NIST Headquarters in Boulder, CO
The most widely used system of measurement is the International System (SI) of units in which length is measured in meters (m), time in seconds (s), and mass in kilograms (kg). Definitions of base and derived units in the SI system can be found on the National Physical Laboratory (NPL) homepage. The SI system is based upon the metric system (the names are used synonomously by most people) which was put forth by the French in the very late 1700's in an attempt to standardize the rather disturbing mishmash of units used in Europe. The meter was first defined as 1 / 10,000,000 of one quarter of the earth's circumference, and the second to be half a complete swing for 1 meter-long simple pendulum. Today the meter has been standardized to the distance light travels in 1/299,792,458 of a second. And the second? Well, it's 9,192,631,770 vibrations of the light emitted from the lowest order electron energy transistion of 133Cs, of course. (Should you be interested, there is a rather extensive dictionary and history on units available, but it takes a while to download.)
In the British System (more correctly, the UK Imperial System), length is measured in yards, time in seconds, and mass in slugs. Yes, that's correct ... slugs. Don't be suprised if you are not familiar with slugs. The quantity most commonly referred to in the British system is the weight of an object, measured in the more familiar units of pounds (lb). Although related to the mass of an object, weight is a different quantity. We will study the difference in great detail in the coming weeks. There are other systems, of course. In Scotland, the unit of weight used is the stone, equivalent to about 14 lbs. In some areas of the Middle East, the ancient unit of the cubit is still used ... about 50 cm.
The governments of most countries maintain an institution responsible for assuring that commercial, industrial, and scientific facilities adhere to the standards. This is critical for maintaining international trade, manufacturing compatibilty and information exchange. In the US, the institution responsible for measurement standards is the National Institute of Standards and Technology (NIST) (under the Commerce Department's Technology Administration). The NIST is involved in an immense range of areas, from the UTC time base to research on the accuracy of price scanners.
The questions below can be answered by a scouting around the links given. As with all the weekly NetResearch projects, there are 5 bonus points to be had. Happy surfing!
Be sure to enter your full name. Enter your email address ONLY if you want the number of points awarded e-mailed to you. Responses should be brief but complete. You must click the SUBMIT button to submit your entry. Entries are due by noon on Monday of next week.
Questions:
Both mass and "amount of substance" are given as base units by the NPL. Briefly, what's the difference?
Among the internationally recognised non SI units, what is the name for 1000 kilograms?
According to the Federal Trade Commission's most recent report, how often is the scanner price of a purchase wrong? (Use the "Search NIST Webspace" engine to find this info.)
Here's one that might require a little independent searching. Why is "lb" the abbreviation for pound? (I highly recommend www.google.com as the best search engine available!)
The most widely used system of measurement is the International System (SI) of units in which length is measured in meters (m), time in seconds (s), and mass in kilograms (kg). Definitions of base and derived units in the SI system can be found on the National Physical Laboratory (NPL) homepage. The SI system is based upon the metric system (the names are used synonomously by most people) which was put forth by the French in the very late 1700's in an attempt to standardize the rather disturbing mishmash of units used in Europe. The meter was first defined as 1 / 10,000,000 of one quarter of the earth's circumference, and the second to be half a complete swing for 1 meter-long simple pendulum. Today the meter has been standardized to the distance light travels in 1/299,792,458 of a second. And the second? Well, it's 9,192,631,770 vibrations of the light emitted from the lowest order electron energy transistion of 133Cs, of course. (Should you be interested, there is a rather extensive dictionary and history on units available, but it takes a while to download.)