# Tag Info

20

It happened long before Newton. In the second century BC Hipparchus used lunar parallax to calculate a value for the minimum and maximum distance of the earth and moon. His results are very close to the modern calculation of this distance. You can read about it here: Toomer G.J. (1974), "Hipparchus on the Distances of the Sun and Moon." Archives for the ...

12

This number has no significance. Its origin is historical. Originally meter was defined as 1/40,000,000 part of the Paris meridian. Based on the measurement of this meridian they made a standard rod in Paris. Since it is inconvenient to base the definition on something which is difficult to measure, meter was soon redefined simply as the length of this rod. ...

10

Ancient Greeks painstakingly avoided negative numbers, although they could have come handy in astronomical calculations and number theory, among other places. Brahmagupta in Correctly Established Doctrine of Brahma (c. 630 AD) uses the language of "fortunes" and "debts", which suggests the merchant origin of the negative number concept, but that remains a ...

9

This is an ill defined question. It can be interpreted as "Who was the first to TRY to measure the distance to the Moon", or "Who was the first to give a correct number", and what is counted as correct number. And even this does not define the question precisely. The crucial question: "in what units"? It is relatively easy to measure the distance in terms ...

6

To a certain extend, the measurement problem (MP) is indeed philosophical, in the end, it still comes down to which interpretation you prefer. However, there are also of course also certain physical results, which come into play here. These are also highly relevant to the various interpretations, which I will try to put in appropiate context. The keyword in ...

5

Some prehistory involving Aristotle, Tartaglia, Galileo and Torricelli can be found in The Impact of Ballistics on Mathematics by McMurran and Rickey. It was more speculative than experimental, and focused more on the trajectories and range of projectiles rather than speed. Euler wrote a short note Meditatio in experimenta explosione tormentorum nuper ...

5

We often forget that even the minute is not an SI unit, only the second and its decimal multiples and fractions are. It is a leftover of the sexagesimal system (base 60), whose use predates the decimals by many centuries, and goes back to the ancient Babylon. So are the angular degrees. Heinrich Hertz was born in 1857, and the International Electrotechnical ...

5

Wikipedia refers to the Julian Date system, which is used, primarily by astronomers, to this day. It is convenient due to irregularities in the standard calendar periods. The Julian days give a continuous count of days since the beginning of the Julian Period, introduced by Scaliger in 1583, i.e. since 1 January 4713 BC (Julian calendar), originally for the ...

4

Issues regarding ancient measure systems are not easy to manage... Galileo Galilei, in Discorsi, uses braccia; the "old" translation by Crew & Di Salvio uses: "cubits". A braccio in Florence was: 583 mm. In ancient Rome: according to Vitruvius, a cubit was equal to $1 \frac 1 2$ Roman feet or 6 palm widths, which is 443.8 mm (17.47 in). According ...

3

It's no more arbitrary than any other measurement unit, including the second. Nearly all modern values were chosed to try to avoid changing existing units' values while providing a source less subject to variation. The most well-known example is the kilogram. There's a standard cylinder platinum&iridium of which served as the original kilogram for ...

3

The unabridged Oxford English dictionary clarifies the "when" part of the question. Also consult the paper in Nature (1949) https://www.nature.com/articles/163427a0 for the historic discussion (paper is open access). However, the modern reference point is triple point of water, "The Celsius scale is defined using the T.Pt. = 0.01 °C with 1 °C made identical ...

3

The earliest extant description of Erathostenes' method is found in a book by Cleomedes written in the 1st century BC, and no wells are mentioned at all, if it's true that it's stated that whenever the Sun, 'being in Crab at the summer solstice, the pointers of the sundials in Syene throw no shadows...'

3

Quoth H. R. Jenemann, Die Geschichte der Dämpfung an der Laboratoriumswaage (1997, p. 240): In 1879, Georg Westphal filed a patent in Celle for a scale which was distinguished by various innovations and featured a similar brush lock19. With this special scale, the scale carrier had no connection to the beam of the scale; it could swing freely about its own ...

3

Fowler's Ratio in Early Greek Mathematics is a standard reference on the subject, see also his book Mathematics Of Plato's Academy (both are freely available). Book V, Definition 3 of Euclid's Elements reads: "A ratio (logos) is a sort of relation in respect of size between two magnitudes of the same kind". Thus, ratios of magnitudes were indeed non-...

3

There are much easier ways to measure a wavelength than by "tromboning" an interferometer. A simple two-slit grating, for example, will give you a pretty decent measurement. You don't need to measure a "meter's worth" of light, just run an experiment where the output data (such as a diffraction pattern) can be used to calculate the wavelength to high ...

3

The OED writes this: "Originally: the Roman unit of distance of 1000 paces (mīlle passus or passuum), reckoned to have been about 1618 yards (approx. 1479 metres). Hence: a unit of distance derived from this used in the British Isles and in other English-speaking countries, and now equal to 1760 yards (approx. 1609 metres). Frequently with a prefixed ...

3

Electricity has nothing to do with the question. Clocks which could count minutes and seconds were purely mechanical and precise mechanical clocks (which could count seconds reliably) were invented in 18th century. Until 1970s most wristwatches were mechanical. They are available nowadays as well but good ones are expensive. People did not count minutes and ...

2

There are (at least) three different English words written and pronounced “scale”. The “scale” of a fish or reptile is a borrowing from an Old French word adopted from a Germanic form cognate with the English word “shell”. A "scale" for weighing is originally a "bowl", borrowed from Old Norse. “Scale” in its various mathematical usages is borrowed from ...

2

It was actually done with a "tromboning" Michelson Interferometer (https://www.bipm.org/en/measurement-units/history-si/former-prototype-metre.html) In 1892 by Michelson. He measured a distance of 10cm to an accuracy of ± 0.00004 mm using a Cadmium lamp . The 1960 re-definition with Krypton used the same data - it was just a matter of measuring the ...

2

See : Bartel van Der Waerden, Science Awakening, Oxford UP (original ed, 1950), page 37 : The sexagesimal system was taken over by the Semitic Babylonians from their predecessors, the Sumerians. This remarkable cultural group, which had also invented the cuneiform script, dominated southern Mesopotamia during the third millenium B.C. Regarding $\pi$, ...

2

The above photo was reproduced in the biography: Lise Meitner, A life in Physics, by Ruth Lewin Sime; University Of California Press,1996, ISBN 0-520-20860-9. A brief description of the parts is given on page 371, bottom and 372 top. The attached photo, describing some of the components, is from those included with the text.

2

Not really. Using multiple liquids to register a single temperature probably would have been impractical, but crude thermometers appear already in antiquity. Philo of Byzantium c. 240 BC used a tube from a hollow sphere to a jug of water. When the sphere was in the sun bubbles were released as air expanded out of the sphere, when moved to the shade, the ...

1

The NIST museum confirms in an email that the Troughton scale is still in a case located to the right of the Standards Vault, although no longer in Washington, D.C. but rather on the NIST campus in Gaithersburg, MD. It is part of the Ferdinand Hassler exhibit. There is an archived photo of it here.

1

Perrin originally defined the Avogadro number as the number of atoms in one gram of hydrogen (later it was redefined as the number of atoms in 12 grams of carbon-12). As such, it was certainly discoverable from measurements. However, picking grams, or hydrogen was not "natural". Neither was picking circles and diameters in the definition of $\pi$. Once they ...

1

Once the definition in terms of the length of the meridian was accepted, the French sent several expeditions to measure the meridian. On the basis of these expeditions, the reference meter (a stick of a special alloy, which has very little thermal expansion) was made and kept under controlled conditions. Later, when more precise measurements of Earth were ...

1

People did not. They generated and stored static electricity, but measuring it, other than by how strong the electic shock felt, was not yet done. Coulomb was the one who invented a way to do it in 1785. For this he used a device called torsion balance. John Michell used it earlier to measure gravity, but Coulomb re-invented the idea, and made it famous. ...

1

First of all, the amplitude of the pendulum swing has a very small effect until you get to rather large swings. That's the beauty of the sine function. :-) . Next, it took rather a while for science to develop the concept of repeatability, let alone repeating this precise pendulum measurement in several locations -- and observing a repeatable difference. ...

1

You probably mean MSL, which is Mean Sea Level. In order to calculate the predicted height of a tide we work with amplitudes relative to a mean level as the tide approximates a sinusoidal behaviour. It was therefore necessary to measure the level of the sea surface relative to some arbitrary reference level, called Chart Datum (C.D.). As the tides vary in ...

1

How did people count seconds before clocks were invented? In general, they didn't, because there was no need to to so. The need for accuracy to the level of a second or less is a very recent need. Before the invention of trains and telegraphs, there was no need for even hour level accuracy, let alone minute or second level accuracy. Whether the roads were ...

1

Scale 3. a graduated range of values forming a standard system for measuring or grading something From Latin scala, ladder For example, in Chaucer, 1391: Next the forseide cercle of the A. b. c., vnder the cros-lyne, is Marked the skale, in Maner of 2 Squyres or elles in Manere of laddres.

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