How can you tell a hard-boiled egg from a fresh egg? The answer is simple – you spin them. The fresh egg will come to rest a lot quicker than the hard-boiled egg. The reason? When spinning a fresh egg, the friction between the yolk and the shell causes a loss of rotational energy within the egg thus slowing it down. In the same way, friction between the earth’s core and the earth’s mantle and the friction between the tides and the seabed causes the earth to slow down, albeit slowly.
Continue reading “Changes to the Definition of the Time of Day”Category: Science
Digital Measuring Devices (Part 2)
In Part 1 of this article, we saw that one of the basic methods by which a digital measuring device operated was the conversion of an analogue signal (often a voltage or an electric current) into a set of digital bits. The number of bits determined the precision with which the device could take a measurement. The article went on to describe the workings of a digital thermometer and how domestic-quality thermometers are often designed around the use of degrees Celsius with displays in degrees Fahrenheit being an add-on where the Fahrenheit display is calculated from the equivalent Celsius measurement.
In this article we will look at how digital weighing devices work.
Continue reading “Digital Measuring Devices (Part 2)”Digital Measuring Devices (Part 1)
In this two-part series, Martin Vlietstra will be looking at how digitisation is applied to measuring devices: In Part 1, he will examine what “digitisation” is and explain how it is applied to thermometers. In Part 2, he will look at how it is applied to weighing devices.
Continue reading “Digital Measuring Devices (Part 1)”A “Quite Interesting” mess
If, like me, you are a regular viewer and fan of QI, the BBC’s long-running “Quite Interesting” trivia game show, you are probably frustrated by the seemingly random choice of measurement units that the programme uses to convey the sizes of things. Viewers are expected to be familiar with a whole host of units that haven’t been taught in schools for more than 50 years.
Report on Measure for Measure Conference
Martin Vlietstra attended the St Cross Centre for the History and Philosophy of Physics (HAPP) one-day conference in Oxford on Saturday 7 June 2025 and has written a report about the conference for Metric Views.
Continue reading “Report on Measure for Measure Conference”HAPP one-day conference on the history of measurement
The St Cross Centre for the History and Philosophy of Physics (HAPP) is holding a one-day conference on the history of measurement at the Mathematical Institute in Oxford on Saturday 7 June 2025 from 10.30 am – 5.00 pm BST. Participants can register to attend in person or online. Everyone is welcome to attend. Registration to attend this conference is free but booking is required to attend the conference in person or online.
Continue reading “HAPP one-day conference on the history of measurement”What are binary prefixes?
When four new SI prefixes were added to the International System of Units (SI) in November 2022, one of the main reasons cited for their need was for their use in data science, where the numbers involved in describing quantities of information have become ever larger. e.g. The amount of data generated by the internet is projected to hit 175 zettabytes by 2025.
Metric system can meet all astronomers’ needs
The metre used with the appropriate prefix is capable of measuring vast distances across the universe and the tiniest particles in the universe. These prefixes remove the need to use enormous numbers with lots of trailing zeroes. So why do astronomers continue to use astronomical units (AU), light years and parsecs? These non-standard units can be replaced by the metric unit of length, the metre, with the appropriate prefix.
Continue reading “Metric system can meet all astronomers’ needs”NASA Voyager 2 reports make poor use of the metric system
In the first half of August 2023, there were reports about NASA accidentally losing contact with the Voyager 2 spacecraft after sending the wrong command and later reports about regaining contact a few days later. Distances of spacecraft from Earth were expressed in billions of kilometres (as well as billions of miles). One thing that NASA and the media ignored is that the common prefixes of the metric system for the extremely large and the extremely small make the use of astronomical numbers unnecessary unlike the imperial system. This is one big advantage that the metric system has over the imperial system.
Continue reading “NASA Voyager 2 reports make poor use of the metric system”Limitations of body-based measurements
The Daily Mail recently published an article on University of Helsinki research about the merits of body-based measurements. The article says that they are easily accessible, enable us to make approximate measurements and give us valuable insights into the history of measurement. However, body parts do not make good measuring devices because everyone is different and even tailors use tape measures. The historical use of body-based measurements led to the proliferation of different handspans, cubits, feet and inches. This caused problems for international trade and co-operation.
Continue reading “Limitations of body-based measurements”
