Conundrums If Time Travel Is Possible

[Moontanman]

Well, I'd expect it, by following this chain of reasoning:

 

1. "Matter" is not infinitely divisible. It's made of particles.

2. Each particle must take up a certain amount of "space" (otherwise, it wouldn't exist).

3. So, saying that "matter is made of particles", is the same as saying that "space is made of particles".

 

I can't say I agree with that, can you give some citation on space/time being made of particles?

 

4. Modern physics claims that "space" is actually the same as "time". Hence we have - "Spacetime".

6. From which it must follow, that if "space" is made of particles, "time" must be too.

7. Therefore there must be time-particles - the "chronotrons".

 

8. QED!

 

 

Since I don't see the connection in the first three it follows I do not in the last three either...

[Guest MacPhee]

I can't say I agree with that, can you give some citation on space/time being made of particles?

 

Why do you want a "citation"? That sounds a bit depressing. Like a retreat to medieval times. When any new proposition had to be backed by a confirmatory "citation" from the ancient works of Aristotle. Science shouldn't work like that! Otherwise, scientists would be mere lawyers, riffling through the textbooks, looking for a previous judgement, or "precedent", to decide the case.

 

Also, if you'll forgive me for saying so, your substituted term "space/time" is somewhat weasely. In modern physics, there's no forward slash - it's "spacetime". A single entity, supposedly.

 

This entity has a "space" component. Which must be made of particles, surely. It can't be a kind of smooth, indivisible, amorphous stuff. Otherwise - how could it clump together to make particles - like protons, neutrons, electrons and so on.

 

And if "space" is a similar thing to "time" (as we apparently assume by conceiving of "spacetime"), then "time" can also clump, to form particles, can't it?

[Buffy]

Spacetime is actually a framework for measuring reality. It's not really reality itself.

 

We use it as a conceptual mechanism by which we can find out where things are.

 

So saying it's the matter itself is kind of like saying that a meter is wood because that's what the measuring stick is constructed with.

 

 

Oh, I'm not particular as to size, only one doesn't like changing so often, you know, :phones:

Buffy

[blamski]

its evident that there are problems about one's future particles already existing in another state if one undertakes 'forwards' time travel, but this would also apply in 'backwards' time travel. one's particles would also be existing in the state they were in before they were you. so in these senses time travel violates some of the fundamental laws of physics, and that's without even getting into the causality thing.

 

what happens if time travel becomes a commercial activity and you can book a ticket on the next journey back to some specified date? some pillock is bound to interfere with something that they know will alter the course of history - apart from the instant absorption of all the particles that were going to be that person in the future.

 

i imagine that time travel would be more like exploring the deep ocean in a submarine. you can't get out and directly engage with the reality around you, but you can take a good look at it from inside your capsule. you don't travel back 'through' time, you travel around it and look in on it from outside in a way that makes it impossible to interfere with it or even become a temporary part of it.

 

i don't know why scientists don't just get on with it and invent the darned thing.

[Guest MacPhee]

Spacetime is actually a framework for measuring reality. It's not really reality itself.

 

We use it as a conceptual mechanism by which we can find out where things are.

 

Buffy

 

Yes, I dig that. It's like "latitude" and "longitude". These make a convenient conceptual framework.

Such a framework enables us to navigate the ocean in a precise manner. By imagining that the Earth is criss-crossed by "lines" of latitude and longitude, our ships can find out where they are. And plot an appropriate course.

 

However the "lines" aren't real physical things. Eg, when a ship sails across Latitude 40 degrees South, the ship's crew don't see a big black line on the surface of the water. I suppose the sailors could describe their ship as a "Latitude Machine". Like a "Time Machine".

 

I'm not sure where this line of reasoning leads though. Does it mean that Space and Time aren't real?

[Buffy]

However the "lines" aren't real physical things. Eg, when a ship sails across Latitude 40 degrees South, the ship's crew don't see a big black line on the surface of the water.

 

Yep. That's certainly true. No reason that they would need to be visible.

 

Of course you could project them onto the image like they do for football or the America's Cup. But they're still just conceptual representations of how we measure things and coordinates and standard measures are translatable at will.

 

I suppose the sailors could describe their ship as a "Latitude Machine". Like a "Time Machine".

 

Sure. Why not? The only problem we as corporeal beings have is that we can't speed up or slow down when travelling in the time dimension, so that seems a bit magical, even though it's really not. Just sitting here I am doing "time travel!" :cheer:

 

I'm not sure where this line of reasoning leads though. Does it mean that Space and Time aren't real?

 

Why should it? What's wrong with the idea that mental concepts are just that, concepts?

 

Measurement creates reality, it does not have to *be* reality. There is value in meta-systems, and leaving them in their designated role is exactly what Kurt Gödel admonishes us to do, telling us that trying to mush a system and it's meta-definition together just leads to fallacies.

 

Consciousness is connected with one unity. A machine is composed of parts, :phones:

Buffy

[Guest MacPhee]

its evident that there are problems about one's future particles already existing in another state if one undertakes 'forwards' time travel, but this would also apply in 'backwards' time travel. one's particles would also be existing in the state they were in before they were you. so in these senses time travel violates some of the fundamental laws of physics, and that's without even getting into the causality thing.

 

That's the point. Physical Time Travel, whether into the Future - or, as you rightly point out, the Past - would necessitate the duplication of particles. Or to put it another way, it would cause an increase in the mass/energy content of the Universe.

 

This would violate fundamental laws of physics, specifically the conservation law. So we can conclude that physical time travel is, under current theory, not possible.

 

However, this doesn't rule out "time-viewing", as your post again percipiently points out.

 

We can view and analyse past events by using such media as photographs, cine-film, VHS tapes, and DVDs. This viewing demonstrably doesn't cause any paradoxes. If we were so inclined, we could set up millions of video-cameras all over the world. And record everything that happens over the entire surface of the Earth.

 

These recordings would enable future generations to "view the past" without physically travelling into the past.

[Rade]

I concur with Feynman that only antimatter can travel backward in time (see this linkhttp://www.paulfriedlander.com/text/timetravel/feynman.htm). So, from this view there is no conundrum for humans on earth concerning travel to a past moment, only healthy imagination of what is not logically possible. See how beautify is the symmetry of the universe if matter travels to future time and antimatter to past time. From this view time translation symmetry (the interaction of superposition of matter + antimatter of asymmetric mass) would result in law of conservation of energy. Thus, the real conundrum is the possibility that all we observe is a conserved emergent property of entities that undergo simultaneous travel to both past and future within each moment of time.

Edited January 18, 2013 by Rade

[blamski]

 

We can view and analyse past events by using such media as photographs, cine-film, VHS tapes, and DVDs. This viewing demonstrably doesn't cause any paradoxes. If we were so inclined, we could set up millions of video-cameras all over the world. And record everything that happens over the entire surface of the Earth.

 

These recordings would enable future generations to "view the past" without physically travelling into the past.

 

 

arguably we are already doing that. if you consider the increasing prevalence of CCTV systems, the phenomena of teenagers uploading their entire lives to youtube via smartphone videos and the efforts of google maps/earth/etc we are making strides towards to a total recording of everything. but this isn't time travel, any more than watching reruns of BBC wildlife documentaries, or the original version of metropolis is. ok, we are witness to the past, but it's not live, unfolding as we see it.

 

something that needs to be question is the motive for time travel. do you want to go back to the past to influence events for your own purposes, or do you just want to witness it out of interest. do you want to get rich, famous and powerful? or do you just need to know if tyrannosaurus really did have feathers?

 

if you want to intervene then we need to deal with the issues which have already been discussed int this thread. if you just want to observe from some kind of temporaly isolated bubble then maybe there are possibilities in some quantum form or other.

[Guest MacPhee]

 

something that needs to be question is the motive for time travel. do you want to go back to the past to influence events for your own purposes, or do you just want to witness it out of interest. do you want to get rich, famous and powerful? or do you just need to know if tyrannosaurus really did have feathers?

 

Yes, that's the essential point. What's the motive? Why should we even premise such a thing as time-travel? It raises such obvious logical paradoxes.

 

By the rules of logic, any premise that leads to a paradox, a contradiction, an absurdity, must be invalid. This principle was of course made essential use of by Euclid. Many of his proofs rely on the "reductio ad absurdum" principle. Suppose the principle were abandoned, by allowing "time-travel" to exist. Wouldn't that undermine the entire basis of Euclidean geometry - and indeed of logical reasoning in general?

 

Nevertheless the idea of time-travel continues to haunt human imagination.

 

It seems to be a result of dreamy human wish-fulfilment:

 

1. We all dislike getting old, and wish we could go back and become young again.

2. We all regret decisions we made in the past, and wish we could go back and change them.

3. We all wish we could go into the future to see next week's lottery numbers.

 

It couldn't really happen, could it?