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The Sand Reckoner

November 23, 2023

"Psammites" redirects here. For other uses, see Psammite.

The Sand Reckoner (Greek: Ψαμμίτης, Psammites) is a work by Archimedes, an Ancient Greek mathematician of the 3rd century BC, in which he set out to determine an upper bound for the number of grains of sand that fit into the universe. In order to do this, Archimedes had to estimate the size of the universe according to the contemporary model, and invent a way to talk about extremely large numbers.

The Sand Reckoner (Arenarius)
AuthorArchimedes
LanguageLatin
GenreGoogology, Astronomy

The work, also known in Latin as Arenarius, is about eight pages long in translation and is addressed to the Syracusan king Gelo II (son of Hiero II). It is considered the most accessible work of Archimedes.[1]

Naming large numbers edit

See also: Exponentiation § History of the notation

First, Archimedes had to invent a system of naming large numbers. The number system in use at that time could express numbers up to a myriad (μυριάς — 10,000), and by utilizing the word myriad itself, one can immediately extend this to naming all numbers up to a myriad myriads (108).[3] Archimedes called the numbers up to 108 "first order" and called 108 itself the "unit of the second order". Multiples of this unit then became the second order, up to this unit taken a myriad-myriad times, 108·108=1016. This became the "unit of the third order", whose multiples were the third order, and so on. Archimedes continued naming numbers in this way up to a myriad-myriad times the unit of the 108-th order, i.e., (108)^(108)

After having done this, Archimedes called the orders he had defined the "orders of the first period", and called the last one,  , the "unit of the second period". He then constructed the orders of the second period by taking multiples of this unit in a way analogous to the way in which the orders of the first period were constructed. Continuing in this manner, he eventually arrived at the orders of the myriad-myriadth period. The largest number named by Archimedes was the last number in this period, which is

 

Another way of describing this number is a one followed by (short scale) eighty quadrillion (80·1015) zeroes.

Archimedes' system is reminiscent of a positional numeral system with base 108, which is remarkable because the ancient Greeks used a very simple system for writing numbers, which employs 27 different letters of the alphabet for the units 1 through 9, the tens 10 through 90 and the hundreds 100 through 900.

Law of exponents edit

Archimedes also discovered and proved the law of exponents,  , necessary to manipulate powers of 10.

Estimation of the size of the universe edit

Archimedes then estimated an upper bound for the number of grains of sand required to fill the Universe. To do this, he used the heliocentric model of Aristarchus of Samos. The original work by Aristarchus has been lost. This work by Archimedes however is one of the few surviving references to his theory,[4] whereby the Sun remains unmoved while the Earth orbits the Sun. In Archimedes's own words:

His [Aristarchus'] hypotheses are that the fixed stars and the Sun remain unmoved, that the Earth revolves about the Sun on the circumference of a circle, the Sun lying in the middle of the orbit, and that the sphere of fixed stars, situated about the same center as the Sun, is so great that the circle in which he supposes the Earth to revolve bears such a proportion to the distance of the fixed stars as the center of the sphere bears to its surface.[5]

The reason for the large size of this model is that the Greeks were unable to observe stellar parallax with available techniques, which implies that any parallax is extremely small and so the stars must be placed at great distances from the Earth (assuming heliocentrism to be true).

According to Archimedes, Aristarchus did not state how far the stars were from the Earth. Archimedes therefore had to make the following assumptions:

  • The Universe was spherical
  • The ratio of the diameter of the Universe to the diameter of the orbit of the Earth around the Sun equalled the ratio of the diameter of the orbit of the Earth around the Sun to the diameter of the Earth.

This assumption can also be expressed by saying that the stellar parallax caused by the motion of the Earth around its orbit equals the solar parallax caused by motion around the Earth. Put in a ratio:

 

In order to obtain an upper bound, Archimedes made the following assumptions of their dimensions:

  • that the perimeter of the Earth was no bigger than 300 myriad stadia (5.55·105 km).
  • that the Moon was no larger than the Earth, and that the Sun was no more than thirty times larger than the Moon.
  • that the angular diameter of the Sun, as seen from the Earth, was greater than 1/200 of a right angle (π/400 radians = 0.45° degrees).

Archimedes then concluded that the diameter of the Universe was no more than 1014 stadia (in modern units, about 2 light years), and that it would require no more than 1063 grains of sand to fill it. With these measurements, each grain of sand in Archimedes's thought-experiment would have been approximately 19 μm (0.019 mm) in diameter.

Calculation of the number of grains of sand in the Aristarchian Universe edit

Archimedes claims that forty poppy-seeds laid side by side would equal one Greek dactyl (finger-width) which was approximately 19 mm (3/4 inch) in length. Since volume proceeds as the cube of a linear dimension ("For it has been proved that spheres have the triplicate ratio to one another of their diameters") then a sphere one dactyl in diameter would contain (using our current number system) 403, or 64,000 poppy seeds.

He then claimed (without evidence) that each poppy seed could contain a myriad (10,000) grains of sand. Multiplying the two figures together he proposed 640,000,000 as the number of hypothetical grains of sand in a sphere one dactyl in diameter.

To make further calculations easier, he rounded up 640 million to one billion, noting only that the first number is smaller than the second, and that therefore the number of grains of sand calculated subsequently will exceed the actual number of grains. Recall that Archimedes's meta-goal with this essay was to show how to calculate with what were previously considered impossibly large numbers, not simply to accurately calculate the number of grains of sand in the universe.

A Greek stadium had a length of 600 Greek feet, and each foot was 16 dactyls long, so there were 9,600 dactyls in a stadium. Archimedes rounded this number up to 10,000 (a myriad) to make calculations easier, again, noting that the resulting number will exceed the actual number of grains of sand.

The cube of 10,000 is a trillion (1012); and multiplying a billion (the number of grains of sand in a dactyl-sphere) by a trillion (number of dactyl-spheres in a stadium-sphere) yields 1021, the number of grains of sand in a stadium-sphere.

Archimedes had estimated that the Aristarchian Universe was 1014 stadia in diameter, so there would accordingly be (1014)3 stadium-spheres in the universe, or 1042. Multiplying 1021 by 1042 yields 1063, the number of grains of sand in the Aristarchian Universe.[6]

Following Archimedes's estimate of a myriad (10,000) grains of sand in a poppy seed; 64,000 poppy seeds in a dactyl-sphere; the length of a stadium as 10,000 dactyls; and accepting 19mm as the width of a dactyl, the diameter of Archimedes's typical sand grain would be 18.3 μm, which today we would call a grain of silt. Currently, the smallest grain of sand would be defined as 50 μm in diameter.

Additional calculations edit

Archimedes made some interesting experiments and computations along the way. One experiment was to estimate the angular size of the Sun, as seen from the Earth. Archimedes's method is especially interesting as it takes into account the finite size of the eye's pupil,[7] and therefore may be the first known example of experimentation in psychophysics, the branch of psychology dealing with the mechanics of human perception, whose development is generally attributed to Hermann von Helmholtz. Another interesting computation accounts for solar parallax and the different distances between the viewer and the Sun, whether viewed from the center of the Earth or from the surface of the Earth at sunrise. This may be the first known computation dealing with solar parallax.[1]

Quote edit

There are some, king Gelon, who think that the number of the sand is infinite in multitude; and I mean by the sand not only that which exists about Syracuse and the rest of Sicily but also that which is found in every region whether inhabited or uninhabited. Again there are some who, without regarding it as infinite, yet think that no number has been named which is great enough to exceed its magnitude. And it is clear that they who hold this view, if they imagined a mass made up of sand in other respects as large as the mass of the Earth, including in it all the seas and the hollows of the Earth filled up to a height equal to that of the highest of the mountains, would be many times further still from recognizing that any number could be expressed which exceeded the multitude of the sand so taken.

But I will try to show you by means of geometrical proofs, which you will be able to follow, that, of the numbers named by me and given in the work which I sent to Zeuxippus, some exceed not only the number of the mass of sand equal in magnitude to the Earth filled up in the way described, but also that of the mass equal in magnitude to the universe.[8]

— Archimedis Syracusani Arenarius & Dimensio Circuli

References edit

  1. ^ a b Archimedes, The Sand Reckoner 511 R U, by Ilan Vardi, accessed 28-II-2007.
  2. ^ Alan Hirshfeld (8 September 2009). Eureka Man: The Life and Legacy of Archimedes. ISBN 9780802719799. Retrieved 17 February 2016.
  3. ^ A history of analysis. H. N. Jahnke. Providence, RI: American Mathematical Society. 2003. p. 22. ISBN 0-8218-2623-9. OCLC 51607350.{{cite book}}: CS1 maint: others (link)
  4. ^ Aristarchus biography at MacTutor, accessed 26-II-2007.
  5. ^ Arenarius, I., 4–7
  6. ^ Annotated translation of The Sand Reckoner Cal State University, Los Angeles
  7. ^ Smith, William — A Dictionary of Greek and Roman Biography and Mythology (1880), p. 272
  8. ^ Newman, James R. — The World of Mathematics (2000), p. 420

Further reading edit

External links edit

  • Original Greek text
  • The Sand Reckoner (Arenario) Italian annotated translation, with notes about Archimedes and Greek mathematical notation and unit of measure. Source file of the Arenarius Greek text (for LaTeX).
  • Archimedes, The Sand Reckoner, by Ilan Vardi; includes a literal English version of the original Greek text

November 23, 2023
sand, reckoner, psammites, redirects, here, other, uses, psammite, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, n. Psammites redirects here For other uses see Psammite This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources The Sand Reckoner news newspapers books scholar JSTOR August 2021 template removal help The Sand Reckoner Greek PSammiths Psammites is a work by Archimedes an Ancient Greek mathematician of the 3rd century BC in which he set out to determine an upper bound for the number of grains of sand that fit into the universe In order to do this Archimedes had to estimate the size of the universe according to the contemporary model and invent a way to talk about extremely large numbers The Sand Reckoner Arenarius AuthorArchimedesLanguageLatinGenreGoogology AstronomyThe work also known in Latin as Arenarius is about eight pages long in translation and is addressed to the Syracusan king Gelo II son of Hiero II It is considered the most accessible work of Archimedes 1 Contents 1 Naming large numbers 1 1 Law of exponents 2 Estimation of the size of the universe 2 1 Calculation of the number of grains of sand in the Aristarchian Universe 2 2 Additional calculations 3 Quote 4 References 5 Further reading 6 External linksNaming large numbers editSee also Exponentiation History of the notation Periods and orders with their intervals in modern notation 2 Period Order Interval log10 of interval1 1 1 Ơ where theunit of the second order Ơ 108 0 8 2 Ơ Ơ2 8 16 k Ơk 1 Ơk 8k 8 8k Ơ ƠƠ 1 Ƥ where theunit of the second period Ƥ ƠƠ 108 108 8 108 8 8 108 799 999 992 800 000 000 2 1 Ƥ ƤƠ 8 108 8 108 1 800 000 000 800 000 008 2 ƤƠ ƤƠ2 8 108 1 8 108 2 k ƤƠk 1 ƤƠk 8 108 k 1 8 108 k Ơ ƤƠƠ 1 ƤƠƠ Ƥ2Ơ 1 Ƥ2 8 2 108 1 8 2 108 1 6 109 8 1 6 109 1 599 999 992 1 600 000 000 Ơ 1 ƤƠ 1 ƤƠ 1Ơ 8 108 108 1 8 108 108 1 1 79 999 999 200 000 000 79 999 999 200 000 008 2 ƤƠ 1Ơ ƤƠ 1Ơ2 8 108 108 1 1 8 108 108 1 2 k ƤƠ 1Ơk 1 ƤƠ 1Ơk 8 108 108 1 k 1 8 108 108 1 k Ơ ƤƠ 1ƠƠ 1 ƤƠ 1ƠƠ ƤƠƠ 1 ƤƠ 8 2 108 1 8 2 108 8 1016 8 8 1016 79 999 999 999 999 992 80 000 000 000 000 000 First Archimedes had to invent a system of naming large numbers The number system in use at that time could express numbers up to a myriad myrias 10 000 and by utilizing the word myriad itself one can immediately extend this to naming all numbers up to a myriad myriads 108 3 Archimedes called the numbers up to 108 first order and called 108 itself the unit of the second order Multiples of this unit then became the second order up to this unit taken a myriad myriad times 108 108 1016 This became the unit of the third order whose multiples were the third order and so on Archimedes continued naming numbers in this way up to a myriad myriad times the unit of the 108 th order i e 108 108 After having done this Archimedes called the orders he had defined the orders of the first period and called the last one 10 8 10 8 displaystyle 10 8 10 8 nbsp the unit of the second period He then constructed the orders of the second period by taking multiples of this unit in a way analogous to the way in which the orders of the first period were constructed Continuing in this manner he eventually arrived at the orders of the myriad myriadth period The largest number named by Archimedes was the last number in this period which is 10 8 10 8 10 8 10 8 10 16 displaystyle left left 10 8 right 10 8 right 10 8 10 8 cdot 10 16 nbsp dd Another way of describing this number is a one followed by short scale eighty quadrillion 80 1015 zeroes Archimedes system is reminiscent of a positional numeral system with base 108 which is remarkable because the ancient Greeks used a very simple system for writing numbers which employs 27 different letters of the alphabet for the units 1 through 9 the tens 10 through 90 and the hundreds 100 through 900 Law of exponents edit Archimedes also discovered and proved the law of exponents 10 a 10 b 10 a b displaystyle 10 a 10 b 10 a b nbsp necessary to manipulate powers of 10 Estimation of the size of the universe editArchimedes then estimated an upper bound for the number of grains of sand required to fill the Universe To do this he used the heliocentric model of Aristarchus of Samos The original work by Aristarchus has been lost This work by Archimedes however is one of the few surviving references to his theory 4 whereby the Sun remains unmoved while the Earth orbits the Sun In Archimedes s own words His Aristarchus hypotheses are that the fixed stars and the Sun remain unmoved that the Earth revolves about the Sun on the circumference of a circle the Sun lying in the middle of the orbit and that the sphere of fixed stars situated about the same center as the Sun is so great that the circle in which he supposes the Earth to revolve bears such a proportion to the distance of the fixed stars as the center of the sphere bears to its surface 5 The reason for the large size of this model is that the Greeks were unable to observe stellar parallax with available techniques which implies that any parallax is extremely small and so the stars must be placed at great distances from the Earth assuming heliocentrism to be true According to Archimedes Aristarchus did not state how far the stars were from the Earth Archimedes therefore had to make the following assumptions The Universe was spherical The ratio of the diameter of the Universe to the diameter of the orbit of the Earth around the Sun equalled the ratio of the diameter of the orbit of the Earth around the Sun to the diameter of the Earth This assumption can also be expressed by saying that the stellar parallax caused by the motion of the Earth around its orbit equals the solar parallax caused by motion around the Earth Put in a ratio Diameter of Universe Diameter of Earth orbit around the Sun Diameter of Earth orbit around the Sun Diameter of Earth displaystyle frac text Diameter of Universe text Diameter of Earth orbit around the Sun frac text Diameter of Earth orbit around the Sun text Diameter of Earth nbsp In order to obtain an upper bound Archimedes made the following assumptions of their dimensions that the perimeter of the Earth was no bigger than 300 myriad stadia 5 55 105 km that the Moon was no larger than the Earth and that the Sun was no more than thirty times larger than the Moon that the angular diameter of the Sun as seen from the Earth was greater than 1 200 of a right angle p 400 radians 0 45 degrees Archimedes then concluded that the diameter of the Universe was no more than 1014 stadia in modern units about 2 light years and that it would require no more than 1063 grains of sand to fill it With these measurements each grain of sand in Archimedes s thought experiment would have been approximately 19 mm 0 019 mm in diameter Calculation of the number of grains of sand in the Aristarchian Universe edit Archimedes claims that forty poppy seeds laid side by side would equal one Greek dactyl finger width which was approximately 19 mm 3 4 inch in length Since volume proceeds as the cube of a linear dimension For it has been proved that spheres have the triplicate ratio to one another of their diameters then a sphere one dactyl in diameter would contain using our current number system 403 or 64 000 poppy seeds He then claimed without evidence that each poppy seed could contain a myriad 10 000 grains of sand Multiplying the two figures together he proposed 640 000 000 as the number of hypothetical grains of sand in a sphere one dactyl in diameter To make further calculations easier he rounded up 640 million to one billion noting only that the first number is smaller than the second and that therefore the number of grains of sand calculated subsequently will exceed the actual number of grains Recall that Archimedes s meta goal with this essay was to show how to calculate with what were previously considered impossibly large numbers not simply to accurately calculate the number of grains of sand in the universe A Greek stadium had a length of 600 Greek feet and each foot was 16 dactyls long so there were 9 600 dactyls in a stadium Archimedes rounded this number up to 10 000 a myriad to make calculations easier again noting that the resulting number will exceed the actual number of grains of sand The cube of 10 000 is a trillion 1012 and multiplying a billion the number of grains of sand in a dactyl sphere by a trillion number of dactyl spheres in a stadium sphere yields 1021 the number of grains of sand in a stadium sphere Archimedes had estimated that the Aristarchian Universe was 1014 stadia in diameter so there would accordingly be 1014 3 stadium spheres in the universe or 1042 Multiplying 1021 by 1042 yields 1063 the number of grains of sand in the Aristarchian Universe 6 Following Archimedes s estimate of a myriad 10 000 grains of sand in a poppy seed 64 000 poppy seeds in a dactyl sphere the length of a stadium as 10 000 dactyls and accepting 19mm as the width of a dactyl the diameter of Archimedes s typical sand grain would be 18 3 mm which today we would call a grain of silt Currently the smallest grain of sand would be defined as 50 mm in diameter Additional calculations edit Archimedes made some interesting experiments and computations along the way One experiment was to estimate the angular size of the Sun as seen from the Earth Archimedes s method is especially interesting as it takes into account the finite size of the eye s pupil 7 and therefore may be the first known example of experimentation in psychophysics the branch of psychology dealing with the mechanics of human perception whose development is generally attributed to Hermann von Helmholtz Another interesting computation accounts for solar parallax and the different distances between the viewer and the Sun whether viewed from the center of the Earth or from the surface of the Earth at sunrise This may be the first known computation dealing with solar parallax 1 Quote editThere are some king Gelon who think that the number of the sand is infinite in multitude and I mean by the sand not only that which exists about Syracuse and the rest of Sicily but also that which is found in every region whether inhabited or uninhabited Again there are some who without regarding it as infinite yet think that no number has been named which is great enough to exceed its magnitude And it is clear that they who hold this view if they imagined a mass made up of sand in other respects as large as the mass of the Earth including in it all the seas and the hollows of the Earth filled up to a height equal to that of the highest of the mountains would be many times further still from recognizing that any number could be expressed which exceeded the multitude of the sand so taken But I will try to show you by means of geometrical proofs which you will be able to follow that of the numbers named by me and given in the work which I sent to Zeuxippus some exceed not only the number of the mass of sand equal in magnitude to the Earth filled up in the way described but also that of the mass equal in magnitude to the universe 8 Archimedis Syracusani Arenarius amp Dimensio CirculiReferences edit a b Archimedes The Sand Reckoner 511 R U by Ilan Vardi accessed 28 II 2007 Alan Hirshfeld 8 September 2009 Eureka Man The Life and Legacy of Archimedes ISBN 9780802719799 Retrieved 17 February 2016 A history of analysis H N Jahnke Providence RI American Mathematical Society 2003 p 22 ISBN 0 8218 2623 9 OCLC 51607350 a href Template Cite book html title Template Cite book cite book a CS1 maint others link Aristarchus biography at MacTutor accessed 26 II 2007 Arenarius I 4 7 Annotated translation of The Sand Reckoner 1 Cal State University Los Angeles Smith William A Dictionary of Greek and Roman Biography and Mythology 1880 p 272 Newman James R The World of Mathematics 2000 p 420Further reading editThe Sand Reckoner by Gillian Bradshaw Forge 2000 348pp ISBN 0 312 87581 9 This is a historical novel about the life and work of Archimedes External links editOriginal Greek text The Sand Reckoner annotated The Sand Reckoner Arenario Italian annotated translation with notes about Archimedes and Greek mathematical notation and unit of measure Source file of the Arenarius Greek text for LaTeX Archimedes The Sand Reckoner by Ilan Vardi includes a literal English version of the original Greek text Retrieved from https en wikipedia org w index php title The Sand Reckoner amp oldid 1168182963, wikipedia, wiki, book, books, library,

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