Nature of Time

Sorry, but it _can_ be. And, as The E said, if you can't look at the field equations and understand why that may be so, you have to learn to do so before you can really become more than a bystander in the discussion [I know - my degree is in physics, but I never pursued quantum field theory to that level and I find myself having to take their word for it when I do read current articles on the subject. Look for your self: arxiv.org is full of articles on quantum cosmology, for example]

It looks as if you have some familiarity with the relativistic concept of space-like vs time-like intervals. At least, the terms in which you posed your original question are those of the Minkowski space in which special relativity is formulated, where the concept is meaningful. The problem is that it looks very much like the entire formalism of relativity - general even more that special - has no connection to reality beyond generating equations that are _very_ good approximations of the correct description. It has been proven both that relativity isn't consistent with any quantum theory and that Einstein's proposed deterministic 'hidden variables' theory is _not_ the underlying structure of quantum theory. OTOH, there is compelling evidence, beginning with Planck's treatment of black-body radiation, that the universe cannot be described by non-discrete classical theories [which is a major pain, because the approximations of General Relativity are _so_ good that not only has it not been possible to build a quantum theory of gravity that clearly supersedes it, it isn't even possible to eliminate any of the several candidates for the role, because they predict exactly the same observables. There's no way to tell them apart on any level we've been able to look at.]

What that means is that the very terms in which you are trying to couch the discussion may or may not have a valid connection to reality. If they do, the answer, like the answer to the question "Is light a wave or a particle?", is not unlikely to be "Both!". If they don't, you're asking the wrong question in the first place.

Michael Everett wrote:

MAD-4A wrote:My question is regarding the actual nature of time, what do we know about the actual nature of time, is it linear or multi-dimensional?

Yes.
And no.
At the same time.
(Probably)

MAD-4A wrote:Sorry - It's either 1 dimensional or multi-dimensional - it can't be both - you can't have exactly 1 donut and multiple donuts at the same time, and it is time so it can't be "at the same time" either.

MAD-4A wrote:According to space-time theory, time is just another dimension of space (the "4th")

That´s just physicists being lazy. They call it a dimension because that makes it easy to throw it into maths.

A dimension is something you can move along.
While we can play around with perception of time, noone has ever actually moved in time.

And i´m >99% certain noone ever will.

The reason being very simple, to travel, you need to have a starting point and a destination point. But only NOW exists, which means if you try travelling in time, you try to go somewhere that no longer exists or that have not yet existed.

This is also why time is obviously not a dimension, as a dimension does not disappear just because you´re not there any more.

MAD-4A wrote:The point I made is that there is no empirical evidence that any timeline other than ours exists.

As much as i love alternate history and multiverse fiction, it just isn´t there most likely.

One problem with multiverse theories is that they ignore that it effectively means nearly infinite matter and energy constantly being created, as otherwise there would be an arbitrary limit on the number of multiverse parts.

Essentially, take the number of particles and subparticles in the universe, then figure out how many positions they can be in at in the next moment, multiplied by possible combinations, and there you have the number of universes you need matter for, next moment.
When you start from the beginning, the number is HIGH, once you´ve done that calculation trillions of trillions of times, the numbers are just laughable because they´re so insane.
And you need to get matter and energy for every new branch.

If you don´t want to accept that, then the problem instead becomes that you´re demanding an intelligent universe...

There´s also a nice little paradox involved.
If multiple universes are alternates of each other, then they have to be connected enough to "know" that. But if they´re connected, they´re not alternate universes any longer, as there is now a way to interact between them.

Otherwise, what you get is an unspecified number of identical universes, because if you start with the same conditions, then you get the same results. Which would mean that the future is already set in stone.
Which is not bloody likely!

MAD-4A wrote:So, if time is a "4th" dimension then you can only move 2 direction in it 4) forward and backwards - not 5) side to side.

Alternate timelines would essentially mean not moving along the nonexistant 4th dimension, but rather jumping sideways from one such dimension to another.

MAD-4A wrote:On another board I was discussing the movie The Final Countdown about the USS Nimitz finding itself back on December 6th 1941 and trying to stop Perl Harbor. Everyone began spouting off "Parallel Universe" ideas, Nuking Hitler etc...

Classic movie. Not the greatest or anything, but good enough and playing around very nicely with ideas and tropes.

I might recommend watching the anime Zipang as well, it´s vaguely similar but from the other side, which adds a LOT more trouble for the displaced crew(of a single upgraded Kongou class DDG), as they don´t really want the junta in Tokyo to win the war, yet unlike in the movie, this ship can´t get back home, and trying to speak nicely with the americans in mid 1942 is not easy for a Japanese warship.

The E wrote:
As for time travel, well. There are interpretations of the theory of relativity that allow backwards time travel, but until we have a theory of quantum gravity that bridges the gap between quantum effects and relativity, we won't know for sure.

One of the prime points of the theory of relativity(at least if you read what Einstein wrote on the subject) is that time is immutable, but our PERCEPTION of time is relative.

And if you look at time dilation, you should quickly be able to note that that is true, because time dilation does not change the rate at which time progress, but the rate at which something time dilated experiences time.

Tenshinai wrote:That´s just physicists being lazy. They call it a dimension because that makes it easy to throw it into maths.

A dimension is something you can move along.
While we can play around with perception of time, noone has ever actually moved in time.

And i´m >99% certain noone ever will.

Actually they have, there have been experiments that proved it. people closer to the planet (source of gravity) and traveling slower "travel" through time faster, and there clocks travel faster with them. The global GPS system has to take time dilation into account or everything would be off and no one would get were they were going. People 'move' through time at different rates and we now know for a fact that we can alter that rate of movement (to some limited extent - so far)

Tenshinai wrote:But only NOW exists, which means if you try travelling in time, you try to go somewhere that no longer exists or that have not yet existed.

No, this is not right, just because you can't perceive it doesn't mean it doesn't exist, as with your analogy, just because I can't perceive my house, right now, doesn't mean it ceased to exist. Yesterday does exist, it's just 1 day behind us in time. If it didn't then we wouldn't be 'here'

Tenshinai wrote:This is also why time is obviously not a dimension, as a dimension does not disappear just because you´re not there any more.

You think your puny 5 senses are capable of perceiving everything that there is? There are many dimensions that we cannot perceive, M theory is trying to map out (what is it now?) 11 different dimensions. We are limited to directly perceiving only 3 of them. What makes you think that the Universe is limited only to dimensions that You can perceive? Are you that special that it has to obey you?

MAD-4A wrote:Actually they have, there have been experiments that proved it. people closer to the planet (source of gravity) and traveling slower "travel" through time faster, and there clocks travel faster with them. The global GPS system has to take time dilation into account or everything would be off and no one would get were they were going. People 'move' through time at different rates and we now know for a fact that we can alter that rate of movement (to some limited extent - so far)

*sigh*

No, that´s perceived time. The time subjectively experienced depending on what you are influenced or not by. There is absolutely no time travelling happening there.

If it actually was, you WOULD be able to travel backwards in time by going faster than light. And NOONE even remotely serious on the subject believes that.

MAD-4A wrote:No, this is not right, just because you can't perceive it doesn't mean it doesn't exist, as with your analogy, just because I can't perceive my house, right now, doesn't mean it ceased to exist. Yesterday does exist, it's just 1 day behind us in time. If it didn't then we wouldn't be 'here'

To take that analogy one step further, if you´re not seeing your house right now, you don´t actually know that it is still there.
Anyway, that´s not really a valid comparison.

However, if your claim is correct, then either the past exists, or the past AND the future exists.
If the past exists, that means you are continually creating a new dimension as you go, the probability of which is beyond miniscule, you could also bring in the issue that you are effectively creating matter and energy to make it happen as well, also an extremely unlikely event.

If BOTH the past and the present exists, then, well then you are saying that precognition by default should be viable among other things...

You are also saying that chaos theory is completely wrong, as the universe was predetermined from the start(as otherwise, the future cannot already exist), something which is also very VERY unlikely, as chaos theory to quite some extent has been shown to be quite "reliable" so to say.

MAD-4A wrote:You think your puny 5 senses are capable of perceiving everything that there is? There are many dimensions that we cannot perceive, M theory is trying to map out (what is it now?) 11 different dimensions. We are limited to directly perceiving only 3 of them. What makes you think that the Universe is limited only to dimensions that You can perceive? Are you that special that it has to obey you?

M-theory among several others are based on reverse engineering reality with nothing but math and then try to figure out something that makes the math "real". But those doing it keep forgetting that math is a REPRESENTATION of reality, it is NOT reality itself.

They are basically saying that the map IS the ground, and then base their work only on the map.

And you´re wrong. If there ARE more dimensions, then it´s just a matter of figuring out HOW to interact with them, not a matter of "we can´t", because if we cannot interact with them in any way, any "surplus" dimensions are not linked to our regular 3.

That´s kinda the thing you see, if we are part of 11 dimensions, no matter if we only inhabit 3, the others would still BE there and interact with US. Yet we see absolutely nothing that suggests that actually happens, nor have anyone managed to come up with a way to interact with those supposed additional dimensions.

Which makes it, most likely, in one word:
Bullshit.

And i don´t expect the universe to "obey" me, even if that would be nice(hey, magic!).
But i did spend most of my time for 2 years in the 90s doing a lot of observing and analysis.

My interest and target at the time was to work out a theoretically workable way to achieve FTL, and i did(just doesn´t work in practice because none of the requried techbase exists, such a bummer). In the process i also rejected the multiverse idea and found timetravel to be inherently impossible among other things. I have found nothing since then that suggests i was wrong.