In 1962, French geologist Michel Siffre climbed into a glacier cave in the Alps with no clock and no sunlight and stayed for two months, and when his team called him up on 14 September he insisted it was still 20 August, some of the earliest evidence that human circadian rhythm drifts free of any external cue

1.0Switzerlandhttps://www.europesays.com/chEUROPE SAYShttps://www.europesays.com/ch/author/europe-says/In 1962, French geologist Michel Siffre climbed into a glacier cave in the Alps with no clock and no sunlight and stayed for two months, and when his team called him up on 14 September he insisted it was still 20 August, some of the earliest evidence that human circadian rhythm drifts free of any external cuerich600338<blockquote class="wp-embedded-content" data-secret="cRQON6CjGR"><a href="https://www.europesays.com/ch/121184/">In 1962, French geologist Michel Siffre climbed into a glacier cave in the Alps with no clock and no sunlight and stayed for two months, and when his team called him up on 14 September he insisted it was still 20 August, some of the earliest evidence that human circadian rhythm drifts free of any external cue</a></blockquote><iframe sandbox="allow-scripts" security="restricted" src="https://www.europesays.com/ch/121184/embed/#?secret=cRQON6CjGR" width="600" height="338" title="“In 1962, French geologist Michel Siffre climbed into a glacier cave in the Alps with no clock and no sunlight and stayed for two months, and when his team called him up on 14 September he insisted it was still 20 August, some of the earliest evidence that human circadian rhythm drifts free of any external cue” — Switzerland" data-secret="cRQON6CjGR" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" class="wp-embedded-content"></iframe><script> /*! This file is auto-generated */ !function(d,l){"use strict";l.querySelector&&d.addEventListener&&"undefined"!=typeof URL&&(d.wp=d.wp||{},d.wp.receiveEmbedMessage||(d.wp.receiveEmbedMessage=function(e){var t=e.data;if((t||t.secret||t.message||t.value)&&!/[^a-zA-Z0-9]/.test(t.secret)){for(var s,r,n,a=l.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),o=l.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),c=new RegExp("^https?:$","i"),i=0;i<o.length;i++)o[i].style.display="none";for(i=0;i<a.length;i++)s=a[i],e.source===s.contentWindow&&(s.removeAttribute("style"),"height"===t.message?(1e3<(r=parseInt(t.value,10))?r=1e3:~~r<200&&(r=200),s.height=r):"link"===t.message&&(r=new URL(s.getAttribute("src")),n=new URL(t.value),c.test(n.protocol))&&n.host===r.host&&l.activeElement===s&&(d.top.location.href=t.value))}},d.addEventListener("message",d.wp.receiveEmbedMessage,!1),l.addEventListener("DOMContentLoaded",function(){for(var e,t,s=l.querySelectorAll("iframe.wp-embedded-content"),r=0;r<s.length;r++)(t=(e=s[r]).getAttribute("data-secret"))||(t=Math.random().toString(36).substring(2,12),e.src+="#?secret="+t,e.setAttribute("data-secret",t)),e.contentWindow.postMessage({message:"ready",secret:t},"*")},!1)))}(window,document); //# sourceURL=https://www.europesays.com/ch/wp-includes/js/wp-embed.min.js </script> https://www.europesays.com/ch/wp-content/uploads/2026/08/in-1962-french-geologist-michel-siffre-c-768x512.jpg600400