#planck constant

the two Doubleclicks songs most likely to give me The Feels are "imposter" which is about the curiosity robot landing on mars, and "kilogram" which is about the official kilogram getting replaced by reference to a universal constant

and like, the songs aren't just about those things, they are sung by those two inanimate objects... the little robot so unsure of herself "I'm just pretending I can do this" and the kilogram wondering "who will I be, if I'm not your kilogram?"

why do I have feelings for these creatures

The new kilogram has finally arrived.

Updates to scientists’ system of measurement went into force May 20, redefining the kilogram and several other units in the metric system. The revamp does away with some outdated standards — most notably, a metal cylinder kept in a vault near Paris that has defined the kilogram for 130 years (SN: 12/8/18, p. 7).

Tinkering with units allows scientists to more precisely measure weights, temperatures, electric currents and other quantities laid out in the International System of Units used around the globe. The kilogram, the basic unit of mass, is now defined by a quantum quantity known as the Planck constant. That value, an immutable constant of nature, is the same everywhere in space and time. That’s an improvement over the Parisian artifact, which could have changed slightly if gunk or scratches marred its surface.

Also redefined, according to an agreement reached in November 2018 at the 26th General Conference on Weights and Measures in Versailles, France, are the kelvin, the unit of temperature; the ampere, the unit of electric current; and the mole, the unit for an amount of substance (SN: 12/8/18, p. 7).

Scientists now have their sights set on updating the unit of time: the second.

NEXT UP Scientists are now considering redefining the unit of time, the second, using optical atomic clocks (one shown in this composite image). These clocks are more precise than the cesium atomic clocks currently used to keep time. CREDIT: N. PHILLIPS/NIST

Currently, the second is defined by atomic clocks made of cesium atoms. Those atoms absorb a certain frequency of light. The wiggling of the light’s electromagnetic waves functions like the pendulum on a grandfather clock, rhythmically keeping time. One second is defined as 9,192,631,770 oscillations of the light.

But a new generation of atomic clocks, known as optical atomic clocks, outdo the cesium clocks (SN: 11/11/17, p. 8). “Their performance is a lot better than what currently defines the second,” says physicist Andrew Ludlow of the National Institute of Standards and Technology in Boulder, Colo. Because those optical atomic clocks operate at a higher frequency, their “ticks” are more closely spaced, making them about 100 times more precise than cesium clocks.

Ideally, the length of a second should be defined using the most precise timepieces available. A switch might happen in the late 2020s, Ludlow says.

The change to the kilogram’s definition was carefully orchestrated so that it wouldn’t affect normal people: A kilogram of flour still makes the same number of biscuits. Any change to the second will be similarly coordinated.

Jason Padgett, co-author Struck by Genius

Earlier this year, the kilogram got a new definition. With it, scientists can now measure mass very accurately with a type of scale that uses electromagnets. A new tabletop version of that device should now make accurate such measurements of mass more accessible to the masses.

Until this spring, the kilogram was defined as the mass of a special metal cylinder kept in a vault near Paris, France. But researchers did away with that standard on May 20. Now the kilogram is pegged instead to a fundamental constant of physics. That number is known as the Planck constant. (A fundamental constant is a number that doesn’t ever change.)

With the new definition, scientists can use a device called a Kibble balance to directly measure masses via the Planck constant. The device is named after Bryan Kibble, the physicist who invented it.

But a full-scale Kibble balance is extremely complex. It requires its own laboratory space and costs millions of dollars to build. And it needs a host of PhD-level scientists to run it.

Now a team at the National Institute of Standards and Technology in Gaithersburg, Md., has created a scaled-down version of the device. They are designing it to measure smaller masses, about 10 grams (0.35 ounce). When the prototype’s kinks are worked out, the apparatus should be accurate to a few ten-thousandths of a percent. The researchers described the tabletop device in the June IEEE Transactions on Instrumentation and Measurement.

The new, suitcase-sized Kibble balance is just over half a meter (1.6 feet) tall, with a price tag of around $50,000. That puts it within reach of labs that frequently need to weigh small things. For example, companies must accurately dole out small doses of the drugs they make.

Traditional balances work by comparing the weights of masses in two different pans. But a Kibble balance compares a mass to the electromagnetic force needed to hold up that mass. Certain measurements, such as voltage and resistance, can be tied back to the Planck constant. That allows a series of equations to connect that quantity to the object’s mass.

The Planck constant has the same value everywhere. That means researchers can directly measure out masses anywhere and anytime. They no longer have to compare things against the Parisian cylinder.

Fun with Legos inspired the new instrument, says Leon Chao. He is a mechanical engineer on the team. The researchers had made a Lego Kibble balance to help teach the public how the instruments work, he says. That experience gave them the idea to make a small-scale real one.