) a bad name.

If we can agree that our universe is in fact "real," and if we can agree that it is in fact evolving according to rules governed by the laws of physics, then I think we should be able to agree that the configuration that existed when the earth had made one fewer revolution (or any arbitrary number of fewer revolutions for that matter) around the sun no longer exists. Therefore, my "reasoning," such as it is, tells me that I cannot "go back" and experience any of those prior configurations. Those trains already have left the station. In order to experience a prior configuration one would need somehow actually to reconstruct that configuration. This is the sort of thing done in Hollywood films to create the illusion of earlier times, but I will go out on a limb here and suggest that doing this on the scale of the entire universe simply is not within the realm of possibility.

“The Moving Finger writes; and, having writ, Moves on: nor all thy Piety nor Wit Shall lure it back to cancel half a Line, Nor all thy Tears wash out a Word of it.”

― Omar Khayyám

J. C. N. Smith

@ J. C. N. Smith

Excellent summary explaining why time travel is impossible.

You can discuss each other ... and get conclusions ... but your conclusions are erroneous ... because you consider Einstein Theory ... correct.

Unfortunately ... is Wrong ... It is your choice to accept and may be you are happy with that ...

If you want to meet Time Travelers ... I can introduce many ... Take care in your confusion ...

@Giovanni A. Orlando

Your arguments don't make sense. The Universe is not time, Einstein was not wrong, you don't know any time travelers. If U are going to contribute to this discussion, at least put in arguments that mske sense, not fake, junk science.

JCN,

Contrary to what you have said, it is exactly our reasoning alone that determined that time dilation is possible! Are you suggesting that this knowledge was magically handed to us on a platter?

Well, I'd say, not at all on a silver platter. It was instead physicists, starting with Fizeau, who were able to say "bunk" to whatever the great thinkers of the past had proclaimed, based on nothing more than their (the great thinkers') internal logical thinking. So in short, every step of the way, the hypotheses had to be verified, to the best of these physicists' abilities, to see whether the natural world truly worked that way.

Thank goodness for skeptics who are also rigorous, as opposed to skeptics who are just shooting from the hip, or waxing verbose on mere feelings and intuition, or worse, religious delusions!

And as I mentioned, there are also skeptics on the whole idea of special relativity. Luckily for us today, they have to justify their skepticism rigorously too. That's why just saying "it's impossible," about time travel, is non-credible.

As to your personal definition of time travel, while it can be a valid model for science fiction, is still not one that science can clearly demonstrate is valid. It is a fictional account. Going back and forth in time, unconstrained, is still not explainable with what we know today. I do have hopes for black holes, but that's, you know, more like philosophy! But going to the future, theoretically/potentially well into the future, that's explainable rigorously enough.

then I think we should be able to agree that the configuration that existed when the earth had made one fewer revolution (or any arbitrary number of fewer revolutions for that matter) around the sun no longer exists. Therefore, my "reasoning," such as it is, tells me that I cannot "go back" and experience any of those prior configurations.

Well, I've never attempted to convince anyone that time travel to the past is explainable by actual science yet, while instead, time to the future is explainable, and demonstrable. And yet, what you say here is not absolute and ultimate fact either. We are now conjecturing.

Just because we can only perceive our four-dimensional existence, i.e. 3D space moving along this orthogonal time axis, doesn't mean that this is all there is. Mathematics can create any multidimensional spaces you can dream up. There is a possibility that the actual universe consists of more than just what we perceive, and that from a higher dimension, the entirety of an object's life cycle can be observed. That travel back and forth, along what we call the time axis, is indeed possible. Our "reasoning" is at best educated by our experiences. Our "reasoning" changes, with knowledge. But let me hastily repeat, this last bit is philosophy, not science!

Albert Manfredi,

So in short, every step of the way, the hypotheses had to be verified, to the best of these physicists' abilities, to see whether the natural world truly worked that way.

Thank goodness for skeptics who are also rigorous, as opposed to skeptics who are just shooting from the hip, or waxing verbose on mere feelings and intuition, or worse, religious delusions!

Amen; we could not be in better agreement on all of that! The scientific method is the way we advance our understanding of the universe. And I applaud philosopher Karl Popper for offering a useful way to distinguish what is science from what is not science; if there is no way to falsify a particular conjecture then that conjecture does not lie within the realm of science.

Our "reasoning" is at best educated by our experiences. Our "reasoning" changes, with knowledge. But let me hastily repeat, this last bit is philosophy, not science!

Agree! And on that note I would like -- if you are willing to do so -- to continue this discussion, but to move it into a somewhat different but tangentially related (and I hope still constructive) direction. I could be wrong, but it's my take on it that we now understand one another's thinking on the topic of time travel, and now that we've agreed to call your "time travel" device an "anti-aging" machine I have no quarrel with your view.

The direction in which I'd like to take our discussion is into the role of paradigms in shaping the direction of scientific thought. I suspect that you're familiar with Thomas S. Kuhn's seminal work on that topic, The Structure of Scientific Revolutions, which might serve as backdrop for such a discussion.

Unfortunately, time is not being my friend today, and I must break off here, but I would like to post at least this much now and hope to return to it later, if you're willing. In attempting to continue our discussion and extend it onto another topic I'm following the advice of Ray Dalio who, in his book Principles, urges people to find others who are "believable" (you certainly fit that description) and who may disagree with our views on important topics. According to Dalio (and I agree with him here) this is how we learn and expand our thinking and knowledge. Thanks.

J. C. N. Smith

Quan Hoang Nguyen, Albert Manfredi

First, let me ask Quan a question: since it was you, Quan, who started this discussion about time machines, what's your thinking about how the discussion has gone? Are there specific aspects of this topic that you'd hoped to explore that have not been discussed to your satisfaction? If so, perhaps we could take another stab at it. Otherwise, however, we may simply be guilty of beating a dead horse, as the saying goes. I suspect that we could never answer your question in a way that would satisfy everyone.

Next, to Mr. Manfredi: if you have any interest in pursuing my suggestion that we look at the role of paradigms in shaping the direction of scientific thought, perhaps we should move that discussion to a new/different thread? (I'm not even sure how we'd do that, should you agree to do so.) Such a discussion would, however, run the serious risk of veering into the dreaded domain of philosophy! Your call, of course!

As an example of the sort of thing I believe it would be interesting to discuss is the historical roles of the Ptolemaic versus Copernican paradigms of cosmology in shaping and guiding scientific thought and research. Had we persisted adamantly in sticking with the Ptolemaic paradigm how would we have managed to plan and execute missions of interplanetary space exploration? Would it even have been possible to do so? And if so, at what cost in terms of needless complexity and difficulty? What, exactly, were the factors that finally tipped the scales in favor of the Copernican paradigm?

Truth in advertising forces me to acknowledge, however, that my ulterior motive is to steer the discussion in such as way that we ultimately would arrive at what I believe is the urgent need for a rethinking of our currently prevailing paradigm for the nature of time, a paradigm that has left us with a long-standing, seemingly irreconcilable disconnect between general relativity and quantum mechanics, which, I believe you might agree, is a scientific problem, but one that is not without philosophical overtones as well. Should you have any interest in my thinking on that topic you'll find a bit of it in my essay 'Toward a Helpful Paradigm for the Nature of Time,' ( https://sites.google.com/site/smithjcnparadigm/ ).

J. C. N. Smith

Dear ... J. C. N. Smith ... and other colleagues ...

We are not beating a dead horse (Time Travel) because the environment of post-and-answer is inconsistent ... not valid ... Is the Science (Actual Science) proven by Gödel's incompleteness give us a view ... and also Gödel's Prove Einstein Universe cannot have Time ...

Are there a Time? ... Of Course there are a Time ... therefore Einstein Theory is wrong ... the Twin Paradox is invalid there are no Paradox ... and Time Travel are perfect possible.

I just make you a favor ... showing another direction ...

Take care ... and have a nice Week-end,

Thanks,

Giovanni.

JCN,

if you have any interest in pursuing my suggestion that we look at the role of paradigms in shaping the direction of scientific thought, perhaps we should move that discussion to a new/different thread? (I'm not even sure how we'd do that, should you agree to do so.) Such a discussion would, however, run the serious risk of veering into the dreaded domain of philosophy!

Indeed, it's a big risk! If you want answers that reflect the natural world, as opposed to arguments that are only consistent internal to themselves!

As an example of the sort of thing I believe it would be interesting to discuss is the historical roles of the Ptolemaic versus Copernican paradigms of cosmology in shaping and guiding scientific thought and research. Had we persisted adamantly in sticking with the Ptolemaic paradigm how would we have managed to plan and execute missions of interplanetary space exploration? Would it even have been possible to do so?

No, because it was too inaccurate. Orbits are not circular, the earth is not the center, so errors kept going up, in that Ptolemaic model. Plus, the location of these heavenly bodies becomes a nightmare to compute, when you start with the wrong premise.

Philosophy and religion are not so different. Copernicus knew to keep his discoveries a secret, until the very end of his life. A decent indictment of a non-scientific society, eh?

Dear J. C. N. Smith and Readers,

Thanks for your discussions. I believe this is still an open question, so all opinions and discussions are welcome, as long as they are constructive and straight to the point.

It'd be good if one can give a short (yes, short) summary of the point you want to argue in favor of or against the existence of such a time machine. Some gave external links (which are good for discussions) and long essays with multiple items to be discussed, which in general are not so easy for readers to follow.

Okay, Quan, here's my short summary:

Time travel to the future is possible even today, but unimpressive. Maybe a few seconds at most, for astronauts. Impressive time travel to the future is theoretically possible, assuming the validity of special relativity theory (which, so far, is proving valid), but it would require engines we do not yet have. Huge amount of power, to reach velocities close enough to c.

Time travel to the past, best we know today, is not possible. Black holes might provide some better insight, however.

Albert Manfredi Thank you.

@ Albert Manfredi.

I don't think we get ever make machines that can travel at speeds near c. So as practical matter, time travel to future is impossible.

Virgil Matthews Can you add some details?

Dear Virgil Matthews and Readers,

Albert has shown a few calculations at the speeds much smaller than c (e.g., v= 0.1c, v= 0.2c). Virgil, what is the speed you may want to work out with Albert?

Time Travel happens at speed about 10,000 c ... or 10x10x10x10=10^4 times c ... where c is 300,000 Km/s ... not fractions of c ... forget ... Please 🙏 ... You will necessarily travel in Time with a vehicle ... Einstein Equations prove is impossible ... See Book Gravitation book - Charles W. Misner, Kip S. Thorne, and John Archibald Wheeler (1973) ... Exercises 6.1-6.2-6.3 ...

The World is not ready to travel Space ... NASA is at the level of Kindergarten Physics ... 9...8...7...6 ... Jajaja ...

You do not necessarily will travel in Time ONLY in Physical mode ... this is almost impossible ... today ...

Scotty, Beam Me Up! ... 🛸 ...

@Giovanni A. Orlando

If takes speeds much > c , you are right. Why do U keep mentioning NASA? Are they only ones capable of trying to build time machines?

@ Quan Hoang Nguyen

Cannot do it at speeds 0.2 or 0.3c. Need speeds at least 0.9c or even greater than c, which are impossible.

Dear Virgil Matthews ... No N.A.S.A. is not the only ...

There are also E.S.A. ... I confess ... I ...

... Leaving Sacred Irony ... before to figure Space Travel ... we need to return to have fast Air-transportation ... I mean Super-sonic like the Old Concorde ... The idea is to travel at the speed of Earth Rotation ... will be sufficient ... from a book I am working on ... "At the equator, the circumference of the Earth is 40,070 kilometers, and the day is 24 hours long so the speed is 1670 kilometers/hour (1037 miles/hr). This decreases by the cosine of your latitude so that at a latitude of 45 degrees, cos(45) = .707 and the speed is .707 x 1670 = 1180 kilometers/hr. You can use this formula to find the speed of rotation at any latitude"

Time machine is feasible only in movies

Albert Manfredi,

Indeed, it's a big risk! If you want answers that reflect the natural world, as opposed to arguments that are only consistent internal to themselves!

You appear to believe that answers that reflect the natural world and answers that are consistent internal to themselves (which, by the way, perfectly describes the internal consistency of relativity) are mutually exclusive. I would maintain that there might be answers that would both reflect the natural world and be consistent internal to themselves. Answers need not be only one or the other.

No, because it was too inaccurate. Orbits are not circular, the earth is not the center, so errors kept going up, in that Ptolemaic model. Plus, the location of these heavenly bodies becomes a nightmare to compute, when you start with the wrong premise. [bold emphasis added]

So it appears to be your view that starting with the wrong premise (the wrong paradigm of cosmology) ultimately would doom efforts to plan and execute missions of interplanetary space exploration using the Ptolemaic paradigm (premise). In just this same way, I would like to suggest that starting with the wrong premise (paradigm) for the nature of time will continue to doom efforts to merge general relativity and quantum mechanics. As you certainly must know, the best minds of science have been working on this problem for nearly a century now. Given this indisputable fact, is is then still totally inappropriate and beyond the pale at least to question whether the problem conceivably might lie in the premise from which these giants of science (including Einstein, among many others) began their quests? Or, alternatively, perhaps all these great scientists simply have not been up to the task? That's certainly one possibility.

Your disdain for philosophy, which appears to verge almost on a form of fear, is interesting! It's almost akin to a fear we might have of walking too near a barnyard lest the scent of manure linger on our clothes next time we meet with our cultured city friends. Fortunately, some well-respected scientists do not share this aversion to philosophy. In fact, the well-known and well-respected theoretical physicist Lee Smolin has even gone so far as to co-author a book with philosopher Roberto Mangabeira Unger: The Singular Universe and the Reality of Time: A Proposal in Natural Philosophy.

One section of that book is titled 'Reinventing Natural Philosophy,' in which the authors write: "We seek here to recover, to reinterpret, and to revise a way of thinking and of writing that has long ceased to exist. It used to be called natural philosophy. Up to the middle of the nineteenth century, natural philosophy remained an accepted genre. It gained a brief after-life in the work of Mach and Poincare in the early twentieth century and continues today to be represented chiefly in the writings of philosophical biologists." Later, they add "What is at stake in the argument of this book is the future of ideas that have shaped both how we do science and how we interpret the meaning of some of its major discoveries." [bold emphasis added]

So even if you walked through a barnyard and a little philosophy got stuck to your shoe it wouldn't be the end of the world. You could scrape it off before being seen by any of your friends.

J. C. N. Smith

J.C.N. Smith

What has your reply to Manfredi about nattural philosophy got to do with original question about time travel?

Virgil,

Cannot do it at speeds 0.2 or 0.3c. Need speeds at least 0.9c or even greater than c, which are impossible.

Speeds of 0.2c are supposed to be possible with matter-antimatter engines, if you look it up. Which should be doable in a matter of decades, you should find in your research. With that speed, the algebra tells us that significant (if not impressive) time travel can occur. I mean, if you go on a trip, and come back home two weeks in the future of where you wound have been, that's nothing to sneeze at.

Obviously, it is more impressive to come back a generation later. But 2 weeks puts a complete kibosh on this idea that time travel is "impossible."

Look at the equation for gamma. There is no "minimum speed" below which time does not dilate. Any speed dilates time, even if by only a minuscule amount..

There's a reason why the French have a saying, "Impossible n'est pas Français."

@ Alfred Manfredi

I don't consider 2 weeks into future to bewhat we are talking about here. As to matter/ anti-matter machines, where are they ? Don't think any ever built.

Virgil Matthews Yes, it does matter. It's still considered a future travel, isn't it?

Is matter all that does NOT move at speed of light? Can a concrete block be accelerated to the speed of light and still be a concrete block during its trajectory or would it materialize only at discrete distances?

Virgil Matthews, Quan Hoang Nguyen

What has your reply to Manfredi about nattural (sic) philosophy got to do with original question about time travel?

Excellent question! If you look back at one of my earlier comments to Mr. Manfredi you'll see that I suggested to him that we move any discussion of other, unrelated issues (I'd suggested discussing the role of paradigms in shaping thinking and research in science, a la Thomas S. Kuhn, for example) to a new, separate thread. Inasmuch as that has not happened yet, and inasmuch as I wanted to reply to one of Mr. Manfredi's posts on this thread, I posted the comment which you -- correctly -- point out is not directly related to this thread.

In fact, however, I could argue -- perhaps with some success -- that the comment you questioned is, in fact, at least tangentially related to the topic of time travel, because it raises a question about the role of natural philosophy in furthering our understanding of the fundamental nature of time, which, in turn, has everything to do with the topic of time travel. Please recall that the book I mentioned in this connection, The Singular Universe and the Reality of Time: A Proposal in Natural Philosophy, which was co-authored by a theoretical physicist and a philosopher, explicitly grapples (as the title suggests) with the nature of time.

So perhaps the post you questioned was not quite so far out of place after all? But thanks for working to keep people on topic!

J. C. N. Smith