HAMNET Report 20th November 2022

HAMNET Western Cape is happy to report that the 5 GigaHerz microwave link between our two Emcomm stations, at Tygerberg Hospital, for the Province, and at Goodwood Disaster Management Centre, for the City of Cape Town, was installed this past week.

Through kind donations of equipment and then the time of professional tower climbers and installers, the work was completed this week. There is still some configuration and set-up work to be done, but the provision of data, files and secure email is now ensured.

Thank you very much to the donors and organizers of the system.

Phys.org has announced this week that international scientists gathered in France voted on last Friday for new metric prefixes to express the world’s largest and smallest measurements, prompted by an ever-growing amount of data.

It marks the first time in more than three decades that new prefixes have been added to the International System of Units (SI), the agreed global standard for the metric system.

Joining the ranks of well-known prefixes like kilo and milli are ronna and quetta for the largest numbers—and ronto and quecto for the smallest.

The change was voted on by scientists and government representatives from across the world attending the 27th General Conference on Weights and Measures, which governs the SI and meets roughly every four years at Versailles Palace, west of Paris.

Since the SI was established in 1960, scientific need has led to a growing number of prefixes. The last time was in 1991, when chemists wanting to express vast molecular quantities spurred the addition of zetta and yotta.

A yottameter is a one followed by 24 zeroes.

But even the mighty yotta is not enough to handle the world’s voracious appetite for data, according to Richard Brown, the head of metrology at the UK’s National Physical Laboratory.

“In terms of expressing data in yottabytes, which is the highest prefix currently, we’re very close to the limit,” Brown told AFP.

“At the bottom end, it makes sense to have a symmetrical expansion, which is useful for quantum science, particle physics—when you’re measuring really, really small things.”

The new prefixes can simplify how we talk about some pretty big objects.

“If we think about mass, instead of distance, the Earth weighs approximately six ronnagrams,” which is a six followed by 27 zeroes, Brown said.

“Jupiter?  That’s about two quettagrams,” he added—a two followed by 30 zeros.

Brown said he had the idea for the update when he saw media reports using unsanctioned prefixes for data storage such as brontobytes and hellabytes. Google in particular has been using hella for bytes since 2010.

“Those were terms that were unofficially in circulation, so it was clear that the SI had to do something,” he said.

However metric prefixes need to be shortened to just their first letter—and B and H were already taken, ruling out bronto and hella.

“The only letters that were not used for other units or other symbols were R and Q,” Brown said.

Convention dictates that the larger prefixes end in an A, and the smaller ones in an O. Hence Ronna or Quetta for very big, and Ronto or Quecto for very small.

Hmm, I think it will be a while before we get a ham allocation in the QuettaHerz band!

Now, another conference in France has voted to do away with leap-seconds, and this is really going to confuse the poor FT8 and JS8 community, as well as all the other systems that require precise time.

Similar to leap years, leap seconds have been periodically added to clocks over the last half century to make up for the difference between exact atomic time and the Earth’s slower rotation.

While leap seconds pass by unnoticed for most people, they can cause problems for a range of systems that require an exact, uninterrupted flow of time, such as satellite navigation, software, telecommunication, trade and even space travel.

It has caused a headache for the International Bureau of Weights and Measures (BIPM), which is responsible for Coordinated Universal Time (UTC)—the internationally agreed standard by which the world sets its clocks.

A resolution to stop adding leap seconds by 2035 was passed by BIPM members and others at the 27th General Conference on Weights and Measures, which is held roughly every four years at the Versailles Palace west of Paris.

The head of BIPM’s time department, Patrizia Tavella, said the “historic decision” would allow “a continuous flow of seconds without the discontinuities currently caused by irregular leap seconds”.

Seconds were long measured by astronomers analysing the Earth’s rotation, however the advent of atomic clocks—which use the frequency of atoms as their tick-tock mechanism—ushered in a far more precise era of timekeeping.

The problem is that Earth’s slightly slower rotation means the two times are out of sync.

To bridge the gap, leap seconds were introduced in 1972, and 27 have been added at irregular intervals since—the last in 2016.

Under the proposal, leap seconds will continue to be added as normal for the time being.

From around 2035, the difference between atomic and astronomical time will be allowed to grow to a larger value than one second, Judah Levine, a physicist at the US National Institute of Standards and Technology, told AFP.

“The larger value is yet to be determined,” said Levine, who spent years helping draft the resolution alongside Tavella.

Levine said it was important to protect UTC time because it is run by “a worldwide community effort” in the BIPM, which has 59 member states and consults with other nations.

GPS time, a potential UTC rival governed by atomic clocks, is run by the United States military “without worldwide oversight”, Levine said.

A possible solution to the problem could be letting the discrepancy between the Earth’s rotation and atomic time build up to a minute.

It is difficult to say exactly how often that might be needed, but Levine estimated anywhere between 50 to 100 years.

Instead of then adding on a leap minute to clocks, Levine proposed a “kind of smear”, in which the last minute of the day takes two minutes.

Reading between the lines here, it seems to me that the problem isn’t the occasional leap second. The problem is that they are added erratically, and can therefore not be planned for in a fashion precise enough to keep the timekeepers happy.

This is Dave Reece ZS1DFR reporting for HAMNET in South Africa.