Hacker News new | more | comments | ask | show | jobs | submit login
To John Wheeler, the race to explain time was personal (nautil.us)
118 points by dnetesn 3 months ago | hide | past | web | favorite | 52 comments

I was lucky enough to have met John Wheeler when I was in grad school. He was a wonderful man who radiated joy and curiosity.

My favorite anecdote about him, which was not widely known, involved what used to be called "nut letters." Before the internet, if you were a famous scientist, particularly a famous physicist, you would receive actual letters from people all over the world asking for help with their perpetual motion machines, time travel devices, and similar nutty theories. Having worked on black holes, gravity, general relativity, and the bomb, Wheeler was quite a nut magnet. He was also blessed with a bit of OCD in the way he organized and categorized all his notes (his annotated bibliography for Misner Thorne and Wheeler Gravitation filled many shelves in the library). John didn't just receive nut letters. He received, read, organized, filed, classified, and acted on nut letters. His preferred response to them was "I'm afraid I'm not very knowledgeable in the area of your work but I believe you should contact _____ who is working on similar conjectures and may be a good source of additional insights" at which point both parties in that conversation would be so ecstatic to be talking with someone recommended to them by the great John Wheeler that they'd never bother him again. While in grad school, I happened to read an article in the New York Times on a perpetual motion machine (their weekly Science Times section was fantastic but did occasionally step into pseudo science topics). At the end of the article the main researcher thanked John Wheeler for having introduced him to the theorist who had helped him refine his understanding of the mechanisms at play in his invention, and I couldn't help but smile at the wonderful successes of John Wheeler's nut dating service.

My colleagues and I used to get these "nut letters" occasionally even as unknown grad students. They were quite a treat to read: the human imagination is a marvel, and curiosity knows no bounds. If they'd taken slightly different paths than they had, some probably would have even been with my colleagues reading those letters instead of writing them.

This reminds me of a run-in we had with a 'nut'. She had looked up the lab on campus and walked in asking for the PI. After some back-and-forth, she mentions that she had been emailing with our PI for a while concerning the government implanted mind-reading device in her brother's brain (I was in a neuro-lab at the time). Without missing a beat, one of the other grad students starts questioning her about the device: when is it active, what is the range, power requirements, etc. She, as a layperson, really has no idea. After some probing about her brother's condition (likely her own condition, but who knows) we get her to accept that the power output of the device would be very tiny and that the government's receivers can't be more than a few meters away at any time. She seemed very satisfied with this conclusion. I think there were some mentions of Faraday cages too that she liked. At the end she mentions that her brother is a schizophrenic but that the medications don't work. Another grad student then took over and started to talk with her about how schizophrenia was thought to behave and the importance of proper medical supervision, but this occurred in another room. After some more time, the 'nut' came back to thank us for talking with her and taking her concerns seriously. She seemed very relieved at the conclusions and was smiling. We never saw her again and I don't think anyone mentioned it to the PI either.

I wonder if any of these nut letters have ever yielded useful scientific discoveries or advances. I figure one or two must have, even if only by accident, or indirectly.

Maybe not the "nut" letters, which are frequently very nutty, but random letters can.

In this episode of Tested Joe DeRisi describes how a random letter from a snake owner led to some interesting published results in molecular biology.


Wow, that's one of the best guests I've heard on that podcast (and in general!). I'm a few months behind, so I hadn't heard this one yet, so thanks.

The title isn't wrong, either, this one is terrifying (so far).

At the fantastic Museum of Jurassic Technology, in Los Angeles, there is a wonderful display of actual letters like this sent to the Mount Wilson Observatory. They are beautiful for their earnest curiosity. Some of these letters are online here: http://www.mjt.org/exhibits/letters/letters.html

I need to get caught up on new developments regarding Wheeler's "Participatory Universe" to find out if anyone else is thinking along these lines, but if observation does result in existence becoming--wave function(s) collapsing into the truly concrete--then essentially the history of the Universe occurred instantly when the first observation of it was made? I don't know where that conscious observer would have been located. Earth? A planet like it? Perhaps on every world (simultaneously of course) where the retrocausal positioning of conscious entities made sense?

> the history of the Universe occurred instantly when the first observation of it was made

Perhaps that history could still collapse into existence in stages, as subsequent observations of it became more detailed. The first observer would see far-off galaxies as small white dots in the sky, but not the composition and interaction of each, so perhaps those aspects don't decohere until later observers see more using telescopes.

And not only history but also laws of physics could come into existence in this way. If earthlings are the only observers in the Universe, perhaps dark matter holding galaxies in a circular shape is a law of physics which only came into existence when observers on Earth could start seeing inside other galaxies.

> The faster you go, the slower time goes. If you could go as fast as light, you’d see time come to a halt and disappear.

No, you wouldn't. Someone observing you would. Am I getting relativity wrong?

You are getting relativity wrong. The layman phrase being used here 'time come to a halt and disappear' encodes what would happen from a relativity perspective. Everything that you would be seeing relative to you, would appear as if time had stopped if you were traveling at c.

If you were traveling at C you would not really see anything [external] at all. Length contraction would be such that everything around you would appear as a single motionless point.

Any incoming light would be blue shifted to infinity, or red shifted to zero, so if any actually touched you there would be infinite energy there. Luckily no light can actually reach you - nothing can. You would have no incoming sensory information at all.

Because of length contraction there's no distance between the start and and of your journey, so from your POV it doesn't take an time at all, since the distance was so short.

If you were traveling at c you would be a photon :-)

Not so fast :) Your own time would not "come to a halt and disappear", would it? If something travels with you at the same speed it would not get frozen in time. So, "everything that you would be seeing" is a bit too inclusive.

Here is what I've found to be the most intuitive way to think about it: everything is always moving at the speed of light through spacetime. When you move through space you are not changing the magnitude of your velocity (through spacetime) at all, only the direction. So the faster you move through space, the slower you move through time. If your velocity through space is v (relative to some reference) then your velocity through time is sqrt(1-(v/c)^2) seconds (from your point of view) per second (from the point of view of the reference against which you are measuring your velocity through space). When v=c, then you are moving through time at zero seconds (from your point of view) per second (from any point of view moving at <c). So your time never advances. You get where you are going (and everywhere in between) at the same time that you left (from your point of view).

Yep. Time still passes for photons, but, at a rate so insanely slow in comparison to how we view it.

10^18 years by our perspective would only be 3 years by the perspective of something traveling at the speed of light.

We observe things going the speed of light all the time =]

Wait, really? I thought that the proper time along a lightlike path was 0?

The 3 years/10^18 figures I used were taken from https://arxiv.org/pdf/1304.2821.pdf :

"Using the largest allowed value for the photon mass from other experiments, we find a lower limit of about 3 yr on the photon rest-frame lifetime. For photons in the visible spectrum, this corresponds to a lifetime around 10^18 yrs."

Which does work under the assumption that photons have a non-zero rest mass, and as such, could decay. I probably should have phrased my post better - this is hardly settled science, and the majority of physicists would almost certainly say that photons, with our current accepted theories, do not have rest mass. SR is pretty explicit on this :). But we can't say for sure that photons have zero rest mass - experiments have allowed us to set an upper bound on the rest mass, but not allow us to deterministically say they have zero rest mass. In such a case that photons do have rest mass, we would need to stop saying "The speed of light", and instead say "The speed of a (rest) massless particle", though this might be worth doing in general - gluons (and gravitons, if they exist) should be similarly massless.

What irks me in articles like this is the term observer. Define observer. Sure, a human is an observer. But can a dog be an observer? A plasmodium? A virus bumping into a molecule and changing its course? Is observing shorthand for any interaction that can collapse a wave function? In that case it seems highly unlikely to me that a photon can travel billions of light years unperturbed.

I prefer the quantum decoherence perspective where being 'observed' basically means interacting with a macroscopic object in a way that's similar to the notion of reaching 'thermodynamic equilibrium' in statistical physics.

"macroscopic object" is unsatisfying though because macroscopic objects are made out of objects that are describable under QM.

Maybe so, but that's a problem shared by both thermodynamics and quantum mechanics. Both have macroscopic objects that exhibit phenomena like temperature, friction, wave function collapse, that simply don't exist on the smaller scale.

The good news is that macroscopic objects exhibit behaviours that are predictable. The bad news is that. while those behaviours are related to the behaviour of the microscopic scale, a full description of systems involving that many particles will likely remain out of our reach forever. Although I could see it happening that we might be able to simulate systems of a sufficient scale to convincingly demonstrate wave function collapse.

I think an observer is a quantum process interacting with another quantum process. Photons are fundamentally different from particles with mass - and they interact differently. Two photons interact like waves at the surface of an ocean - amplitudes and phases changing, for instance. But photons interact with particles with mass by either being absorbed and, later, re-emitted by the other particle or being completely absorbed and altering the particle with mass' state in some way (speed/momentum).

I remember reading somewhere about a geometry which described photons' existences as fundamentally different from particles with mass. Particles with mass have lifelines that change over the course of time. Particles without mass, such as photons, don't experience time and never change themselves. Photons etch out a straight line in this geometry from fixed points to other fixed points. The fixed points represent particles with mass. (something like that)

> The relevant literature is famously contentious and obscure. I believe it will remain so until someone constructs, within the formalism of quantum mechanics, an “observer,” that is, a model entity whose states correspond to a recognizable caricature of conscious awareness … That is a formidable project, extending well-beyond what is conventionally considered physics

Wilczek, 2006. Quoted in a paper[0] that I like for its thorough stab at actually specifically defining the observer. It’s a tough task indeed!

[0] https://www.frontiersin.org/articles/10.3389/fpsyg.2014.0057...

On observers creating the universe, I’ve sometimes wondered if given the simulation hypothesis, that simulating quantum mechanics is so computationally expensive that it isn’t done unless we’re looking at it, and that the high energy levels required to probe smaller and smaller length scales is an artifact of the computational requirements of simulating it.

That's an interesting thought. It it's true, it seems to have some implications:

* Whoever is running the simulation cares about whether we're looking.

* They had a good reason for going with quantum mechanics rather than something that would be easier to simulate.

I know some people would say that's because they're interested in simulating conscious life and quantum mechanics is essential for consciousness. However, I find it very implausible that quantum mechanics is essential for consciousness so I'd prefer a different hypothesis for why they went with a difficult-to-simulate physics in their simulated universe. Any ideas?

Idea: their reality is much more computationally complex than quantum mechanics, so much so the difference between classical and quantum is irrelevant from a cost point of view and matters only from a results point of view.

Another possibility is simply that they've got wildly more resources than we can imagine. It's ferociously expensive to run the universe on a classical simulation of QM, but finite. We have no particular reason to believe this "higher reality" doesn't have this level of resources. I've often pondered our universe as the moral equivalent of an elementary school demonstration; what if we're some metaphorical elementary kid's homework, because our physics is relatively simple (assuming some ToE that may actually be simpler than meets the current eye) and produces interesting results?

We can reasonably discuss the feasibility of simulating our universe using our universe. We can do some reasonable discussion of "universes that run something like ours but with some differences". We are profoundly ignorant about everything else.

I can't help but find it unsettling listening to a subject of the universe describe it as "relatively simple". Simple relative to what?! Some arbitrary more complex system? Well Sure!

Frankly, I don't think it's a question of complexity, or even expressivity, but more one of encapsulation and information hiding.

The fundamental laws of the universe, at present, seem to be a whole lot simpler than many of the things that arise from them. That's as much of a statement in that direction as I think can be supported.

"I can't help but find it unsettling listening to a subject of the universe describe it as "relatively simple". Simple relative to what?!"

For one, simple relative to every universe we've ever created, such as Minecraft, World of Warcraft, Second Life, etc., all of which are megabytes upon megabytes (if not gigabytes) of ad-hoc rules, specifications, hard-coded geometry, etc. Even if we ignore the visualization aspects, they are all very complicated.

It is very likely that whatever the ultimate Theory of Everything is would fit comfortably into kilobytes. Very dense kilobytes, kilobytes you could spend your entire life understanding, but kilobytes. Certainly the entire Standard Model could be packed into kilobytes even starting from a fairly simple axiomatic mathematics, with a half-decent encoding. Its complexity comes from the number of particles interacting under its rules, and the fact our human brains aren't particularly suited to running QM calculations and confuses that difficulty with "complexity", since very few people have a grasp on what complexity truly is [1]. Most of the complexity of the Standard Model would actually be building up from the simple axioms and defining imaginary numbers and the other basic mathematic operations; once that was done, the fundamental equations to evolve state and the table of constants would not be very large. (Assuming that the parameters are not infinitely complicated real numbers, and that we can cut them off safely aften 40 or 50 decimal places without noticing a difference.)

The real universe's complexity does not appear to stem from its core building blocks necessarily, but from the staggering amount of space it occupies and the amount of computation it does, with both the Planck space and Planck time constants being staggeringly low on the one end, and the age of the universe and the expected age it should be able to survive staggeringly large on the other.

[1]: Defining it correctly is way beyond the scope of this post. But to get an idea, go here, look at the initial state, and then hit "start": http://pmav.eu/stuff/javascript-game-of-life-v3.1.1/ It looks like all sorts of complicated stuff is happening, right? However, the rule set is a small rule about what cells live or die based on neighbors, that small initial state, and if we're getting really technical, the iteration counter. What is on your screen may be visually complicated, but mathematically, it's very, very simple.

What's really shocking is that the Life rule set is probably sufficient to describe our universe. It's Turing Complete, and there's a sense in which any TC set of rules is equivalent to any other. However, it is also very likely that running our universe on Life rules would also require a massively complicated initial state, making it an unappealing theory to explain the real universe for that and several other reasons. We'd like to see something where the sum total of the complexity of the rule set and the initial state isn't that great, or is at least proportional to the amount of "stuff" the universe seems to have started out with.

Maybe because quantum mechanics has interesting dynamics and produces interesting results?

Hey, there's a seed for a hard sci-fi novel: we live in a simulation (or pocket universe), the laws of which were intelligently designed to produce aggressive life forms in order to make entertaining viewing for the builders and their clients. So all the wars we decry actually saved our universe by keeping it 'interesting'.

(I find it interesting that I'm willing to allow that evolution as we know it is just a quirk of our universe's dynamics, but I assume that commerce is universal...)

Watch South Park's "Canceled".

There is a theory that says that everytime somebody is close to understanding the structure and mechanics of the universe, the universe would immediately be replaced by something even more strange and incomprehensible. Another theory says this already has happened several times.

This would explain both our progress in physics and the strangeness of QM, and give credence to the idea that we are in a simulation.

You could make a humorous extension to that theory re: a priorly flat earth.

Whoever is running the simulation cares about whether we're looking. They had a good reason for going with quantum mechanics rather than something that would be easier to simulate.

The power running the Universe doesn't have infinite CPU/GPU/RAM resources at their disposal, any more than a game developer at this level of reality does. Some optimizations (or hacks, to be less charitable) are necessary. Quantum behavior is one of those hacks, part of the code that manages the potentially-visible set. It would be wasteful to render or run physics on particles that nothing is interacting with.

The only questions are whether God is an Nvidia fanboy or an AMD die-hard, and if He signed an exclusive deal with Sony or Nintendo at some point in the future.

Perhaps our bodies are a shell for their consciousness. That's why they're so interested in "our" observations. We are the VR headset for them.

> that simulating quantum mechanics is so computationally expensive that it isn’t done unless we’re looking at it

This is a common misconception. It's more difficult to simulate a quantum system than a classical system. To simulate a classic system you have to simulate one posible state. To simulate a quantum system you must simulate all possible path.

This is the advantage of quantum computers. With the hardware for only N qbits, you can calculate 2^N states (for some very specific problems that are quantum-computer-friendly).

I'm by no means an expert, but how about using Pilot Wave Theory to do the simulation? As I understand, you wouldn't need to simulate an exponential number of states, you just simulate the pilot wave.

See also (very accessible): https://www.quora.com/Why-dont-more-physicists-subscribe-to-...

You must simulate the value of the wave at every point of the universe, or at least a grid that has enough points to have the correct precision. It's even more work. Imagine simulating all the waves in all the ocean in the Earth, but worse because there are some nonlocality effects.

You can probably do some kind of smart representation of the wave, were you decompose it in some smart functional base of smooth waves. With a very optimized representation the calculations would be equivalent to the usual quantum mechanics calculations. With a not smart enough representation you would get something that needs more calculations.

> You must simulate the value of the wave at every point of the universe

Maybe I'm not getting it, but that still sounds simpler than simulating an exponential number of states for the entire universe.

Take a look at https://en.wikipedia.org/wiki/Pilot_wave_theory#Mathematical...

The problem is that if you have five particles then the function ψ(r1, r2, r3, r4, r5, t) is a function on 3*5+1=15 coordinates. If we assume that for each particle we use a 100x100x100=1000000 grid, then for the 5 particles we need a grid of (1000000)^5=1000000000000000000000000000000 points. The space were the wave is defined grows exponentially. (As a rule of thumb, with a current notebook, you can do up to 1000000000 or 1000000000000 calculations in a few seconds/minutes/hours.)

The equations are not simpler, there is no “just”.

I was wondering how this article would read from a Bohmian perspective. It would seem to be an alternative to creating the universe as a result of perceptions in the modern era. (Damn Copenhagen interpretation)

I was also wondering about entropy as the arrow of time -- positrons are just as subject to entropy, no?

I find it funny how people are so ready to believe the universe must be computing the same way our models must. The universe simply exists - it's not necessary for it to adhere to our human perceptions - not be a long shot. There's a vast gulf between the model and the modeled. That our theories quickly become uncomputable says more about their unfitness than the universe's functioning. To say otherwise is to negate the fundamental autonomy of the universe. We should be humbled by the universe precisely because our best models to understand it quickly diverge to where our minds and tools may not.

What autonomy does the universe possess?

For one, it exists before any of our feeble explanations of how it works. It's always correct and we try to play catch up.

Simulating the Mandelbrot set is also awfully computationally expensive. Unless you know the trick.

So you're saying the Universe is Lazy-Evaluated[0]?


First read this as "the race to explain that time was personal".

> "the race to explain that time was personal"

That's special relativity in a nutshell.

> He Revolutionized Physics

Did he, really?

Applications are open for YC Summer 2019

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact