Text 8. Gravitational constant is up in the air

 

Isaac Newton,  one  of  the  greatest  men  in  the  history  of  science,  began  studying the theory of  gravity when he was  twenty- two.  Having  been  brought, by the fall of the  apple,  to the conclusion  that the apple and the  earth were    pulling one another, he began to think of the same pull of gravity extending far beyond the earth. Newton deduced and calculated the force of gravity acting between the sun and the planets, thus establishing the law of gravitation in its most general form. His great work “Principia”, published in 1687, gave an insight into the structure and mechanics of the universe.

More than three centuries after Isaac Newton proposed his theory of gravity, physicists are still not sure how strong the force is.

At a meeting in Washington DC of the American Physical Society and the American Association of Physics Teachers, three research teams reported their latest measurements of Newton’s gravitational constant, G, which determines gravity’s strength. Two are markedly lower than the accepted value and the other is sharply higher.

The accepted value of G, 6·6726 x 10^-11 metres ³ per second² per kilogram, is based on measurements made 15 years ago by Gabriel Luther of Los Alamos National Laboratory in New Mexico. To measure G, researchers measure the movement of small masses in response to the gravitational fields of larger objects.

Tim Armstrong and Mark Fitzgerald of the Measurement Standards Laboratory of New Zealand in Gracefield placed large masses on either side of a smaller mass hanging on a thread. The small mass tries to twist towards the larger masses, but can be held in place by an electric field. From measurements of the strength of the field needed to hold the small mass still, the New Zealand team came up with a value for G of 6·6659, or 0·1 per cent below the accepted value. For a fundamental constant of nature, that is a major discrepancy.

A group led by Hinrich Meyer at the University of Wuppertal in Germany, meanwhile, has set G at 6·6685. Meyer’s team measured the distance between two small pendulums. When large masses are placed on either side of the pendulums, the masses’ gravitational fields cause them to move apart.

The third new measurement of G is higher than the accepted figure. Winfried Michaelis and his colleagues at the Federal Physical-Technical Institute in Brunswick, Germany, measured G by floating a small mass in liquid mercury and placing large masses nearby. Their figure is 6·71540.

No one has a ready explanation for the discrepancies. One possibility, however, is that objects outside the experiments are disrupting the measurements. Luther recalls that when he placed his apparatus close to an outside wall, even the mass of falling rain could affect the results. “I could also see when somebody moved two tonnes of books over a weekend two floors above”, he says. Luther now intends to resolve the controversy by measuring G in the New Mexico desert, well away from any disturbances.

Vincent Kiernan. New Scientist, 1995

Vocabulary and Comprehension Exercises

I. Translate these into your own language:

•                    gravitational constant

•                    the theory of gravity

•                    research teams

•                    the latest measurements

•                    gravity’s strength

•                    the accepted value

•                    in response to

•                    on either side of the pendulums

•                    to twist towards the larger masses

•                    a major discrepancy

•                    to cause them to move apart

•                    in liquid mercury

•                    to affect the results

•                    disturbances

II. State the part of speech of the following words and translate them into your own language:

gravity - gravitational, theory - theoretical, nature - natural, to conclude -

conclusion, to calculate - calculation, to measure - measurement, to accept - acception, to resolve - resolution, to move - movement, to place - to displace - displacement, sharp - sharply, close - closely, strong - strongly.

III. Give synonyms of the following words:

fundamental, movement floating, research, determine, strength, constant

IV. Give the principal forms of the following verbs:

to be, to come, to give, to intend, to move, to pull, to begin, to fall, to hold, to measure, to place, to see.

V. Translate the sentences paying attention to non-finite forms of the verb.

•                    Having been brought, by the fall of the apple, to the conclusion that the apple and the earth were pulling one another, he began to think of the same pull of gravity extending far beyond the earth.

•                    The accepted value of G is based on measurements made 15 years ago by Gabriel Luther.

•                    To measure G, researchers measure the movement of small masses in response to the gravitational fields of larger objects.

•                    Luther now intends to resolve the controversy by measuring G in the New Mexico desert, well away from any disturbances.

VI. Finish the sentences according to the text.

•                    The accepted value of G is based on measurements made 15 years ago by ..... .

•                    One possibility is that objects outside the experiments are disrupting the ..... .

•                    It was Newton who proposed his ..... .

•                    Luther now intends to resolve the controversy by ..... .

•                    More than three centuries after Isaac Newton proposed his theory of gravity, physicists are still not sure ..... .

•                    No one has a ready explanation for the ..... .

•                    Two are markedly lower than the accepted value and the other is .....

•                    In 1995 three research teams reported their measurements of Newton’s gravitational constant, G, which determines ..... .

VII. Which sentences don’t correspond to the sense of the text?

1. Newton deduced and calculated the force of gravity acting between the sun and the planets.

•                    Newton’s experiments with light and colour led him to theorize on the nature of light.

•                    The accepted value of G was found by measuring the movement of small masses in response to the gravitational fields of larger objects.

•                    The measurements of G were reported by three research teams in 1995.

•                    The scientists have a ready explanation for the discrepancies found.

•                    The scientists decided to accept the value of G, 6·6726 x 10^-11 metres³ per second² per kilogram, and not to set off new experiments.

VIII. Answer the questions:

•    Who proposed the theory of gravity and discovered the law of gravitation?

•    What determines gravity’s strength?

•    Do physicists know for sure the meaning of Newton’s gravitational constant, G?

•    How was the accepted value of G measured?

•    What measurements were done by three research teams in 1995? Were they equal to the accepted value?

•    How did the first team measure G?

•    What method did the second team use to measure G?

•    How was the third meaning of G found?

•    Do the scientists have a ready explanation for the discrepancies?

•    How does Luther intend to resolve the controversy?

 

IX.  Write a summary in English (or in your own language).

•                    Give each paragraph a suitable title in English (or in your own language).

•                    Develop the titles of the paragraphs into topic sentences. Join the topic sentences together.

•                    Re-read your summary and make sure that the sentences are presented in a logical order.