Gathering perspectives: space and time
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15-04-2014, 02:15 PM
Gathering perspectives: space and time
Third round of perspectives. When you use the word "space" and when you use the word "time", what do you mean?

Thanks!
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15-04-2014, 02:33 PM
RE: Gathering perspectives: space and time
I used to know, after investigation a bit about the science of space and time I have no complete idea of what they are...

I do use the terms in the colloquial sense of "where stuff happens" and "when stuff happens" respectively

But that shit is too weird. Hobo

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15-04-2014, 02:59 PM
RE: Gathering perspectives: space and time
(15-04-2014 02:33 PM)nach_in Wrote:  I do use the terms in the colloquial sense of "where stuff happens" and "when stuff happens" respectively
I certainly cannot think of a shorter way to put it!

Thanks, nach_in. It seems like a reasonable view, although I wonder if it could be complemented in any way. If there is anything you'd like to add, please feel free to do so.

Have a good day!
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15-04-2014, 03:19 PM
RE: Gathering perspectives: space and time
(15-04-2014 02:59 PM)living thing Wrote:  
(15-04-2014 02:33 PM)nach_in Wrote:  I do use the terms in the colloquial sense of "where stuff happens" and "when stuff happens" respectively
I certainly cannot think of a shorter way to put it!

Thanks, nach_in. It seems like a reasonable view, although I wonder if it could be complemented in any way. If there is anything you'd like to add, please feel free to do so.

Have a good day!

Sure, space and time is always defined in a relative way, from an arbitrary starting point. That makes it harder to think about them in an absolute abstract way. So we have to be cautious not to assume they are absolute.

There's a lot to add in the sciency department, but I can't say it better than some of the documentaries out there, so I won't try Tongue

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15-04-2014, 04:01 PM
RE: Gathering perspectives: space and time
(15-04-2014 03:19 PM)nach_in Wrote:  I can't say it better than some of the documentaries out there, so I won't try Tongue
No worries, I thank you for sharing your view nonetheless.
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16-04-2014, 01:16 PM
RE: Gathering perspectives: space and time
Hmmm… I hope the web server can handle such a massive response! :-)

Meanwhile, I’ll try to describe how I use those terms, although please do remember that you are reading the philosophy section of an internet forum. I share these thoughts for other people’s consideration as potential possibilities (meaning that the ideas described might not even be possible in reality), but they are not, in any way, claims of any sort of objective truth. If the notions I may suggest appear to be false from your point of view, then they may very well be false. Skepticism and critical thinking is always welcome.

I don’t think that space and time are things that exist out there, not in the sense that I use the word. What appears to exist out there, at least from my tiny perspective as a tiny living thing, are plenty of material structures constantly changing their relative locations and/or relative orientations with respect to most other things out there.

But one thing I have observed is that, in order for matter to be able to move, it needs room to move. When I’ve been stuffed inside the subway during the rush hour, along with what appeared to be seven billion other people, the activity I found least easy to perform was changing my location and/or orientation. I did have a little bit of room above my head, but the huge planet below the subway prevented me from going very far up. And even if it hadn’t, I am almost sure that the roof above me would have soon stopped any upwards motion I might have gained from flapping my nostrils (one of the only parts of my anatomy that retained its normal mobility).

However, when I’ve been out in an open field, I’ve been able to run, jump (still not very far up, but certainly more than when I’m tightly surrounded by things), turn…

In my view, space is not the place where things are because things are not located anywhere in relation to space; things are located somewhere in relation to other things. I find it easier to understand space as an abstract notion describing the fact that, as long as nothing else interferes with its motion, matter can move in any direction along three orthogonal axes (up/down, left/right, forth/back); space is the lack of things around things that does not prevent things from moving.

Matter’s ability to move seems to occur in any location provided that its motion is not restricted by its interactions with more matter, which means that there is no geographical limit of space; regardless of where you are in relation to the rest of the universe, if your motion is not prevented by more matter you will be able to move in any direction along three ortogonal axes. At least, I cannot see why you wouldn’t. Thus, the abstract notion of space can be described using two rather complementary entities that are also abstract, zero and infinity: space is the infinite set of distances around any object occupied by zero instances of matter.

And what about time?

Well, not only I have observed that matter can move; I have also observed that matter is constantly moving in relation to more matter. In my view, the passage of time seems another abstract notion reflecting the fact that the universe is constantly changing. Whenever I perceive time to progress from one instant to another, it always implies that something has changed its location and/or orientation in relation to something else.

Space and time are related in a very simple way: it takes time for matter to move across the nothingness of empty space. They are also related in that both provide different contexts in which information may appear. However, I find at least one difference between them: spatial directions are bidirectional, whereas the “axis” of time seems to occur only in one way. Why?

Let’s consider a hollow steel cylinder, with a fixed wall on one side and a movable piston on the other, filled with a gas. “Initially”, the distribution of gas molecules within the volume enclosed by the cylinder is homogeneous; the probability of finding a molecule anywhere inside that volume is the same regardless of the location within the volume. Each molecule is constantly moving in relation to other molecules in the gas, and also in relation to the walls of the container, but the direction of its motion keeps changing due to interactions with those other objects. Over time, the net sum of all that inner motion is zero: the mass of gas does not change its shape.

Let’s now imagine that we pulled the piston in order to double the cylinder in length, but so quickly that the distance covered by the fastest molecule in the gas during the process were negligible. We would be left with a cylinder twice as long, half of it “full” of gas (although sparsely) and the other half “full” of nothing (although not full at all). What would happen next?

Those molecules moving towards the full side of the cylinder would soon interact with other molecules that are already there, causing their motion to change. However, those molecules moving towards the empty side of the cylinder would have little chance of interacting with anything until they reached the new location of the movable wall, because there would be nothing there to interact with them. For as long as the chance of bumping into something were higher in one direction than the opposite, a preferential net direction of motion would be established, from the full side to the empty side of the cylinder. The mass of gas would change its shape until its distribution were homogeneous again.

Whenever there is an asymmetric distribution of matter and/or motion, matter moves and motion propagates from wherever there is more of it to wherever there is less of it. Heat flows from a hot body to a colder body and water can flow from a full bottle to an empty glass but not the opposite; water cannot flow from an empty glass to a full bottle because if there is no water in the glass, there is no water that can go anywhere.

It might be this “directionality” in the behaviour of matter and motion what is perceived in our brains as “time going forward”. As times progresses, things move outwards in all possible directions. But an experiment you can fairly easily perform is recording a video clip of a drinking glass being broken into pieces that are scattered in all possible directions on the floor, and then play that clip backwards. You’ll see that, as time regresses, things move inwards from all possible directions. Could the expansion of the universe and the fact that we perceive time to go forward but not backwards be related? I don’t know; all these are thoughts, not universally binding truths.

But the good thing about not believing in the existence of space or time is that I am not bothered by the question of how they came into existence.

Have a good planetary rotation!
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16-04-2014, 01:40 PM
RE: Gathering perspectives: space and time
They are very broad terms and have multiple meanings. Spacetime is the one thing that blows my mind the most and I get giddy listening to podcasts or reading about.
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16-04-2014, 01:52 PM
RE: Gathering perspectives: space and time
PS, since time appears to emerge from entanglement I have a suggestion. Next time you are on that subway you can *ahem* have something emerge, thus you will gain more space (though time may slow down for others, relative to, well... you know).

Ok gross, carry on with serious conversation. Shy
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16-04-2014, 02:27 PM
RE: Gathering perspectives: space and time
(16-04-2014 01:52 PM)LadyJane Wrote:  PS, since time appears to emerge from entanglement I have a suggestion. Next time you are on that subway you can *ahem* have something emerge, thus you will gain more space (though time may slow down for others, relative to, well... you know).

Ok gross, carry on with serious conversation. Shy
Will people in the crowded subway insist on the measurement of my emergence? Oh, well, I suppose length is relative.

(16-04-2014 01:40 PM)LadyJane Wrote:  They are very broad terms and have multiple meanings. Spacetime is the one thing that blows my mind the most and I get giddy listening to podcasts or reading about.
They are broad terms indeed and they can have multiple meanings. That's the goal behind the thread: learning some of those meanings.

In my view, if space is an abstract notion and time is an abstract notion, the combination of both is probably abstract too, and I already explained in my introductory post that I don't believe that abstract notions exist outside my mind. What I find outside my mind is that matter is located somewhere in relation to more matter, that its location and/or orientation can change in relation to that of other material structures, and that its location and/or orientation is constantly changing in relation to that of more matter.

But my view is just one view, and I'd like to know other views. If there is anything you would like to add to this topic, I'll be happy to read it. Until then, have a great... time :-)
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21-04-2014, 08:26 AM (This post was last modified: 21-04-2014 03:20 PM by living thing.)
RE: Gathering perspectives: space and time
Carrying on with a conversation started elsewhere,
(20-04-2014 06:45 PM)cjlr Wrote:  (...) Relativistic spacetime simply is the material structure of the universe!
Are you suggesting that spacetime is some kind of arrangement of matter out there? And if you are, may I kindly ask you to provide evidence to back that claim?

I can understand what "curving" and "bending" may mean when I apply them to a material structure; they imply that the relative location and/or orientation of some of the inner constituents in the structure are changing in relation to other inner constituents of the same structure. But unless spacetime itself consists of inner constituents, what exactly does it mean to say that it "curves" or "bends"?

(20-04-2014 06:45 PM)cjlr Wrote:  Our naive physical intuition, then, is the simplified abstraction - we're never going to have an instinctive feel for gravitational distortions, the way we have an instinctive feel for things like "my textbook is on the far side of the room, it will take me five seconds to go get it". But "if I move farther out of the Earth's gravity well, my clocks will run differently as compared to those who stay within it" is also indisputably true - that's how GPS works.
The claim I often hear is that if relativistic time dilation were not taken into account, the locations calculated by the system would drift because the atomic clocks on board of the satellites run at a different rate than they do on the earth's surface.

However, that cannot be entirely true. My phone has a GPS receiver, and it can calculate my location to a great degree of accuracy, but it does not even have an atomic clock in it, just a quartz crystal typical of low cost electronic circuits, sensitive to factors other than my motion, such as the temperature of my environment. The timing device in my GPS receiver is surely drifting with respect to the timing device on board of the satellites, by a random factor that no relativistic formula can account for. However, the calculated location does not drift. Why?

Because the time in my receiver is not used at all in the calculations; my receiver uses the time encoded in the radio signal that the satellite is emitting from up there. Since the satellite's time is never compared against the time informed by my device, the possible loss of synch between both clocks due to relativistic effects is irrelevant.

GPS is often cited as some sort of "proof" for general or special relativity, but I don't understand how it supports it. Would you like to please explain to me how it does?

Thank you!

(Edited to fix an omission)
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