<p>I am trying to sharpen the convex hull of what seems like a (surprisingly) stubborn concept to enclose based on answers here, as well as conversations with others, around the nature of what actually constitutes a computation.</p>
<p>As a motivating scenario for the question, consider the following:</p>
<p>Around some distant star in a some faraway godforsaken galaxy, exists a boring gas cloud. Here, two protons careen towards each other on an inevitable collision course. The protons' repel each other, and their trajectories inevitably change and off they go.</p>
<p>Has a computation taken place?</p>

CC BY-SA 4.0
2021-10-12T02:53:12.257Z
Luckily for us, in TCS "computation" is just a word for the process that a computer does when it executes, and a "computer" is a well-defined *mathematical abstraction* (e.g. a Turing Machine).  Not a physical device, so from this perspective, physical processes do not do computation, and the answer to your question would be no, and furthermore, what normal people call computers (actual computers) don't do computation either.  If you want to reason about the real world or physics as it models the real world, maybe you should ask a philosopher or a physicist how they define "computation"?
Neal Young
CC BY-SA 4.0
2021-10-12T14:46:54.810Z
@NealYoung To make sure I understand you: Are you claiming that there exist a multitude of (possibly contradictory) *formal* definitions of computation?
dnnct
CC BY-SA 4.0
2021-10-12T19:37:49.123Z
No, just that TCS has one.  I can't speak for other fields.  And implicitly I am suggesting that there are philosophical (and somewhat gray) issues when applying any formal concept and asking whether a given real-world situation actually realizes it.  Or for that matter, any concept, formal or otherwise.  Our conceptual world only provides models.  Models are never the same as the underlying reality.  And probably "underlying reality" is itself never precisely knowable.
Neal Young
CC BY-SA 4.0
2021-10-13T01:34:34.240Z
@NealYoung Ok - if we focus on the definition you provided for TCS, then it seems like you're saying that it does not make sense to even talk about computation, without talking about _mathematical abstractions_. However mathematical abstractions are mental models, hence, it does not make sense to talk about computation, without invoking a being that possesses mental models and the capacity to create mathematical abstractions to begin with.
dnnct
CC BY-SA 4.0
2021-10-13T01:43:13.283Z
Strange, I do it all the time with other people, and we don't seem to have trouble making sense of it.  On the other hand, I don't know how to talk about, say beings, and feel like I'm making sense quite so precisely.  Perhaps mathematics is the only domain where the kind of precision your question seems to be asking for seems possible, and maybe that's because mathematicians are seeking exactly that kind of thinking.  :-)
Neal Young
CC BY-SA 4.0
2021-10-13T02:05:04.733Z
@NealYoung: you mean we can't say that oracle machines do computations? What do they do, if you can't call the things they do "computations".
Peter Shor 
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2021-10-13T14:22:36.003Z
@PeterShor, Hi Peter!  By oracle machines I assume you mean TM's extended definitionally to allow use of an oracle.  I don't mean that the vanilla TM is the only definition that TCS has for computation.  So oracle machines can be another.  I mean that in TCS when we talk precisely about computation we generally have in mind a shared mathematical definition of what it means --- we are working in the space of mathematical models.  We do *sometimes* care to what extent they are realized in the real word, e.g. when trying to build a quantum computer.. But we know "realized" is a fuzzier concept.
Neal Young
CC BY-SA 4.0
2021-10-13T14:32:28.563Z
To bring this back to the OP, I would say the question is a little like asking how many angels could fit on the head of a pin.. which we eventually replace by some more precise mathematical models for infinity.  Right now, the standard models of computation (AFAIK) don't apply to OP's situation, so those models would not say computation has occurred.  Although there are [some (fringe) models](https://en.wikipedia.org/wiki/Programming_the_Universe) of the universe as essentially information-theoretic and doing computation, and in those models *every* physical event is a computation.
Neal Young
CC BY-SA 4.0
2021-10-18T00:32:21.157Z
@NealYoung not sure what was confusing about my earlier comment. I was asking if you viewed any computation as necessarily needing an agent/being doing a computation, since you used "mathematical model" as a (seeming) pre-requisite. Hence, my question to you was if any conversation about computation, necessitated the existence of a being "at least being able to possess abstract mathematical models". Simple q. Im trying to understand you not argue with you.
dnnct
CC BY-SA 4.0
2021-10-18T00:46:38.827Z
@NealYoung To rephrase: What are the minimum _physical_ requirements before which we can claim a computation has taken place?
dnnct
CC BY-SA 4.0
2021-10-18T13:24:31.713Z
Sorry, not trying to argue, nor did I find your comment confusing.  My point is that (IMO) "computation" *in the physical world* does not have a precise definition, so there is no clear answer to the original question (or whether *anything* in the physical world ever constitutes a computation).   As for whether we have to invoke beings if we are to discuss anything conceptual, the answer IMO is no, we discuss e.g. computation (and many other well-defined concepts) all the time without invoking beings.  So to me that seems a red herring, at least from a TCS perspective.
Neal Young
CC BY-SA 4.0
2021-10-18T20:17:52.043Z
@NealYoung I will take this offline with you.
dnnct
<turing-machines><it.information-theory><universal-computation><church-turing-thesis>
Does any physical process constitute a "computation"?
dnnct
# Does any physical process constitute a "computation"?

(Asked by: username_0 on 2021-10-11)

I am trying to sharpen the convex hull of what seems like a (surprisingly) stubborn concept to enclose based on answers here, as well as conversations with others, around the nature of what actually constitutes a computation.

As a motivating scenario for the question, consider the following:

Around some distant star in a some faraway godforsaken galaxy, exists a boring gas cloud. Here, two protons careen towards each other on an inevitable collision course. The protons' repel each other, and their trajectories inevitably change and off they go.

Has a computation taken place?

**Tags:** turing-machines, it.information-theory, universal-computation, church-turing-thesis

> **Comments:**
> **username_1**: Luckily for us, in TCS "computation" is just a word for the process that a computer does when it executes, and a "computer" is a well-defined *mathematical abstraction* (e.g. a Turing Machine).  Not a physical device, so from this perspective, physical processes do not do computation, and the answer to your question would be no, and furthermore, what normal people call computers (actual computers) don't do computation either.  If you want to reason about the real world or physics as it models the real world, maybe you should ask a philosopher or a physicist how they define "computation"?  
> **username_0**: @NealYoung To make sure I understand you: Are you claiming that there exist a multitude of (possibly contradictory) *formal* definitions of computation?  
> **username_1**: No, just that TCS has one.  I can't speak for other fields.  And implicitly I am suggesting that there are philosophical (and somewhat gray) issues when applying any formal concept and asking whether a given real-world situation actually realizes it.  Or for that matter, any concept, formal or otherwise.  Our conceptual world only provides models.  Models are never the same as the underlying reality.  And probably "underlying reality" is itself never precisely knowable.  
> **username_0**: @NealYoung Ok - if we focus on the definition you provided for TCS, then it seems like you're saying that it does not make sense to even talk about computation, without talking about _mathematical abstractions_. However mathematical abstractions are mental models, hence, it does not make sense to talk about computation, without invoking a being that possesses mental models and the capacity to create mathematical abstractions to begin with.  
> **username_1**: Strange, I do it all the time with other people, and we don't seem to have trouble making sense of it.  On the other hand, I don't know how to talk about, say beings, and feel like I'm making sense quite so precisely.  Perhaps mathematics is the only domain where the kind of precision your question seems to be asking for seems possible, and maybe that's because mathematicians are seeking exactly that kind of thinking.  :-)  
> **username_2**: @NealYoung: you mean we can't say that oracle machines do computations? What do they do, if you can't call the things they do "computations".  
> **username_1**: @PeterShor, Hi Peter!  By oracle machines I assume you mean TM's extended definitionally to allow use of an oracle.  I don't mean that the vanilla TM is the only definition that TCS has for computation.  So oracle machines can be another.  I mean that in TCS when we talk precisely about computation we generally have in mind a shared mathematical definition of what it means --- we are working in the space of mathematical models.  We do *sometimes* care to what extent they are realized in the real word, e.g. when trying to build a quantum computer.. But we know "realized" is a fuzzier concept.  
> **username_1**: To bring this back to the OP, I would say the question is a little like asking how many angels could fit on the head of a pin.. which we eventually replace by some more precise mathematical models for infinity.  Right now, the standard models of computation (AFAIK) don't apply to OP's situation, so those models would not say computation has occurred.  Although there are [some (fringe) models](https://en.wikipedia.org/wiki/Programming_the_Universe) of the universe as essentially information-theoretic and doing computation, and in those models *every* physical event is a computation.  
> **username_0**: @NealYoung not sure what was confusing about my earlier comment. I was asking if you viewed any computation as necessarily needing an agent/being doing a computation, since you used "mathematical model" as a (seeming) pre-requisite. Hence, my question to you was if any conversation about computation, necessitated the existence of a being "at least being able to possess abstract mathematical models". Simple q. Im trying to understand you not argue with you.  
> **username_0**: @NealYoung To rephrase: What are the minimum _physical_ requirements before which we can claim a computation has taken place?  
> **username_1**: Sorry, not trying to argue, nor did I find your comment confusing.  My point is that (IMO) "computation" *in the physical world* does not have a precise definition, so there is no clear answer to the original question (or whether *anything* in the physical world ever constitutes a computation).   As for whether we have to invoke beings if we are to discuss anything conceptual, the answer IMO is no, we discuss e.g. computation (and many other well-defined concepts) all the time without invoking beings.  So to me that seems a red herring, at least from a TCS perspective.  
> **username_0**: @NealYoung I will take this offline with you.  

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## 0 answers

