Physics

The surprise came when he looked more closely at the higher bending (flexural) modes: in that case, the frequency increased at higher loads. “The bar becomes more fixed so the actual wavelength of the bar is less,” Langlois explained. “With a set wave speed, wavelength is inversely proportional to the rate of oscillation, so we get a higher frequency. This is something we did not foresee happening. So the barbell is likely to matter.”

...

Precisely which features make for the best barbell is still a puzzle. Olympic barbells have the same weight, diameter, and length, but other aspects can differ from brand to brand, such as the materials used. Most are made of some sort of steel, with stainless and chrome-coated being the most common, and the respective mechanical properties can make a small difference to a given bar’s whip, according to Langlois. Specifically, the stiffness of the bar (the Young’s modulus) can vary quite a bit. “We don’t have a good feel for this because no barbell manufacturers will tell you exactly how they make the bar,” he said. “It’s all proprietary.”

The linked article covers some ways to tap a touch screen without a finger. That’s probably the most comprehensive document on the topic yet those options all seem impractical for my needs.

So here’s my problem:

Travel websites are increasingly enshitified and consumer-hostile (and often Tor-hostile). They are also protectionist with the data as they use anti-bot tech (which really amounts to anti-human tech b/c bots serve humans). Kiosks are a refuge of a sort (almost, kind of).

Some kiosks have useful information without the anti-bot shenanigans, but they are also still designed to be labor intensive. Kiosks that sell train or bus tickets force users to supply a specific date of travel and specific destination. For me, the date of travel depends on the price of the ticket, but the UI does not allow users to know the price until after they fill out a form. Sometimes I don’t even know the destination because the city I visit depends on the price as I look for a cheap trip somewhere.

What we need is a tool that will enter all combinations of queries for ranges of travel dates and times and for sets of origin-destination pairs. Is there hardware that can handle this job? If the kiosk is a touch screen, my knee-jerk instinct was for a laser do the job of a finger. But after further checks, I don’t think a laser can have an electro magnetic effect or whatever is needed.

Apart from convenience of being able to harvest a dataset and do my own queries, I also imagine some handicapped people (e.g. without the use of arms) have the same problem and would benefit from the same solution. The dataset could then be openly published to everyone, not just the exclusive demographic who is able to reach the website of the carrier and tolerate the enshitification.

I graduated from my bachelors in December, and I'm feeling burnt-out about job hunting. This is a project I wrote during my degree, in my spare time, to try out some ideas from my lectures and to learn OpenGL.

I took this screenshot while I was testing out monochromatic lighting. The ships are rotating clockwise.

I found it interesting that the receding ships bunch more closely together, that really convinced me that I had it working right.

The code is on GitHub jarrydac/gl_relativity. It's quite rough.

Adularescence is an optical phenomenon that is produced in gemstones like moonstone. It is best described as a milky, bluish luster or glow originating from below the surface of the gemstone. The luster, appearing to move as the gemstone is turned or as the light source is moved, gives the impression of moonlight floating on water. It is most typically produced in adularia, an orthoclase. This photograph shows adularescence in a moonstone cabochon from Minas Gerais, Brazil.

Photographer: Didier Descouens

CC BY-SA 4.0

cross-posted from: https://lemmy.world/post/46186805

Paywall removed

Author: Inductiveload, NASA

CC BY-SA 3.0

cross-posted from: https://lemmy.world/post/45992308

This is a map of the universe. The Dark Energy Spectroscopic Instrument (DESI) at Kitt Peak National Observatory, Arizona, has finished its five-year survey. It observed more than 47 million galaxies and quasars and created a 3D map centered on the Earth. Today's featured image shows a thin slice of these data: the black gaps indicate where our Galaxy obscures distant objects. The feathery web in the inset shows the large scale structure of the universe. Light of the most distant galaxies shown here travelled for 11 billion years to reach the Earth. Galaxies cluster throughout cosmic history under the competing influences of gravity and dark energy, responsible for the accelerated expansion of the universe. Analysis of early DESI results hinted at the possibility that dark energy, described as a cosmological constant by Albert Einstein, may not be constant after all. But we still have to wait for the analysis of the now complete dataset. The nature of dark energy is the biggest mystery of cosmology.

Source

Chasing absolute zero

Dilution refrigerators are roughly human-size plumbing systems that use rare helium-3 (He-3) to chill tiers of copper plates to millikelvins (mK), near absolute zero. These temperatures are required for sensitive technologies, such as the chips that power quantum computers.

"It is amazing that there is so much to do on just a single layer of graphene even after 20 years of discovery," says Arindam Ghosh, Professor at the Department of Physics, IISc, and one of the corresponding authors of the study.

...

To uncover this behavior, the team created exceptionally clean graphene samples and carefully measured how they conduct both electricity and heat. What they found was unexpected. Instead of increasing together, the two properties moved in opposite directions. As electrical conductivity rose, thermal conductivity dropped, and vice versa.

This result directly contradicts the Wiedemann-Franz law, a well-established principle that states heat and electrical conduction in metals should be proportional. The researchers observed deviations from this law by more than 200 times at low temperatures, revealing a striking separation between how charge and heat move through the material.

This type of laser takes a tiny pulse of light, stretches it out so it doesn’t blast optics to pieces, and amplifies it until, for a brief instant, it carries more power than the entire US electrical grid. Then it compresses the pulse back to a trillionth of a second to create a star in a vacuum chamber.

On a typical shot day, the target might be a piece of metal foil thinner than a human hair, a jet of gas or a tiny plastic pellet—each designed to answer a different scientific question.

Scientists from across the country applied for time on TPW to study everything from the physics of stellar interiors and fusion energy to new approaches for cancer treatment.

https://www.youtube.com/watch?v=1ud6LNtX014

https://www.stochasticnetwork.com//

It is often claimed that the bits in a quantum computer have no values until you look at them, then they "collapse" into a definite state. However, such a belief is not required by the mathematics but is a personal choice, as it is possible to represent any arbitrary quantum circuit as a Markov chain.

In classical probabilistic computing, you represent the bits using a probability vector we can call p⃗, which holds the current probability distribution for the bits, and we represent logic gates in terms of stochastic perbutations given by the Markov matrix Γ.

The evolution rule then just becomes:

• p⃗'=Γp⃗

The mathematical description does not track the definite values of the bits, but those are indeed believed to exist, because you can create a simulation whereby you start with well-defined values for the bits and stochastically perturb them to new definite values based on the probabilities given by Γ, and the statistics on such a system will reproduce p⃗ at every time step.

Quantum computers use a different evolution rule:

• ψ'=Uψ

Where U is a unitary matrix and ψ is the wavefunction. The main difference is that U and ψ are complex-valued, so it is not obvious what they physically represent or how this could relate to a Markov chain in any way.

Complex numbers aren't magic. They just represent a system with two degrees of freedom. That means we can get rid of the complex numbers by decomposing them into two separate real-valued vectors. Specifically, we can perform a polar decomposition on ψ.

• p⃗=|ψ|²
• φ⃗=arg(ψ)

Notice that, if we perform a polar decomposition on ψ, then one of the two degrees of freedom is quite literally a probability vector. Something interesting happens if we write an update rule for this p⃗ directly so we can evolve p⃗ directly without having to constantly convert back and forth between p⃗ and ψ.

We get this evolution rule:

• p⃗'=Γp⃗+q⃗ where Γ=|U|²

We get what looks like a classical Markov process but with a non-linear correction term called q⃗, which accounts for interference effects. The equation for computing q⃗ has a dependence upon φ⃗, and so φ⃗ acts like a memory effect which can cause the same logic gate to give different behavior if the value of φ⃗ is different at that time.

A prime example is the Hadamard gate. Apply it once then p⃗=[0.5; 0.5]. Apply it twice then the bit deterministically goes back to where it came from. That means it needs a way to "remember" where it came from, and that "memory" is stored in φ⃗. If you apply the Hadamard gate when the bit value begins with a value of 0, then φ⃗=[0; 0]. If you apply it when the bit value begins with 1, then φ⃗=[0; π].

Rather than using φ⃗ to compute q⃗, which is a correction term for Γp⃗, we can instead use φ⃗ to correct Γ, such that the same logic gate can give us a different Γ if the state of φ⃗ is different at a given time. If we do that, then we can represent each logic gate in terms of these corrected Γ, and thus fit the entire system to the evolution rule given by: p⃗'=Γp⃗.

There would be no need to correct Γp⃗ with q⃗ because we already built that correction into our corrected Γ. The method to correct Γ also turns out to be trivially simple, you just apply an algorithm called iterative proportional fitting which comes from optimal transport, which will adjust the initial Γ=|U|² as little as possible such that Γp⃗ maps you to the correct p⃗'.

That means we can fit the entire circuit to a Markov chain where the qubits have definite bit values at all times and each logic gate represents a stochastic pertubation upon the bits that merely permutes them randomly to a new definite configuration, and if you collect statistics on that stochastic process at every step, it will always match the Born rule distribution at that step.

What is an observer?

We have long assumed that “an observer observes the world.”

But what if—

observation itself is not something we do, but something that only appears when certain conditions are met?

Two independent systems align only at specific moments.

Yet this alignment cannot be explained by causality, correlation, or measurement.

So who is observing?

Or rather—

does the observer emerge only when observation becomes possible?

Summary 👇 https://docs.google.com/document/d/19nDAJ_9MgrUFv4Ggyd9yvZIy4YCH9EqSlVOZPr_VuPs/edit?usp=drivesdk

What do you think about this perspective?

What if frequencies aren't properties of sound — they're permissions granted by geometry? A 4m room only allows wavelengths that fit its boundaries. The allowed set follows a dyadic ladder: 42.875 → 85.75 → 171.5 → 343 Hz Each step doubles. Each doubling halves the mode cell area. The room isn't a container for sound. It's a filter. Same math governs CMB power spectrum anomalies at cosmological scale. Boundary conditions all the way down. @physics

When placed in water, their long flagella—tails that propel them forward—create a so-called active bath. This dynamic environment helps form gel-like aggregates by acting like a small fire and raising the "temperature" to an equivalent of 2,000°C, similar to one a blacksmith needs to craft metals. It even manages to spin tiny micro disks.

...

The scientists, therefore, needed to take a step back and come up with an experiment to clarify what was happening. To do so, Grober used a 3D nanoprinter to create smooth, symmetrical micro disks similar to hockey pucks. After introducing these "pucks" into the active baths filled with E. coli, they were surprised to see them spin clockwise, which negated the earlier hypothesis that symmetrical shapes do not turn.

...

"It is a well-known result in our field that the counter-rotation of the body and flagella (tail) of an E. coli cause it to swim in clockwise circles near a solid surface," Grober explains.

"We realized that we could flip these dynamics upside down by confining the E. coli in a microscopic channel beneath the puck. These experiments utilize the exact same hydrodynamic effect to create, essentially, a microscopic and contactless engine, which drives the persistent rotation of the puck."