Sumbangan Eratosthenes dalam Geografi, Ini Penjelasannya (2024)

Kompas.com - 27/08/2021, 11:29 WIB

Nadia Faradiba

Penulis

Sumbangan Eratosthenes dalam Geografi, Ini Penjelasannya (1)

Lihat Foto

Bumi(pixabay)

KOMPAS.com -Erasthothenes adalah seorang ilmuwan asal Yunani. Dia hidup sekitar 250 tahun sebelum Masehi.

Erasthothenes memiliki semangat yang luar biasa untuk belajar. Bahkan, di masa mudanya, ia pergi hingga ke Athena untuk belajar.

Dia memiliki banyak talenta. Dia terkenal sebagai pustakawan, ahli geografi, ahli matematika, astronom, sejarawan, dan penulis puisi. Oleh karena itu, dia mendapatkan julukan Pentathlos. Julukan tersebut memiliki makna seseorang yang berkompetisi dalam lima kegiatan yang berbeda.

Peran Eratosthenes dalam geografi

Sumbangan Eratosthenes dalam geografi adalah mengukur panjang meridian Bumi. Selain itu, dia juga menemukan sistem garis lintang dan garis bujur yang menjadi acuan peta dunia.

Selain itu, dia juga meyakinkan bahwa Bumi berbentuk seperti bola. Sebagian besar orang yang mempelajari ini sejak zaman Aristoteles pada tahun 380 sebelum masehi telah mengetahui bentuk ini. Namun, tidak ada seorang pun yang mengetahui berapa besar ukurannya.

Erastosthenes menghitung panjang meridian Bumi dengan metode geometri dan trigonometri.
Ia melakukan pengamatan Matahari di dua tempat, yaitu Syene dan Alexandria. Syene saat ini kenal dengan Aswan.

Baca juga: Jarak Bumi dan Bulan Kian Jauh, Ini Efeknya Bagi Waktu

Setiap satu hari dalam satu tahun pada puncak tengah hari, Matahari akan bersinar tegak lurus. Ini berbeda dengan kebanyakan hari yang biasanya Matahari akan bersinar sedikit miring.

Hal tersebut diamati dari jatuhnya bayangan. Eratosthenes menyimpulkan bahwa pada hari itu, Matahari berada tepat di atas kepala. Satu hari ini biasanya akan jatuh diantara 20 Juni sampai 22 Juni setiap tahunnya.

Pada tempat kedua di Alexandria, ia juga mengamati hal yang sama. Bedanya, Matahari yang ia amati jatuh lebih selatan dibandingkan lokasi sebelumnya.

Dengan mengetahui fakta tersebut, jarak antara Alexandria dan Syene, serta mengetahui lengkung Bumi, Eratosthenes berhasil menghitung panjang meridian Bumi.

Cara mengukur jarak yang digunakan

Eratosthenes mengukur panjang bayangan yang dihasilkan oleh kedua Matahari pada waktu yang sama. Setelah membandingkan keduanya, diperoleh angka 7,2 derajat.

Sebelumnya telah diketahui bahwa Bumi berbentuk bulat, artinya memiliki sudut total 360 derajat. Artinya, jarak Alexandria dengan Syene adalah 7,2 per 360 derajat keliling Bumi.

Ia juga membuat estimasi bahwa jarak Alexandria ke Syene adalah 5.000 stadia atau setara 800 kilometer. Dengan membandingkan kedua fakta tersebut, ditemukanlah bahwa jarak keliling Bumi adalah 40.008 kilometer.

Baca juga: Apa Bintang Paling Jauh dari Bumi dan Bagaimana Cara Mengukur Jaraknya?

Namun, pengukuran ini sebenarnya sedikit kurang akurat karena perbedaan satuan stadia di kedua negara yang ditempati oleh Eratosthenes. Di Yunani, 1 stadia setara dengan 185 meter, sedangkan di Mesir, 1 stadia setara dengan 157,5 meter.

Kita tidak mengetahui stadia mana yang digunakan oleh Eratosthenes. Walau begitu, keduanya tidak akan mengubah keliling Bumi terlalu jauh, namun hanya berbeda kurang dari 2 persen.

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Tag

  • sumbangan eratosthenes dalam geografi
  • meridian bumi
  • jarak keliling bumi
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' + item.method.toUpperCase()); } else { var sourceDiv = createElement('div', null, null, [cssClasses.source], resultObj.engine['type']); } var textWrapper = createElement('div', null, null, [cssClasses.text_wrapper]); textWrapper.appendChild(categoryDiv); textWrapper.appendChild(titleDiv); textWrapper.appendChild(sourceDiv); recItemWrapper.appendChild(imgWrapper); recItemWrapper.appendChild(textWrapper); recItemWrapperA.appendChild(recItemWrapper); recItem.appendChild(recItemWrapperA); widgetWrapper.appendChild(recItem); // hook up the click handler for this item // recItem.onclick = handleClick.bind(null, jxRecHelper, itemUrl + tracker_params, index); recItemWrapperA.onclick = handleClick.bind(null, jxRecHelper, itemUrl + tracker_params, index); }); } // end while var endDate = new Date(); var loadtime = (endDate.getTime() - startDate.getTime()); trackEventGa('AIML Article Recommendation', 'Content Loaded', 'algsrc='+algsrc+',site=SAINS,device=desktop,loadtime=' + loadtime) let domain = window.location.hostname; if(domain=='www.kompas.com'){ var url=window.location.href.split("/"); domain=url[2]+'/'+url[3] } let user_subs_type = "Gues"; let subs_type = ""; let is_lgn = 0; let engine = algsrc; if(getCookie('kmps_usrid')){is_lgn=1}; let time_load = loadtime; resolve(); /*** * JXRECSDK NOTES 3 of 5 - * pass all the info about the items to the rec helper * each one is an object: ALL MANDATORY * div * id * pos */ jxRecHelper.items(widgetItemArr); /*** * JXRECSDK NOTES 4 of 5 - * Call the ready() of the helper object when the recommendation * results have been populated to the widget * (This will register the action=ready event) */ if (resultObj.engine['type'] == 'api-1') { jxRecHelper.ready(resultObj.options.algo + ":" + resultObj.options.version); } else { jxRecHelper.ready(resultObj.engine['type']); } } else { jxRecHelper.error(204); console.error("Error: no recommendation items"); return; } } catch (err) { jxRecHelper.error(901); console.log(err.stack); let domain = window.location.hostname; if(domain=='www.kompas.com'){ var url=window.location.href.split("/"); domain=url[2]+'/'+url[3] } let user_subs_type = "Gues"; let subs_type = "" let is_lgn = 0; let engine = algsrc; if(getCookie('kmps_usrid')){is_lgn=1}; let endDate = new Date(); let time_load = (endDate.getTime() - startDate.getTime()); } }); } const _jxRecSdkURL = 'https://scripts.jixie.media/jxrecsdk.1.0.min.js'; var startDate = new Date(); class OneWidget { constructor() { //this is also the one we will pass to the JX rec helper object when //we instantiate it: //In this implementation most of these come from the options obj //on the publisher page. this._options = { accountid: '9262bf2590d558736cac4fff7978fcb1', pageurl: 'https://www.kompas.com/sains/read/2021/08/27/112900423/sumbangan-eratosthenes-dalam-geografi-ini-penjelasannya', widget_id: '1000183-6xWeiWZFIM', type: 'pages', container: 'rekomendasi-konten-pilihan-untukmu-aiml', keywords: content_tags, title: title, customid: "23", count: 14, }; this._containerId = this._options.container; this._container = document.getElementById(this._containerId); this._engines = [{"url":"https:\/\/recommendation.jixie.media\/v1\/recommendation","method":"GET","pageurl":"https:\/\/www.kompas.com\/sains\/read\/2021\/08\/27\/112900423\/sumbangan-eratosthenes-dalam-geografi-ini-penjelasannya","system":"jx","type":"api-1","tracker_params":"?source=widgetML","tracker_algsrc":"V","count":14,"page_status":"read","excludeitemids":"20210827112900423"}]; } kickOff() { startDate = new Date(); const rand = Math.floor(Math.random() * 1000); /*const randSystem = Math.floor(Math.random() * 3); this._engine = this._engines[randSystem] if (location.hostname.indexOf('lestari') != -1) { this._engine = this._engines[1] }*/ this._engine = this._engines[0]; this._options.system = this._engine['system'] trackEventGa('AIML Article Recommendation', 'Widget load', 'algsrc=' + this._engine['tracker_algsrc'] + ',site=SAINS,device=desktop') let promJXSDK = fetchJSFileP(_jxRecSdkURL); let thisObj = this; // first we wait on the JX REC SDK to be loaded and initialized let recHelperObj = null; let recResults = null; promJXSDK .then(function() { /*** * JXRECSDK NOTES 1 of 5 - INSTANTIATION OF A JX REC HELPER OBJECT * Call this AFTER JX REC SDK is loaded but BEFORE you call your REC * backend. * * param: MANDATORY options object * options object must at a minimal have * accountid: get from jixie * widgetid: get from jixie * container: DIV ID of the destination div to house the widget * (for jixie widget this is just the options object passed from the page) * * (This will also register the action=load event) */ recHelperObj = jxRecMgr.createJxRecHelper(thisObj._options); let basicInfo = thisObj._options; basicInfo.engine = thisObj._engine if (basicInfo.engine.type == 'api-1') { var options = { count: basicInfo['count'], adpositions: "", keywords: basicInfo['keywords'], title: basicInfo['title'], date_published: "2021-08-27", pagecategory: "SAINS", algo: "mixed" }; if(getCookie('kmps_usrid')){ var kg = { pagetype:basicInfo.engine.page_status, uid:getCookie('kmps_usrid'), ukid:getCookie('kmp_uid') } if(basicInfo.engine.page_status=='read'){ kg['excludeitemids'] = basicInfo.engine.excludeitemids; kg['multiFormat'] = true; } options['additional'] = { kg:kg }; } return recHelperObj.getJxRecommendations(options); } else { return fetchRecommendationsP(basicInfo, recHelperObj.getJxUserInfo()); } }) .then(function(resp) { if (thisObj._engine.type == 'api-3') { recResults = new Object recResults.items = resp.docs.result; } else { recResults = resp; } recResults.engine = thisObj._engine; if (!resp || !recResults.items || recResults.items.length == 0) { /*** * JXRECSDK NOTES 2 of 5 - * Call the error() function on the recHelper when either an error * has occured in the fetching or there are no recommended items * * (This will register the action=error event) */ recHelperObj.error(204); throw "no recommendation results"; } }) .then(function() { // everything is ready (recommendation results, css): document.getElementById("rekomendasi-konten-pilihan-untukmu-aiml").classList.remove("-loading"); document.querySelector('.wSpec-list').remove(); createDisplay(rand, thisObj._container, recResults, recHelperObj) .then(function() { toggleDropdown(); //observe lozad lozad('.lozad', { load: function(el) { el.src = el.dataset.src; el.onload = function() { el.classList.add('fade') } } }).observe() }) }) .catch(function(error) { console.log(`Unable to create recommendations widget ${error.stack} ${error.message}`); }); } } var limit_gtm_ready = 1; function check_gtm_ready() { if ('ga' in window) { // create a new instance of our widget based on the options const newW = new OneWidget(); newW.kickOff(); } else { const timeout_gtm_ready = setTimeout(check_gtm_ready, 500) limit_gtm_ready += 1; if (limit_gtm_ready > 10) { clearTimeout(timeout_gtm_ready); const newW = new OneWidget(); newW.kickOff(); } } } check_gtm_ready() document.querySelector('.wSpec-secret').addEventListener('click', function(e) { e.preventDefault(); let wSl = document.querySelectorAll('.wSpec-source'); if (wSl.length > 0) { for (let i = 0; i < wSl.length; i++) { wSl[i].classList.toggle('show') } } }) function trackEventGa(category, action, label) { if ("ga" in window) { ga(function() { tracker = ga.getAll()[0]; if (tracker) { tracker.send("event", category, action, label); console.log('track event ', category, action, label) } }) } } function formBody(obj) { let formBody = []; for (var property in obj) { let encodedKey = encodeURIComponent(property); let encodedValue = encodeURIComponent(obj[property]); formBody.push(encodedKey + "=" + encodedValue); } return formBody.join("&"); } function getCookie(name) { var name = name + '='; var cookies = decodeURIComponent(document.cookie).split(';'); for (var i = 0; i < cookies.length; i++) { var c = cookies[i]; while (c.charAt(0) == ' ') { c = c.substring(1); } if (c.indexOf(name) == 0) { return c.substring(name.length, c.length); } } } function get_guid(url) { const videoPath = url.match(/\/watch\/(\d+)/); if (videoPath) { return `video.${videoPath[1]}`; } let arrayUrl = url.split('/'); let readPath = arrayUrl.indexOf('read'); if (arrayUrl[readPath + 1] == 'xml') { readPath += 1; } let year = arrayUrl[readPath + 1]; let month = arrayUrl[readPath + 2]; let date = arrayUrl[readPath + 3]; let id = arrayUrl[readPath + 4]; let guid = `.xml.${year}.${month}.${date}.${id}`; return guid; } function toggleDropdown() { let tdd = document.querySelectorAll('[data-dropdown]') if (!!tdd) { tdd.forEach((el) => { el.addEventListener('click', function() { el.parentElement.classList.toggle('-active') let saved = el.parentElement.getAttribute('data-saved') let kmps_usrid = getCookie('kmps_usrid'); if (kmps_usrid && !saved && el.parentElement.classList.contains('-active')) { let url = el.parentElement.getAttribute('data-url'); let guid = get_guid(url); check_bookmark( kmps_usrid, guid ).then(function(resp) { if (resp.hasOwnProperty('total_data')) { if (resp.total_data > 0) { el.parentElement.querySelector('.buttonBookmark').classList.add('-active'); el.parentElement.querySelector('.buttonBookmark').innerHTML = 'Hapus dari tersimpan'; el.parentElement.setAttribute('data-saved', 'true'); } else { el.parentElement.setAttribute('data-saved', 'false'); } } }) } }) document.addEventListener("click", function(e) { // console.log(e.target) if (el.contains(e.target)) { // console.log(tdd) } else { el.parentElement.classList.remove('-active') } }); }); } } function check_bookmark(kmps_usrid, guid) { let url = `https://api.kompas.com/2021/reaction/bookmark/list?kmps_usrid=${kmps_usrid}&guid=${guid}`; return new Promise(function(resolve, reject) { var xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { resolve(JSON.parse(this.responseText)) } }; xmlhttp.open("GET", url, true); xmlhttp.send(); }); } function do_bookmark(pageurl, pos, userFeedback) { const wSpecItem = document.querySelector(`.wSpec-item[data-index="${pos}"]`); const btnBookmark = wSpecItem.querySelector('.buttonBookmark'); const kmps_usrid = getCookie('kmps_usrid'); const guid = get_guid(pageurl); const type = pageurl.match(/\/watch\/(\d+)/) ? 'video' : 'article'; if (kmps_usrid) { if (btnBookmark.classList.contains('-active')) { set_unbookmark({ guid: guid, kmps_usrid: kmps_usrid, type: type }).then(function(resp) { btnBookmark.classList.remove('-active'); btnBookmark.innerHTML = 'Simpan artikel'; reactionToast('Artikel berhasil dihapus dari list yang disimpan'); userFeedback.event('un-save'); }).catch(function(resp) { // message: "Data doesn't exists" if (resp.hasOwnProperty('message') && resp.message.includes('exist')) { btnBookmark.classList.remove('-active'); btnBookmark.innerHTML = 'Simpan artikel'; reactionToast('Artikel berhasil dihapus dari list yang disimpan'); } }) } else { const user_bookmark_url = "https://activity.kompas.com/saved?order=desc"; set_bookmark({ guid: guid, kmps_usrid: kmps_usrid, type: type, publisher: 'kompas', platform: 'desktop' }).then(function(resp) { btnBookmark.classList.add('-active'); btnBookmark.innerHTML = 'Hapus dari tersimpan'; reactionToast('Artikel berhasil disimpan', user_bookmark_url); userFeedback.event('save'); }).catch(function(resp) { // message: "Data already exist" if (resp.hasOwnProperty('message') && resp.message.includes('exist')) { btnBookmark.classList.add('-active'); btnBookmark.innerHTML = 'Hapus dari tersimpan'; reactionToast('Artikel berhasil disimpan', user_bookmark_url); } }) } } else { const login_url = "https://account.kompas.com/login/a29tcGFz/" + btoa(window.location.href); window.location.href = login_url; } } function set_bookmark(data) { const url = "https://api.kompas.com/2021/reaction/bookmark/add"; return new Promise(function(resolve, reject) { const xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 201) { resolve(JSON.parse(this.responseText)); } else if (this.readyState == 4 && this.status == 400) { reject(JSON.parse(this.responseText)); } }; xmlhttp.open("POST", url, true); xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8"); xmlhttp.send(formBody(data)); }); } function set_unbookmark(data) { const url = "https://api.kompas.com/2021/reaction/bookmark/delete"; return new Promise(function(resolve, reject) { const xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { resolve(JSON.parse(this.responseText)); } else if (this.readyState == 4 && this.status == 400) { reject(JSON.parse(this.responseText)); } }; xmlhttp.open("POST", url, true); xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8"); xmlhttp.send(formBody(data)); }); } class UserFeedback { constructor(engine, pageurl, jxRecHelper, pos) { this.engine = engine; this.pageurl = pageurl; this.jxRecHelper = jxRecHelper; this.pos = pos; } event(feedback) { if (this.engine == 'C') { const xmlhttp = new XMLHttpRequest(); let params = { domain: 'kompas.com', ce_userid: getCookie('kmps_usrid'), ce_sessionid: getCookie('ukid'), ce_pageurl: this.pageurl, engine: 'C', ce_feedback: feedback } xmlhttp.open("GET", 'https://apis.kgdata.dev/v1/aiml/feedback-widgetml' + formatParams(params)); xmlhttp.send(); } else if (this.engine == 'V') { if (feedback == 'share') { this.jxRecHelper.shared(this.pos); } else if (feedback == 'save') { this.jxRecHelper.bookmarked(this.pos); } else if (feedback == 'not-interested') { this.jxRecHelper.hidden(this.pos); } else if (feedback == 'un-not-interested') { this.jxRecHelper.unhidden(this.pos); } } } } function formatParams(params) { return "?" + Object .keys(params) .map(function(key) { return key + "=" + encodeURIComponent(params[key]) }) .join("&") } document.addEventListener("click", function(e){ let dx = document.querySelectorAll('[data-dropdown]') if(dx) { dx.forEach(function(el){ if(el.contains(e.target)) { el.parentElement.classList.toggle('-active') } else { el.parentElement.classList.remove('-active') } }) } })

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