Latest news with #NationalMeasurementInstitute
The Guardian
08-07-2025
- Science
- The Guardian
Why is the Earth spinning faster? Is time speeding up? Australia's experts give us their second opinion
Time flies, and three days in July and August could flit by faster than usual this year – but only if your clocks are set to astronomical time. A standard Earth day is 86,400 seconds. But on 9 July, 22 July and 5 August, scientists expect the planet's rotation to quicken relative to the sun, truncating the days by a millisecond or more. In this period of great acceleration, is time itself now speeding up? And will global timekeepers have to skip a second to keep things tidy? Before the 1950s, the length of a day was defined by the Earth's rotation and the apparent position of the sun. 'The Earth rotates once per day, you divide that by 86,400, that's one second,' says Dr Michael Wouters, time and frequency lead at the National Measurement Institute - Australia's legal time keeper and the ultimate referee for what constitutes a second. 'We've always needed to do certain things at certain times, with varying levels of accuracy, like knowing when to plant your crops,' he says. 'As society got more and more complicated, it became necessary to know time more accurately.' Sign up for Guardian Australia's breaking news email These days, the institute keeps track of time using atomic clocks, capable of measuring in nanoseconds (a billionth of a second), which are synchronised globally to Coordinated Universal Time (UTC). 'We have atomic clocks here at our Lindfield lab. One of those is the source of time, and then we have others that we just use for checking that one's working correctly,' Wouters says. These precise measurements matter when it comes to technology, according to Dr David Gozzard, an experimental physicist who specialises in technologies for precisely keeping and synchronising time at the University of Western Australia. Computers, servers, GPS systems, banking and electricity networks, as well as large telescopes, all rely on incredibly accurate synchronisation, sometimes within a fraction of a billionth of a second, he says. 'We're transmitting data so quickly, and it all needs to be time tagged, so computers know what data goes where.' Unlike an atomic clock, the rotation of the Earth can be irregular. One day can be a millisecond, or a fraction of a millisecond, shorter or longer than average. Gozzard says one of the contributing factors is the 'gravitational dance' between the Earth and moon. Sometimes the moon acts like a handbrake, – creating ocean tides, which bulge towards it and slightly slow the spin of the Earth. When the moon is furthest from the equator, the effect is weakened. Oleg Titov, a Geoscience Australia scientist says acceleration and deceleration follow seasonal trends. The shortest day every year is around July and August, which is followed by deceleration over November to March. Scientists have noticed a slight quickening in the Earth's spin since 2020. The fastest day recorded so far, on 5 July 2024, was 1.66 milliseconds shorter than average. 'There is a general consensus the Earth will slow down again (deceleration will win), but there is a risk that acceleration may be effective for a few decades,' Titov says. As the milliseconds accumulate, the system of time based on the Earth's rotation (known as Universal Time 1) drifts further away from the official system of coordinated universal time (UTC), measured by highly precise atomic clocks. To minimise the gap, global timekeepers began inserting something called 'leap seconds', adding an extra second here and there when needed. The first was added in 1972, the most recent in 2016. 'Atomic clocks and our computer networks are the new, far superior form of time measurement, but we're forcing them to keep in sync with this older form of measurement,' Gozzard says. He is pleased the international community has agreed to stop adding leap seconds from 2035. But if the speed-up continues, the situation might require a different, and unprecedented kind of adjustment. Instead of adding a leap second, timekeepers might have to subtract one. That could cause problems, Wouters says. 'People do not expect time to go backwards.' A few milliseconds here or there won't make much of a difference to most people, Gozzard says. Especially given that we add or subtract an hour 'arbitrarily' with daylight savings and apply the same timezones across hundreds of kilometres. Wouters says a millisecond's difference would be imperceptible to the human eye and brain. Even if several seconds in difference accumulated over a century, 'nobody's really going to notice'.
ABC News
20-05-2025
- Politics
- ABC News
Lab Notes: Why a metre is a metre long
Belinda Smith: Exactly 150 years ago, delegates from 17 countries gathered on a Parisian spring day to sign what may be one of the most important and influential treaties ever. It wasn't about politics or war or human rights. It was about the metre. Yeah, the metre. This Treaty of the metre would literally change how we measured the world, the universe around us, and transform trade and science. Because as history shows, if we're not talking the same measurement language, things can go terribly wrong. News Grab: I'm sorry to report that we have a serious problem with the Mars Climate Orbiter. We may in fact be facing a loss of mission. Belinda Smith: So how did this language of measurement come about? And how has it changed since that Treaty of the metre was signed all those years ago? Hi, I'm Belinda Smith, and you're listening to Lab Notes, the show that dissects the science behind new discoveries and current events. To explain how the definition of the metre has changed and why it all matters is Bruce Warrington from the National Measurement Institute, where he is CEO and Chief Metrologist. Now, first things first, well before the Treaty of the metre, someone had to come up with the idea of a metre. How did that happen? Bruce Warrington: Both the metre and the kilogram are French inventions. Belinda Smith: In the wake of the French Revolution of the late 1700s... Bruce Warrington: The new republic was trying for a particularly lofty and rational goal. They wanted the language of measurement that the new France would use to have a couple of key properties. It should be available to everybody at all time, and it should rest on the fundamental properties of nature. It should rest on something drawn from science, not from the length of the king's arm or something that changed over time. Belinda Smith: So if you can't use the king's arm, what can we use? Bruce Warrington: Their aim for the metre, they said, let's take the length of a line that runs from the North Pole to the equator on the meridian that goes through Paris, take that length, the length of that line, and divide it into 10 million pieces, and each piece is a metre. And the kilogram, by extension, came from, you take a box of a certain size measured in centimetres and fill it with pure water, and that becomes a kilogram. And so the kilogram comes from the metre in its original definition. Belinda Smith: Just working out how long that line would be from the North Pole to the equator through Paris just seems like a gigantic headache and logistical nightmare to me, let alone then divvy that up into 10 million bits, and there's your metre. That's, it seems wild to me. How do you even measure that? Bruce Warrington: It's a brave thing. It's a brave definition to go for, isn't it? Belinda Smith: Brave is one word for it, yep. Bruce Warrington: Well, they thought big, and they did want exactly, as we've said, something that wouldn't change. And so what they were essentially trying to do was draw on the best science of the day that they had for surveying. And so they really did try and figure out the length of that line by sending surveyors, not to do the whole thing, not to go all the way from the Pole to the equator, but to go from Dunkirk, so right at the northern part of France, all the way to Barcelona. And then by measuring part of that line, extrapolating it out by knowing how much longitude you'd covered, essentially. Belinda Smith: Quite the undertaking, and one that took a pair of astronomers seven years. Once they calculated the length of the metre, they took it to the French Academy of Sciences, who made a platinum bar, which they called the metre of the archive. Then in 1875, the Treaty of the Metre, or the Metre Convention, was signed in the metre's home country of France. Bruce Warrington: So the Metre Convention is the international agreement whereby the nations of the world work on the metric system. They kind of work to use a single language for measurement, for trade and for innovation, and to keep that system evolving to stay at the forefront of trade and technology. Belinda Smith: So a metre in Germany would be the same length as a metre in, say, Venezuela, two of the original signatories. Here in Australia, we weren't on board to begin with, because, you know, this all went down well before Federation, but we did sign on in 1947, which helped solve a few inconsistencies. Bruce Warrington: Part of the challenge as Australia was settled was speaking that same language between states, particularly, for example, railway gauges. You can see where disagreements or different approaches might cause you problems. Speaker 5: Australia badly needs a uniform gauge railway system. We have inherited as a nation 30,000 miles of different-sized railway lines, a muddled mess, a legacy of folly from the last century which has added hundreds of millions of pounds... Yeah, it Bruce Warrington: was all a bit of a dog's breakfast. And as manufacturing demanded more precise measurements, the definition of the metre also had to change. Belinda Smith: So early in the 20th century, science was understanding measurements using light. Bruce Warrington: Light travels in waves, and scientists can measure their wavelength, literally the length of the wave. So if you think of a metre as being divided into 100 centimetres or 1,000 millimetres, you can also divide it into 1,650,763.73 wavelengths of a very specific reddish-orange light. So in 1960, this became the definition of the metre. Bruce Warrington: It was more stable, it was more accurate. It's not subject to some of those things that can skew a measurement or a comparison. Belinda Smith: But the evolution of the metre didn't end there. Bruce Warrington: It essentially goes back to clocks. So in the interim between those two definitions, there'd been a lot of progress made on measuring time very accurately. And time today is still the quantity we can measure most accurately. Atomic clocks are the most accurate measurement standards. So if you have a clock with a very accurate second, and you fix the speed of light as a fundamental constant, so light travels this many metres in a second, then that essentially fixes the metre. You take that number, 299,792,458 is the number. That's how many metres light travels in a second. So you take the distance light travels in a second and divide it by that number, that's one metre. Belinda Smith: Okay, so by this point, we can put the definition of the metre conversation to bed because this is how the metre is defined today. And currently, more than 100 countries have signed the metre treaty, including some that seem to refuse to go fully metric. The US springs to mind. Bruce Warrington: There are one or two holdouts that you might know. Each country gets to choose exactly when it adopts that system. But even the United States, for example, has at the core of its civil measurement, the metric system. So its national standards are the kilogram and the metre, just like everybody else's. Belinda Smith: And now we have people like Bruce. He's one of hundreds of metrologists in Australia. Bruce Warrington: A metrologist is a measurement scientist. So meteorology is weather, that's something quite different. But a metrologist studies the science of measurement and how measurement can be applied to other sciences, to trade, to innovation generally. Belinda Smith: That includes doing things like calibrating equipment, you know, like weigh stations and the like. Bruce Warrington: It's that thing where you don't need to know about it, but somebody needs to know about it. For everybody to have the confidence for trade and for innovation to work. Belinda Smith: And metrologists don't just deal in metres and kilograms. A handful of other units of measurement were added to the treaty over the years, like the second and the ampere or amp, which is a measure of electrical current. These all form what's known as the International System of Units. You might know them as SI units. So why is it important to have these, including the metre, defined to such an exact level? Bruce Warrington: It comes down to what you can do with it. So if you are measuring distances across the earth, the accuracy of those surveying measurements originally was the challenge. You didn't necessarily need more accuracy than that. As you go through the industrial revolution and manufacturing starts to advance, you have to start thinking about tolerances for the big heavy engineering systems that you are designing and manufacturing and how much tolerance can you accept in a manufactured piece of equipment before it stops working. Belinda Smith: Today, the frontier for manufacturing is on the smallest of scales. Bruce Warrington: It's down at the level of billionths of a metre, nanometres or even smaller. So if you think about the scale of a transistor in an integrated circuit in your smartphone, it's of order nanometres. The physical scale of the electronic fabrication is at that level. So you need rulers that can check for the quality of that manufacturing at that level and can control manufacturing at that level. And so the old definition wouldn't do it, but laser interferometry, lasers as a way of using the new definition can. And so there's always a tension between our ability to measure something and our ability to make something. Belinda Smith: Precision is one thing. Making sure everyone uses the same measurements is equally important as engineers working on NASA's $300 million Mars Climate Orbiter discovered in the late 90s. Bruce Warrington: In the design of that probe, the thrusters for the probe, two different teams were speaking two different measurement languages. One was using kind of imperial units and one was using metric units. And so the satellite comes in too low and burns up. And so the whole thing's lost because people are not using the same language of measurement. Belinda Smith: So there are high stakes scenarios like that one, but there are also everyday measurement discrepancies, which, well, give Bruce the Bruce Warrington: irrits. If you're cooking or baking, for example, then what's a teaspoon, what's a tablespoon, what's a cup can also change. And I find it slightly frustrating as a professional measurement nerd that an Australian tablespoon is four teaspoons, whereas almost everywhere else in the rest of the world, it's three teaspoons. And so- Belinda Smith: See, I didn't know that. Bruce Warrington: It is. So an Australian tablespoon is 20 mils, 20 milliliters. And most of other places use 15 milliliters. So what that means is if you're cooking something, then you might need to know whether the recipe came from Australia or came from somewhere else to get the tablespoon right. Belinda Smith: You've just blown my mind. That is, oh my gosh, okay, wow. Because that's a whole other layer. Like you said, a cup is not a cup. We've got two sets of measuring cups. They're not the same. The one cup is not the same. And so it drives me nuts. I'm like, do I go the big cup or the smaller cup? Which is why I like it when recipes have weights, they say, you know. There you Bruce Warrington: go. You see, that is the metric system. If you use milliliters and grams, it's absolutely unambiguous. And so even in something as simple as a recipe, if you're not sure, then you can get in trouble. Belinda Smith: That was Bruce Warrington, CEO and Chief Metrologist of the National Measurement Institute. And thanks for listening to Lab Notes on ABC Radio National, where every week we dissect the science behind new discoveries and current events. I'm Belinda Smith. This episode was produced on the lands of the Wurundjeri and Menang Noongar people. Fiona Pepper's the producer, and it was mixed by Riley Mellis. What science-y story would you like us to get under the bonnet of? Send us an email, labnotes at We'll catch you next week.
ABC News
20-05-2025
- Science
- ABC News
The metre originated in the French Revolution, but its definition has changed many times since
The next time you pick up a bag of spuds from the supermarket or fill up the car with petrol, you can thank a treaty signed 150 years ago for the metric system that underpins daily life. On May 20, 1875, delegates from 17 countries assembled on a Parisian spring day and signed the Metre Convention, also known as the Treaty of the Metre. At the time, it wasn't uncommon for countries, states and even cities to have entirely different ways of measuring distance and mass, hampering trade and holding back progress in science. To standardise and unify these definitions, the Treaty of the Metre established the International Bureau of Weights and Measures, which initially defined the metre and kilogram. Over the years, more countries signed the Treaty of the Metre, including Australia in November 1947. A handful of other units of measurement were also included to form the International System of Units, the basis of the metric system. But the metre's inception predates the treaty that bears its name by nearly 100 years. And its story begins during the French Revolution. During the late 1700s, revolutionaries shaping the new republic of France shed old traditions bound to royalty and religion. This reinvention included creating a new system of measurement. This system would be available to everyone, and be tied to fundamental properties of nature, "not from the length of the king's arm, or something that changed over time", Bruce Warrington, CEO and chief metrologist at the National Measurement Institute, says. So mathematicians and scientists of the time decreed that the length of a metre — from the Greek word "metron", meaning "a measure" — was equal to one 10-millionth of the distance from the North Pole to the equator through the Paris Observatory. It fell to a pair of astronomers to calculate this distance, and after seven years, in 1799, they presented their final measurement to the French Academy of Sciences which made a "Metre of the Archives" in the form of a platinum bar. (It was later found the astronomers were a bit off in their calculations, and the metre as we know it is 0.2 millimetres shorter than it should've been.) The Metre of the Archives and its copies were eventually replaced by around 30 metre bars made of a stable platinum-iridium alloy. They were distributed around the world in the late 1890s, and remained the "standard" metre for decades. But as science progressed, the definition of the metre changed too. This change started early last century, when scientists discovered they could measure distances using light. Light travels in waves. If you know the distance between each wave — called the wavelength, literally the length of the wave — it's possible to use light "as a very fine ruler", Dr Warrington says. And in 1960, the platinum alloy bars were out and a new definition of the metre was introduced. Pass an electrical current through a lamp filled with krypton gas and the krypton atoms throw off light, including a reddish orange wavelength. One metre equalled 1,650,763.73 times the wavelength of this specific reddish orange light. Meanwhile, electronics fabrication kicked off and the scale of manufacturing shrunk to the incredibly tiny. Think transistors in a smartphone integrated circuit, which are only a few billionths of a metre wide. "So you need rulers that can check for and control the quality of that manufacturing at that level," Dr Warrington says — something the krypton lamp metre definition could not do. Since 1960, there'd been a lot of progress made on measuring time accurately with atomic clocks. Their "ticking" is produced by oscillations of radiation emitted when atoms are bathed in laser light. And they can tick billions of times every second. This new ability to divvy up the second into increasingly tinier slices, coupled with a universal physical constant, the speed of light, redefined the metre. From 1983, a metre was considered the distance that light travels in a vacuum in 1/299,792,458 of a second (because light travels 299,792,458 metres per second). This new definition incorporating time and the speed of light opened up new ways of measuring length, Dr Warrington says. For instance, scientists use it to accurately measure Earth's distance to the Moon. "The Apollo astronauts left a kind of fancy mirror on the surface of the Moon, and to this day, you can still fire a laser at that reflector, and time the round trip for the light to go all the way to the Moon and back," Dr Warrington says. "And you can turn that into a very careful measurement of the distance between the Earth and the Moon." These measurements show the Moon is slowly pulling away from Earth at around 3.8 centimetres each year. Even as the metre and other units of measurement were being redefined, it was up to each Metre Treaty signatory to adopt the metric system in their own time. It took Australia more than 20 years after signing the Metre Treaty to officially adopt the metric system when the Metric Conversion Act was passed in 1970. Other countries have been far slower to go metric. One of the original signatories of the Metre Treaty was … the US. Today, while day-to-day life in the US tends to use imperial units, the metric system is legally recognised and is "at the core of its civil measurement", Dr Warrington says. "So its national standards [for mass and distance] are the kilogram and the metre, just like everybody else's." Even in Australia today you don't have to look far to see imperial units in, for example, men's trouser waistbands and television screen size. One area that still suffers inconsistencies in measurement is in the kitchen, Dr Warrington says. "I find it slightly frustrating as a professional measurement nerd that an Australian tablespoon is four teaspoons, whereas almost everywhere else in the rest of the world, it's three teaspoons. For more on the history of the metre, check out the full episode of Lab Notes.
