Editing 2073: Kilogram
Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.
The edit can be undone.
Please check the comparison below to verify that this is what you want to do, and then save the changes below to finish undoing the edit.
Latest revision | Your text | ||
Line 8: | Line 8: | ||
==Explanation== | ==Explanation== | ||
+ | {{incomplete|Created by a CONSTANT PLANCK. Links to resources would be good. Explanation should include how the metric system is interconnected (ex: 1L of water weighs 1KG.). Please mention here why else this explanation isn't complete. Do NOT delete this tag too soon.}} | ||
− | + | On the day of this comic, the International Committee for Weights and Measures voted to redefine the kilogram by fixing it to the value of Planck's Constant. This is done by passing a measured current through an electromagnet to exert a force to balance 1 kg. The change will take effect on May 20, 2019, when the platinum cylinder International Prototype Kilogram that defines the unit will be retired. This means that the mass of a kilogram will no longer be tied to a physical object, but to the fundamental properties of the universe. | |
− | + | The comic is accurate in that the International Committee for Weights and Measurements did just vote to redefine the kilogram; however, it was '''not''' to make it be the same as the pound, or indeed to make it different in any practical way from its current weight. The problem they are trying to solve is that the current method of confirming that a kilogram is accurate is to use physical metal weights measuring exactly one kilogram, periodically transporting them around the world to an official weight lab to confirm they still weigh the same. Over time these physical objects have changed very slightly in their mass making them unreliable in the long run. Note that these weights and comparisons are so precise that a fingerprint on one of the weights could throw them off. | |
− | + | In this comic, Black Hat announces that the kilogram has been redefined as equal to one pound. Ponytail and Cueball seem to think this makes things simpler, but Megan is rightfully alarmed. The metric system of measurement is the one used by most of the world and is the standard system used in science. It is considered superior to the {{w|United States Customary System}} (which the pound is part of). Therefore, redefining the kilogram to be based on the pound would make things much, much worse and outrage supporters of the metric system. | |
− | + | To add to the confusion, the pound is officially defined as 0.45359237 kilograms, or less than half a kilogram. This makes defining a kilogram as one pound impossible as they are then stuck in a loop, as the pound must weigh less than half of a kilogram, but then the kilogram will have to be updated to match the new pound mass. (actually not true: 0.45359237 x = x has a solution, namely 0). | |
− | + | The title text continues the joke by saying that the meter has been defined as exactly three feet. The yard, the closest US measurement to the meter, is three feet. However, a meter is about 9 centimeters longer than a yard. As with the pound, the metric system is used to define the yard as it is officially defined as 0.9144 meters. | |
− | + | Note: There is another system, not used outside the US and Britain, that uses pounds and feet. It is called the {{w|Imperial system}}. | |
− | |||
− | |||
==Transcript== | ==Transcript== | ||
Line 36: | Line 35: | ||
Nevertheless, there really are constants of nature. For example, one of them is ‘''c''’, the speed of light in a vacuum. The expressed value of ''c'' depends on your choice of the unit of distance and the unit of time, but it’s a constant in those units. Now just suppose we all had a reproducible way to define a specific unit of time, which just for fun we call a ‘second’. You might not know the length of a ‘meter’, but if I told you that measured in meters per second the universal constant value of ''c'' is exactly 299792458 meters per second, then I would have fixed the length of a meter to be exactly the distance light travels in a vacuum in 1/299792458 seconds. And in fact this is what the international body responsible for defining our SI units has done. | Nevertheless, there really are constants of nature. For example, one of them is ‘''c''’, the speed of light in a vacuum. The expressed value of ''c'' depends on your choice of the unit of distance and the unit of time, but it’s a constant in those units. Now just suppose we all had a reproducible way to define a specific unit of time, which just for fun we call a ‘second’. You might not know the length of a ‘meter’, but if I told you that measured in meters per second the universal constant value of ''c'' is exactly 299792458 meters per second, then I would have fixed the length of a meter to be exactly the distance light travels in a vacuum in 1/299792458 seconds. And in fact this is what the international body responsible for defining our SI units has done. | ||
− | + | One second is defined to be a specific number of certain state transitions of a cesium 133 atom. The specific number was set in the year 1965, so as to match a previous astronomical standard called Ephemeris Time to the limit of human measuring ability at the time. The 1965 definition didn’t change the actual duration of a second, but it did make its measurement forever reproducible. | |
In 1983 the value of ''c'' was fixed to the value noted above. Prior to that it had been measured with respect to existing definitions of a meter, and had to be expressed with a measure of uncertainty. For example in 1973 a team at the US National Bureau of Standards refined ''c'' to 299,792,457.4 m/s ± 1 m/s. But from 1983 onwards, with an exact integer value for ''c'' that is quite close to that Bureau measurement, the length of a meter is now fixed with no plus/minus uncertainty. Furthermore, both the second and the meter match their predecessor definitions for all intents and purposes. | In 1983 the value of ''c'' was fixed to the value noted above. Prior to that it had been measured with respect to existing definitions of a meter, and had to be expressed with a measure of uncertainty. For example in 1973 a team at the US National Bureau of Standards refined ''c'' to 299,792,457.4 m/s ± 1 m/s. But from 1983 onwards, with an exact integer value for ''c'' that is quite close to that Bureau measurement, the length of a meter is now fixed with no plus/minus uncertainty. Furthermore, both the second and the meter match their predecessor definitions for all intents and purposes. | ||
Line 44: | Line 43: | ||
To expand on this even further, three additional universal constants that were previously measured and that had uncertainty values have been assigned fixed values, resulting in exact definitions of three corresponding units of measurement without affecting their applicability. Fixing the unit of elementary charge, ''e'', serves to define the unit of electric current, the Ampere. Fixing the unit of luminous efficacy ''K<sub>cd</sub>'' serves to define the unit of luminous intensity, the candela. And fixing the Avogadro constant ''N<sub>A</sub>'' serves to define the unit of amount of substance, the mole. | To expand on this even further, three additional universal constants that were previously measured and that had uncertainty values have been assigned fixed values, resulting in exact definitions of three corresponding units of measurement without affecting their applicability. Fixing the unit of elementary charge, ''e'', serves to define the unit of electric current, the Ampere. Fixing the unit of luminous efficacy ''K<sub>cd</sub>'' serves to define the unit of luminous intensity, the candela. And fixing the Avogadro constant ''N<sub>A</sub>'' serves to define the unit of amount of substance, the mole. | ||
− | A Wikipedia article about redefining the SI units of measure in terms of newly fixed values of things taken to be universal constants is {{w| | + | A very recent Wikipedia article about redefining the SI units of measure in terms of newly fixed values of things taken to be universal constants is {{w|Redefinition of SI base units}}. |
− | |||
− | |||
{{comic discussion}} | {{comic discussion}} |