It’s been the topic of a weighted discussion for quite some time, but today it has been decided: “Le Grand K” will no longer be used to define a kilogram.
“Le Grand K” is not a big box of Special K, but a platinum-iridium cylinder stored by the International Bureau of Weights and Measures in an underground vault in Paris that has defined a kilogram of mass since 1889. There are a few official copies, and many more copies, so each country has their own kilogram to calibrate to.
Last Friday (November 16th) the kilogram has been redefined so it no longer depends on a material object. Because a material object can be scratched, chipped or destroyed. Or stolen. Or accidentally thrown into the bin. And it can degrade – in fact, “Le Grand K” weighs about 50 µg lighter than its six official copies. You don’t really want to gold – ahem, I mean platinum-iridium – standard for weight to change in weight, right?
So now the kilogram will be defined based on a universal, unchangeable constant. Much better, I think you would agree. The constant of choice here is the Plank’s constant, a number that converts the macroscopic wavelength of light to the energy of individual constants of light. Representatives from 58 countries universally agreed on this new definition, so from next year, the kilogram will be constant forever.
The ampere (electrical current), the kelvin (temperature) and the mole (amount of chemical substance) have also been redefined. That means that all seven units in the International System of Units (S.I.) will be defined by universal constants:
unit of length
Originally defined as a 10-millionth of the distance between the North Pole and the Equator along the meridian through Paris, later as the distance between two scratches on a bar of platinum-iridium metal
Since 1983 defined as the distance traveled by a light beam in vacuum in 1/299,792,458th of a second, with 299,792,458 m/s being the universally constant speed of light.
unit of mass
Initially defined in terms of one liter of water, but since as a small ~47 cm3 cylinder stored in a basement in Paris.
Now redefined in terms of the Plank constant h = 6.62607015×10−34 J*s (J = kg*m2*s−2)
unit of time
Originally defined as 1/86,400th of a day
Since 1967 it has been defined as the time it takes an atom of cesium-133 to vibrate 9,192,631,770 times
unit of electrical current
Originally defined as a tenth of the electromagnetic current flowing through a 1 cm arc of a circle with a 1 cm radius creating a field of one oersted in the center
Now redefined in terms of the fixed numerical value of the elementary charge e (1.6602176634×10−19 C with C = A*s and second defined as above)
unit of temperature
The centigrade scale was originally defined by assigning the freezing and boiling point of water as 0 °C and 100 °C respectively. Note: absolute zero is the lowest temperature (0K = -273.16 °C)
Now redefined in terms of the Boltzmann constant k = 1.380649×10−23 J⋅K−1
unit to describe the amount of substance
Since 1967 defined as the amount of substance which has as many elementary particles as there are atoms in 0.012 kg of carbon-12.
Now one mole substance contains exactly 6.02214076 × 10^23 particles. This constant is known as Avogadro’s number*
unit to describe the intensity of light
Originally taken as the luminous intensity of a whale blubber candle in the late 19th century.
Since 1979 the light intensity of a monochromatic source that emits radiation with a frequency 5.4 x 1014 hertz and has a radiant intensity of 1/683 watt per steradian in a given direction **
So that was “this week in science.” I’ll leave y’all with a related joke:
Both of my subscription magazines – *I’m so sophisticated* – had articles about the advances in space exploration last week (though by now it’s more two weeks ago). It’s been a while since I read so much of my subscription magazines, I usually leaf through most of it – *gone sophistication* – because I’m stuck in the illusion that I don’t have any time.
Which is ridiculous, check my Netflix record.
But nothing better to bring me back into good reading habits than some good ol’ articles about space. And nothing better to get me back to blogging about science subjects again as well. Because let’s be honest, it’s quite difficult to get me to shut up about space.
It had been quiet for a while, in the space news column of your daily/weekly/monthly newspaper. Apart from some back-and-forth travel to and from ISS and the occasional news blast when a countryman was sent up (for me this was Frank De Winne and more recently Tim Peake). But in the last few months, the interest for space has rekindled. Whether it is due to the recent abundance of space movies (Interstellar, Gravity, The Martian), astronomy breakthroughs (LIGA) or NASA’s call for astronauts last year (18400 applicants!), I do not know, but astrosciences has been back in the press.
The most recent exciting news has probably been the discovery of Proxima Centauri b (from now on referred to as PCb). PCb orbit’s the sun’s nearest neighbour, Proxima Centauri, making it close enough to have a very laggy conversation with potential inhabitants of the planet. The possibilities scream to the imagination. It might have an atmosphere. It might have water. It is only 4 light years away. It orbits the Goldilocks zone of Proxima Centauri; 7 million km from it (which is about 1/20 of earth’s to its sun) . It has an estimated weight of 1.3 to 3 that of earth. It is presumed to be rocky. It has an orbit of 11 days, making me 875 orbits of age. (Read more about PCb in the original article.)
Okay, I realise, and so does the research community, that we barely know anything about PCb. But that’s not really the issue. The possibilities are the issue. It’s closeness, it’s “just right”-ness and its promise of potential life forms are enough to get us all excited. And excitement is quite an understatement, you can be sure of that.
Luckily for us, a new form of space exploration has taken place. A first change is the commercialisation of space travel. It’s no longer just for governments to prove their superiority by making it to a certain satellite first. Several visionaries who happen to be billionaires are investing in space travel. For industry and the commercial sector, such as telecommunication, but also towards tourism. This helps to lower the cost of space travel, making “a trip to orbit” more than a very vivid dream.
Luckily for us, we have an Elon Musk, who dreams of a self-sufficient colony on Mars. Luckily for us, we have a Richard Branson, who wants to make space tourism reality. Luckily for us, we have a Jeff Bezos, who thinks that eventually there will be thousands of satellites in orbit employing millions of people. This idea of “great inversion” could allow us to change the earth into one giant nature reserve.
Luckily for us, the billionaires of the world – or at least some of them – are not only driven by profit but also by curiosity.
On the other hand, minaturisation is driving a new way of space exploration. We wouldn’t necessarily need to send enormous, fuel-consuming, costly rockets off to the planets and comets and space we’d like to explore. They can be tiny. Made out of components that are already mass produced. Relatively cheap to make. Of course, I love the idea of still sending humans to space, and I’m quite sure they will continue to do so, but the amount of data and knowledge we can gain from small satellites, such as Planet’s “Doves”, is extremely exciting on its own.
So let’s keep exploring. There is so much out there for us to learn about, and we are making the tools to do it.
Today is “Dag tegen Kanker” (this is Dutch for: day against cancer). They have set up a inflatable walk-through sized intestine to show people how intestinal cancer develops. Unfortunately, the video is in Dutch, but it shows the walk-through bit in the beginning.
As my PhD project is on the mechanics of gut tissue in health and disease (the latter being cancer), I thought this was relevant.
Colorectal cancer is the 2nd most common cancer for women and 3rd most common for men. A lot of people don’t realise they have it, until it is too late.
So, research in the topic, leading to more understanding of onset of cancer, the pathways involved and novel diagnostic methods (for earlier detection) are of great importance. No, I’m not saying that because it involves my own research.