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I (and every one I guess) perceive space as an extended region where things happen. In contrast, time is perceived as a lucky of slice. Also in space I can choose in which direction I want to move, and also how much I want to move. In time I am obliged to move in the future direction, and cannot even decide if I want to move much or a little bit. Time just passes in contrast to space that "is always there".

Why is this so?

Has this to do with the minus sign attached to the time coordinate (in Special Relativity)? How would we experience space and time if two coordinates, instead of one, have negative sign? In this case, would we experience a 2D space and two time directions to choose a sort of "time direction" in wich to move? And would we be able to chose how much to move in this 2D time sub-space?

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closed as off-topic by John Rennie, StephenG, Chris, Kyle Kanos, Jon Custer Mar 8 '18 at 14:08

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I've been thinking about the nature of time in physics myself lately.

I think really the reason why we experience only one slice of time at a time (so to speak) but all of space at once, is because those are the very philosophical assumptions of our common-sense understanding of the world. That is, we assume this characterisation of the world a priori, and it seems to integrate well with much of our everyday experience.

But it is not apparent that you are "obliged" to move forward in time. You experience a difference between one moment and the next because your memory is recording a representation of previous states. You could certainly choose personally not to do so - for example, by being knocked out, by lobotomy, or by death - although we suppose in that case that your body would continue to experience time even if "you" do not perceive it.

So too, why do the dead not rise out of graves then end their lives by climbing into the womb? Well, there is no physical reason why that cannot happen. It is simply that the processes necessary to form a human body from the soil and then have it deteriorate (in a manner of speaking) into a baby which a woman then forces into her womb to dissolve and consume nutrients from, have not been implemented.

But simpler processes can certainly be performed in reverse under human control - for example, burning oil into combustion products and heat, can be performed in reverse in which heat and combustion products are brought together and combined into oil. Obviously, humans alone cannot turn the entire universe back, but given the limited means at our disposal, why ought we be able to (and why would our lack of means imply anything about the natural principles in play)?

Another point about time is that, if the universe were completely still in space and nothing moved, it is not apparent that any time would pass, or could pass. I've come to the conclusion myself that the hypothesis of "time" is closely related to spatial dynamics, and that it's not an independent dimension or something that itself "moves" (except in a metaphorical or analogous sense), but is something very closely related to what is occurring in the spatial arena.

I also came across this article the other day which, whilst I don't agree with the solutions which the author Muller advances, it does a very good job of summarising the questions that have occurred to me lately (and reassures me that I'm not the only one to whom they have occurred).

It also refers to a dissertation by Rakić, N. (1997) Common Sense Time and Special Relativity, but unfortunately I haven't been able to find a freely available copy of it.

Needless to say however, the philosophical nature of time in physics seems to be an unresolved question, not least because of all the philosophical upsets that have been introduced by developments in 20th century physics.

I hope this is some food for thought on the matter, anyway, and I hopefully won't spend too much of my reputation on it.

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    $\begingroup$ I suspect the preemptive whining about downvotes doesn't really help your problem there... $\endgroup$ – Chris Mar 8 '18 at 9:07
  • $\begingroup$ @Chris, haha, well by its nature it's not exactly a decisive answer, although hopefully some help to the OP, and I'm just waiting for the anti-philosophy brigade! Its function is not so much as a whine but, as you say, as a pre-emption - a lightning rod. $\endgroup$ – Steve Mar 8 '18 at 9:54

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