{"id":834,"date":"2020-02-10T08:09:51","date_gmt":"2020-02-10T08:09:51","guid":{"rendered":"http:\/\/disciple4.com\/?p=834"},"modified":"2023-04-09T11:51:23","modified_gmt":"2023-04-09T11:51:23","slug":"the-sound-so-loud-that-it-circled-the-earth-four-times","status":"publish","type":"post","link":"https:\/\/disciple4.com\/index.php\/2020\/02\/10\/the-sound-so-loud-that-it-circled-the-earth-four-times\/","title":{"rendered":"The Sound So Loud That It Circled the Earth Four Times"},"content":{"rendered":"\n

Some events are just too big to believe. In spite of the fact that many of us (just don\u2019t admit it to anyone), when we hear about an earthquake, we are somewhat disappointed that only 30 of 40 or 200 people died. In the 2006 earthquake in Indonesia, 220 000 people died. Up till today, 7 February 2020, \u201conly\u201d<\/em> 500 people are reported to have died because of the Coronavirus and \u201conly\u201d<\/em> 25 000 are infected by it. During the Black Flu in 1918, nearly 50 million people died. Shame on us. But unfortunately, it is true. We heart about four houses that have been burned down to the foundation. How many people died? Nobody? Well, why do you tell me about it? (Luckily it wasn\u2019t my house).<\/p>\n\n\n\n

Try to deny it. <\/p>\n\n\n\n

With all the news and videos and a massive amount\nof information, we want something \u201cbigger\u201d. We want something really big.<\/p>\n\n\n\n

But then we hear about something that is just\ntoo big. It is a bit too big to believe. <\/p>\n\n\n\n

Let me tell you about something really big. But\nbig comes at a price \u2013 basically always.<\/em><\/p>\n\n\n\n

On the Island of Krakatoa \u2013 27 August 1883,\n10:02 a.m. – the world made a noise that has not been surpassed since then.<\/p>\n\n\n\n

This sound emerged from the island of\nKrakatoa, which sits between Java and Sumatra in Indonesia. It was heard 1,300\nmiles away in the Andaman and Nicobar islands (\u201cextraordinary sounds were\nheard, as of guns firing\u201d); 2,000 miles away in New Guinea and Western\nAustralia (\u201ca series of loud reports, resembling those of artillery in a\nnorth-westerly direction\u201d); and even 3,000 miles away in the Indian Ocean\nisland of Rodrigues, near Mauritius* (\u201ccoming from the eastward, like the distant roar of heavy guns.\u201d1<\/sup>) In all, it was heard by people in\nover 50 different geographical locations, together spanning an area covering a\nthirteenth of the globe.<\/p>\n\n\n\n

Think, for a moment, just how crazy this is.\nIf you\u2019re in Boston and someone tells you that they heard a sound coming from\nNew York City, you\u2019re probably going to give them a funny look. But Boston is a\nmere 200 miles from New York. What we\u2019re talking about here is like being in\nBoston and clearly hearing a noise coming from Dublin, Ireland. Travelling at\nthe speed of sound (766 miles or 1,233 kilometres per hour), it takes a noise\nabout 4 hours to cover that distance. <\/p>\n\n\n\n

This is the most distant sound that has ever\nbeen heard in recorded history. So what could possibly create such an\nearth-shatteringly loud bang? A volcano on Krakatoa had just erupted with a\nforce so great that it tore the\nisland<\/a> apart,\nemitting a plume of smoke that reached 17 miles into the atmosphere, according\nto a geologist who witnessed it1<\/sup>. This explosion created a deadly\ntsunami with waves over a hundred feet (30 meters) in height. One hundred\nsixty-five coastal villages and settlements were swept away and entirely\ndestroyed. In all, the Dutch (the colonial rulers of Indonesia at the time)\nestimated the death toll at 36,417, while other estimates exceed 120,0002,3<\/sup>.<\/p>\n\n\n\n

The British ship Norham Castle was 40 miles\nfrom Krakatoa at the time of the explosion. The ship\u2019s captain wrote in his\nlog, \u201cSo violent are the explosions that the ear-drums of over half my crew\nhave been shattered. My last thoughts are with my dear wife. I am convinced\nthat the Day of Judgement has come.\u201d<\/p>\n\n\n\n

It was the hardest sound in known history. To\nput that in context, if you were operating a jackhammer you\u2019d be subject to\nabout 100 decibels. The human threshold for pain is near 130 decibels, and if\nyou had the misfortune of standing next to a jet engine, you\u2019d experience a 150\ndecibel sound. (A 10-decibel increase is perceived by people as sounding\nroughly twice as loud.) The Krakatoa explosion registered 172 decibels at 100\nmiles from the source. This is so astonishingly loud, that it\u2019s inching up\nagainst the limits of what we mean by \u201csound.\u201d<\/p>\n\n\n\n

By 1883, weather stations in scores of cities\nacross the world were using barometers to track changes in atmospheric\npressure. Six hours and 47 minutes after the Krakatoa explosion, a spike of air\npressure was detected in Calcutta. By 8 hours, the pulse reached Mauritius in\nthe west and Melbourne and Sydney in the east. By 12 hours, St. Petersburg\nnoticed the pulse, followed by Vienna, Rome, Paris, Berlin, and Munich. By 18\nhours the pulse had reached New York, Washington DC, and Toronto1<\/sup>.\n Amazingly, for as many as 5 days after the explosion, weather stations in\n50 cities around the globe observed this unprecedented spike in pressure\nre-occurring like clockwork, approximately every 34 hours. That is roughly how long it\ntakes<\/a> sound\nto travel around the entire planet. This sound and\/or spikes of air pressure\ncircled the world 4-5 times.<\/p>\n\n\n\n

If you want something big. This was quite big.\nBut it came with a price. Big always has a price.<\/em><\/p>\n\n\n\n

For those who want to know more<\/em><\/strong><\/p>\n\n\n\n

In general, sounds <\/strong>are caused not by the end of the world but by\nfluctuations in air pressure. A barometer at the Batavia gasworks (100 miles\naway from Krakatoa) registered the ensuing spike in pressure at over 2.5 inches\nof mercury1,2<\/sup>. That converts to over 172 decibels of sound pressure,\nan unimaginably loud noise. This is so astonishingly loud, that it\u2019s inching up\nagainst the limits of what we mean by \u201csound.\u201d<\/p>\n\n\n\n

When you hum a note or speak a word, you\u2019re\nwiggling air molecules back and forth dozens or hundreds of times per second,\ncausing the air pressure to be low in some places and high in other places. The\nlouder the sound, the more intense these wiggles, and the larger the\nfluctuations in air pressure. But there\u2019s a limit to how loud a sound can get.\nAt some point, the fluctuations in air pressure are so large that the low-pressure regions hit zero pressure\u2014a vacuum\u2014and you can\u2019t get any lower than\nthat. This limit happens to be about 194 decibels for a sound in Earth\u2019s\natmosphere. Any louder, and the sound is no longer just passing through the\nair, it\u2019s actually pushing the air along with it, creating a pressurized burst\nof moving air known as a shock wave<\/a>.<\/p>\n\n\n\n

Closer to Krakatoa, the sound was well over\nthis limit, producing a blast of high-pressure air so powerful that it ruptured\nthe eardrums of sailors 40 miles away. As this sound travelled thousands of\nmiles, reaching Australia and the Indian Ocean, the wiggles in pressure started\nto die down, sounding more like a distant gunshot. Over 3,000 miles into its\njourney, the wave of pressure grew too quiet for human ears to hear, but it\ncontinued to sweep onward, reverberating for days across the globe. The\natmosphere was ringing like a bell, imperceptible to us but detectable by our\ninstruments.<\/p>\n\n\n\n

In all, the pressure waves from Krakatoa\ncircled the globe three to four times in each direction. (Each city felt up to\nseven pressure spikes because they experienced shock waves travelling in\nopposite directions from the volcano1<\/sup>.) Meanwhile, tidal stations as\nfar away as India, England, and San Francisco measured a rise in ocean waves\nsimultaneous with this air pulse, an effect that had never been seen before. It\nwas a sound that could no longer be heard but that continued moving around the\nworld, a phenomenon that people nicknamed \u201cthe great air-wave.\u201d<\/p>\n\n\n\n

When the volcano erupts, it produces a sudden\nspike in air pressure; you can actually watch as it moves through the air,\ncondensing water vapour into clouds as it travels. The people taking the video\nare (fortunately) far enough away that pressure wave takes a while to reach\nthem. When it does finally hit the boat, some 13 seconds after the explosion,\nyou hear what sounds like a huge gunshot accompanied by a sudden blast of air.\nMultiplying 13 seconds by the speed of sound tells us that the boat was about\n4.4 kilometres, or 2.7 miles, away from the volcano. This is somewhat akin to\nwhat happened at Krakatoa, except the \u2018gunshot\u2019 in that case could be heard not\njust three but three thousand miles, away, a mind-boggling demonstration of the\nimmense destructive power that nature can unleash.<\/p>\n\n\n\n

Aatish Bhatia is a recent physics Ph.D.\nworking <\/em>at Princeton University<\/em><\/a> to bring science and engineering to a\nwider audience. He writes the award-winning science blog <\/em>Empirical Zeal<\/em><\/a>, hosted at <\/em>Wired, and is on Twitter as <\/em>@aatishb<\/em><\/a>.<\/em><\/p>\n\n\n\n

References<\/strong><\/p>\n\n\n\n

[1] Judd, John Wesley, et al.<\/em> The Eruption\nof Krakatoa: And Subsequent Phenomena<\/a>. Tr\u00fcbner & Company, 1888. (a\ncomprehensive data-filled report of the Krakatoa eruption commissioned by the\nRoyal Society, accessible for free under public domain)<\/em><\/p>\n\n\n\n

[2] Winchester, Simon. Krakatoa: The Day\nthe World Exploded<\/a>.\nPenguin UK, 2004.<\/p>\n\n\n\n

[3] Simkin, Tom, and Richard S. Fiske.<\/em> Krakatau, 1883, the\nVolcanic Eruption and Its Effects<\/a>. Smithsonian Inst Pr, 1983.<\/em><\/p>\n\n\n\n

Thanks to <\/em>Nicole Sharp<\/em><\/a> and <\/em>Will Slaton<\/em><\/a> for helpful discussions about the physics of the Krakatoa explosion.<\/em><\/p>\n\n\n\n

Life comes in stories: use this link to subscribe to occasional stories via email: https:\/\/tinyurl.com\/vfd32z4<\/a>
<\/p>\n","protected":false},"excerpt":{"rendered":"

Some events are just too big to believe. In spite of the fact that many of us (just don\u2019t admit it to anyone), when we hear about an earthquake, we are somewhat disappointed that only 30 of 40 or 200 people died. In the 2006 earthquake in Indonesia, 220 000 people died. Up till today, 7 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[],"class_list":["post-834","post","type-post","status-publish","format-standard","hentry","category-quotes"],"_links":{"self":[{"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/posts\/834","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/comments?post=834"}],"version-history":[{"count":1,"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/posts\/834\/revisions"}],"predecessor-version":[{"id":1409,"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/posts\/834\/revisions\/1409"}],"wp:attachment":[{"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/media?parent=834"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/categories?post=834"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/disciple4.com\/index.php\/wp-json\/wp\/v2\/tags?post=834"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}