Pushed Around by the Stars • Hacker News Board

Re: Pushed Around by the Stars

#21

Post by antognini » Thu, Dec 02, 2021, 6:30 PM UTC

pfdietz wrote: post #12

antognini wrote: post #11

Earlier quoted context omitted.

I think that for extremely small perturbations the discrepancy will be linear until it reaches a critical threshold, at which point the trajectories diverge exponentially. Basically, you need to get to the point where the path of one atom diverges by ~atomic radius. But until that happens, there is no non-linear mechanism to increase the divergence. For example, if you just consider a billiard ball bouncing between t…

> I think that for extremely small perturbations the discrepancy will be linear until it reaches a critical threshold An error of epsilon on the angle of a path toward the scatter will cause an error of ~(distance to scatter/size of scatter) epsilon in the angle from the center of the scatterer to the "impact point". So the errors should grow exponentially in the number of scatterings. The (effective) curvature of th…

I spent a bit more time thinking about this, and yes you are correct. Each scattering event increases the discrepancy by ~mean free path / atomic radius, which is about five orders of magnitude. So even starting from a 10^-78 discrepancy, it only takes ~10 collisions to get an order unity discrepancy. I was thinking that the discrepancy due to collisions was negligible compared to the accumulated tidal acceleration, but this is clearly wrong.

Re: Pushed Around by the Stars

#22

Post by pfdietz » Thu, Dec 02, 2021, 11:05 PM UTC

antognini wrote: post #21

pfdietz wrote: post #12

Earlier quoted context omitted.

> I think that for extremely small perturbations the discrepancy will be linear until it reaches a critical threshold An error of epsilon on the angle of a path toward the scatter will cause an error of ~(distance to scatter/size of scatter) epsilon in the angle from the center of the scatterer to the "impact point". So the errors should grow exponentially in the number of scatterings. The (effective) curvature of th…

I spent a bit more time thinking about this, and yes you are correct. Each scattering event increases the discrepancy by ~mean free path / atomic radius, which is about five orders of magnitude. So even starting from a 10^-78 discrepancy, it only takes ~10 collisions to get an order unity discrepancy. I was thinking that the discrepancy due to collisions was negligible compared to the accumulated tidal acceleration,…

About three orders of magnitude, not five, but yeah.

Re: Pushed Around by the Stars

#23

Post by perl4ever » Fri, Dec 03, 2021, 12:17 AM UTC

dsizzle wrote: post #20

perl4ever wrote: post #19

Earlier quoted context omitted.

You sound like you are champing at the bit to get into the argument about whether there is a difference between rain in "reality" and rain in a simulation. All I have to say about the question of whether there is a difference between physics and metaphysics is to quote "Reality is that which, when you stop believing in it, doesn’t go away". Which is really the same thing as Samuel Johnson kicking a stone: "I refute i…

Conversely you now seem focused on getting into an argument about simulations -- I gave an example of what I meant that doesn't involve simulations and is purely physical but you didn't comment on that. It's true I've focused on something that wasn't the meat of the original post -- but it's also true that I challenged a direct quote that is arguably the most profound claim in the post, and that's what I'm most inter…

>Conversely you now seem focused on getting into an argument about simulations

I gave a definition of reality, and definitions can't really be debated; thus, I don't see them as encouraging argument.

>I gave an example of what I meant that doesn't involve simulations and is purely physical

I'm uncertain what that was. Do you mean your "thing-ier example"? That compares simulated melting with actual melting?

Re: Pushed Around by the Stars

#24

Post by dsizzle » Fri, Dec 03, 2021, 3:12 AM UTC

perl4ever wrote: post #23

dsizzle wrote: post #20

Earlier quoted context omitted.

Conversely you now seem focused on getting into an argument about simulations -- I gave an example of what I meant that doesn't involve simulations and is purely physical but you didn't comment on that. It's true I've focused on something that wasn't the meat of the original post -- but it's also true that I challenged a direct quote that is arguably the most profound claim in the post, and that's what I'm most inter…

>Conversely you now seem focused on getting into an argument about simulations I gave a definition of reality, and definitions can't really be debated; thus, I don't see them as encouraging argument. >I gave an example of what I meant that doesn't involve simulations and is purely physical I'm uncertain what that was. Do you mean your "thing-ier example"? That compares simulated melting with actual melting?

Yes to your first question: the example was that quarks (sub-nuclear particles) can be justifiably ignored completely in understanding/predicting some physical properties of matter, like the melting point of metals (even though metals are composed of quarks). Or more generally, quantum chromodynamics mostly has no effect on solid state physics -- and these are both sub-branches of physics! When you consider all of science/reality there are many such levels where phenomena appear at only some levels.

I don't really understand where you're going with the metaphysics/reality discussion. It seems you consider software part of metaphysics? The laptop I'm typing this on is real in Johnson's sense, as are the patterns of photons projected from the screen, and these can't be understood much of the time without having some understanding of the software it's running.

Just to establish some common ground: I agree that metaphysics is different from physics. I also agree that a thing is different from a simulation of the same thing. I get that software is more abstract than the particle interactions described in the article, and that that is perhaps a distracting difference in the example I first used, as you pointed out. If there's an interesting discussion/disagreement here it's somewhere in the neighborhood of the question: "is math part of reality?" That's something of an open philosophical question https://www.journals.uchicago.edu/doi/abs/10.1086/289138. I think that's even more tangential than my original comment though.

Re: Pushed Around by the Stars

#25

Post by smegger001 » Sat, Dec 04, 2021, 12:01 AM UTC

autokad wrote: post #8

finite_jest wrote: post #6

Earlier quoted context omitted.

This video by Veritasium on the unexpected effects of the cosmic rays is pretty interesting: https://odysee.com/@veritasium:f/how-distant-galaxies-mess-w... .

yeah, pretty funny how a cosmic ray can flip an election.

and frustrating that ECC ram is not standard

Re: Pushed Around by the Stars

#26

Post by thaumasiotes » Sat, Dec 04, 2021, 1:01 AM UTC

dsizzle wrote: post #24

perl4ever wrote: post #23

Earlier quoted context omitted.

>Conversely you now seem focused on getting into an argument about simulations I gave a definition of reality, and definitions can't really be debated; thus, I don't see them as encouraging argument. >I gave an example of what I meant that doesn't involve simulations and is purely physical I'm uncertain what that was. Do you mean your "thing-ier example"? That compares simulated melting with actual melting?

Yes to your first question: the example was that quarks (sub-nuclear particles) can be justifiably ignored completely in understanding/predicting some physical properties of matter, like the melting point of metals (even though metals are composed of quarks). Or more generally, quantum chromodynamics mostly has no effect on solid state physics -- and these are both sub-branches of physics! When you consider all of sc…

You seem to be arguing that "everything affects everything else" is false because, moving to a concrete example, if Kristin Kreuk is beautiful, then she's beautiful in an objective sense that can't be affected by the motion of space dust.

But this doesn't matter, because every time her beauty is assessed, the assessment itself is affected by space dust. Her objective, Platonic beauty is only relevant in that it affects how often she is assessed to be beautiful. But this is precisely the statistical description that the OP argues for. In the world of things that happen, everything affects everything else.

Re: Pushed Around by the Stars

#27

Post by dsizzle » Sat, Dec 04, 2021, 4:35 AM UTC

thaumasiotes wrote: post #26

dsizzle wrote: post #24

Earlier quoted context omitted.

Yes to your first question: the example was that quarks (sub-nuclear particles) can be justifiably ignored completely in understanding/predicting some physical properties of matter, like the melting point of metals (even though metals are composed of quarks). Or more generally, quantum chromodynamics mostly has no effect on solid state physics -- and these are both sub-branches of physics! When you consider all of sc…

You seem to be arguing that "everything affects everything else" is false because, moving to a concrete example, if Kristin Kreuk is beautiful, then she's beautiful in an objective sense that can't be affected by the motion of space dust. But this doesn't matter, because every time her beauty is assessed , the assessment itself is affected by space dust. Her objective, Platonic beauty is only relevant in that it affe…

It seems in this example you do accept that there's an objective reality (beauty) that isn't affected by space dust? If so, I don't understand why you say that doesn't matter, and instead attach significance to the camera noise or whatever measurement artifacts that space dust causes. A central goal of science -- and making sense of the world more generally -- is to distinguish between such measurement artifacts and more interesting theories that describe what's really out in the world.

I would reserve the usage "X affects Y" to where there's an interesting theory involving both, and I had the impression the OP did as well.

Re: Pushed Around by the Stars

#28

Post by thaumasiotes » Sat, Dec 04, 2021, 6:04 AM UTC

dsizzle wrote: post #27

thaumasiotes wrote: post #26

Earlier quoted context omitted.

You seem to be arguing that "everything affects everything else" is false because, moving to a concrete example, if Kristin Kreuk is beautiful, then she's beautiful in an objective sense that can't be affected by the motion of space dust. But this doesn't matter, because every time her beauty is assessed , the assessment itself is affected by space dust. Her objective, Platonic beauty is only relevant in that it affe…

It seems in this example you do accept that there's an objective reality (beauty) that isn't affected by space dust? If so, I don't understand why you say that doesn't matter, and instead attach significance to the camera noise or whatever measurement artifacts that space dust causes. A central goal of science -- and making sense of the world more generally -- is to distinguish between such measurement artifacts and…

> It seems in this example you do accept that there's an objective reality (beauty)

Think about why I might have picked beauty for the example.

Re: Pushed Around by the Stars

#29

Post by JPLeRouzic » Sat, Dec 04, 2021, 9:22 AM UTC

> Everything affects everything else, and the correct questions to ask are how much?

I wish this kind of statement would be applied to biology, indeed there is system biology, but it does not seems to be used widely.

I read avidly everything which is published in neurodegenerative diseases. Most of academic publications claim that one or another of ten of thousands molecules have a positive influence on these diseases.

Clearly the biotech or pharmaceutical industries does not trust most of these publications as little of these suggestions are translated in clinical trials.

I do not want to say that the biotech/pharma industries are more rational either as it happens that:

- They seems to apply one molecule to multiple unrelated diseases until they find a suitable target (which more than often they do not find)

- They apply repetitively the same molecule to the same disease even when clinical trials show it is not effective (for example memantine and ALS).

Re: Pushed Around by the Stars

#30

Post by dsizzle » Sat, Dec 04, 2021, 5:25 PM UTC

thaumasiotes wrote: post #28

dsizzle wrote: post #27

Earlier quoted context omitted.

It seems in this example you do accept that there's an objective reality (beauty) that isn't affected by space dust? If so, I don't understand why you say that doesn't matter, and instead attach significance to the camera noise or whatever measurement artifacts that space dust causes. A central goal of science -- and making sense of the world more generally -- is to distinguish between such measurement artifacts and…

> It seems in this example you do accept that there's an objective reality (beauty) Think about why I might have picked beauty for the example.

I don't know, I did think it was an odd example, but you also referred to beauty in an objective sense twice. Are you saying... everything is subjective?