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I'm sorry for my naivety! What is 'now'? How is it different from 'now' that was dt ago, or the 'now' that is dt in the future? That is, what quality might the 'now' possess which the set of all other points does not?

If a point in space-time, then why is it that 'now' appears to a conscious mind to have the special quality of carrying the intense and unfolding moment of causality?

Is 'now' a special case of the set of all points in space-time to consciousness?

Is 'now' the moment of collapse of the wave function? The moment of 'observation' or information passage?

Is it that 'now' can be described by different models (SR, QM, thermodynamics) and that I'm seeking the satisfaction of a anthropic 'now'; really a false question?

Perhaps, I should admit the frame of the question and ask: what is it that, for a human being, gives the experience of life which is only ever contained in the fizzling 'nowness' of a point (or is it the (dt,dx,dy,dz)) in space-time? Why does it appear to move, causally tracing a world line?

Lupey Bear
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  • In what way is the notion of 'now' any more confusing than the notion of 'here', though? Or is it every bit as misterious to you? Perhaps thinking about this helps. – Guillermo BCN Jan 28 '20 at 10:02
  • Thanks Guillermo. 'Here' is the same category of question. To say 'here' is to identify a point in space-time. I think that 'here' is always 'now'. And 'now' is probably always 'here'. – Lupey Bear Jan 28 '20 at 10:53
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    Unless 'here' is (xnow,ynow,xnow,t) and 'now' is (x,y,z,tnow)? – Lupey Bear Jan 28 '20 at 11:01
  • Related: https://physics.stackexchange.com/q/235511/123208 – PM 2Ring Jan 28 '20 at 11:02
  • Arguably, 'now' is a state of mind more than anything, localizable in spacetime by the spatio-temporal position of your body and affected by the corresponding past light cone. – Christoph Jan 28 '20 at 11:06
  • BTW, I think you're on the right track regarding "here & now". In relativity, it doesn't make a lot of sense to talk about spatial position independently of time. So the notions of "now" without specifying location, or "here" without specifying the time, aren't very useful. – PM 2Ring Jan 28 '20 at 11:14
  • There are lots of corollary reflections here which are fun.I want to try to understand whether 'now', perhaps 'here and now' being the same, is a special case? – Lupey Bear Jan 28 '20 at 11:42
  • But what of my 'now', now? And your 'now' as you read this: 'now'? What's happening at these moments (S-T points) that is not happening there when the 'now' has gone elsewhere? Given no universal time, there is presumably no universal 'now'. All 'now's are relative. But even so, what bestows 'now'-ness to a moment? – Lupey Bear Jan 28 '20 at 11:50
  • Perhaps all moments ('events') are equally 'now'. That's known as B-theory of time. – Christoph Jan 28 '20 at 12:17
  • Another angle: is there a moment of transformation? I think this is A-theory? This is how human experience seems to work. We're always in the present 'now' where a moment of future passes through and becomes the past. Either side of the 'now' time is utterly inaccessible to us. I don't even know how to think about width of the dt with live in. – Lupey Bear Jan 28 '20 at 13:09
  • In a Turing Machine there is a 'now' that is a state register. As the tape moves, a transformation occurs updating the state register. SR means there is no process of transformation - all S-T is flat and ready-made? Our 'now's are then illusory; why the illusion and what is being fooled? – Lupey Bear Jan 28 '20 at 13:18
  • Move your hands. Only you can move them. What is different in those hands, that is not in other hands? Not anything related to physics. Same for your question: physics has no answer. – Stéphane Rollandin Jan 28 '20 at 13:33
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    You may want to try asking this on the Philosophy Stack Exchange. Because of your use of words like "mind" "consciousness" and "causality," you are probably seeking more of a philosophical foundation upon which you can build a physical interpretation. Those are topics dealt with quite thoroughly in philosophy. – Cort Ammon Jan 28 '20 at 15:04

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I don't consider this a physics question, although it is an interesting one.

But what of my 'now', now? And your 'now' as you read this: 'now'? What's happening at these moments (S-T points) that is not happening there when the 'now' has gone elsewhere? Given no universal time, there is presumably no universal 'now'. All 'now's are relative. But even so, what bestows 'now'-ness to a moment?

From a physics standpoint, that is applying reductionism as far as possible, my opinion would be:

The events outside your brain are not considered in the now, as time has passed since your observations and they cannot be assumed not to have undergone changes since you observed them.

Inside your brain, where we might consider the most accurate experience of the now can be found, causality also applies. I have no idea what causes consciousness, but if we assume that a group of cells of some indeterminate minimum number will always be involved, there is still no absolute now, as it takes time for communication between these mininum number of cells.

So I would guess there is no absolute now, unless you believe that your consciousness arises from some other process, outside the realm of physics.

I think this question is a better fit for philosophySE, rather than any of the physical sciences sites.

  • Reminds me of Spaceballs. Everything that's happening now, happened then. What happened to now? We passed now. When? Just then! When will then be now? Soon. – Nuclear Hoagie Jan 28 '20 at 17:13
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As I put in my comments, "now" is more of a philosophical concept, especially when you want to think of it as special.

Given that "now" is as tricky of a word as you think it is, science typically strives to identify models in which "now" is not special -- any "now" is as good as any other "now." If it can make the model independent of any specific "now," then it can sidestep the fact that "now" is poorly defined.

Cort Ammon
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