Tag: physics

Scale can weigh a proton

Ricci’s sensor can achieve ~1% accuracy. 1 goal for such precise sensors is to create high-resolution images of individual proteins and other molecules. Bachtold is developing similar sensors made of carbon nanotubes. You could place a single molecule in a magnetic field, which rotates the molecule’s constituent atoms. Because distinct elements rotate at different rates, a nearby force sensor could detect the rate of rotation of the atoms to identify them.

88 OOM Dark Matter Search

physicist Davide D’Angelo and geomicrobiologist Jennifer Macalady travel to Laboratori Nazionali del Gran Sasso to see one of the latest efforts to detect dark matter, the SABRE detector. As with the search for neutrinos, looking for dark matter needs to happen under conditions of “cosmic silence” — in this case, beneath a mountain in Italy. D’Angelo, who is a collaborator on the project, likens the search to “hunting ghosts”.

2020-11-24:

the search spans 10e-21 eV to 10e67 eV, 88 orders of magnitude. perhaps the broadest search ever? The lightest that dark matter could possibly be is about one-thousandth of a trillionth of a trillionth of the electron’s mass — which would result in a particle that’s like an extremely low-energy wave, with a wavelength the size of a small galaxy. Lighter (and therefore longer) entities would be too diffuse to explain why galaxies stick together. The heaviest is a black hole of 30 solar masses.

Prime Numbers Patterns

A new analysis has uncovered patterns in primes that are similar to those found in the positions of atoms inside certain crystal-like materials. The discovery may aid research in both mathematics and materials science. “Prime numbers have beautiful structural properties, including unexpected order, hyperuniformity and effective limit-periodic behavior. The primes teach us about a completely new state of matter.”

Liquefying cargo

Solid bulk cargoes – defined as granular materials loaded directly into a ship’s hold – can suddenly turn from a solid state into a liquid state, a process known as liquefaction. And this can be disastrous for any ship carrying them – and their crew. 10 “solid bulk cargo” carriers have been lost at sea each year for the last 10 years. Solid bulk cargoes are typically “2-phase” materials as they contain water between the solid particles. When the particles can touch, the friction between them makes the material act like a solid (even though there is liquid present). But when the water pressure rises, these inter-particle forces reduce and the strength of the material decreases. When the friction is reduced to zero, the material acts like a liquid (even though the solid particles are still present). A solid bulk cargo that is apparently stable on the quayside can liquefy because pressures in the water between the particles build up as it is loaded onto the ship. This is especially likely if, as is common practice, the cargo is loaded with a conveyor belt from the quayside into the hold, which can involve a fall of significant height. The vibration and motion of the ship from the engine and the sea during the voyage can also increase the water pressure and lead to liquefaction of the cargo. When a solid bulk cargo liquefies, it can shift or slosh inside a ship’s hold, making the vessel less stable. A liquefied cargo can shift completely to one side of the hold. If it regains its strength and reverts to a solid state, the cargo will remain in the shifted position, causing the ship to permanently tilt or “list” in the water. The cargo can then liquefy again and shift further, increasing the angle of list. At some point, the angle of list becomes so great that water enters the hull through the hatch covers, or the vessel is no longer stable enough to recover from the rolling motion caused by the waves. Water can also move from within the cargo to its surface as a result of liquefaction and subsequent sloshing of this free water can further impact the vessel’s stability. Unless the sloshing can be stopped, the ship is in danger of sinking.

Computation & time travel

Consider a science-fiction scenario wherein you go back in time and dictate Shakespeare’s plays to him. Shakespeare thanks you for saving him the effort, publishes verbatim the plays that you dictated, and centuries later the plays come down to you, whereupon you go back in time and dictate them to Shakespeare, etc. Notice that, in contrast to the grandfather paradox, here there is no logical contradiction: the story as we told it is entirely consistent. But most people find the story “paradoxical” anyway. After all, somehow Hamlet gets written, without anyone ever doing the work of writing it! As Deutsch perceptively observed, if there is a “paradox” here, then it is not one of logic but of computational complexity. Now, some people have asked how such a claim could possibly be consistent with modern physics. For didn’t Einstein teach us that space and time are merely 2 aspects of the same structure? 1 immediate answer is that, even within relativity theory, space and time are not interchangeable: space has a positive signature whereas time has a negative signature. In complexity theory, the difference between space and time manifests itself in the straightforward fact that you can reuse the same memory cells over and over, but you can’t reuse the same moments of time. Yet, as trivial as that observation sounds, it leads to an interesting thought. Suppose that the laws of physics let us travel backwards in time. In such a case, it’s natural to imagine that time would become a “reusable resource” just like space is—and that, as a result, arbitrary PSPACE computations would fall within our grasp. But is that just an idle speculation, or can we rigorously justify it?

Looking for red

The world lacks a great all-around red. Always has. We’ve made do with alternatives that could be toxic or plain gross. The gladiators smeared their faces with mercury-based vermilion. Titian painted with an arsenic-based mineral called realgar. The British army’s red coats were infused with crushed cochineal beetles. For decades, red Lego bricks contained cadmium, a carcinogen. More than 200 natural and synthetic red pigments exist today, but each has issues with safety, stability, chromaticity, and/or opacity.

Petawatt proton beams

NIF is the world’s only facility capable of achieving conditions like those in the interiors of stars and giant planets. Using ARC short-pulse generated proton beams for ultrafast heating of matter to extreme states will enable opacity and equation-of-state measurements at unprecedented energy-density states. In addition, “protons deposit their energy very specifically. That’s why protons are promising for applications such as tumor therapy. You can send a beam of protons toward a tumor and get it to deposit all of its energy exactly where you want it to without damaging other areas of the body. Likewise with a solid material. The proton beam deposits its energy where you want it to very quickly, so you can heat up a material really fast before it has time to hydrodynamically expand — your material stays dense, and that’s the name of the game — high energy, high density.”

SI Updates

The updated constants include
the Boltzmann constant (which relates temperature to energy), and
the Planck constant (which can relate mass to electromagnetic energy),
the charge of the electron and
the Avogadro constant (the quantity that defines one mole of a substance).

“There are no dramatic changes. The Boltzmann constant is very consistent with earlier values. The temperature experts requested 8 digits for the constant and the last digit happened to be 0”.

The Planck constant has shifted downward by 15 parts per billion from its earlier value, due to new data collected since 2014. The Planck constant was determined by 2 experimental techniques, known as the Kibble balance and the Avogadro method. All of the measurements that were used for determining the new Planck value met previously agreed-upon international guidelines for levels of accuracy and consistency with one another.

The Planck constant can be used to define the kilogram, and using a fundamental constant for defining mass will solve many problems. Mass must be measured over a very large scale, from an atom to a pharmaceutical to a skyscraper. “At the low end, you currently use 1 type of physics to determine mass; at the high end, you use another type of physics”.

But the Planck constant will provide a consistent way for defining mass across all of these scales, with whatever laboratory method is used to measure mass.

The volt will change as well, since the Planck constant will also help to define it in the revised SI. A volt based purely on the fundamental constants will be very slightly smaller, ~100 parts per billion, than the current scientific realization of the volt, established in 1990. The top-level metrology labs will have to recalibrate their high-precision voltage measurements.