Weights and Measures Act 1985 (Definitions of “Metre” and “Kilogram”) (Amendment) Order 2020

Lord Blencathra Excerpts

Wednesday 20th May 2020 Lords Chamber

[Lord Blencathra (Con)]

My Lords, I thank my noble friend the Minister for giving us the chance to speak on this important subject. Indeed, we used to speak of nothing else but the Planck and Avogrado constants in the Bishops’ Bar, so let me make some mischievous points today.

The current definitions have been in effect since 1985, and they have worked perfectly. Since 1889, the IPK has been used to define the mass of the kilogram. It is a golf ball-sized object made of 90% platinum and 10% iridium and is regarded as the most perfect object to define its weight because of its stability. There is the original IPK itself, six sister copies and hundreds of national prototypes that are held by world Governments.

The excuse for this change is that the boffins say that the IPKs are unstable because their weight varies over time by up to the weight of 50 specks of dust. Their masses are calibrated as offset values. For instance, K20, the US’s primary standard, originally had an official mass of 1 kilogram minus 39 micrograms in 1889. In 1948, it was down 19 micrograms, or 19 specks of dust, but the latest verification shows it to be precisely identical to its original 1889 value. These specks of dust variations are accounted for all the time by using offset values. It is like the North Pole and magnetic variation, which everyone simply recalculates by taking the variation into account. For 130 years, there has never been a problem with any national IPK distorting the weight of a kilogram, so why change it?

The 1985 Act states that a metre is defined as:

“the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.”

Can my noble friend tell the House whether that simple definition has caused any errors over the past 35 years? Have there been critical measurement mistakes because the second has not been defined as

“taking the fixed numerical value of the caesium frequency Delta nu caesium, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom.”

Will I have to return my tape measure to B&Q since the metre scale no longer corresponds to 1.09361 yards? Will the Minister tell us what practical differences these changes will make?

In conclusion, I would prefer my noble friend to tackle the law-breaking by many councils which are illegally introducing metric measures on road signs. The law is absolutely clear: metric units are not permitted on distance signs, whether by themselves or in conjunction with imperial units. Distances must be in miles and yards only, and that applies to all traffic signs, not just those for motorists. Yet there are countless examples of councils erecting illegal signs in metric units. Will my noble friend therefore take up this matter urgently with the Department for Transport to make sure that all councils obey the law of this country and not what they might wish it to be?