Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: allan marsh on 17/07/2014 19:27:48
-
There are quite clearly three dimensions of space.
My question why do we not consider the three dimensions of time, as past, present, and future?
[mod edit- please phrase subjects as questions in line with AUP]
-
It is easiest to look at time as one dimensional, from past to present to future. I.E. a timeline.
"Present" is essentially a single point, although it could be defined as tightly or as broadly as one's needs at the time.
This millisecond.
This second
This minute
This hour
Today.
This week
This month
This year
This decade
This century
This millennium.
etc.
But, still, present occupies a single point on your timeline.
Now, the question is what you would gain from taking a single dimensional entity of time, and making it into a 2 or 3 dimensional entity. Especially since there is so much uncertainty in the future. Would you truly get some kind of a space-filling structure, or would it still regress back to the single dimensional timeline?
-
A loose description of the number of dimensions is the shortest set of instructions you have to give someone to go from an arbitrary start point to an arbitrary end point, assuming they aren't blocked by anything. In space, you need three items in your instructions. For example, you can say to move forward by X units, move left by Y units and up by Z units. Or you can tell someone to rotate about two axes so they're facing the proper direction, then to move forward by a certain distance.
In time, we don't have the freedom to move backwards, but we only need to know a single number to move forward in time (how long to wait), and if we had a time machine, we'd need to know how far back to go. To specify a point in space-time, you need four numbers (hence why we say space-time is 4 dimensional in relativity): three numbers for how to go to a point in space and one number for the time of arrival.
-
Space is everywhere, time is always now.
Past and future are concepts in our minds, not physically exist.
Time will not slow down, the meter will if the force runs the meter decreased.
-
Maybe time is the clock itself
The wave front carries the universe moving
When the wine in the glass is gone
Fill up another one my friend
I miss those good old time
-
In time, we don't have the freedom to move backwards, but we only need to know a single number to move forward in time (how long to wait), and if we had a time machine, we'd need to know how far back to go.
Great explanation as always. To be a bit more precise, the number dimensions of a set is how many numbers it takes to uniquely determine an element in the set. In order to specify a point in time one needs only one single number. To uniquely determine a point in spacetime one needs four numbers.
Space is everywhere, time is always now.
That's incorrect. The present is always now. Saying like you did is like saying space is always where
I am, which certainly isn't true.
Time will not slow down, the meter will if the force runs the meter decreased.
That's not quite right either. Time does slow down depending on what one means by that. We know that the rate at which time passes in one frame relative to another depends on the relative speeds of the two frames. Also, as reckoned observers outside a gravitational field, time runs slower for those in a gravitational field.
-
If you think of a clock only counting its own existence as a clock then the deeper you take one into a gravity well the longer its exists in the present. It is the duration of the clock, or age, that is getting longer just as if you move the clock faster through space it is a longer amount of time occupied that changes the clock's count. Keeping in mind that space is time.
-
Einstein concluded that the past, present, and future were all occurring simultaneously.
http://everythingforever.com/einstein.htm
-
Keeping in mind that space is time.
Nope. That's very wrong. Relativity does not say that space is time.
-
Einstein concluded that the past, present, and future were all occurring simultaneously.
http://everythingforever.com/einstein.htm
Einstein never said that nor has any relativist ever suggested such a thing. Where in that page do you claim that it says Einstein said that?
-
You travel from a to b takes time t. You travel back from b to a takes time t1. you spent t + t1 time total.
No mater which way you travel, time adds up, how can you travel back in time? How can you spend spent money?
Why don't we have a time conservation law? t>=0.
-
Why don't we have a time conservation law? t>=0.
A conservation law only means that the sum of something remains constant. I.e. the numerical value does not change in time. That's not what you're talking about.
-
Time is the measure of relative change.
You can say that the relative changing in one direction is different than another direction and thus claim different "times" for each orthogonal direction. That would give you "3 dimensional time". But of what use is it?
In practical physics, there is almost never a case of concern for the measure of changing in one direction being different than another and also affecting the overall time dilation enough to measure or be concerned about. The differences, although capable of being calculated are minuscule. Even the effort to measure how much changing took place in one direction verses another would be pretty tough.
So as a convention, time is accepted as merely the measure of the overall relative changing, thus a single dimension of measure.
-
Why don't we have a time conservation law? t>=0.
Causality is used as a constraint on feasible solutions, for example by assuming that nothing (not even information) can travel faster than the speed of light, nor can it travel backwards in time.
Many equations in physics can be written with the sign of time reversed - in fact a positron can be regarded mathematically as an electron traveling backwards in time.
So causality is more an assumption than a proof - but some strange things could occur if someone did manage to travel backwards in time.
The laws of thermodynamics only work when time is going "forwards", and human lives are inherently bounded by thermodynamics.
See: http://en.wikipedia.org/wiki/Causality#Physics
-
Einstein concluded that the past, present, and future were all occurring simultaneously.
http://everythingforever.com/einstein.htm
Einstein never said that nor has any relativist ever suggested such a thing. Where in that page do you claim that it says Einstein said that?
In the very first sentence Pete: "Albert Einstein concluded in his later years that the past, present, and future all exist simultaneously."
How could you have missed it if you had indeed read it?
-
In the very first sentence Pete: "Albert Einstein concluded in his later years that the past, present, and future all exist simultaneously."
How could you have missed it if you had indeed read it?
I didn't read it. I don't have the time to read everything people tell me to read. I only read the stack of textbooks sitting on my side table in order to prepare myself for graduate school. I looked at it somewhat and I am quite surprised that I missed that. Se la vie! :)
I don't buy that interpretation though. Nothing exists in relativity that could lead to such a conclusion. I e-mailed a friend of mine. He used to be the editor of the Einstein papers project and as such as an extremely good knowledge of Einstein's writings. I'll let you know what he has to say about it.
-
In the very first sentence Pete: "Albert Einstein concluded in his later years that the past, present, and future all exist simultaneously."
How could you have missed it if you had indeed read it?
I didn't read it. I don't have the time to read everything people tell me to read. I only read the stack of textbooks sitting on my side table in order to prepare myself for graduate school. I looked at it somewhat and I am quite surprised that I missed that. Se la vie! :)
I don't buy that interpretation though. Nothing exists in relativity that could lead to such a conclusion. I e-mailed a friend of mine. He used to be the editor of the Einstein papers project and as such as an extremely good knowledge of Einstein's writings. I'll let you know what he has to say about it.
Thanks for the feedback Pete, I will also be interested to hear what your friend has to say about this..................regards.......Ethos
-
Seems Einstein is God for scientists.
I heard that he doesn't know how to play his sail boat.
-
Causality and the existence of the past and future are issues of ontology and beyond the scope of physics. Einstein might have made some comment about it or anything else (such as God). That doesn't mean it is a declaration of physical law.
You can't expect a doctor to explicate the meaning of life.
-
Thanks for the feedback Pete, I will also be interested to hear what your friend has to say about this..................regards.......Ethos
He wrote back just now and said
If you look at the quotes from Einstein in the article you cite:
In 1952, in his book Relativity, in discussing Minkowski's Space World interpretation of his theory of relativity, Einstein writes:
Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence.
Einstein wrote a letter to Besso's family, saying that although Besso had preceded him in death it was of no consequence, "...for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one."
you will see that neither uses the word "simultaneously."
What the first quote says is that one should conceive of processes as primary, rather than reducing them to the evolution in time of sets of spatially simultaneous events.
The second says that "the separation between past, present, and future is only an illusion," which is a consequence that can be drawn from the first: the primacy of process.
Which is exactly correct as I see it too.
Another expert on the subject I wrote to said Well, it's an obvious misuse of the word "simultaneous". which also agrees with what I said.
I wish people would simply take my word for these things. I can't tell you how many thousands of times I've consulted with my expert friends in instances like this only for them to tell me in all cases that I'm right. They're getting the idea that because I ask them these questions whose answers are obvious to us that I should know the answer myself and may be getting tired of me asking things I already know the answer to.
-
Another expert on the subject I wrote to said Well, it's an obvious misuse of the word "simultaneous". which also agrees with what I said.
Thanks for the clarification Pete, it appears that misquotes are abundant on the internet.
I wish people would simply take my word for these things.
But this is how most of us fall into error, by just taking someone's word for these things. Case in point, me trusting a quote from what I thought was a reputable source. And that's not to say that I mistrust you Pete, we are all responsible to research our source material and my mistake was not doing that.
Peace my friend..........................Ethos_
-
But this is how most of us fall into error, by just taking someone's word for these things. Case in point, me trusting a quote from what I thought was a reputable source. And that's not to say that I mistrust you Pete, we are all responsible to research our source material and my mistake was not doing that.
Peace my friend..........................Ethos_
I said I wish. I didn't say it'd be best. :) I know how people feel about these things and I know people certainly don't take me as an authority on any of these fields. I might be thought of as an expert in SR but certainly not an authority. So I really don't expect that people should just take my word for it. It'd just make my life easier by not appearing ignorant to my friends.
-
But this is how most of us fall into error, by just taking someone's word for these things. Case in point, me trusting a quote from what I thought was a reputable source. And that's not to say that I mistrust you Pete, we are all responsible to research our source material and my mistake was not doing that.
Peace my friend..........................Ethos_
I said I wish. I didn't say it'd be best. :) I know how people feel about these things and I know people certainly don't take me as an authority on any of these fields. I might be thought of as an expert in SR but certainly not an authority. So I really don't expect that people should just take my word for it. It'd just make my life easier by not appearing ignorant to my friends.
I'm confident that no one here thinks that you're ignorant Pete, I certainly don't. In fact, I appreciate the knowledge you share with us but as I said, we are all ultimately responsible to seek out the truth where ever we find it. And proving our source material is a personal and individual responsibility.
-
I'm confident that no one here thinks that you're ignorant Pete, ....
Thanks buddy. That's awfully kind of you to say. You're one of the brighter posters yourself if you don't mind me saying. [:)]
-
thanks folks for all your thoughts and interactions.
Einstein's world of thought was based on imagineering in lifts and acceleration bodies. his ability like you and me is to use one aspect of human consciousness..... that of imagination in forms and time.
I can imagine the past as well as the future, deciding points in time to review.
if we did not have this ability to imagine, our evolution would depend on random accidents or just luck!
is not our ability to imagine points in time, a form of dimensions
-
is not our ability to imagine points in time, a form of dimensions
However many points we imagine, they are all in one dimension. It takes only one figure to designate a particular point. 1066, 2014 and 2190, for example, are all in the single dimension of time, although they represent past, present and future.
-
Seriously, what is past or future? Does the universe knows?
Past and future has no mass, no charge, no position, no volume, nothing at all that we can detect but imagination.
-
Past and future has no mass, no charge, no position, no volume, nothing at all that we can detect but imagination.
Does time have any of those properties?
-
Yes, now has all those.
We can breathing, see river flowing, thinking and doing now.
-
Yes, now has all those.
We can breathing, see river flowing, thinking and doing now.
I don't see how this gives mass, charge, position or volume to time.
-
Everything is within now/time. Nothing is left without now.
When can we measuring anything?
-
Everything is within now/time. Nothing is left without now.
When can we measuring anything?
We can't do anything "now"; because doing something requires a passage of (through) time and "now" has no determinable extent.
Unless I'm missing something - which I could well be - you have still not answered my previous query.
-
Everything is within now/time. Nothing is left without now.
When can we measuring anything?
We can't do anything "now"; because doing something requires a passage of (through) time and "now" has no determinable extent.
Unless I'm missing something - which I could well be - you have still not answered my previous query.
You didn't. Dear Bill.
I just don't want to bluff on Sundays. I love my God.
-
Can't stay away from this one it seems :)
time is time. It's something that allow us to exist, it gives us a past, a present, and a future. Without it no radioactive decay, no changes and so no universe. In the end we live by measuring, and that measurement presumes a time for it to be done in.
What I see Einstein as doing is to lift up the difference between some global definition of a same unchanging time, and the local definition. In the local definition no one has a problem with defining what time is, neither the conscious observer, nor the lump of uranium 'ticking away' (decaying). Locally defined there can be no illusion. We assume that this local time is shared by a whole universe, and I think it's true, as long as we only define it locally. To see how I think there one can ask oneself what would happen if we superimposed two observers in a 'point like' identical configuration. Would their 'decay' be the same? It's a weird world, and what it has to do with, to me then, is a lot of other questions. As for example what we mean by a 'seamless universe' shared by us all? How is it 'seamless'?
==
This way of defining it is no stranger than the idea of constants. We presume constants to exist and be the same throughout a 'infinite universe'. You can see that two ways, as something permeating the universe, as well as something being locally true in each point of a universe, when locally measured.
And when you measure, it's always locally. As when you measure, you use that 'local clock and ruler', that becomes your golden standard. Locally defined this standard should be considered 'equivalent', as I see it. If it wasn't that way I would expect you to fall into grave difficulties defining how a constant can exist.
===
In fact, I think I easily can stretch this definition to encompass any definition of a homogeneous and isotropic universe, where we find conservation laws and entropy. It must be homogeneous and isotropic, if each point is equivalent when it comes to constants as your clock and ruler, and whatever conservation laws would become from a strict local definition, the same thinking should hold there, that it should be in some motto equivalent, as I then most probably would define them as a result of this.
=
And if we from such a local definition accepting the idea of constants existing, also define the arrow, as what your wristwatch describes for you (your proper time) as a constant, locally equivalent to 'c', we get ourselves an added definition of 'c'. No longer just a measurement of a distance, relative ones proper time, but also a constant describing what that clock really is.
Then your local time, equivalent to 'c', becomes a (local) constant. And it 'ticks' constantly and evenly, locally measured, no matter where you are, or how 'fast' you define it to be. That is one reason I find Planck units so interesting, as it all gets together there. sometimes I wonder if that is where discreteness ends? It depends if it really is a universal constant naturally. You could argue that by changing the numbers to something else we also change the constant, but to my notion that must be wrong. The constant if true should have a same equilibrium, no matter if counted binary or decimally for example. the same should then go for exchanging digits, as long as it is done in a proportional manner.
Although, even if it is a universal constant, to me then meaning 'locally true (equivalent) in each point', I don't think it state that this is where it ends. Just as decoherence doesn't tell you where things become 'real' to you. It's your imagination that will decide what is real, and the logic you use, and experiments naturally.
==
All of this is presuming that the universe like to keep it as simple as possible. Without a locally measurable equivalence in each point (of a universe) you still 'might' be able to define some sort of adjustable constants, giving us a 'universal' equilibrium, but I would think it should be really hard to do, to me involving very convoluted thinking.
===
And no, to me it's not about three dimensions. Time described as change, is to me more like a sheet, or some screen if you like, called the 'present' or 'now'. On which your local pattern change with the arrow ticking. The pattern defining 'you' with, as well as relative, everything else. But that pattern, or sheet, moves also for inanimate objects, as that lump of uranium, and it doesn't really need anyone to 'move'.
and ticking is a discrete way to describe it, ending at Planck scale, although the arrow as some ideal proposition might also be smooth. Think of decoherence.
=
As I'm getting slightly wild here :) there's an alternative in where we might presume that the arrow is a result of interactions, creating that local clock. But as we also define it equivalent your locally measured constant 'c' we then have to presume that the same then must go for our definition of 'c', as well as for all, and any, other constants. Now, wouldn't that become a rather remarkable universe? :) I most certainly wonder how such a universe could come to be?
==
And 'now' exist, but only locally defined. On the other tentacle there is no other way to experimentally define it than from a local perspective. That I theoretically can play 'God', doesn't make it so experimentally.
-
A thing that more and more has come to make me wonder is just decoherence. To me it's a description of from where a reality comes to be, from probabilities and statistics, to something I can touch. If you think of it this 'local definition' of a arrow also, in some way, becomes a ideal definition. We find it to be true everywhere, meaning that ideally defined (what I think of as superimposing) two objects must share the same clock. This thought experiment is as valid at a event horizon as on earth.
But it builds up just as decoherence, as there is no 'positional lock' to what we mean by that local time, unless we make that ideal thought experiment. You can't tell me that you know where that (yours) 'local time' is situated, but it holds for you and me both, just the same, made out from particles, that each one of us are defined to its own 'local time keeping'. In that motto even my local time becomes a illusion. The only way I can define it is either from super imposing, ideally identical objects upon each other. Or making a definition of 'ideal points', which then uses some sort of idea of a discrete universe, making it up, all 'points' equivalent to each other when it come to that 'local clock and ruler'. The rest should then be how those 'points' interacts, as possibly what geometry we find, giving a density? There is relative speeds, accelerations, to consider too, but that is not locally defined. To me both are a result of frames of reference interacting.
Actually, accelerations are a local property, I think it should be so even ideally defined? But I'm not sure? Either that or a locally expressed acceleration need a universe to come to be. But when it comes to a density of something, you need frames of reference, the same goes for relative motion.
Constant uniform accelerations and gravity? That's one of the most breathtaking ideas I know of. Even though I personally think it is correct, I'm not sure what it says about this seamlessly 'all inclusive universe' we find ourselves to exist in?
Or, 'time' is a flow :) In which case we still can use discreteness for defining particles. As for laws, rules and properties coming from time existing I don't know. We define it such as constants exist, we also define it such as properties as spin and polarization exist. Both are ideal definitions to me, as I personally know no classical counterpart that really fits. So maybe you need them too to be a 'cosmic blueprint', with time starting entropy.
Although, to me, it's particles that define time, a cosmos without particles should be very hard to measure a change in. Any measurement needs particles existing to be made, like thermometers measuring temperatures. Theoretically we assume that something alike radiation spontaneously can create particles (rest mass), as that first instant of a Big Bang, where we presume particles to be spontaneously created.
=
If that last proposition is correct, then I think I will call the arrow a 'property' too, preexisting even before particles. There is no way I see myself able to imagine a particle creation without a past, a 'now', and if so, most probably a future too.
Whatever you want to call it, or define it too, time exist.
Lastly, if you consider the idea of several probabilities co-existing 'somewhere', us only able to observe one of their outcomes, you also presume another reality, where the 'clock' is absent. Then the question becomes what it is starting that clock, and keeping it ticking. A property?
=
You could say that we exist inside this 'locally moving' sheet, or 'plane' if you like, it defining a future as well as a past, always defined from local measurements though. The sheet moves to a clock, no way it can change without it. And I think you need this co-existing 'timelessness' for it. It's not as if this timelessness is discrete, just existing in between outcomes. To me it's what is really real :) And now I'm getting mystical again.
=
The point :) with accelerations being existent even inside a 'ideal point', actually making it into a property locally defined. Yeah, properties are one weird idea, in some ways taking us as far away from a clock work universe that I can imagine. Then again, so does thoughts, or do you believe thoughts are discreet entities, 'composites' of some sort, created by your brain that you can measure on? I don't think you can measure on them, as you can on radiation, never the less they exist.
-
After all that lovely talk about Einstein . That would lead to the question, where is he now?
And at what age or should I say time.
At least quantum mechanics will demonstrate superposition in the form known as resurrection N,est pas ?
-
good time, old time, mean time.
-
good time, old time, mean time.
Waste of time?
We could go on for ever (figuratively) discussing whether time is a real "thing" or just a concept we use to measure change, and still end up in the graveyard of circuitous threads.
Such a discussion seems to have this in common with string theory: it may never go anywhere, but it could throw up some interesting points along the way.
-
Time is illusion of the human mind.
Since we live by now, in now, with now, past and future also illusions.
Time is the passage of force in motion, nothing more.
-
Time is illusion of the human mind.
Since we live by now, in now, with now, past and future also illusions.
Time is the passage of force in motion, nothing more.
Not if things are moving with a constant velocity. That is inertia and is not a force. Time does measure change. That could be zero change over time, although that should never happen in practice because of conservation of momentum. Everything is constantly in flux.
-
That could be zero change over time, although that should never happen in practice because of conservation of momentum.
Wouldn't HUP prevent that, as well?
-
That could be zero change over time, although that should never happen in practice because of conservation of momentum.
Wouldn't HUP prevent that, as well?
Exactly Bill.