By timing the eclipses of Jupiter's moon Io, Rømer estimated that light would take about 22 minutes to travel a distance equal to the diameter of Earth's orbit around the Sun.
Dengan mencatat waktu gerhana satelit Jupiter Io, Rømer memperkirakan bahwa cahaya memerlukan waktu sekitar 22 menit untuk bergerak dengan jarak diameter orbit Bumi mengelilingi Matahari.
However, it quickly gained support among other natural philosophers of the period such as Christiaan Huygens and Isaac Newton.
Namun, teorinya cepat mendapat dukungan di kalangan filsuf alam lainnya pada periode itu, seperti Christiaan Huygens dan Isaac Newton.
It was finally confirmed nearly two decades after Rømer's death, with the explanation in 1729 of stellar aberration by the English astronomer James Bradley.
Teori Rømer akhirnya dikonfirmasi hampir dua dasawarsa setelah meninggalnya Rømer, dengan penjelasan aberasi bintang pada tahun 1729 oleh astronom Inggris James Bradley.
The determination of east–west positioning (longitude) was a significant practical problem in cartography and navigation before the 1700s.
Penentuan posisi barat-timur (garis bujur) merupakan masalah praktis yang signifikan dalam kartografi dan navigasi sebelum 1700-an.
Galileo proposed a method of establishing the time of day, and thus longitude, based on the times of the eclipses of the moons of Jupiter, in essence using the Jovian system as a cosmic clock; this method was not significantly improved until accurate mechanical clocks were developed in the eighteenth century.
Galileo mengusulkan metode menentukan waktu dalam sehari, dan sebagai akibatnya garis bujur, berdasarkan waktu gerhana satelit Jupiter, pada dasarnya menggunakan sistem satelit Jupiter sebagai jam kosmis; metode ini tidak mendapat perbaikan signifikan hingga dikembangkannya jam mekanis pada abad ke-18.
He was invited to France by Louis XIV to set up the Royal Observatory, which opened in 1671 with Cassini as director, a post he would hold for the rest of his life.
Dia diundang ke Prancis oleh Louis XIV untuk mendirikan Observatorium Kerajaan, yang dibuka pada tahun 1671 dengan Cassini sebagai direkturnya, jabatan yang akan dia pegang selama sisa hidupnya.
Picard was to observe and time the eclipses of Jupiter's moons from Uraniborg while Cassini recorded the times they were seen in Paris.
Picard ditugaskan mengamati dan mencatat waktu gerhana satelit Jupiter dari Uraniborg sementara Cassini mencatat waktu diamatinya gerhana di Paris.
If Picard recorded the end of an eclipse at 9 hours 43 minutes 54 seconds after midday in Uraniborg, while Cassini recorded the end of the same eclipse at 9 hours 1 minute 44 seconds after midday in Paris – a difference of 42 minutes 10 seconds – the difference in longitude could be calculated to be 10° 32' 30".
Jika Picard mencatat akhir suatu gerhana terjadi 9 jam 43 menit 54 detik setelah tengah hari di Uraniborg, sementara Cassini mencatat akhir gerhana yang sama terjadi 9 jam 1 menit 44 detik setelah tengah hari di Paris – selisih 42 menit 10 detik – selisih antara garis bujurnya bisa dihitung bernilai 10° 32' 30".
Picard was helped in his observations by a young Dane who had recently completed his studies at the University of Copenhagen – Ole Rømer – and he must have been impressed by his assistant's skills, as he arranged for the young man to come to Paris to work at the Royal Observatory there.
Picard dibantu dalam pengamatannya oleh seorang orang Denmark muda yang baru menyelesaikan pendidikannya di Universitas Copenhagen, Ole Rømer, yang dia urus kedatangannya ke Paris untuk bekerja di Observatorium Kerajaan di sana.
Io is the innermost of the four moons of Jupiter discovered by Galileo in January 1610.
Io adalah satelit yang paling dalam di antara keempat satelit Jupiter yang ditemukan oleh Galileo pada Januari 1610.
Rømer and Cassini referred to it as the "first satellite of Jupiter".
Rømer dan Cassini menyebutnya "satelit pertama Jupiter".
It orbits Jupiter once every 42½ hours, and the plane of its orbit is very close to the plane of Jupiter's orbit around the sun.
Io mengorbit Jupiter sekali setiap 42½ jam, dan bidang orbitnya sangat dekat dengan bidang orbit Jupiter mengelilingi Matahari.
Io suddenly disappears, as it moves into the shadow of Jupiter.
Io tiba-tiba menghilang, ketika Io bergerak ke dalam bayangan Jupiter.
Io suddenly reappears, as it moves out of the shadow of Jupiter.
Io tiba-tiba menghilang, ketika Io bergerak ke dalam bayangan Jupiter.
At the point of opposition (point H in the diagram below), both the immersion and the emergence would be hidden by Jupiter.
Di titik oposisi (titik H di diagram di bawah), terbenam dan terbit keduanya akan disembunyikan oleh Jupiter.
For about four months before the opposition (from F to G), immersions of Io into Jupiter's shadow can be observed, and about four months after the opposition of Jupiter (from L to K in the diagram below), emergences of Io from its eclipses can be observed.
Selama sekitar empat bulan setelah oposisi Jupiter (dari L ke K di diagram di bawah), terbitnya Io dari gerhananya bisa dilihat, sedangkan selama sekitar empat bulan sebelum oposisi (dari F ke G), tenggelamnya Io ke banyangan Jupiter bisa dilihat.
Even during the periods before and after opposition, many eclipses of Io cannot be observed from a given location on the Earth's surface: some will occur during the daytime and some will occur while Jupiter is below the horizon (hidden by the Earth itself).
Bahkan dalam periode sebelum dan setelah oposisi pun, tidak semua gerhana Io bisa diamati dari suatu lokasi tertentu di permukaan Bumi: beberapa gerhana terjadi pada siang hari di lokasi tertentu, sedangkan gerhana lainnya akan terjadi ketika Jupiter berada di bawah cakrawala (disembunyikan oleh Bumi).
Most of Rømer's papers were destroyed in the Copenhagen Fire of 1728, but one manuscript that survived contains a listing of about sixty observations of eclipses of Io from 1668 to 1678.
Kebanyakan karangan Rømer hancur pada Kebakaran Copenhagen 1728, tetapi satu manuskrip yang selamat berisi sebuah daftar enam puluh pengamatan gerhana Io dari 1668 hingga 1678.
In particular, it details two series of observations on either side of the oppositions of 2 March 1672 and 2 April 1673.
Khususnya, manuskrip tersebut memberikan rincian mengenai dua rangkaian pengamatan di kedua sisi oposisi pada 2 Maret 1672 dan 2 April 1673.
Rømer comments in a letter to Christiaan Huygens dated 30 September 1677 that these observations from 1671 to 1673 form the basis for his calculations.
Rømer berkomentar dalam sebuah surat bertanggal 30 September 1677 kepada Christiaan Huygens bahwa pengamatan-pengamatannya dari 1671–73 dijadikan dasar perhitungannya.
The surviving manuscript was written some time after January 1678, the date of the last recorded astronomical observation (an emergence of Io on 6 January), and so was later than Rømer's letter to Huygens.
Manuskrip yang selamat ditulis setelah Januari 1678, tanggal pengamatan astronomi terakhir yang dicatat (terbitnya Io pada 6 Januari), setelah surat Rømer kepada Huygens.
The document also records the observations around the opposition of 8 July 1676 that formed the basis for the announcement of Rømer's results.
Dokumen tersebut juga mencatat pengamatan yang dilakukan pada oposisi 8 Juli 1676 yang menjadi dasar pengumuman hasil Rømer.
He may also have stated the reason: This second inequality appears to be due to light taking some time to reach us from the satellite; light seems to take about ten to eleven minutes [to cross] a distance equal to the half-diameter of the terrestrial orbit.
Ketaksamaan yang kedua ini tampaknya disebabkan cahaya memerlukan waktu untuk mencapai kita dari satelit; cahaya kelihatannya memerlukan sekitar sepuluh sampai sebelas menit
Most importantly, Rømer announced the prediction that the emergence of Io on 16 November 1676 would be observed about ten minutes later than would have been calculated by the previous method.
Yang paling penting, Rømer mengumumkan prediksi bahwa terbitnya Io pada 16 November 1676 akan diamati sekitar sepuluh menit setelah waktu yang diperhitungkan menggunakan metode yang sebelumnya.
With this experimental evidence in hand, Rømer explained his new method of calculation to the Royal Academy of Sciences on 21 November.
Dengan bukti percobaan ini, Rømer menjelaskan metode perhitungan barunya kepada Akademi Sains Kerajaan pada 22 November.
The original record of the meeting of the Royal Academy of Sciences has been lost, but Rømer's presentation was recorded as a news report in the Journal des sçavans on 7 December.
Catatan asli dari pertemuan Akademi Sains Kerajaan telah hilang, tetapi presentasi Rømer dicatat sebagai laporan berita di Journal des sçavans pada 7 Desember.
This anonymous report was translated into English and published in Philosophical Transactions of the Royal Society in London on 25 July 1677.
Laporan anonim ini diterjemahkan ke bahasa Inggris dan diterbitkan di Philosophical Transactions of the Royal Society di London pada 25 Juli 1677.
However Cassini, Rømer's superior at the Royal Observatory, was an early and tenacious opponent of Rømer's ideas, and it seems that Picard, Rømer's mentor, shared many of Cassini's doubts.
Tetapi Cassini, atasan Rømer di Observatorium Kerajaan, merupakan penentang keras ide Rømer, dan kelihatannya Picard, mentor Rømer, memiliki keraguan yang sama dengan Cassini.
Cassini's practical objections stimulated much debate at the Royal Academy of Sciences (with Huygens participating by letter from London).
Bantahan praktis Cassini menyebabkan banyak perdebatan di Akademi Sains Kerajaan (dengan Huygens ikut serta melalui surat dari London).
Rømer replied that it was much more difficult to accurately observe the eclipses of the other moons, and that the unexplained effects were much smaller (for Io) than the effect of the speed of light: however, he admitted to Huygens that the unexplained "irregularities" in the other satellites were larger than the effect of the speed of light.
Rømer membalas dengan mengatakan bahwa lebih sulit untuk mengamati gerhana satelit yang lain secara akurat, dan efek-efek yang tidak dijelaskan pengaruhnya lebih kecil (untuk Io) daripada pengaruh efek laju cahaya: tetapi, dia mengakui kepada Huygens bahwa "penyimpangan" yang tidak bisa dijelaskan di satelit lain lebih besar daripada pengaruh laju cahaya.
The dispute had something of a philosophical note: Rømer claimed that he had discovered a simple solution to an important practical problem, while Cassini rejected the theory as flawed as it could not explain all the observations.
Rømer mengklaim bahwa dia telah menemukan solusi sederhana untuk masalah praktis yang penting, sedangkan Cassini menolak teori yang dia anggap punya kelemahan karena tidak bisa menjelaskan semua pengamatan.
Cassini was forced to include "empirical corrections" in his 1693 tables of eclipses, but never accepted the theoretical basis: indeed, he chose different correction values for the different moons of Jupiter, in direct contradiction with Rømer's theory.
Cassini terpaksa memasukkan "perbaikan empiris" ke dalam tabel gerhana 1693-nya, tetapi tidak pernah menerima dasar teoretisnya: dia memilih nilai koreksi yang berbeda untuk satelit-satelit Jupiter yang berbeda, secara langsung menyangkal teori Rømer.
Although Robert Hooke (1635–1703) dismissed the supposed speed of light as so large as to be virtually instantaneous, the Astronomer Royal John Flamsteed (1646–1719) accepted Rømer's hypothesis in his ephemerides of eclipses of Io.
Meskipun Robert Hooke (1635–1703) menganggap laju cahaya terlalu besar sehingga tidak ada bedanya dengan bergerak seketika, Astronomer Royal John Flamsteed (1646–1719) menerima hipotesis Rømer dalam efemeris gerhana Io-nya.
Edmond Halley (1656–1742), a future Astronomer Royal, was an early and enthusiastic supporter.
Edmond Halley (1656–1742), yang di masa mendatang menjadi Astronomer Royal, juga merupakan pendukung awal yang antusias.
Isaac Newton (1643–1727) accepted Rømer's idea, giving a value of "seven or eight minutes" in his 1704 book Opticks for light to travel from the Sun to Earth, closer to the true value (8 minutes 19 seconds) than Rømer's initial estimate of 11 minutes.
Isaac Newton (1643–1727) juga menerima gagasan Rømer; dalam buku 1704-nya Opticks ia memberikan nilai "tujuh atau delapan menit" untuk waktu yang cahaya perlukan untuk bergerak dari Matahari ke Bumi, lebih dekat ke nilai yang sebenarnya (8 menit 19 detik) daripada perkiraan awal Rømer 11 menit.
While it was difficult for people such as Hooke to conceive of the enormous speed of light, acceptance of Rømer's idea suffered a second handicap in that it was based on Kepler's model of the planets orbiting the Sun in elliptical orbits.
Selain sulit bagi banyak orang (seperti Hooke) untuk membayangkan laju cahaya yang sangat besar, diterimanya gagasan Rømer menghadapi hambatan lainnya yaitu gagasan Rømer didasarkan pada model Kepler di mana planet mengelilingi Matahari dalam orbit yang berbentuk elips.
Rømer's view that the velocity of light was finite was not fully accepted until measurements of stellar aberration were made in 1727 by James Bradley (1693–1762).
Pandangan Rømer bahwa kecepatan cahaya bersifat terbatas tidak sepenuhnya diterima hingga pengukuran aberasi bintang dilakukan pada tahun 1727 oleh
Bradley, who succeeded Halley as Astronomer Royal, calculated a value of 8 minutes 13 seconds for light to travel from the Sun to Earth.
Bradley, yang kemudian menjadi penerus Halley sebagai Astronomer Royal, menghitung nilai 8 menit 13 detik bagi cahaya untuk bergerak dari Matahari ke Bumih.
Ironically, stellar aberration had first been observed by Cassini and (independently) by Picard in 1671, but neither astronomer was able to give an explanation for the phenomenon.
Ironisnya, aberasi cahaya pertama kali diamati oleh Cassini dan (secara terpisah) oleh Picard pada tahun 1671, tetapi keduanya tidak mampu memberikan penjelasan bagi fenomena ini.
Swedish astronomer Pehr Wilhelm Wargentin (1717–83) used Rømer's method in the preparation of his ephemerides of Jupiter's moons (1746), as did Giovanni Domenico Maraldi working in Paris.
Astronom Swedia Pehr Wilhelm Wargentin (1717–83) menggunakan metode Rømer dalam persiapan efemeris satelit Jupiternya (1746), dan begitu pula Giovanni Domenico Maraldi ketika bekerja di Paris.
The remaining irregularities in the orbits of the Galilean moons would not be satisfactorily explained until the work of Joseph Louis Lagrange (1736–1813) and Pierre-Simon Laplace (1749–1827) on orbital resonance.
Penyimpangan lainnya dalam orbit satelit Galileo tidak dijelaskan secara memuaskan hingga penelitian Joseph Louis Lagrange (1736–1813) dan Pierre-Simon Laplace (1749–1827) mengenai resonansi orbit.
In 1809, again making use of observations of Io, but this time with the benefit of more than a century of increasingly precise observations, the astronomer Jean Baptiste Joseph Delambre (1749–1822) reported the time for light to travel from the Sun to the Earth as 8 minutes 12 seconds.
Pada tahun 1809, dengan menggunakan pengamatan Io lagi, tetapi kali ini dengan keuntungan seabad pengamatan yang semakin tepat, astronom Jean Baptiste Joseph Delambre (1749–1822) melaporkan waktu yang diperlukan cahaya untuk bergerak dari Matahari ke Bumi adalah 8 menit 12 detik.
Depending on the value assumed for the astronomical unit, this yields the speed of light as just a little more than 300,000 kilometres per second.
Bergantung pada nilai yang diasumsikan untuk satuan astronomi, ini menghasilkan nilai laju cahaya yang hanya sedikit lebih kecil dari 300.000 kilometer per detik.
The first measurements of the speed of light using completely terrestrial apparatus were published in 1849 by Hippolyte Fizeau (1819–96).
Pengukuran laju cahaya pertama yang hanya menggunakan peralatan terestrial diterbitkan pada tahun 1849 oleh Hippolyte Fizeau (1819–96).
Compared to values accepted today, Fizeau's result (about 313,000 kilometres per second) was too high, and less accurate than those obtained by Rømer's method.
Bila dibandingkan dengan nilai yang diterima sekarang, hasil pengukuran Fizeau (sekitar 313.000 kilometer per detik) terlalu tinggi, dan tidak seakurat hasil yang diperoleh menggunakan metode Rømer.
It would be another thirty years before A. A. Michelson in the United States published his more precise results (299,910±50 km/s) and Simon Newcomb confirmed the agreement with astronomical measurements, almost exactly two centuries after Rømer's announcement.
Baru tiga puluh tahun kemudian A. A. Michelson di Amerika Serikat menerbitkan hasil yang lebih tepat (299.910±50 km/s) dan Simon Newcomb mengonfirmasi bahwa nilai tersebut sesuai dengan pengukuran astronomis.
Several discussions have suggested that Rømer should not be credited with the measurement of the speed of light, as he never gave a value in Earth-based units.
Beberapa diskusi mengusulkan bahwa pengukuran laju cahaya sebaiknya tidak diatribusikan kepada Rømer, karena dia tidak pernah memberikan nilai dalam satuan yang berdasrkan Bumi.
These authors credit Huygens with the first calculation of the speed of light.
Orang-orang yang mengemukakan usulan tersebut mengatribusikan perhitungan laju cahaya yang pertama kepada Huygens.
Huygens's estimate was a value of 110,000,000 toises per second: as the toise was later determined to be just under two metres, this gives the value in SI units.
Perkiraan Huygens adalah 110.000.000 toise per detik: karena toise kemudian ditentukan bernilai sedikit di bawah dua meter, ini memberikan nilainya dalam satuan SI.
However, Huygens's estimate was not a precise calculation but rather an illustration at an order of magnitude level.
Namun, perkiraan Huygens bukanlah perhitungan yang mementingkan presisi melainkan merupakan suatu ilustrasi tingkat besaran.
For, supposing that KL is no more than 22 thousand of these diameters, it appears that being traversed in 22 minutes this makes the speed a thousand diameters in one minute, that is 16-2/3 diameters in one second or in one beat of the pulse, which makes more than 11 hundred times a hundred thousand toises; Huygens was obviously not concerned about the 9% difference between his preferred value for the distance from the Sun to Earth and the one he uses in his calculation.
For, supposing that KL is no more than 22 thousand of these diameters, it appears that being traversed in 22 minutes this makes the speed a thousand diameters in one minute, that is 16-2/3 diameters in one second or in one beat of the pulse, which makes more than 11 hundred times a hundred thousand toises; Huygens tidak terlalu memikirkan selisih 9% antara nilai jarak Matahari ke Bumi yang dia sukai dengan nilai yang dia gunakan dalam perhitungannya.
Nor was there any doubt in Huygens's mind as to Rømer's achievement, as he wrote to Colbert: I have seen recently, with much pleasure, the beautiful discovery of Mr. Romer, to demonstrate that light takes time in propagating, and even to measure this time; Neither Newton nor Bradley bothered to calculate the speed of light in Earth-based units.
Tidak ada keraguan dalam pikiran Huygens terhadap pencapaian Rømer, sebagaimana yang dia kirimkan kepada Colbert (tekanan ditambahkan): I have seen recently, with much pleasure, the beautiful discovery of Mr. Romer, to demonstrate that light takes time in propagating, and even to measure this time; Newton dan Bradley tidak mencoba menghitung laju cahaya dalam satuan berbasis Bumi.
The next recorded calculation was probably made by Fontenelle: claiming to work from Rømer's results, the historical account of Rømer's work written some time after 1707 gives a value of 48203 leagues per second.
Perhitungan tercatat berikutnya kemungkinan dilakukan oleh Fontenelle: mengaku bekerja menggunakan hasil pengamatan Rømer, dalam catatan sejarah mengenai karya Rømer yang ditulis setelah tahun 1707, memberikan nilai 48203 league per detik.