I ask the question because of a paradox: Take the scenario of a vehicle accelerating from a stationary position. At what point does it 'move'?
Let's concentrate on the period before and after the vehicle moves and break that period into, say, 2-seconds, we can say the vehicle starts to move at a mid-point between 2-seconds: -1,0,+1.
Is there a point where that 2-seconds of time becomes indivisible, ie. where the vehicle is neither stationary nor moving?
Originally posted by Roy P: How long does the 'present' last? Is it a discrete package like the frame of a movie, or does it flow like water?
The present doesn't last. It's a strange little shock in between the past (which exists only in memory) and the future (which exists only in imagination).
It's more like being unexpectedly hit on the head with a sledgehammer, only it happens so often we don't notice.
I'm a bit confused as to what you're on about Roy P, you're talking about time in discreet lumps as if it were a film roll, but surely time is continuous? Is the car not moving the nano-second it, er, moves? Feel free to enlighten me as i'm a biologist not a physicist! Actually I was pretty rubbish at physics in school, I think you have to have a certain type of brain to understand mechanics :-)
Originally posted by SamD: I'm a bit confused as to what you're on about Roy P,
I suppose what I'm getting at is; is time infinitely divisible? If so, that raises the philosophical dilemma of there being no intermediate (moving or stationary) state for the car to be in -- doesn't it?
Originally posted by Roy P: I suppose what I'm getting at is; is time infinitely divisible? If so, that raises the philosophical dilemma of there being no intermediate (moving or stationary) state for the car to be in -- doesn't it?
Ok, I can see that now, ooh, yes I suppose so. Mmm. It's one of those things if you think about it too much you might realise that life is in fact impossible and cease to exist!! I sometimes think about where we are in the universe and imagine the earth is a molecule in a person on another earth and so on, too huge for us to comprehend.....
Originally posted by Roy P: How long does the 'present' last? Is it a discrete package like the frame of a movie, or does it flow like water?
Have to do a bit of research on this first but from memory (subject to later amendment then ) I believe the present (and future) is really an abstract concept all that truly exists is the past. Consider a timeline - on this events may be noted as they happen (the past) these events always exist once formed since they have occured and have a cause-effect to the events which precede and come after. The present however is only an abstract since it actually occupies the newest point of a timeline which is continually moving forward. In essence to consider the present is nonsensical since any consideration of an event classed as present would actually be a consideration of an event by then part of the timeline and in the past.
There really is no paradox in your vehicle example the answer is that technically the vehicle is always in motion (from a QM point of view). We merely assume that the vehicle is stationary since we cannot detect the quantum motions.
If you wish to merely state a point at which the vehicle moves in the macro world then you would have to first set some parameters. What constitutes movement, a nano or picometer? Of course the more stringent that parameter the more difficult you make it to measure the exact point in time (precision of timepiece) though a nuclear clock would suffice, probably. It really would be a case of setting your parameters within limits which allow time measurement (a technology limit) and a physics limit (Uncertainty Principle). The closer you put your measurement to these limits then the harder it would be to get an accurate reading.
Originally posted by Joobs: Have to do a bit of research on this first but from memory. . . <snip> . . .then the harder it would be to get an accurate reading.
Pow! Profound food for thought there, Joobs. I can understand the 'present' being an abstract concept on the timeline. QM has to be part of the equation but I'm still getting my head around that.
Howsabout we use the analogy of a tube gradually filling with water, with the surface of the water being a two dimensional representation of the present. Actually it would have to be an inverted cone with the surface area increasing in three dimensional time. . . Or would it?
Originally posted by Roy P: Yes, Sam. I've had exactly the same thoughts!
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Originally posted by Joobs: Have to do a bit of research on this first but from memory. . . <snip> . . .then the harder it would be to get an accurate reading.
Pow! Profound food for thought there, Joobs. I can understand the 'present' being an abstract concept on the timeline. QM has to be part of the equation but I'm still getting my head around that.
Howsabout we use the analogy of a tube gradually filling with water, with the surface of the water being a two dimensional representation of the present. Actually it would have to be an inverted cone with the surface area increasing in three dimensional time. . . Or would it?
Actually, this is really doing my head in
Anything which involves QM usually has that effect, at least to us mere lay people.
Most diagrams used to illustrate time effects use an inverted cone (various reasons). But in truth it really depends what you are trying to say with your argument or question? Of course if you are considering time effects in relation to wormholes and timespace then other diagrams such as a U shape may be better.
For instance, to describe a hypothetical time machine using a wormhole:
The timeline would be the U and the wormhole would join between the two uprights of the U to create a sort of time travel machine. Don't get your hopes up though since first you need a spacecraft which can achieve near light speed (for relativistic effects) and also a means to stop the wormhole you have created from collapsing (the energy required make it virtually impossible).
Originally posted by Joobs: But in truth it really depends what you are trying to say with your argument or question?
I can't for the life of me remember where I read about this, but I've just found a page on the web illustrates the 'paradox'.
Democritus' cone scroll down to; 6. Indivisibility and Mathematics, Para 4. "He argues that if a cone is sliced anywhere parallel to its base, the two faces thus produced must either be the same in size or different. If they are the same, however, the cone would seem to be a cylinder; but if they are different, the cone would turn out to have step-like rather than continuous sides."
If time is measured using a cone, as above with smoothly sloped sides, you'd expect the exposed surface of the top part of the cone to be smaller than the exposed surface of the base. In which case, the cone is constructed of discrete 'slices' of time. Slices that can also be infinitely divisible.
Linking this to the movement of the car; there will always be a period of time between movement and rest. However, your QM answer put paid to that.
Yup, I can understand the *theory* of time travel. It's mind boggling isn't it! Bit like the Enterprise's transporter -- how do they always end up perfectly placed on the surface of whatever they're beamed to? Why not half-an-inch above or below the surface?! Ha-ha-ha. That's for a different thread.
Originally posted by Roy P: I can't for the life of me remember where I read about this, but I've just found a page on the web illustrates the 'paradox'.
Democritus' cone scroll down to; 6. Indivisibility and Mathematics, Para 4. "He argues that if a cone is sliced anywhere parallel to its base, the two faces thus produced must either be the same in size or different. If they are the same, however, the cone would seem to be a cylinder; but if they are different, the cone would turn out to have step-like rather than continuous sides."
If time is measured using a cone, as above with smoothly sloped sides, you'd expect the exposed surface of the top part of the cone to be smaller than the exposed surface of the base. In which case, the cone is constructed of discrete 'slices' of time. Slices that can also be infinitely divisible.
Yes I've seen arguments like this before and my problem with them is that whilst they make sense I fear there is a basic problem in that they are trying to apply mathematics to an abstraction. After all the cone is only a way of representing time not actually time itself. I think that if you applied maths to a drawing of a tree then doubtless you'd be able to say that trees are not as they really are.
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Linking this to the movement of the car; there will always be a period of time between movement and rest. However, your QM answer put paid to that.
Proves QM is useful for something then.
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Yup, I can understand the *theory* of time travel. It's mind boggling isn't it!
Personally I doubt it will ever actually be found to be possible as it always invokes paradoxes which could occur. Obviously I haven't the skill nor quals to prove this, it's just a gut feeling, I just don't think it'd be allowable since laws of physics would appear to be "bendable" IYSWIM were it so.
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Bit like the Enterprise's transporter
Ah, the good old "science" of Star Trek.
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how do they always end up perfectly placed on the surface of whatever they're beamed to? Why not half-an-inch above or below the surface?! Ha-ha-ha. That's for a different thread.
Know what you mean, whilst I don't mind progs such as ST (preferred B5 though) in general I do think they have a bad side in that some people actually believe certain things "could" be possible because of it. Problem is that whilst much of it is based on known physics they just take it to extremes which would (probably) never be possible.
Originally posted by Joobs: I just don't think it'd [time travel] be allowable since laws of physics would appear to be "bendable" IYSWIM were it so.
*Absolutely*. Plus the fact that I don't believe it's possible to interfere with the destination's physical makeup. The introduction of just one atom would have a profound consequence -- Butterfly effect.
Actually, the butterfly effect has fascinated me since I first heard about it. People don't realise just how *powerful* it is. I'm perched here writing this, and a thought flashed through my mind about something I had to do tomorrow. It interrupted for a split second what I wanted to write. Had it not come to mind, the knock-on effect would have changed the future of the world.
Sounds crazy, but if you think deeply about the consequences of your actions and their effects. . .
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Know what you mean,
Can't have this, Joobs; you're a man who thrives on combat
Originally posted by Roy P: Can't have this, Joobs; you're a man who thrives on combat
That's the problem with debating on online fora. Obviously one appears to be more argumentative or single minded than one truly is. (Or maybe I just delude myself and I really am a grumpy old git. )
) I believe the present (and future) is really an abstract concept all that truly exists is the past. Consider a timeline - on this events may be noted as they happen (the past) these events always exist once formed since they have occured and have a cause-effect to the events which precede and come after. The present however is only an abstract since it actually occupies the newest point of a timeline which is continually moving forward. In essence to consider the present is nonsensical since any consideration of an event classed as present would actually be a consideration of an event by then part of the timeline and in the past.
)
