All objects and some questions | Hacker News Reader

All objects and some questions

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38 pointsnotpushkin19 comments

We changed the URL from https://kottke.org/23/09/the-plot-of-all-objects-in-the-univ....

(Kottke is great but usually these are best changed to the original source. That URL is still a good place to start.)

Neat; it's a bit dense for non-physicists, though. Who's up for creating an SVG version of this with links for the words? I don't think I could do it justice with my very minimal understanding of physics and SVG.

The linked article goes into more detail. Still pretty dense, but better than this treatment.

I am not sure whether I agree with the "Compton limit." A particle can be spatially localized as much as you want if you include high velocities in its wave function, and that can happen in tight bound states as well as in high energy processes. To offer an example of the former, the radius of the s1 atomic orbital shrinks as the nuclear charge increases, and if there is a limit on nuclear charge it is determined by processes unrelated to the electron itself. For the latter, the total energies of all particles eventually start acting like photons w.r.t velocity as their rest mass is overwhelmed, and the gravitation or inertia of a beam of light is impossible to rationalize as mass or put on that chart.

When plotted that way, it is indeed strange that the trend in density of large-scale structures (from Sun up to superclusters) is heading towards an intersection with the "black holes" line (Schwarzschild radius?)

It's even stranger that when you calculate Schwarzschild radius for the mass of the universe, it is roughly the radius of the observable universe (1e53kg --> 15 billion ly)

The 1e53 kg estimate is based on the observable universe (radius 46 Gly) being flat, and ordinary matter being 4.8% of what's keeping it flat.[1]

Is it meaningful that just this baryonic matter has a Schwarzschild radius near that of the Hubble (14.5 Gly) and Cosmic Event (16.7 Gly) horizons?[2][3]

Then there's the question of how much baryonic matter we actually see...[4]

[1] https://en.wikipedia.org/wiki/Observable_universe#Estimates_...

[2] https://en.wikipedia.org/wiki/Cosmological_horizon

[3] https://physics.stackexchange.com/questions/60519/can-space-...

[4] https://en.wikipedia.org/wiki/Missing_baryon_problem

My brain keeps thinking the axes are in decibels than plain logarithms. I think I have never seen a graph with a log axis compressed so hard that the major tick interval is over 1.

Why is it "sub-Plankian unknown" but "forbidden by gravity"? Are things smaller than the Plank unit not forbidden? I thought it was an absolute.

Presumably it's just a coincidence we are pretty close to the middle?

It's because we're not that big or small in terms of height and mass. That's why fleas are right in the middle.

No, presumably it's about as hard to detect things on ever larger scales as it is on ever smaller scales, so we'd expect to always be approximately in the middle.

There's some interesting discussion of this in Wolfram's "The Concept of the Ruliad" article in his physics project.

https://writings.stephenwolfram.com/2021/11/the-concept-of-t...

Is it a coincidence that you are in the middle of your surroundings?

No, they are directly related. All the objects, and measurements, are defined by humans according to human experience.

But the upper and lower limits are not defined by human experience.

Of course they are! Very limited, derivative human experience, in the realm of squinting at numbers coming out of exotic research instruments and theories thereof -- but still human experience.

A being the size of the solar system would not be able to see any farther into the universe than we can with our telescopes, because it's about what light has reached the solar system and not at all about our sense of scale in interpreting it.

Yes, assuming this being is constrained to human senses + technologies. But why would we assume that?

“Creatures” in the Game of Life operate at roughly the level of that automata world’s minimum distance.

Their is no a priori reason we would be in the middle.

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