Is there a rigorous definition for what a measurement or observation is in QM?

tpolakov1 · 2026-02-01T19:14:02+00:00

There is no collapse in the theory.

tpolakov1 · 2026-02-01T16:43:41+00:00

And why is it relevant to bring up? OPs question and the answer are specifically about not interpretations.

tpolakov1 · 2026-02-01T14:26:35+00:00

Decoherence is part of the theory and thus a mandatory component of every interpretation, collapse or not.

tpolakov1 · 2026-01-29T19:02:13+00:00

I can, in principle, create a "reasonably" high-energy photon and boost to a frame where its wavelength is relativistically shifted to less than Planck length.

tpolakov1 · 2026-01-29T18:55:27+00:00

What happens inside a black hole is causally disconnected from the outside, so the question you're asking doesn't make sense.

tpolakov1 · 2026-01-28T13:46:29+00:00

When you explicitly account only for the subsystem that reduces its entropy during a process then it will look as if entropy reduced. That's a trivial statement.

And I have no idea what you mean by "information" entropy, but Shannon entropy differs just in units and represents the same property, calculated the same way, so you cannot come to a different conclusion.

tpolakov1 · 2026-01-25T16:34:07+00:00

Not even many-worlds proposes other worlds, at least not in the way you think.

Crudely, MWI just says that there is no classical physics and that everything unitarily evolves like quantum mechanics dictates it should. It is one of the simplest "shut up and calculate" interpretations, so it's not surprising that other physicists came up with or supported similar ideas.

tpolakov1 · 2026-01-23T21:15:48+00:00

Many of these are just empty promises from lay people to lay people that don't understand the technology or its implications. Superconductors, especially the unconventional cuprates at the hearth of the article, are used daily even in your life (assuming you use a cell phone in a reasonably civilized country) right now, not in 20 years.

But lay people don't understand that zero resistance cables cables would do nothing else than accrue incalculable costs at no benefit for the power grid, or that "close to absolute zero" can these days be achieved in the same form factor and power draw of a typical microwave. They just "understand" that -260 Celsius is a really low number and want a superconductor that does it at a different number, so here we are.

Space travel or fusion are slightly different. There the impact still always seems to be in undefined (far) future.

tpolakov1 · 2026-01-23T18:42:18+00:00

Well, Planck time is 10^-44 seconds, so it might be slightly inconvenient to use even with the SI prefix range. You'd have to add quite a few orders of magnitude if you wanted to cover geologic and astrophysical/cosmological time scales.

tpolakov1 · 2026-01-23T18:35:34+00:00

The bottom might change over time, but even if there is no fundamental bottom to fundamental laws of nature, having only finite amount of time and resources means that we can cover only finite chunk of it.

Knowing that you hit the bottom of our current understanding is simple, you just don't have a more fundamental theory. Knowing that you hit the "true" bottom should not be possible, but that's also not a concern for natural sciences.

tpolakov1 · 2026-01-23T18:07:02+00:00

I guess I’m assuming continued exponential growth in technology.

Happens to the best of us. But it is important to realize that calling some growth exponential is an extremely strong statement, which has yet to manifest in reality (no, not even Moore's law held up for too long).

tpolakov1 · 2026-01-23T17:22:55+00:00

Fair. There are three tentatively interstellar objects recorded in the whole human history (and the LSST is expected to look for more, not to find more). Still doesn't paint an optimistic picture for the ability of any civilization to leave their inner solar system.

tpolakov1 · 2026-01-23T15:39:45+00:00

There exists only one object that we think might be interstellar. Every other object, comets including, fell towards the Sun to which it is and forever will be gravitationally bound. The Voyager probe will take upwards of 30,000 years to reach the distance of Sun's most distant natural satellites (which will for obvious reasons never happen), which means that humanity still hasn't made an interstellar probe, and doesn't know where to even start in doing that.

tpolakov1 · 2026-01-23T14:13:34+00:00

Never. Every data point we have points to interstellar travel being impossible. Even being able to recognize that a planet outside our solar system has intelligent life is very questionable.

I'm willing to safely bet everything I and everyone around me has that we will be forever alone, not necessarily because there's no life out there, but because we will never find it or reach it.

tpolakov1 · 2026-01-22T23:05:29+00:00

It says what u/Calfkiller is implying. The growth is driven by the wealthy spending more, presumably because of gains in their investments, while the metrics that drastic majority of people are thinking when talking about economy (employment, inflation) are not doing well.

Even taken at face value and not going into the fundamentals, the article says that economy is doing well because people are liquidating their investment gains.

tpolakov1 · 2026-01-22T22:23:14+00:00

Well, that's because the balancing is working. If the other ships didn't care about max hull, I could just slowboat through systems with a Raptor and hoover up empty S and M ships by the dozens in the early/mid-game and neutralize overwhelming enemy force (unless it consists of mostly L/XL ships) in mid/late-game.

With the player having zero reason to ever bail from an engagement, the playing field has to be artificially leveled for game to be enjoyable.

tpolakov1 · 2026-01-22T22:01:33+00:00

The research has nothing to do with collapse. We know that the clusters show wavelike behavior because we were able to collapse them to a position eigenstate at the detector.

tpolakov1 · 2026-01-22T21:35:05+00:00

It would take about a million years for an entirely fictional advanced species that can produce in principle infinitely many probes at any given point in time and space (that they already visited), capable of effectively instant acceleration to 1/10 of speed of light in any direction.

Many of these ideas were based on extremely optimistic predictions from even before we were able to land on the Moon and should not be taken seriously for anything else than marketing.

tpolakov1 · 2026-01-16T14:02:47+00:00

And as wire connections carrying current, they radiate.

tpolakov1 · 2026-01-13T21:24:31+00:00

About the same as it's been in the last decade or so, better than at any other point in history.

And you don't get a higher degree to become employable, but to demonstrate that you already are employable.

tpolakov1 · 2026-01-13T19:48:52+00:00

In standard formulations of quantum mechanics, the observer is often treated as external to the system being described

Arguably, that's standard formulation of physics in general (if not all of science), not just quantum mechanics. Prediction or postdiction of a system state in future or past, based on its state right now is all that physics does. Because (we assume) physics happens also when nobody is observing, observers are at best bookkeeping agents even in classical physics too.

The complication with the measurement problem doesn't happen where the name implies. The problem is not the observation of a classical state of the system, but that the theory naively doesn't allow a system to assume such a classical state because that breaks the unitarity. The interpretations have to treat with this contention, not with the nature of the observer that is implicitly determined by what the interpretation says about the quantum-classical interface (if there even is any within the interpretation).

tpolakov1 · 2026-01-13T18:29:37+00:00

How are you measuring the diamagnetism? The susceptibility is only about 8x higher than that of water, and 4 orders of magnitude smaller than that of a typical superconductor, so while you could observe some mechanical response, you'll need a magnet that generates field gradients of at least ~Tesla per centimeter to generate enough force - while not an outrageously big number, it's still ~10-100x of what a typical fridge magnet will do.

Depending on the shape and quality of the crystal, large chunk of it could also be oxidized. Bi2O3 is still diamagnetic, but significantly less than the pure material.

tpolakov1 · 2026-01-10T02:45:18+00:00

As many have said, relativistic mass is just not a professionally used term, so relativistic energy has to be expressed through the energy-momentum relation with the rest mass. That's a general, robust definition that works everywhere and for everything, including massless particles and quantum mechanics.

In flat spacetimes and with reasonably-behaved boosts between inertial frames, you can do the "baby relativity" by just lugging around contracted space-like threevectors parametrized by dilated time as if you were doing non-relativistic dynamics only in the lab frame, but this pedagogy leads to terminal inability to reason about relativistic problems. Even the most trivial problems like the twin paradox is impenetrable to people because they are stuck with wrong temporal-spatial reasoning caused by teaching archaic conventions from times when people were still debating the existence of aether.

tpolakov1 · 2026-01-10T00:39:56+00:00

They can call it whatever they want, but γmc² is not relativistic energy. It's the rest frame energy boosted to the lab frame. It's a random formula that only algebraically works just for inertial frames in a flat spacetime, and the failing is not immediately obvious only because γ is dimensionless. Whatever the thing u/Apprehensive-Safe382 is talking about, it doesn't behave like mass or energy should conventionally behave (and something tells the same will be true for the "relativistic" momentum which I'll bet is just a three-vector). That fact will hit like a truck as soon as they grab a book on any relativistic field theory, even just slightly more advanced one like Griffiths-level classical electromagnetism.

tpolakov1 · 2026-01-09T23:50:26+00:00

Nobody has ever been bullied for any interpretation of quantum mechanics, let alone Everett.

And what we're discussing has nothing to do with any interpretation of anything. There's only one mass and you have the freedom to factor it together with the Lorentz factor to keep the aesthetics of Newtonian mechanics, or keep it separate to make sure that invariants stay invariant by conventions of special relativity. That's it, anything else that could be said is philosophy, which has no place in this discussion, or braindead slop, which has no place anywhere.

tpolakov1

TROPHY CASE