Ralph Caspers investigates how the units of length, time and weight came about and why this is important to us. We use units of measurement every day and everyone knows what is meant when we talk about meters, seconds or kilograms. That's a good thing, because then everyone can measure for themselves - and get the same result. It only gets confusing for us in Europe when distances are not given in meters and kilometers, but in yards and miles, as in the USA. Ralph explains in the video what dramatic consequences this has had. Fortunately, we understand each other better when it comes to measuring time and know when a second, a minute or an hour has passed all over the world. But for a long time, uniform units were not so obvious. Who actually decided that a meter is exactly one meter long? And how was it defined how long a second lasts? And on what basis? In the course of history, a wide variety of units of measurement have been used and changed again and again. The world was much smaller before the invention of fast means of transport for people. They usually stayed in one place and only had contact with the people in their immediate surroundings. There they used the units of measurement defined by the respective rulers. Often the unit used to determine lengths was the royal cubit, i.e. the forearm of the king or queen. This gradually became impractical when trading between different kingdoms or principalities - for example when measuring larger distances. But how did agreement finally come about? Ralph explains how today's meter took shape and which universal definition has only been in use since 1983. The definition of time units, particularly the second, also had to be corrected again and again. Astronomical measurements, especially the position of the sun and the day-night cycle, determined time measurement for a long time. The Greek mathematician Claudius Ptolemy eventually divided minutes and seconds into increments of 60. How did he get to 60? Ralph demonstrates it to you on his own body in this video. Meters, seconds, kilograms - how our units are defined today using natural constants and why these definitions have had to become more and more complicated over the centuries - Ralph explains this in the video. Chapters: 00:00 Introduction 00:30: How were units of measurement defined? 03:15: Nature as the basis for units of time 05:32: How did the meter get its length? Authors: Dirk Gilson, Ralph Caspers Editing/Graphics: Klaus Wache Sound design: Klaus Wache Editor: Max Ostendorf Sources: Physikalisch-Technische Bundesanstalt (PTB) PTB communications: Experiments for the new International System of Units (SI). 2nd edition 07/2018 https://www.ptb.de/cms/fileadmin/inte... Bureau International des Poids et Mesures (BIPM) History of the SI. https://www.bipm.org/en/history-si From artefacts to atoms - A new SI for 2018 to be based on fundamental constants. Dr. Terry Quinn, Science Direct, Volumes 65–66, October–December 2017, Pages 8-20 https://www.sciencedirect.com/science... The Measure of All Things. Ken Alder. The Free Press, New York, 2002 http://www.kenalder.com/measure/index... Physikalisch-Technische Bundesanstalt, Nationales Metrologieinstitut The legal units in Germany https://www.ptb.de/cms/fileadmin/inte... NASA, Solar System Exploration. Our Galactic Neighborhood Missions, Mars Climate Orbiter https://solarsystem.nasa.gov/missions... Physikalisch-Technische Bundesanstalt, Nationales Metrologieinstitut What is a second? https://www.ptb.de/cms/ptb/fachabteil... More on the topic: Quarks.de: New units of measurement - good, but complicated https://www.quarks.de/gesellschaft/wi... MDR Doku: Who determines the measure of things • Video Did you like the video? Then subscribe now to the official Quarks channel with Ralph Caspers @DimensionRalph on YouTube! Also visit the official Quarks channel on YouTube: @Quarks #quarks on Instagram: / quarks.de / beautyquarks Quarks on Twitter: / quarkswdr Quarks on Facebook: / quarks.de #measurementunits #measurementunits #meter #seconds #ralphcaspers #history #dimensionralph