Skip to main content

Kilogram to be defined by Planck constant instead of a lump of metal

Kilogram to be defined by Planck constant instead of a

 lump of metal: 

Au revoir, Le Grand K
By Leah Crane
There’s a new kilogram in town. Scientists from around the world met today at the General Conference on Weights and Measures in Versailles, France, and unanimously voted for a new definition of the kilogram – one based on fundamental physical constants rather than a lump of metal held in a vault in France.
The change will go into effect on 20 May 2019, and when this happens, it will mean all of our standard units are now defined using unchanging, universal numbers, instead of physical objects.
Since 1879, we have officially defined the kilogram using a cylinder of platinum and iridium called Le Grand K or the International Prototype Kilogram. If Le Grand K were to get scratched and lose a little weight, the value of a kilogram would officially go down. Other measures of weight, like pounds and ounces, have also been defined by the weight of Le Grand K for the last 139 years.
Copies have been distributed around the world so that more people could calibrate weights and measures. But because there are discrepancies between Le Grand K and its copies, we know that our official definition of the kilogram has been slowly changing despite stringent measures to keep the reference weights safe from the elements.
All of that is to change. From May, the official kilogram will be defined by the Planck constant, which describes the size of the smallest possible packet of energy. The Planck constant is incredibly small, so it’s measured with a specialised piece of equipment called a Kibble balance. So far, only two labs have managed to make Kibble balances, but the hope is that eventually anyone will be able to accurately weigh anything without having to fly it to France to compare it with Le Grand K.

Comments

Post a Comment

Popular posts from this blog

Major surgery associated with small, long term decline in brain functioning

Major surgery is associated with a small long-term decline in cognitive functioning -- equivalent, on average, to less than five months of natural brain ageing, finds a study in  The BMJ  today. But the odds of substantial cognitive decline also increase after surgery -- approximately doubling -- although the likelihood of this is much lower than after admission to hospital for a medical condition, the findings show. Cognitive decline is the gradual loss of brain functioning that occurs with ageing. It often starts decades before the conventional definition of old age and accelerates with ageing and the presence of an increasing number of underlying health conditions. Certain health issues, such as stroke, can lead to a large "step change" in cognitive decline, and there have been concerns that surgery might also do this, with some patients refusing beneficial surgical procedures as a result, say the researchers. Few previous studies have looked at the potential im...
Post a Comment
Read more

Dark matter may be older than the Big Bang

Dark matter, which researchers believe make up about 80% of the universe's mass, is one of the most elusive mysteries in modern physics. What exactly it is and how it came to be is a mystery, but a new Johns Hopkins University study now suggests that dark matter may have existed before the Big Bang. The study, published August 7 in  Physical Review Letters , presents a new idea of how dark matter was born and how to identify it with astronomical observations. "The study revealed a new connection between particle physics and astronomy. If dark matter consists of new particles that were born before the Big Bang, they affect the way galaxies are distributed in the sky in a unique way. This connection may be used to reveal their identity and make conclusions about the times before the Big Bang too," says Tommi Tenkanen, a postdoctoral fellow in Physics and Astronomy at the Johns Hopkins University and the study's author. While not much is known about its origins,...
Post a Comment
Read more

Scientists challenge notion of binary sexuality with naming of new plant species

A collaborative team of scientists from the US and Australia has named a new plant species from the remote Outback. Bucknell University biology postdoctoral fellow Angela McDonnell and professor Chris Martine led the description of the plant that had confounded field biologists for decades because of the unusual fluidity of its flower form. The discovery, published in the open access journal  PhytoKeys , offers a powerful example of the diversity of sexual forms found among plants. The new species of bush tomato discovered in remote Australia provides a compelling example of the fact that sexuality among Earth's living creatures is far more diverse -- and interesting -- than many people likely realize. Bucknell University postdoctoral fellow Angela McDonnell and biology professor Chris Martine led the study following an expedition last year to relocate populations of the new plant, which were first noted by Australian botanists during the 1970s. Herbarium specimens from th...
Post a Comment
Read more