Comment by bschmidt1 | Hacker News Reader

Comment by bschmidt1 | Hacker News Reader

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There are things that are simultaneously true/false depending on how you look at it - and looking at something 1 way makes the other incompatible.

Thought experiment:

I live on a planet near Star A and you live 6 trillion miles away on a planet near Star B. Each of us can see each other's host star as a bright star in our respective skies. Suddenly, both of our host stars supernova and burn out at the exact same time.

However, survivors on my planet observe that Star A supernova'd, and then about 1 year later Star B supernova'd (due to how long the light takes to reach Star A from Star B). And survivors on your planet observe the opposite: That Star B blew up first, and 1 year later Star A followed.

Only an observer precisely equidistant from both stars would have observed the stars burn out simultaneously. But there's nothing special about this vantage point - this vantage point isn't "the truth" either.

This means that a concept like the order of events is not an absolute measurement. To come up with a new function that explains what "really happened" here, accounting for relativity and lightspeed, would be to leave out at least that detail. Each additional function that answers new mysteries abstracts further and leaves out other details by necessity.

I think of it like fine-tuning a model to increase accuracy, it necessarily de-tunes it in other ways.

> simulating a bouncing ball at all levels, with no reduction

It wouldn't fully be the same thing (although could be a very good approximation).

It's not that we're "leaving out a detail" or "abstracting" it's that there genuinely isn't a global reference frame and the events genuinely cannot be globally ordered.

You have it backwards. Events not having a globally consistent order is reality. Events seeming like they do is your intuition and leaves out details.

All these are true:

- A happened before B

- B happened before A

- A & B happened at the exact same time

- Neither / there is no "before"/"after"

Considering this is the case with anything measured, what explanatory "truth" would be left when you consider a perfect description of reality? One that accounts for the global reference frames of every possible metric (not just order of events)?

There's no absolute "truth" to any of the mainstays:

Where things are

When they happened

In what order they happened

Even whether or not they happened (there is a perspective where all the values of a measured thing can be zero - like mirroring the velocity of a speeding object to reduce its speed to zero, or rotating a plane to make its height zero - and the different physical implications therein).

We correlate observed "locations in space" and the "passage of time" to heuristical approximations that work (as scientific theories) for our intents and purposes on a hyper local level (a tiny fraction of just our galaxy), but they break down on macro levels because they aren't really accurate descriptions of reality. Our physics doesn't work at scale - not smaller than atoms, nor larger than ~solar systems, without theories falling apart.

Space

The XYZ coordinate system we understand as "3D space" works great for locating and measuring the size of objects locally, we could perfectly track a tiny marble bouncing down a huge mountain with a granular enough XYZ coordinate system and telemetry. But that wouldn't work on larger scales like comparing the movement of subatomic particles with the movement of stars in the same graph. The graph couldn't accurately chart that without normalizing data or adjusting the reference frame toward one bias or the other (see scale invariance, vacuum catastrophe). We can only neatly slap a fixed reference frame over a scoped area, invent units and call it a "field", if we expect any predictive utility.

Time

There's not really an absolute "arrow of time" with a past and future, where A happened, then B happened, etc. in an absolute sense. As shown in the star example, it completely depends on the orientation and velocity of the observer, and other factors. No one perspective is more true than the other.

We all happen to hang out in the same frames, so it seems like some of these are rigid laws - they effectively are, for us - but they aren't really, ultimately. When you eliminate the heuristics that give value to science there's nothing left - which as mentioned above is a possible and potential state.

Relativity is not the same as relativism. Theory of relativity gives us a precise description of the relation between A and B... it's just not the kind of relation we would naively expect. But we can still calculate the answer from the perspective of any reference frame. (Also, it is possible to have other events C and D such that C happened before D in every reference frame.)

Instead of living in a 3D universe with an absolute time, we are living in a 4D universe where time is a relative direction in the space-time. That doesn't mean we can't model things in principle, it just means we need to model them as things existing in 4D space-time.

> Relativity is not the same as relativism

True, really just meant "not absolute".

> such that C happened before D in every reference frame

If that's possible, considering the seemingly infinite number of instances where it'd have to both happen and in that way/order, I would consider those kinds of events to be the fundamental/baseline "forces" or asymmetries.

The keywords related to this are "spacelike" and "timelike". https://en.wikipedia.org/wiki/Causal_structure

For example, the distance between Earth and Moon is about 1.3 light-seconds. That means that is A happens on Earth now, and B happens on Moon 1 second later (from our perspective), it is possible that from someone else's perspective B happened before A.

(Note that "someone else" in this example does not refer to the Moon, because its perspective is very similar to the perspective of the Earth. It refers to a hypothetical alien spaceship flying at an extremely high speed in a line parallel to the line between the Earth and the Moon.)

However, if C happens on Earth now, and D happens on Moon 2 seconds later (from our perspective), then C happened before D from everyone's perspective. Individual aliens would disagree on the exact time interval between C and D, where 0.7 would be the smallest possible value, but it could be any larger value. (You get the smallest possible value when you are not moving relatively to the Earth and the Moon.)

This is because a hypothetical light particle emitted at A couldn't reach B in time, but a hypothetical light particle emitted at C could reach D in time. The speed of light is the speed of causality, kind of. Events A and B couldn't possibly have caused each other (they could have a common cause X, but that's different), but C hypothetically could have caused D, which is why C happened before D from everyone's perspective.

> because a hypothetical light particle emitted at A couldn't reach B in time

Fascinating insights - it can be seen as causality, or at scale that there is a multi-dimensional reality where some timelines are inaccessible/impossible to each other (yet exist in their own right).

1. Truth itself is an invention of the human mind to try and sort physical observations / claims about the external world into two neat buckets.

2. Time as a linear description is the same, a way of sorting the physical world into a series of events.

Both have generalizations. Topos Theory generalizes Set Theory with different notions of what is "true." There are several variations on temporal logic with Linear Temporal Logic being only one such idea.

With all that in mind, your thought experiment does not cause any issues because you can say that the framework for reasoning about the example is _itself_ the problem. Hence, it fails as a counterexample for our inability to potentially understand reality without flaw.

> It fails as a counterexample for our inability to potentially understand reality without flaw

In both comments I assert that phenomena cannot be wholly modeled (or replicated). The gist is that descriptions and replicas are always lossy to some extent.

The second comment just expands on why, relating it ultimately to physical limitations (features) of physical reality.

You can get uncannily precise and predictive with some knowledge - engineering, manufacturing, math - that any lossiness is truly negligible. Especially the smaller the scope and more "medium sized" the object or idea in question. But compounded, and at extreme scales, the incompleteness of our understanding of reality shows.

I agree with your 1 & 2.

When it comes to mathematics do you use the law of excluded middle? I ask out of curiosity. Wondering if your physical intuitions are “natural” (for lack of a better word) enough that it affects your view of mathematical logic.

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