# PARAGRAPH,WORDS AND MEANINGS

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Topic of the day Full Circle: On The Change In Kilogram’s Definition

How The Kilogram Has Come To Be Defined, Once Again, In Terms Of Universal Constants

As of May 20, the kilogram joined a bunch of other units — second, metre, ampere, kelvin, mole and candela — that will no longer be compared with physical objects as standards of reference. The change comes after nearly 130 years: in 1889 a platinum-iridium cylinder was used to define how much mass one kilogram represented. Now, a more abstract definition of the kilogram has been adopted in terms of fundamental constants, namely, the Planck’s constant h, and the metre and second which already have been defined in terms of universal constants such as the speed of light. With this redefinition, the range of universality of the measurement has been extended in an unprecedented way. Earlier, if a mass had to be verified to match with a standard kilogram, it would be placed on one of the pans of a common balance, while the prototype would have to be placed in the other pan — and mass would be measured against mass. Now, by using a Kibble balance, which balances mass against electromagnetic force, to measure the mass of an unknown piece, the very methodology of verification has been altered. The constants involved are known precisely and are universal numbers. Hence, whether the mass is measured on earth or, say, on the moon, it can be determined with precision.This is the culmination of a series of historical changes, which are also described by Richard S. Davis et al in their 2016 article in the journal Metrologia. Originally the definition of mass was in terms of what was then thought of as a universal physical constant. In 1791, 1 kg was defined as the mass of one litre of distilled water at its melting point. Thus, the density of water was the physical constant on which this definition hinged. In 1799, the kilogram came to be defined using a cylinder of platinum – the first time an artefact was used for this purpose. But it was also defined as equivalent to the mass of one litre of distilled water at atmospheric pressure and at about 4 degrees Celsius, the temperature at which water has the maximum density. This was done away with in 1889 when the community adopted the International Prototype of the Kilogram — a cylinder made of an alloy that’s 90% platinum and 10% iridium. The reference to the ‘physical constant’, i.e. mass of one litre of water, was abandoned. Now, as a culmination of this historical process, we come back full circle and find that the kilogram is defined again in terms of a fundamental physical constant — the Planck’s constant. Planck’s constant is a robust number to match. Not until the art of travelling at relativistic speeds, close to the speed of light, is mastered, will we have to redefine these abstract definitions. Until then, it looks like metrologists are on a stable berth.

MEANINGS AND WORDS

1. Bunch

Meaning: several things, typically of the same kind, growing or fastened together.

Synonyms: bouquet, spray, posy, nosegay, corsage

Antonyms: spread out, release

Example Sentence: “a bunch of grapes”

1. standards

Meaning: a level of quality or attainment.

Synonyms: quality, level, grade, degree, worth, calibre, merit

Antonyms: Abnormal, Atypical

Example Sentence: physical objects as standards of reference

1. reference

Meaning: the action of mentioning or alluding to something.

Synonyms: mention of, allusion to, comment on, remark about

Example Sentence: “he made reference to the enormous power of the mass media”

1. Represented

Meaning: be entitled or appointed to act or speak for (someone), especially in an official capacity.

Synonyms: be elected by, be the councillor/MP for, have the vote of

Example Sentence: “Wade represented Great Britain”

1. Abstract

Meaning: existing in thought or as an idea but not having a physical or concrete existence.

Synonyms: Theoretical, conceptual, notional, intellectual, metaphysical

Antonyms: actual, concrete

Example Sentence: “abstract concepts such as love or beauty”

Meaning: choose to take up, follow, or use.

Synonyms: Embrace, Take on, Acquire, Affect, Espouse

Antonyms: Abandon

Example Sentence: “this approach has been adopted by many big banks”

1. unprecedented

Meaning: never done or known before.

Synonyms: Unparalleled, unequalled, unmatched, unrivalled

Antonyms: Normal, common

Example Sentence: “the government took the unprecedented step of releasing confidential correspondence”

1. prototype

Meaning: a first or preliminary version of a device or vehicle from which other forms are developed.

Synonyms: Original, first example, first model, master, mould

Antonyms: Descendant

Example Sentence: “the firm is testing a prototype of the weapon”

1. altered

Meaning: change in character or composition, typically in a comparatively small but significant way.

Synonyms: change, make changes to, make different, make alterations to

Antonyms: preserve, stay the same

Example Sentence: “Eliot was persuaded to alter the passage”

1. precisely

Meaning: in exact terms; without vagueness.

Synonyms: Exactly, sharp, on the dot

Antonyms: Questionably, Unsure

Example Sentence: “the guidelines are precisely defined”

1. precision

Meaning: the quality, condition, or fact of being exact and accurate.

Synonyms: Exactness, exactitude, accuracy, accurateness

Antonyms: Inaccuracy, Disregard, Ignorance

Example Sentence: “the deal was planned and executed with military precision”

1. culmination

Meaning: the highest or climactic point of something, especially as attained after a long time.

Synonyms: Climax, pinnacle, peak, high point, highest point, height

Example Sentence: “the deal marked the culmination of years of negotiation”

1. distilled

Meaning: (of a liquid) having been purified by undergoing heating and condensation.

Example Sentence: “the report is a distilled version of the main accounts”

1. equivalent

Meaning: equal in value, amount, function, meaning, etc.

Synonyms: equal, identical; similar, parallel, analogous

Antonyms: different, dissimilar

Example Sentence: “one unit is equivalent to one glass of wine”

1. hinged

Meaning: attached or joined with a hinge / attach or join with or as if with a hinge.

Synonyms: depend, hang, rest, turn, pivot, centre

Example Sentence: “the ironing board was set into the wall and hinged at the bottom”

1. abandoned

Meaning: having been deserted or left.

Synonyms: Deserted, forsaken, cast aside/off

Example Sentence: “an abandoned car”

1. relativistic

Meaning: accurately described only by the theory of relativity.

Example Sentence: “the relativistic nature of human experience”

1. robust

Meaning: strong and healthy; vigorous.

Synonyms: strong, vigorous, sturdy, tough, powerful

Antonyms: Weak, frail

Example Sentence: “the Caplan family are a robust lot”

1. stable

Meaning: (of an object or structure) not likely to give way or overturn; firmly fixed. Synonyms: Firm, solid, steady, secure, fixed, strong, fast, stout,

Antonyms: Unstable, rickety

Example Sentence: “specially designed dinghies that are very stable”

1. melting

Meaning: becoming liquefied by heat.

Synonyms: Liquefy, thaw, unfreeze, defrost, soften

Antonyms: Appear, Arrive

Example Sentence: “the film will feature a car chase across a melting glacier”

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