Ask a physicist anything. (6)

[Maxwell511]

The way I see it, if "god" has total and complete knowledge and knows every decision one will ever make in life, can one have free will if one can never make a decision contrary to the known outcome?

Science and logic and the studies of them have progressed a lot since the classical times, when people thought God could have total knowledge.

If God knows the outcome of all events it is most likely that God knows at least two contradictions to be true. His knowledge cannot be complete and consistent*. As per Godel.

*The main argument against this, is that God is not subject to human logic and the human law of non-contradiction. My retort to is that any conversations about the matter are then pointless cos if He doesn't obey the simple logical laws, the question of His existence is meaningless, cos a person that defies logic can both exist and not exist without any contradiction.

Basically if God is mentioned, don't bother trying to make a logical argument. The premises will be inconsistent and therefore you could prove anything using logical reasoning.

 

[Maxwell511]

Well all philosophy boils down to physics, so I suppose this falls under my jurisdiction

If you honestly believe that you have never studied science or philosophy properly. Science kicks philosophies ass as an epistemology method, but we will need a philosophical answer why that is case.

How and Why questions are very different.

 

[mzungu]

If you honestly believe that you have never studied science or philosophy properly. Science kicks philosophies ass as an epistemology method, but we will need a philosophical answer why that is case.

How and Why questions are very different.

A question can be posed in a philosophical way and if there is any merit to it then Science can enter the scene and answer the question. A example being: Can I go back in time and shoot myself? This is basically a philosophical question. The scientific answer will be No; Because this will cause a paradox and paradoxes are not allowed. The exact answer needs many pages and is beyond the scope of this post.

 

[Wiccan_Child]

If you honestly believe that you have never studied science or philosophy properly. Science kicks philosophies ass as an epistemology method, but we will need a philosophical answer why that is case.

I was joking. Winking emoticon, and all that.

I wonder, did I just make a secular Poe?

How and Why questions are very different.

I disagree:

"Why does the Sun burn?"
"How do you solve this equation?"
"Why do good things happen to bad people?"
"How should we treat black people?"

I've never understood why people say "Science answer's the how, religion/philosophy answers the why", when they're just English adverbs, grammatical fillers that say "This is a question". Whether science or philosophy answers one or the other is surely contextual, not grammatical.

 

[Wiccan_Child]

Science and logic and the studies of them have progressed a lot since the classical times, when people thought God could have total knowledge.

If God knows the outcome of all events it is most likely that God knows at least two contradictions to be true. His knowledge cannot be complete and consistent*. As per Godel.

I don't believe that's what Godel said. He said that any first-order logical language capable of basic arithmetic cannot be both complete (all terms uniquely defined without self-reference) and consistent (no paradoxes, contradictions, etc). Why does that mean an omniscient being cannot have complete and consistent knowledge?

Perhaps it would help if 'omniscience' were defined. If we're going to be sensible and talk about a logically coherent being, I would say it's absolute and total knowledge of everything - that isn't logically impossible to know. He doesn't know how to square the circle, for instance.

 

[Wiccan_Child]

To be fair, we were discussing responsibility of the creator for the evil in the world and how free will relates to that, so if you subscribe to the idea of deterministic free will as compatible with omniscience than (I think) responsibility still carries through.

I would say the responsibility falls squarely on the omniscient creator who knowingly and willingly created a world full of suffering. The bullet may cause the suffering more directly than the gun, but the shooter is still morally culpable.

A more physics related question: is "non-determinism" still non-deterministic if you know the result ahead of time (eg via time machine or "omniscience")?

Hmm. It depends on who the time-machine works, how the 'laws of time' operate - is it Terminator-style 'delayed inevitability', Star Trek-style alternate timelines, Stargate-style 'many worlds'?

An omniscience could know ahead of time, by dint of knowing everything.

 

[Wiccan_Child]

A question can be posed in a philosophical way and if there is any merit to it then Science can enter the scene and answer the question. A example being: Can I go back in time and shoot myself? This is basically a philosophical question. The scientific answer will be No; Because this will cause a paradox and paradoxes are not allowed. The exact answer needs many pages and is beyond the scope of this post.

Well, scientifically, there could be alternate timelines and suchlike which mean you travel back in time to an alternate past. Arguably, you can't go back in time at all because simply being there will alter the universe - so you go back in time to a different universe.

 

[Assyrian]

A example being: Can I go back in time and shoot myself? This is basically a philosophical question. The scientific answer will be No; Because this will cause a paradox and paradoxes are not allowed.

I would have thought the scientific answer would be "lets try it and see". Your hypothesis is that paradoxes are not allowed but surely that needs to be tested? I have a sneaking suspicion our universe only cares about immediate causality, the fact that someone popped into existence three months ago and shot you. The problem that you will never get to travel back in time in the future will not change what has already happened in the past.

 

[mzungu]

I would have thought the scientific answer would be "lets try it and see". Your hypothesis is that paradoxes are not allowed but surely that needs to be tested? I have a sneaking suspicion our universe only cares about immediate causality, the fact that someone popped into existence three months ago and shot you. The problem that you will never get to travel back in time in the future will not change what has already happened in the past.

One cannot avoid causing a paradox in time travel. Such oddities can exist only at the plank level in the quantum foam where wormholes appear and due to paradoxes being not allowed the wormholes close up almost instantly.

Even with parallel universes; One cannot transverse from one universe time interval into another universe time interval. Because by doing so you will essentially be adding mass into another universe and that mass was not transformed from energy that pre-existed in that universe. Thus a paradox arises and that mass (you) cannot exist there and you will immediately be sent back! . Actually in my opinion; You can go to the future by suspended animation and see the past by using distance but you cannot vice versa the two.

This may shed some light: Time Trip | Watch Free Documentary Online

 

[Wiccan_Child]

One cannot avoid causing a paradox in time travel. Such oddities can exist only at the plank level in the quantum foam where wormholes appear and due to paradoxes being not allowed the wormholes close up almost instantly.

Even with parallel universes; One cannot transverse from one universe time interval into another universe time interval. Because by doing so you will essentially be adding mass into another universe and that mass was not transformed from energy that pre-existed in that universe.

Agreed, even if you 'displace' the air and send it into the future, you could still 'add' mass to the parallel universe.

Thus a paradox arises and that mass (you) cannot exist there and you will immediately be sent back!

Wait, where's the paradox?

 

[Assyrian]

One cannot avoid causing a paradox in time travel. Such oddities can exist only at the plank level in the quantum foam where wormholes appear and due to paradoxes being not allowed the wormholes close up almost instantly.

Even with parallel universes; One cannot transverse from one universe time interval into another universe time interval. Because by doing so you will essentially be adding mass into another universe and that mass was not transformed from energy that pre-existed in that universe. Thus a paradox arises and that mass (you) cannot exist there and you will immediately be sent back! . Actually in my opinion; You can go to the future by suspended animation and see the past by using distance but you cannot vice versa the two.

This may shed some light: Time Trip | Watch Free Documentary Online

I'm more a trouser leg of time man than multiple universes, going back in time you go back in time in your own universe, but your actions send the universe down the other trouser leg. Though the result is the universe ending up with the extra mass of you plus dead you. But that isn't the creation of mass, that is stealing it from another version of the future that never happened (or at least didn't stay happened). Which does start to sound like the kind of thing that happens on the quantum foam level.

 

[mzungu]

Agreed, even if you 'displace' the air and send it into the future, you could still 'add' mass to the parallel universe.


Wait, where's the paradox?

Well let's think about it for a moment. We send mass to the past in a parallel universe. Since this is the past and this mass did not exist in this past then how can a mass from the future be added to this universe? This to me looks like a paradox. It does not have to be killing yourself to be a paradox. The mere presence of this mass creates a paradox; And is automatically disallowed and will disappear as it cannot be sustained in that universe. Remember that when a paradox is present then it is not allowed to manifest itself.

Of course I will be more than happy to be refuted! After all anyone who loves science also enjoys progress!

 

[mzungu]

I'm more a trouser leg of time man than multiple universes, going back in time you go back in time in your own universe, but your actions send the universe down the other trouser leg. Though the result is the universe ending up with the extra mass of you plus dead you. But that isn't the creation of mass, that is stealing it from another version of the future that never happened (or at least didn't stay happened). Which does start to sound like the kind of thing that happens on the quantum foam level.

Remember that all mass comes from the pre-existing energy in the universe. How can you add more energy? What I mean is that by adding mass you are essentially adding energy and this is something that cannot be allowed.

I like your trouser analogy!

 

[Wiccan_Child]

Well let's think about it for a moment. We send mass to the past in a parallel universe. Since this is the past and this mass did not exist in this past then how can a mass from the future be added to this universe? This to me looks like a paradox.

You have made an assumption here: "Since.. this mass did not exist in this past" - evidently, it did exist in the past, as you just put it there.

Imagine three eras in time: t < 0 is before you arrive in the past, t > T is after you left the future, and 0 < t < T is between those two events. The mass M(t) of the universe at a time t is:

M(t<0) = M[sub]0[/sub]
M(0<t<T) = M[sub]0[/sub] + m
M(t>T) = M[sub]0[/sub]

In other words, for that brief period between the two time-travel events, the displaced mass m (the mass that arrives in the past minus the mass that was already in the area in space where you arrived) is a small addition to the universe. Once we hit t = T, the original you travels back in time, restoring the universe to its original mass.

And even in that relatively brief window, all that happens is that the universe has a bit more (or, potentially, less) mass than it originally did.

It does not have to be killing yourself to be a paradox. The mere presence of this mass creates a paradox; And is automatically disallowed and will disappear as it cannot be sustained in that universe. Remember that when a paradox is present then it is not allowed to manifest itself.

Of course I will be more than happy to be refuted! After all anyone who loves science also enjoys progress!

I'm interested in how you see paradoxes being resolved. Do you see the universe as 'knowing' a paradox is about to occur, and actively stopping it? Or are paradoxes prevented by the universe's own natural consistency? That is, if time-travel can lead to paradoxes, then time-travel is necessarily impossible due to some law of physics - or does the universe wink the excess matter out of existence shortly after it tries to go back in time?

Moreover, I'm confused as to why the extra mass is itself a paradox. What is paradoxical about it?

 

[Assyrian]

Remember that all mass comes from the pre-existing energy in the universe. How can you add more energy? What I mean is that by adding mass you are essentially adding energy and this is something that cannot be allowed.

But if you are talking about time travel you are stepping outside this space time continuum and bringing the matter from somewhere or some when else.

I like your trouser analogy!

Can't claim credit though. The trouser leg of time is a Terry Pratchett's idea

 

[chris4243]

Well, scientifically, there could be alternate timelines and suchlike which mean you travel back in time to an alternate past. Arguably, you can't go back in time at all because simply being there will alter the universe - so you go back in time to a different universe.

I think there's a resolution that allows time travel in GR. It involves closed time-like loops, and also you cannot travel back in time to before the time machine was built (because there either is a closed time-like loop or there isn't at any given point). It still messes with causality, I think, yet part of it is that a time travel event either happened or didn't and so you can't change the past because the time-travel event is part of that past already.

 

[chris4243]

Even with parallel universes; One cannot transverse from one universe time interval into another universe time interval. Because by doing so you will essentially be adding mass into another universe and that mass was not transformed from energy that pre-existed in that universe. Thus a paradox arises and that mass (you) cannot exist there and you will immediately be sent back!

Well there's two possibilities. 1) The law of conservation of energy is not tested as forbidding a transfer between universes. 2) Trading mass from one universe to another would avoid that problem (also to conserve charge, baryon number, lepton number, etc).

 

[Wiccan_Child]

I think there's a resolution that allows time travel in GR. It involves closed time-like loops, and also you cannot travel back in time to before the time machine was built (because there either is a closed time-like loop or there isn't at any given point). It still messes with causality, I think, yet part of it is that a time travel event either happened or didn't and so you can't change the past because the time-travel event is part of that past already.

That would seem to blow free will out of the water, then - if causality can be mucked around with, but history is fixed, then our actions are set in stone.

Plus, physicists tend to err on the side of QM in cases where it conflicts with GR, which suggests that the latter isn't quite as airtight as we'd like.

 

[Maxwell511]

A question can be posed in a philosophical way and if there is any merit to it then Science can enter the scene and answer the question. A example being: Can I go back in time and shoot myself? This is basically a philosophical question. The scientific answer will be No;"

If science can answer it.

"Because this will cause a paradox and paradoxes are not allowed. The exact answer needs many pages and is beyond the scope of this post.

That is a philosophical answer. If it is not verifiable through sources beyond human reason, it is philosophy and not science.

 

[Maxwell511]

I've never understood why people say "Science answer's the how, religion/philosophy answers the why", when they're just English adverbs, grammatical fillers that say "This is a question". Whether science or philosophy answers one or the other is surely contextual, not grammatical.

My understanding is that the "How" and "Why" are labels for types of questions and not how the question is grammatically formed. So, "Is my subjective experience of colour the same as yours?", is a Why question. Even though there is no way I can think of framing that grammatical starting with a Why. Similarly, questions that start with How can actually belong to the Why category.