CINXE.COM

<!DOCTYPE html> <html lang="en-GB"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta http-equiv="Referrer-Policy" content="origin, strict-origin-when-cross-origin"> <link rel="profile" href="http://gmpg.org/xfn/11"> <link rel="pingback" href="https://physicsworld.com/xmlrpc.php"> <link rel="preconnect" href="https://use.typekit.net" crossorigin /> <link rel="preload" href="https://cdn-cookieyes.com/client_data/32a66075cd31d8fea8d5fadf/script.js" as="script" /> <link rel="preconnect" href="https://www.googletagmanager.com" crossorigin /> <link rel="preconnect" href="https://cdn.ampproject.org" crossorigin /> <link rel="preconnect" href="https://in.hotjar.com" crossorigin /> <meta http-equiv="X-UA-Compatible" content="IE=edge" >  <script src="//use.typekit.net/mfv1unu.js"></script> <script>try{Typekit.load({ async: true, active: function() { jQuery('body').addClass('typekit'); } });}catch(e){}</script>  <link href="https://physicsworld.com/wp-content/themes/iopp/static/css/font-awesome.min.css" rel="stylesheet" type="text/css" />  <script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start': new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0], j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src= 'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f); })(window,document,'script','dataLayer','GTM-TQRT9K38');</script>  <meta name='robots' content='index, follow, max-image-preview:large, max-snippet:-1, max-video-preview:-1' />  <title>Our portfolio – Physics World</title> <meta name="description" content="Physics World represents a key part of IOP Publishing's mission to communicate world-class research and innovation to the widest possible audience. The website forms part of the Physics World portfolio, a collection of online, digital and print information services for the global scientific community." /> <link rel="canonical" href="https://physicsworld.com/p/our-portfolio/" /> <meta property="og:locale" content="en_GB" /> <meta property="og:type" content="article" /> <meta property="og:title" content="Our portfolio – Physics World" /> <meta property="og:description" content="Physics World represents a key part of IOP Publishing's mission to communicate world-class research and innovation to the widest possible audience. The website forms part of the Physics World portfolio, a collection of online, digital and print information services for the global scientific community." /> <meta property="og:url" content="https://physicsworld.com/our-portfolio/" /> <meta property="og:site_name" content="Physics World" /> <meta property="article:publisher" content="https://www.facebook.com/physicsworld/" /> <meta property="article:modified_time" content="2024-03-28T15:18:30+00:00" /> <meta name="twitter:card" content="summary_large_image" /> <meta name="twitter:site" content="@PhysicsWorld" /> <script type="application/ld+json" class="yoast-schema-graph">{"@context":"https://schema.org","@graph":[{"@type":"WebPage","@id":"https://physicsworld.com/our-portfolio/","url":"https://physicsworld.com/our-portfolio/","name":"Our portfolio – Physics World","isPartOf":{"@id":"https://physicsworld.com/#website"},"datePublished":"2017-08-09T18:10:34+00:00","dateModified":"2024-03-28T15:18:30+00:00","description":"Physics World represents a key part of IOP Publishing's mission to communicate world-class research and innovation to the widest possible audience. The website forms part of the Physics World portfolio, a collection of online, digital and print information services for the global scientific community.","breadcrumb":{"@id":"https://physicsworld.com/our-portfolio/#breadcrumb"},"inLanguage":"en-GB","potentialAction":[{"@type":"ReadAction","target":["https://physicsworld.com/our-portfolio/"]}]},{"@type":"BreadcrumbList","@id":"https://physicsworld.com/our-portfolio/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://physicsworld.com/"},{"@type":"ListItem","position":2,"name":"Our portfolio"}]},{"@type":"WebSite","@id":"https://physicsworld.com/#website","url":"https://physicsworld.com/","name":"Physics World","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://physicsworld.com/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-GB"}]}</script>  <meta name="oas:article-id" content="12553" /> <meta name="oas:article-type" content="static-page" /><link rel='dns-prefetch' href='//cdn.jsdelivr.net' /> <link rel='dns-prefetch' href='//players.brightcove.net' /> <link rel='stylesheet' id='wp-block-library-css' href='https://physicsworld.com/wp-includes/css/dist/block-library/style.min.css?ver=6.6.1' type='text/css' media='all' /> <style id='safe-svg-svg-icon-style-inline-css' type='text/css'> .safe-svg-cover{text-align:center}.safe-svg-cover .safe-svg-inside{display:inline-block;max-width:100%}.safe-svg-cover svg{height:100%;max-height:100%;max-width:100%;width:100%} </style> <style id='powerpress-player-block-style-inline-css' type='text/css'> </style> <style id='classic-theme-styles-inline-css' type='text/css'> /*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} </style> <style id='global-styles-inline-css' type='text/css'> :root{--wp--preset--aspect-ratio--square: 1;--wp--preset--aspect-ratio--4-3: 4/3;--wp--preset--aspect-ratio--3-4: 3/4;--wp--preset--aspect-ratio--3-2: 3/2;--wp--preset--aspect-ratio--2-3: 2/3;--wp--preset--aspect-ratio--16-9: 16/9;--wp--preset--aspect-ratio--9-16: 9/16;--wp--preset--color--black: #000000;--wp--preset--color--cyan-bluish-gray: #abb8c3;--wp--preset--color--white: #ffffff;--wp--preset--color--pale-pink: #f78da7;--wp--preset--color--vivid-red: #cf2e2e;--wp--preset--color--luminous-vivid-orange: #ff6900;--wp--preset--color--luminous-vivid-amber: #fcb900;--wp--preset--color--light-green-cyan: #7bdcb5;--wp--preset--color--vivid-green-cyan: #00d084;--wp--preset--color--pale-cyan-blue: #8ed1fc;--wp--preset--color--vivid-cyan-blue: #0693e3;--wp--preset--color--vivid-purple: #9b51e0;--wp--preset--gradient--vivid-cyan-blue-to-vivid-purple: linear-gradient(135deg,rgba(6,147,227,1) 0%,rgb(155,81,224) 100%);--wp--preset--gradient--light-green-cyan-to-vivid-green-cyan: linear-gradient(135deg,rgb(122,220,180) 0%,rgb(0,208,130) 100%);--wp--preset--gradient--luminous-vivid-amber-to-luminous-vivid-orange: linear-gradient(135deg,rgba(252,185,0,1) 0%,rgba(255,105,0,1) 100%);--wp--preset--gradient--luminous-vivid-orange-to-vivid-red: linear-gradient(135deg,rgba(255,105,0,1) 0%,rgb(207,46,46) 100%);--wp--preset--gradient--very-light-gray-to-cyan-bluish-gray: linear-gradient(135deg,rgb(238,238,238) 0%,rgb(169,184,195) 100%);--wp--preset--gradient--cool-to-warm-spectrum: linear-gradient(135deg,rgb(74,234,220) 0%,rgb(151,120,209) 20%,rgb(207,42,186) 40%,rgb(238,44,130) 60%,rgb(251,105,98) 80%,rgb(254,248,76) 100%);--wp--preset--gradient--blush-light-purple: linear-gradient(135deg,rgb(255,206,236) 0%,rgb(152,150,240) 100%);--wp--preset--gradient--blush-bordeaux: linear-gradient(135deg,rgb(254,205,165) 0%,rgb(254,45,45) 50%,rgb(107,0,62) 100%);--wp--preset--gradient--luminous-dusk: linear-gradient(135deg,rgb(255,203,112) 0%,rgb(199,81,192) 50%,rgb(65,88,208) 100%);--wp--preset--gradient--pale-ocean: linear-gradient(135deg,rgb(255,245,203) 0%,rgb(182,227,212) 50%,rgb(51,167,181) 100%);--wp--preset--gradient--electric-grass: linear-gradient(135deg,rgb(202,248,128) 0%,rgb(113,206,126) 100%);--wp--preset--gradient--midnight: linear-gradient(135deg,rgb(2,3,129) 0%,rgb(40,116,252) 100%);--wp--preset--font-size--small: 13px;--wp--preset--font-size--medium: 20px;--wp--preset--font-size--large: 36px;--wp--preset--font-size--x-large: 42px;--wp--preset--spacing--20: 0.44rem;--wp--preset--spacing--30: 0.67rem;--wp--preset--spacing--40: 1rem;--wp--preset--spacing--50: 1.5rem;--wp--preset--spacing--60: 2.25rem;--wp--preset--spacing--70: 3.38rem;--wp--preset--spacing--80: 5.06rem;--wp--preset--shadow--natural: 6px 6px 9px rgba(0, 0, 0, 0.2);--wp--preset--shadow--deep: 12px 12px 50px rgba(0, 0, 0, 0.4);--wp--preset--shadow--sharp: 6px 6px 0px rgba(0, 0, 0, 0.2);--wp--preset--shadow--outlined: 6px 6px 0px -3px rgba(255, 255, 255, 1), 6px 6px rgba(0, 0, 0, 1);--wp--preset--shadow--crisp: 6px 6px 0px rgba(0, 0, 0, 1);}:where(.is-layout-flex){gap: 0.5em;}:where(.is-layout-grid){gap: 0.5em;}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}:where(.wp-block-columns.is-layout-flex){gap: 2em;}:where(.wp-block-columns.is-layout-grid){gap: 2em;}:where(.wp-block-post-template.is-layout-flex){gap: 1.25em;}:where(.wp-block-post-template.is-layout-grid){gap: 1.25em;}.has-black-color{color: var(--wp--preset--color--black) !important;}.has-cyan-bluish-gray-color{color: var(--wp--preset--color--cyan-bluish-gray) !important;}.has-white-color{color: var(--wp--preset--color--white) !important;}.has-pale-pink-color{color: var(--wp--preset--color--pale-pink) !important;}.has-vivid-red-color{color: var(--wp--preset--color--vivid-red) !important;}.has-luminous-vivid-orange-color{color: var(--wp--preset--color--luminous-vivid-orange) !important;}.has-luminous-vivid-amber-color{color: var(--wp--preset--color--luminous-vivid-amber) !important;}.has-light-green-cyan-color{color: var(--wp--preset--color--light-green-cyan) !important;}.has-vivid-green-cyan-color{color: var(--wp--preset--color--vivid-green-cyan) !important;}.has-pale-cyan-blue-color{color: var(--wp--preset--color--pale-cyan-blue) !important;}.has-vivid-cyan-blue-color{color: var(--wp--preset--color--vivid-cyan-blue) !important;}.has-vivid-purple-color{color: var(--wp--preset--color--vivid-purple) !important;}.has-black-background-color{background-color: var(--wp--preset--color--black) !important;}.has-cyan-bluish-gray-background-color{background-color: var(--wp--preset--color--cyan-bluish-gray) !important;}.has-white-background-color{background-color: var(--wp--preset--color--white) !important;}.has-pale-pink-background-color{background-color: var(--wp--preset--color--pale-pink) !important;}.has-vivid-red-background-color{background-color: var(--wp--preset--color--vivid-red) !important;}.has-luminous-vivid-orange-background-color{background-color: var(--wp--preset--color--luminous-vivid-orange) !important;}.has-luminous-vivid-amber-background-color{background-color: var(--wp--preset--color--luminous-vivid-amber) !important;}.has-light-green-cyan-background-color{background-color: var(--wp--preset--color--light-green-cyan) !important;}.has-vivid-green-cyan-background-color{background-color: var(--wp--preset--color--vivid-green-cyan) !important;}.has-pale-cyan-blue-background-color{background-color: var(--wp--preset--color--pale-cyan-blue) !important;}.has-vivid-cyan-blue-background-color{background-color: var(--wp--preset--color--vivid-cyan-blue) !important;}.has-vivid-purple-background-color{background-color: var(--wp--preset--color--vivid-purple) !important;}.has-black-border-color{border-color: var(--wp--preset--color--black) !important;}.has-cyan-bluish-gray-border-color{border-color: var(--wp--preset--color--cyan-bluish-gray) !important;}.has-white-border-color{border-color: var(--wp--preset--color--white) !important;}.has-pale-pink-border-color{border-color: var(--wp--preset--color--pale-pink) !important;}.has-vivid-red-border-color{border-color: var(--wp--preset--color--vivid-red) !important;}.has-luminous-vivid-orange-border-color{border-color: var(--wp--preset--color--luminous-vivid-orange) !important;}.has-luminous-vivid-amber-border-color{border-color: var(--wp--preset--color--luminous-vivid-amber) !important;}.has-light-green-cyan-border-color{border-color: var(--wp--preset--color--light-green-cyan) !important;}.has-vivid-green-cyan-border-color{border-color: var(--wp--preset--color--vivid-green-cyan) !important;}.has-pale-cyan-blue-border-color{border-color: var(--wp--preset--color--pale-cyan-blue) !important;}.has-vivid-cyan-blue-border-color{border-color: var(--wp--preset--color--vivid-cyan-blue) !important;}.has-vivid-purple-border-color{border-color: var(--wp--preset--color--vivid-purple) !important;}.has-vivid-cyan-blue-to-vivid-purple-gradient-background{background: var(--wp--preset--gradient--vivid-cyan-blue-to-vivid-purple) !important;}.has-light-green-cyan-to-vivid-green-cyan-gradient-background{background: var(--wp--preset--gradient--light-green-cyan-to-vivid-green-cyan) !important;}.has-luminous-vivid-amber-to-luminous-vivid-orange-gradient-background{background: var(--wp--preset--gradient--luminous-vivid-amber-to-luminous-vivid-orange) !important;}.has-luminous-vivid-orange-to-vivid-red-gradient-background{background: var(--wp--preset--gradient--luminous-vivid-orange-to-vivid-red) !important;}.has-very-light-gray-to-cyan-bluish-gray-gradient-background{background: var(--wp--preset--gradient--very-light-gray-to-cyan-bluish-gray) !important;}.has-cool-to-warm-spectrum-gradient-background{background: var(--wp--preset--gradient--cool-to-warm-spectrum) !important;}.has-blush-light-purple-gradient-background{background: var(--wp--preset--gradient--blush-light-purple) !important;}.has-blush-bordeaux-gradient-background{background: var(--wp--preset--gradient--blush-bordeaux) !important;}.has-luminous-dusk-gradient-background{background: var(--wp--preset--gradient--luminous-dusk) !important;}.has-pale-ocean-gradient-background{background: var(--wp--preset--gradient--pale-ocean) !important;}.has-electric-grass-gradient-background{background: var(--wp--preset--gradient--electric-grass) !important;}.has-midnight-gradient-background{background: var(--wp--preset--gradient--midnight) !important;}.has-small-font-size{font-size: var(--wp--preset--font-size--small) !important;}.has-medium-font-size{font-size: var(--wp--preset--font-size--medium) !important;}.has-large-font-size{font-size: var(--wp--preset--font-size--large) !important;}.has-x-large-font-size{font-size: var(--wp--preset--font-size--x-large) !important;} :where(.wp-block-post-template.is-layout-flex){gap: 1.25em;}:where(.wp-block-post-template.is-layout-grid){gap: 1.25em;} :where(.wp-block-columns.is-layout-flex){gap: 2em;}:where(.wp-block-columns.is-layout-grid){gap: 2em;} :root :where(.wp-block-pullquote){font-size: 1.5em;line-height: 1.6;} </style> <link rel='stylesheet' id='nine3-style-css' href='https://physicsworld.com/wp-content/themes/iopp/dist/css/main.d85b8b6e29494c1a81f4c002bb8e1b11.css?ver=6.6.1' type='text/css' media='all' /> <link rel='stylesheet' id='brightcove-pip-css-css' href='https://players.brightcove.net/videojs-pip/1/videojs-pip.css?ver=2.8.7' type='text/css' media='all' /> <link rel='stylesheet' id='brightcove-playlist-css' href='https://physicsworld.com/wp-content/plugins/brightcove-video-connect/assets/css/brightcove_playlist.min.css?ver=2.8.7' type='text/css' media='all' /> <script src="https://physicsworld.com/wp-includes/js/jquery/jquery.min.js?ver=3.7.1" id="jquery-core-js"></script> <script src="https://physicsworld.com/wp-includes/js/jquery/jquery-migrate.min.js?ver=3.4.1" id="jquery-migrate-js"></script> <script id="real3d-flipbook-forntend-js-extra"> var rootFolder = ["https:\/\/physicsworld.com\/wp-content\/plugins\/real3d-flipbook\/"]; </script> <script src="https://physicsworld.com/wp-content/plugins/real3d-flipbook/js/frontend.js?ver=3.61" id="real3d-flipbook-forntend-js"></script> <link rel="https://api.w.org/" href="https://physicsworld.com/wp-json/" /><link rel="alternate" title="JSON" type="application/json" href="https://physicsworld.com/wp-json/wp/v2/pages/12553" /><link rel="EditURI" type="application/rsd+xml" title="RSD" href="https://physicsworld.com/xmlrpc.php?rsd" /> <link rel='shortlink' href='https://physicsworld.com/?p=12553' /> <link rel="alternate" title="oEmbed (JSON)" type="application/json+oembed" href="https://physicsworld.com/wp-json/oembed/1.0/embed?url=https%3A%2F%2Fphysicsworld.com%2Fp%2Four-portfolio%2F" /> <link rel="alternate" title="oEmbed (XML)" type="text/xml+oembed" href="https://physicsworld.com/wp-json/oembed/1.0/embed?url=https%3A%2F%2Fphysicsworld.com%2Fp%2Four-portfolio%2F&format=xml" /> <script id="dzsap-main-settings" type="application/json">{"dzsap_site_url":"https:\/\/physicsworld.com\/","pluginurl":"https:\/\/physicsworld.com\/wp-content\/plugins\/dzs-zoomsounds\/audioplayer\/","dzsap_curr_user":0,"version":"6.50","ajax_url":"https:\/\/physicsworld.com\/wp-admin\/admin-ajax.php","action_received_time_total":"send_total_time"}</script> <script type="text/javascript"> </script>  <meta name="onesignal" content="wordpress-plugin"/> <script> window.OneSignal = window.OneSignal || []; OneSignal.push( function() { OneSignal.SERVICE_WORKER_UPDATER_PATH = "OneSignalSDKUpdaterWorker.js.php"; OneSignal.SERVICE_WORKER_PATH = "OneSignalSDKWorker.js.php"; OneSignal.SERVICE_WORKER_PARAM = { scope: "/" }; OneSignal.setDefaultNotificationUrl("https://physicsworld.com"); var oneSignal_options = {}; window._oneSignalInitOptions = oneSignal_options; oneSignal_options['wordpress'] = true; oneSignal_options['appId'] = '7322d010-59eb-4b97-8b58-47d4ecec27f1'; oneSignal_options['allowLocalhostAsSecureOrigin'] = true; oneSignal_options['welcomeNotification'] = { }; oneSignal_options['welcomeNotification']['title'] = "Physics World"; oneSignal_options['welcomeNotification']['message'] = ""; oneSignal_options['path'] = "https://physicsworld.com/wp-content/plugins/onesignal-free-web-push-notifications/sdk_files/"; oneSignal_options['promptOptions'] = { }; oneSignal_options['notifyButton'] = { }; oneSignal_options['notifyButton']['enable'] = true; oneSignal_options['notifyButton']['position'] = 'bottom-right'; oneSignal_options['notifyButton']['theme'] = 'default'; oneSignal_options['notifyButton']['size'] = 'medium'; oneSignal_options['notifyButton']['showCredit'] = true; oneSignal_options['notifyButton']['text'] = {}; OneSignal.init(window._oneSignalInitOptions); OneSignal.showSlidedownPrompt(); }); function documentInitOneSignal() { var oneSignal_elements = document.getElementsByClassName("OneSignal-prompt"); var oneSignalLinkClickHandler = function(event) { OneSignal.push(['registerForPushNotifications']); event.preventDefault(); }; for(var i = 0; i < oneSignal_elements.length; i++) oneSignal_elements[i].addEventListener('click', oneSignalLinkClickHandler, false); } if (document.readyState === 'complete') { documentInitOneSignal(); } else { window.addEventListener("load", function(event){ documentInitOneSignal(); }); } </script>  <script> (function(h,o,t,j,a,r){ h.hj=h.hj||function(){(h.hj.q=h.hj.q||[]).push(arguments)}; h._hjSettings={hjid:788234,hjsv:6}; a=o.getElementsByTagName('head')[0]; r=o.createElement('script');r.async=1; r.src=t+h._hjSettings.hjid+j+h._hjSettings.hjsv; a.appendChild(r); })(window,document,'https://static.hotjar.com/c/hotjar-','.js?sv='); /* Hotjar user attributes */ window.hj( 'identify', null, { Language: window.navigator.language, }); </script> <script async src="https://securepubads.g.doubleclick.net/tag/js/gpt.js"></script> <script> "use strict"; /** * Returns the OpenGraph type of this page (as set by Yoast) * * Cannot use `getMetaContent` for this as it uses the "property" attribute * instead of the expected "name". * * @return {string} OpenGraph type */ function getOgType() { let og_type = document.querySelector('meta[property="og:type"]'); return ( og_type && og_type.content ? og_type.content : '' ); } /** * Returns the content attribute of the named <meta> tag * * @param {string} name - Meta name * @return {string} Meta content */ function getMetaContent( name ) { let element = document.querySelector('meta[name="' + name + '"]'); return element ? element.content : ''; } /** * Defines a GA slot only if the slot actually exists * * @param {string} ref - Slot reference * @param {Array} dimensions - Target dimensions * @param {string} slot_id - Element ID * @param {PubAdsService} service - Service to bind to */ function defineIfSlot(ref, dimensions, slot_id, service) { const element = document.getElementById(slot_id); // No ad slot if (!element) return; return googletag.defineSlot(ref, dimensions, slot_id).addService(service); } window.googletag = ( window.googletag || { cmd: [] } ); googletag.cmd.push( function() { const pubads = googletag.pubads(); // Conditionally define slots only if the element actually exists defineIfSlot('/21821800277/pw/pw_r2_ap', [300, 250], 'div-gpt-ad-1567436410454-0', pubads); defineIfSlot('/21821800277/pw/pw_m_ap', [[300,250]], 'div-gpt-ad-3759129-1', pubads); defineIfSlot('/21821800277/pw/pw_x01_gs', [[160,60]], 'div-gpt-ad-3759129-2', pubads); defineIfSlot('/21821800277/pw/pw_x02_gs', [[160,60]], 'div-gpt-ad-3759129-3', pubads); defineIfSlot('/21821800277/pw/pw_x03_gs', [[160,60]], 'div-gpt-ad-3759129-4', pubads); defineIfSlot('/21821800277/pw/pw_x04_gs', [[160,60]], 'div-gpt-ad-3759129-5', pubads); defineIfSlot('/21821800277/pw/pw_x05_gs', [[160,60]], 'div-gpt-ad-3759129-6', pubads); defineIfSlot('/21821800277/pw/pw_x06_gs', [[160,60]], 'div-gpt-ad-3759129-7', pubads); defineIfSlot('/21821800277/pw/pw_r_ap', [300, 250], 'div-gpt-ad-1563268425067-0', pubads); defineIfSlot('/21821800277/pw/pw_r1_ap', [[300,250]], 'div-gpt-ad-3759129-11', pubads); defineIfSlot('/21821800277/pw/pw_x10_ss', [[160,60]], 'div-gpt-ad-3759129-12', pubads); defineIfSlot('/21821800277/pw/pw_x11_ss', [[160,60]], 'div-gpt-ad-3759129-13', pubads); defineIfSlot('/21821800277/pw/pw_x12_ss', [[160,60]], 'div-gpt-ad-3759129-14', pubads); defineIfSlot('/21821800277/pw/pw_x13_ss', [[160,60]], 'div-gpt-ad-3759129-15', pubads); defineIfSlot('/21821800277/pw/pw_x14_ss', [160, 60], 'div-gpt-ad-1563269243507-0', pubads); defineIfSlot('/21821800277/pw/pw_x15_ss', [[160,60]], 'div-gpt-ad-3759129-17', pubads); const leaderboard = googletag.sizeMapping() .addSize([970, 0], [[970, 90], [728, 90]]) // Larger screen ads .addSize([768, 0], [[728, 90]]) // Smaller (laptop) screen ads .addSize([0, 0], [[300, 250], [320, 50]]) // Mobile screen ads .build(); // Homepage & listing ads const t_1 = defineIfSlot('/21821800277/pw/pw_t_hp', [[970,90],[728,90],[729,90],[300,250],[320,50]], 'div-gpt-ad-3759129-18', pubads); const t_2 = defineIfSlot('/21821800277/pw/pw_t1_hp', [[970,90],[728,90],[729,90],[300,250],[320,50]], 'div-gpt-ad-3759129-19', pubads); const t_3 = defineIfSlot('/21821800277/pw/pw_t2_hp', [[970,90],[728,90],[729,90],[300,250],[320,50]], 'div-gpt-ad-3759129-20', pubads); // Only map if they actually exist t_1 && t_1.defineSizeMapping(leaderboard); t_2 && t_2.defineSizeMapping(leaderboard); t_3 && t_3.defineSizeMapping(leaderboard); // Search results const headerSize = googletag.sizeMapping() .addSize([970, 0], [[970, 90]]) .addSize([0, 0], [[320, 50]]) .build() // Header ad (always appears) googletag.defineSlot('/21821800277/pw/pw_h_sw', [[970,90], [320, 50]], 'div-gpt-ad-5400963-20').defineSizeMapping(headerSize).addService(pubads); // Only apply targeting if values exist const article_og = getOgType(); if ( article_og ) { pubads.setTargeting( "articleTag", article_og ); } const article_type = getMetaContent( "oas:article-type" ); if ( article_type ) { pubads.setTargeting( "articleType", article_type ); } const article_category = getMetaContent( "oas:category" ); if ( article_category ) { pubads.setTargeting( "category", article_category ); } const article_sub = getMetaContent( "oas:sub-category" ); if ( article_sub ) { pubads.setTargeting( "subCategory", article_sub ); } pubads.setTargeting( "articleId", "12553" ); // Add class to body if ads are visible pubads.addEventListener( "impressionViewable", function () { document.body.classList.add("has-ads"); }); pubads.enableSingleRequest(); pubads.collapseEmptyDivs(); // Start! googletag.enableServices(); }); </script>  </head> <body class="page-template-default page page-id-12553 page-parent not-logged-in"> <a class="sr-only" href="#main-content">Skip to main content</a>  <noscript aria-hidden="true"> <iframe src="https://www.googletagmanager.com/ns.html?id=GTM-TQRT9K38" height="0" width="0" style="display:none;visibility:hidden" > </iframe> </noscript>  <header class="physics-world-nav"> <span class="mpu align-none" aria-hidden="true"> <div id='div-gpt-ad-5400963-20' class="advert">  <script> googletag.cmd.push(function() { googletag.display('div-gpt-ad-5400963-20'); }); </script> </div> </span> <div class="top-bar"> <div class="top-bar__left"> <a href="https://ioppublishing.org/" class="top-bar__logo" target="_blank" rel="noopener"> <img src="https://physicsworld.com/wp-content/themes/iopp/static/img/iop-publishing-logo-white.png" width="198" height="31" alt="" /> <span class="sr-only">IOP Publishing site</span> </a> </div> <button class="top-bar__menu--mobile"> Menu </button> <div class="top-bar__right"> <div class="top-bar__user"> <ul class="top-bar__links"> <li><button class="sign-in-btn"><span class="top-bar__icon"></span>Sign in</button></li> <li><button class="register-btn">Register</button></li> </ul> </div> </div> </div> <div class="physics-world-nav__wrapper"> <div class="physics-world-nav__left"> <a href="https://physicsworld.com" class="physics-world-nav__logo"> <span class="sr-only">Back to homepage</span> <img src="https://physicsworld.com/wp-content/themes/iopp/static/img/svg/pw-logo-red.svg" alt="IOP Physics World logo" width="217" height="40" /> </a> </div> <div class="physics-world-nav__right"> <nav class="nav-items__wrapper"> <button class="physics-world-nav__dropdown">Topics</button> <div class="topic-dropdown" aria-expanded="false"> <div class="wrapper"> <div class="topic-content-container"> <div><img width="798" height="449" src="https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-1024x576.jpg" class="attachment-large size-large" alt="" decoding="async" fetchpriority="high" srcset="https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-1024x576.jpg 1024w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-211x119.jpg 211w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-317x178.jpg 317w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-768x432.jpg 768w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-711x400.jpg 711w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-732x412.jpg 732w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-720x405.jpg 720w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-635x357.jpg 635w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-350x197.jpg 350w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-257x145.jpg 257w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-300x169.jpg 300w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-160x90.jpg 160w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights-128x72.jpg 128w, https://physicsworld.com/wp-content/uploads/2024/09/KR-centred-abstract-torus-of-lights.jpg 1200w" sizes="(max-width: 798px) 100vw, 798px" /><h2>Browse articles by topic</h2></div> <ul class="topic-dropdown__list"> <li> <a href="https://physicsworld.com/c/astronomy-space/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Astronomy_and_space_164193.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Astronomy and space</span> </a> </li> <li> <a href="https://physicsworld.com/c/atomic-molecular/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Atomic_and_molecular__774E92.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Atomic and molecular</span> </a> </li> <li> <a href="https://physicsworld.com/c/biophysics-bioengineering/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Biophysics_and_bioengineering__05958E-1.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Biophysics and bioengineering</span> </a> </li> <li> <a href="https://physicsworld.com/c/condensed-matter/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Condensed_matter__774E92.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Condensed matter</span> </a> </li> <li> <a href="https://physicsworld.com/c/culture-history-society/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2024/03/Culture.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Culture, history and society</span> </a> </li> <li> <a href="https://physicsworld.com/c/environment-energy/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Environment_and_energy__85AD21-1.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Environment and energy</span> </a> </li> <li> <a href="https://physicsworld.com/c/instrumentation-measurement/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Instrumentation_and_measurement__9D9D9C.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Instrumentation and measurement</span> </a> </li> <li> <a href="https://physicsworld.com/c/materials/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Materials__0085C8.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Materials</span> </a> </li> <li> <a href="https://physicsworld.com/c/mathematics-computation/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Mathematics_and_computation__EC660F.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Mathematics and computation</span> </a> </li> <li> <a href="https://physicsworld.com/c/medical-physics/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Medical_physics__05958.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Medical physics</span> </a> </li> <li> <a href="https://physicsworld.com/c/optics-photonics/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Optics_and_photonics__774E92.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Optics and photonics</span> </a> </li> <li> <a href="https://physicsworld.com/c/particle-nuclear/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Particle_and_nuclear__774E92.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Particle and nuclear</span> </a> </li> <li> <a href="https://physicsworld.com/c/people/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2024/10/People-icon-purple.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">People</span> </a> </li> <li> <a href="https://physicsworld.com/c/quantum/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2017/08/Quantum__774E92.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Quantum</span> </a> </li> <li> <a href="https://physicsworld.com/c/scientific-enterprise/"> <span class="topic-dropdown__icon" style="background-color:;"> <img src="https://physicsworld.com/wp-content/uploads/2024/03/Enterprise-cogs.svg" alt="" loading="lazy" /> </span> <span class="topic-dropdown__title">Scientific enterprise</span> </a> </li> </ul> </div> </div>  </div> <div class='primary-nav'><ul class='menu'><li class='menu-item-has-children'><button class='menu-item-button' aria-expanded='false'>Latest content</button><ul class='sub-menu'><li class='menu-item__featured-content'><div><img width="798" height="394" src="https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-1024x506.jpg" class="attachment-large size-large" alt="" decoding="async" srcset="https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-1024x506.jpg 1024w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-211x104.jpg 211w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-317x157.jpg 317w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-768x380.jpg 768w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-809x400.jpg 809w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-732x362.jpg 732w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-720x356.jpg 720w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-635x314.jpg 635w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-350x173.jpg 350w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-257x127.jpg 257w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-300x148.jpg 300w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-160x79.jpg 160w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB-128x63.jpg 128w, https://physicsworld.com/wp-content/uploads/2023/04/big-data-concept-2055335264-shutterstock_greenbutterfly-WEB.jpg 1200w" sizes="(max-width: 798px) 100vw, 798px" /><h2>Browse articles by content type</h2></div></li><li><h2>Short reads</h2><ul class='sub-menu'><li><a href='https://physicsworld.com/l/research-updates/'>Research updates</a></li><li><a href='https://physicsworld.com/l/news/'>News</a></li><li><a href='https://physicsworld.com/l/blog/'>Blog</a></li><li><a href='https://physicsworld.com/l/innovation-showcases/'>Innovation showcases</a></li><li><a href='https://physicsworld.com/events/'>Events</a></li></ul></li><li><h2>Long reads</h2><ul class='sub-menu'><li><a href='https://physicsworld.com/l/features/'>Features</a></li><li><a href='https://physicsworld.com/l/opinion-reviews/'>Opinion and reviews</a></li><li><a href='https://physicsworld.com/l/interviews/'>Interviews</a></li><li><a href='https://physicsworld.com/l/analysis/'>Analysis</a></li></ul></li><li><h2>Multimedia</h2><ul class='sub-menu'><li><a href='https://physicsworld.com/l/audio/'>Podcasts</a></li><li><a href='https://physicsworld.com/l/videos/'>Video</a></li><li><a href='https://physicsworld.com/l/webinars/'>Webinars</a></li></ul></li></ul></li><li class=''><a href='https://physicsworld.com/p/magazine/archive/'>Magazine</a></li><li class=''><a href='https://physicsworld.com/p/physics-world-live/'>Physics World Live</a></li></ul></div> <a href="https://www.physicsworldjobs.com" target="_blank" class="nav__link-img link-img--pw-jobs"> <span class='screen-reader-text'>IOP Physics World Jobs logo</span> <svg width="121" height="18" fill="none" xmlns="http://www.w3.org/2000/svg"><g clip-path="url(#a)"><path fill-rule="evenodd" clip-rule="evenodd" d="M84.433 9.612V7.308c0-.324-.105-.792-.281-1.08-.352-.864-1.02-1.44-1.97-1.44-1.971 0-2.183 2.52-2.183 4.032 0 1.584.176 4.176 2.288 4.176.492 0 .915-.144 1.302-.468.844-.72.844-1.836.844-2.916Zm1.478 4.428h-1.337V12.6c-.598 1.116-1.443 1.656-2.71 1.656-2.815 0-3.554-2.88-3.554-5.256 0-2.34.775-5.508 3.59-5.508 1.196 0 2.006.504 2.533 1.62V.9h1.478v13.14Z" fill="#9460A4"/><path d="M8.879 8.783c0-2.124-.563-5.22-3.237-5.22-1.197 0-1.725.72-2.288 1.692V3.707H.75V17.53h2.78v-4.248c.528.613 1.091.937 1.936.937 2.815-.037 3.413-3.133 3.413-5.436Zm-2.92-.072c0 .755.034 2.34-.388 2.987-.211.36-.457.468-.88.468-1.302 0-1.196-1.296-1.196-2.268v-2.52c0-.864.211-1.907 1.267-1.907 1.302 0 1.196 2.196 1.196 3.095v.144ZM17.29 14.04V7.164c0-1.908-.211-3.672-2.534-3.672-1.126 0-1.83.324-2.463 1.296V.9H9.478v13.14h2.815V7.488c0-.936.105-1.728 1.196-1.728 1.056 0 .986.792.986 1.692v6.588h2.815ZM25.207 3.709H22.78l-1.302 6.3-1.372-6.3H17.29l2.885 10.152c-.317 1.116-.492 1.476-1.654 1.476a5.65 5.65 0 0 1-.81-.072v2.268c.423.108.81.18 1.197.18 2.288 0 2.71-1.62 3.273-3.492l3.026-10.512ZM32.387 10.872c0-2.016-1.408-2.592-2.992-3.168-.316-.108-.95-.324-1.267-.54-.281-.216-.422-.468-.422-.864 0-.54.352-.9.88-.9.88 0 1.232.648 1.478 1.404l2.006-.612c-.458-1.764-1.654-2.7-3.414-2.7-1.935 0-3.59 1.188-3.59 3.276 0 1.944 1.409 2.7 3.027 3.24.352.108.88.288 1.197.504.317.216.422.468.422.864 0 .684-.528.936-1.09.936-.986 0-1.408-.612-1.62-1.548l-2.217.36c.317 2.196 1.69 3.06 3.801 3.06 2.006.072 3.8-1.08 3.8-3.312ZM35.8 3.709h-2.816v10.332H35.8V3.709ZM35.8.9h-2.816v1.908H35.8V.9ZM44.527 10.188l-2.64-.18c-.035.792-.175 1.908-1.16 1.908-1.373 0-1.338-2.232-1.338-3.168 0-.972.035-3.096 1.408-3.096.95 0 1.055 1.224 1.09 1.944l2.64-.108c-.106-1.224-.211-2.052-1.091-2.952-.774-.792-1.654-1.044-2.71-1.044-3.132 0-4.187 2.52-4.187 5.364 0 2.772.914 5.4 4.047 5.4 2.568 0 3.66-1.584 3.94-4.068ZM52.34 10.872c0-2.016-1.408-2.592-2.992-3.168-.316-.108-.95-.324-1.267-.54-.281-.216-.422-.468-.422-.864 0-.54.352-.9.88-.9.88 0 1.231.648 1.478 1.404l2.006-.612c-.458-1.764-1.654-2.7-3.414-2.7-1.935 0-3.59 1.188-3.59 3.276 0 1.944 1.408 2.7 3.027 3.24.352.108.88.288 1.197.504.316.216.422.468.422.864 0 .684-.528.936-1.09.936-.986 0-1.409-.612-1.62-1.548l-2.217.36c.317 2.196 1.69 3.06 3.8 3.06 2.007.072 3.802-1.08 3.802-3.312Z" class="svg-fill-colour"/><path fill-rule="evenodd" clip-rule="evenodd" d="M63.002 3.709h-1.231l-1.83 7.848-1.865-7.848h-1.091l-1.69 7.74-1.759-7.74h-1.478l2.499 10.332h1.372l1.619-7.272 1.724 7.272h1.267l2.463-10.332ZM70.568 9c0-2.664-.739-5.58-3.87-5.58-3.062 0-3.872 2.844-3.872 5.472 0 2.628.81 5.436 3.836 5.436 3.027 0 3.906-2.7 3.906-5.328Zm-1.654-.108c0 1.476-.21 4.14-2.217 4.14-2.005 0-2.217-2.664-2.217-4.176s.247-4.14 2.217-4.14c2.006 0 2.217 2.664 2.217 4.176ZM75.495 5.184V3.456c-.106-.036-.211-.036-.352-.036-.563 0-1.055.288-1.443.612-.598.54-.809 1.08-1.09 1.836v-2.16h-1.338V14.04h1.513V8.712c0-1.584.458-3.564 2.358-3.564.07 0 .246 0 .352.036Z" fill="#9460A4"/><path d="M77.712.9h-1.513v13.14h1.513V.9Z" fill="#9460A4"/><path d="M89.395.9h-.352v15.948h.352V.9ZM92.844 16.848c-.422 0-.774-.072-1.161-.18v-1.26c.351.108.668.18 1.02.18 1.161 0 1.161-.828 1.161-1.764V3.924h1.478v9c.036 1.944 0 3.924-2.498 3.924ZM93.829 2.7V.9h1.619v1.8h-1.619ZM100.339 14.545c-3.026 0-3.836-2.808-3.836-5.436s.81-5.472 3.871-5.472c3.132 0 3.871 2.88 3.871 5.58-.035 2.592-.915 5.328-3.906 5.328Zm0-9.612c-1.97 0-2.217 2.628-2.217 4.14 0 1.512.211 4.176 2.217 4.176 1.971 0 2.217-2.664 2.217-4.14 0-1.512-.211-4.176-2.217-4.176ZM108.926 14.473c-1.372 0-1.935-.432-2.569-1.656-.14.468-.246.972-.387 1.44h-.774V.29h1.478v5.004c.633-1.008 1.337-1.584 2.569-1.584 2.815 0 3.519 2.988 3.519 5.328 0 2.628-.809 5.436-3.836 5.436Zm.035-9.468c-1.654 0-2.252 1.836-2.252 3.276v1.584c0 1.584.317 3.348 2.217 3.348 2.112 0 2.182-2.628 2.182-4.212 0-1.62-.07-3.996-2.147-3.996ZM116.739 14.544c-2.006 0-3.203-.936-3.625-2.952l1.408-.324c.281 1.332.985 1.98 2.322 1.98.986 0 2.041-.54 2.041-1.692 0-1.872-3.237-1.728-4.504-2.88a2.592 2.592 0 0 1-.845-1.908c0-1.872 1.549-3.096 3.308-3.096.915 0 1.795.324 2.428 1.008.423.468.563.972.739 1.62l-1.302.324c-.316-.972-.879-1.656-1.97-1.656-.915 0-1.725.576-1.725 1.584 0 .828.599 1.224 1.302 1.476 1.725.54 4.118 1.008 4.118 3.384-.036 2.052-1.83 3.132-3.695 3.132Z" class="svg-fill-colour"/></g><defs><clipPath id="a"><path fill="#fff" transform="translate(.75)" d="M0 0h120v18H0z"/></clipPath></defs></svg> </a> </nav> <button class="physics-world-nav__search-btn"> <i class="fa fa-search" aria-hidden="true"></i> Search<span class="sr-only">Open Search Dialog</span> </button> </div> </div> <div class="homepage-search" aria-expanded="false"> <form action="https://physicsworld.com"> <label for="input-home-search">Search by content type, topic, person, research area and more</label> <div class="homepage-search__form-container"> <input id="input-home-search" type="search" name="s" placeholder="Search..." value="" /> <button type="submit"> <i class="fa fa-search" aria-hidden="true"></i>Search<span class="sr-only">Submit search</span> </button> </div> </form> </div> <div class="other-sites"> <ul class="items"> <li> <a href="https://ioppublishing.org" target="_blank" rel="noopener"> IOP Publishing </a> </li> </ul> <ul class="top-bar__social"> <li> <a href="https://www.facebook.com/physicsworld/" target="_blank" rel="noreferrer"> <i class="fa fa-facebook" aria-hidden="true"></i> <span class="sr-only">Follow us on Facebook</span> </a> </li> <li> <a href="https://twitter.com/PhysicsWorld" target="_blank" rel="noreferrer"> <i class="fa fa-twitter" aria-hidden="true"></i> <span class="sr-only">Follow us on Twitter</span> </a> </li> <li> <a href="https://www.linkedin.com/company/physics-world" target="_blank" rel="noreferrer"> <i class="fa fa-linkedin" aria-hidden="true"></i> <span class="sr-only">Follow us on LinkedIn</span> </a> </li> <li> <a href="https://www.youtube.com/PhysicsWorldTV" target="_blank" rel="noreferrer"> <i class="fa fa-youtube-play" aria-hidden="true"></i> <span class="sr-only">Watch us on Youtube</span> </a> </li> <li> <a href="https://physicsworld.com/feed" target="_blank" rel="noreferrer"> <i class="fa fa-rss" aria-hidden="true"></i> <span class="sr-only">RSS Feed</span> </a> </li> </ul> <ul class="items"> <li> <a href="https://www.physicsworldjobs.com/" target="_blank" rel="noopener"> Jobs </a> </li> </ul> </div> </header> <div class="popup sign-in"> <div class="popup__tabs"> <button class="popup__tab popup__tab--active popup__tab-sign-in" data-tab="0">Sign in</button> <button class="popup__tab popup__tab-register" data-tab="1">Register</button> <button class="fa fa-times-circle btn--close popup__close"></button> </div> <div class="popup__content"> <div class="sign-in__content popup__row popup__row--active ajax_container"> <form action="#" method="POST" data-ajax="login" class="login-form ajax__content" data-dest=".sign-in__content" data-keep="1"> <div class="flex flex--rows popup__row__content"> <div class="popup__col"> <input type="hidden" name="redirect" value="https://physicsworld.com/p/our-portfolio"> <input type="hidden" name="page" value="https://physicsworld.com/p/our-portfolio"> <ul class="sign-in__inputs"> <li> <label for="input-signin-email">Enter e-mail address</label> <input id="input-signin-email" type="email" name="user-email" required oninvalid="this.setCustomValidity('Please enter a valid e-mail address')" oninput="this.setCustomValidity('')"/> </li> <li class="password-input"> <label for="input-signin-password">Enter password</label> <input type="password" name="user-password" id="input-signin-password" class="password-field" required oninvalid="this.setCustomValidity('Please enter a password')" oninput="this.setCustomValidity('')"/> <input type="checkbox" name="password" id="show-pw" /> <label for="show-pw" class="password-label">Show</label> </li> <li> <div> <input type="checkbox" name="remember-me" id="form-checkbox" class="form-checkbox" /> <label for="form-checkbox"><span></span>Remember me</label> </div> <div> <a href="#" class="forgot-btn">Forgot your password?</a> </div> </li> </ul> <aside class="register__benefits"> <strong>Are you an IOP member?</strong> <p>Sign into your <em>Physics World</em> account to get access to all available digital issues of the monthly magazine. Your <em>Physics World</em> account is separate to any IOP accounts you may have</p> </aside> </div> <div class="popup__col"> <div class="field__attempts"> <strong>Sign in to</strong> <ul> <li>Access more than 20 years of online content</li> <li>Manage which e-mail newsletters you want to receive</li> <li>Read about the big breakthroughs and innovations across 13 scientific topics</li> <li>Explore the key issues and trends within the global scientific community</li> </ul> </div> </div> </div> <div class="popup__actions"> <input type="submit" value="Sign in" class="btn btn--green" /> </div> </form> </div> <div class="register__form popup__row"> <form action="/" class="form-register ajax__content " method="POST" data-ajax="register" data-dest=".register__form" data-keep="1"> <div class="flex flex--rows popup__row__content"> <ul class="register__email gutter "> <li class="col-xs-12 col-sm-6"> <label for="input-register-email">Enter e-mail address</label> <input id="input-register-email" type="email" name="user-email" required oninvalid="this.setCustomValidity('Please enter a valid e-mail address')" oninput="this.setCustomValidity('')"/> <div class="tooltip"> <span class="fa fa-question-circle"></span> <span class="tooltip__content">This e-mail address will be used to create your account</span> </div> <aside class="register__benefits"> <strong>Are you an IOP member?</strong> <p>Create a <em>Physics World</em> account to get access to all available digital issues of the monthly magazine. Your <em>Physics World</em> account is separate to any IOP accounts you may have.</p> <p><strong>Note:</strong> The verification e-mail to complete your account registration should arrive immediately. However, in some cases it takes longer. Don't forget to check your spam folder.</p> <p>If you haven't received the e-mail in 24 hours, please contact <a href="mailto:customerservices@ioppublishing.org">customerservices@ioppublishing.org</a>.</p> </aside> </li> <li class="register__info col-xs-12 col-sm-6"> <strong>Registration is free, quick and easy</strong> <br /> <ul> <li>Access more than 20 years of online content</li> <li>Choose which e-mail newsletters you want to receive</li> <li>Read about the big breakthroughs and innovations across 13 scientific topics</li> <li>Explore the key issues and trends within the global scientific community</li> </ul> </li> </ul> </div> <div class="popup__actions"> <input type="submit" value="Register" class="btn btn--green" /> </div> </form> </div> </div> </div> <div class="popup forgot-password "> <div class="popup__tabs"> <h4 class="popup__tab popup__tab--full">Reset your password</h4> <i class="fa fa-times-circle btn--close popup__close"></i> </div> <div class="popup__content forgot-parent ajax__container"> <form class="popup__row popup__row--active ajax__content forgot-form " action="/" method="POST" data-ajax="forgot" data-dest=".forgot-parent" data-keep="1"> <div class="popup__row__content"> <p>Please enter the e-mail address you used to register to reset your password</p> <p><strong>Note:</strong> The verification e-mail to change your password should arrive immediately. However, in some cases it takes longer. Don't forget to check your spam folder.</p> <p>If you haven't received the e-mail in 24 hours, please contact <a href="mailto:customerservices@ioppublishing.org">customerservices@ioppublishing.org</a></p> <label for="input-ajax-forgotten-email">Enter e-mail address</label> <input id="input-ajax-forgotten-email" type="email" name="user-email" required oninvalid="this.setCustomValidity('Please enter a valid e-mail address')" oninput="this.setCustomValidity('')"/> </div> <div class="popup__actions"> <input type="submit" value="Reset my password" class="btn btn--green" /> </div> </form> <div class="ajax__content forgot__message popup__row--active"> </div> </div> </div> <div class="popup popup-message autoclose "> <div class="popup__tabs"> <h4 class="popup__tab popup__tab--full">Registration complete</h4> <i class="fa fa-times-circle btn--close popup__close"></i> </div> <div class="popup__content ajax__container"> <div class="popup__row__content"> <p><strong>Thank you for registering with <em>Physics World</em></strong><br /> If you'd like to change your details at any time, please visit My account</p> </div> <div class="popup__actions"> <a class="btn btn--green" href="/">Close</a> </div> </div> </div>  <div class="overlay "></div> <main class="site-window" id="main-content"> <div class="type-bar type-bar--noicon"> <h1 class="type-bar__heading"> Our portfolio </h1> </div> <div class="m39 wrapper"> </div> <div class="hero-top-banner"> <img width="1171" height="400" src="/wp-content/uploads/2021/10/PW-devices_web.jpg" class="attachment-hero size-hero" alt="PW portfolio" > </div> <div></div> <div class="m39 wrapper"> <section class="headline-v2"> <div class="row"> <div class="col-md-12"> <div class="section-breaks"> <!><div class="headline-intro"></!> <h1>Explore the world's leading physics magazine</h1> <h3><i>Physics World</i> is the world's leading physics magazine. Every month it is sent to all members of the <a href="http://www.iop.org/">Institute of Physics</a>, a leading scientific society that works to advance physics for the benefit of all.</h3> <h3>Each issue of <i>Physics World</i> covers the big stories and key issues that matter to scientists in all parts of the world, including features from acclaimed physicists and science writers, comprehensive news and analysis, and incisive opinion pieces. Every month you鈥檒l also find valuable careers advice, reviews of the best new books, and updates on the latest research breakthroughs and physics-based technologies.</h3> <h3><i>Physics World</i> has been highly commended at the <a href="https://www.onlinemediaawards.net/online-media-awards/the-drum-online-media-awards-2019#95201">The Drum Online Media Awards</a> in the category of "Specialist News Site". It also received an honourable mention at the <a href="https://www.foliomag.com/go/2019-eddie-and-ozzie-awards/">2019 Eddie & Ozzie Awards</a>.</h3> </div> </div> </section> </br></div> <div class="m39 wrapper"> <style> .headline-v2 .section-breaks h3 { padding: 0; margin:10px 0 15px 0; } .headline-v2 .section-breaks img { margin: 10px 0 ; } h1 { font-family: "franklin-gothic-urw-cond",Arial,"Helvetica Neue",Helvetica,sans-serif; margin: 20px 0 0 0; } </style></div> <div class="m39 wrapper"> <section class="headline-v2"> <div class="row"> <div class="col-md-12"> <div class="section-breaks"> <h3>Subscribe to <i>Physics World</i></h3> <h3><em>Physics World</em> is published once a month in print and as a digital edition exclusively for members of the Institute of Physics. To receive a copy and gain access, you'll need to <a href="https://membership.iop.org/">become an IOP member</a>.</h3> <h3><em>Physics World</em> is now available in an easy-to-use, digital format. Find out more at <a href="https://physicsworld.com/magazine">physicsworld.com/magazine</a>.</h3> <h3> Subscriptions are also available for libraries, companies and institutions. To order or enquire about these, e-mail <a href="mailto:customerservices@ioppublishing.org">customerservices@ioppublishing.org</a>. </h3> </div> </section> </br></div> <div class="m39 wrapper"> <section class="headline-v2"> <div class="row"> <div class="col-md-12"> <div class="section-breaks"> <h3><i>Physics World Jobs</i></h3> <h3><a href="https://www.physicsworldjobs.com/"><i>Physics World Jobs</i></a> is the latest addition to the <i>Physics World</i> portfolio, building on our extensive coverage of careers over the past 20 years. Whether you鈥檙e still working out your career pathway or have a specific role in mind, we鈥檙e here to help. Bringing you a diverse range of opportunities for all career stages, we鈥檒l help you take the next step and find your perfect job.</h3> </div> </div> </section> </br></div> <div class="m33 wrapper m33-c"> <div class="row"> <div class="col-md-3"> <div class="section-breaks"> <h2 class="section-breaks__heading">Physics World Careers</h2> </div> <div class="content-block"> <p>Produced in conjunction with <a href="https://www.physicsworldjobs.com/"><em>Physics World Jobs</em></a>, this annual guide showcases the diverse range of career opportunities available to physics graduates. In addition to comprehensive profiles of leading employers, <a href="https://physicsworld.com/p/magazine/archive/physics-world-careers-2024/#PWCareers24_1"><em>Physics World Careers</em></a> includes insightful case studies and sound careers advice to help early-career scientists make informed choices about their future.</p> </div> </div> <div class="col-md-3"> <div class="section-breaks"> <h2 class="section-breaks__heading">Physics World Briefings</h2> </div> <div class="content-block"> <p><em>Physics World Briefings</em> are the subject-focused supplements to <em>Physics World</em>. Each issue contains key research updates, interviews with leading figures and in-depth features focusing on a specific topic in physics.</p> </div> </div> <div class="col-md-3"> <div class="section-breaks"> <h2 class="section-breaks__heading">Physics World Newsletters</h2> </div> <div class="content-block"> <p>We publish a range of newsletters to help you stay up to date with the latest news from <em>Physics World</em>. Covering a variety of subjects, they bring you the latest news straight to your inbox. You can manage your newsletter subscriptions within <a href="https://physicsworld.com/p/account/">your account</a>.</p> </div> </div> <div class="col-md-3"> <div class="section-breaks"> <h2 class="section-breaks__heading">Physics World Discovery</h2> </div> <div class="content-block"> <p>This series of short-form ebooks, written by leading voices from across the scientific community, offers expert insights into some of the hottest topics in physics. The <a href="http://iopscience.iop.org/bookListInfo/physicsworld-discovery">Physics World Discovery</a> collection is an ideal starting point for anyone seeking to understand these fast-moving fields.</p> </div> </div> </div> </div> <div class="printer-only push-me">Copyright © 2024 by IOP Publishing Ltd and individual contributors</div> </main> <footer class="footer hide-for-printer"> <div class="wrapper"> <div class="row"> <div class="footer__container"> <div class="pw__info footer__grid-col--1"> <img src="https://physicsworld.com/wp-content/themes/iopp/src/svg/pw-logo-white-red-text.svg" alt="Physics World logo" width="228px" height="42px"> <ul class="footer__social"> <li> <a href="https://www.facebook.com/physicsworld/" target="_blank" rel="noreferrer" alt="Follow us on Facebook"> <i class="fa fa-facebook" aria-hidden="true"></i> <span class="sr-only">Follow us on Facebook</span> </a> </li> <li> <a href="https://twitter.com/PhysicsWorld" target="_blank" rel="noreferrer" alt="Follow us on X"> <svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" shape-rendering="geometricPrecision" text-rendering="geometricPrecision" image-rendering="optimizeQuality" fill-rule="evenodd" clip-rule="evenodd" viewBox="0 0 512 462.799"><path fill-rule="nonzero" fill="currentColor" d="M403.229 0h78.506L310.219 196.04 512 462.799H354.002L230.261 301.007 88.669 462.799h-78.56l183.455-209.683L0 0h161.999l111.856 147.88L403.229 0zm-27.556 415.805h43.505L138.363 44.527h-46.68l283.99 371.278z"/></svg> <span class="sr-only">Follow us on X</span> </a> </li> <li> <a href="https://www.linkedin.com/company/physics-world" target="_blank" rel="noreferrer" alt="Follow us on LinkedIn"> <i class="fa fa-linkedin" aria-hidden="true"></i> <span class="sr-only">Follow us on LinkedIn</span> </a> </li> <li> <a href="https://www.youtube.com/PhysicsWorldTV" target="_blank" rel="noreferrer" alt="Watch us on Youtube"> <i class="fa fa-youtube-play" aria-hidden="true"></i> <span class="sr-only">Watch us on Youtube</span> </a> </li> <li> <a href="https://physicsworld.com/feed" target="_blank" rel="noreferrer" alt="RSS Feed"> <i class="fa fa-rss" aria-hidden="true"></i> <span class="sr-only">RSS Feed</span> </a> </li> </ul> <a href="https://physicsworld.com/account/sign-in/" class="btn btn--sign-in">Sign in</a> <a href="https://physicsworld.com/account/register/" class="btn">Register</a> </div> <div class="col__border-top footer__grid-col--2"> <h4 class="footer__heading">Our mission</h4> <p><i>Physics World</i> represents a key part of IOP Publishing’s mission to communicate world-class research and innovation to the widest possible audience. The website forms part of the <a href="https://physicsworld.com/p/our-portfolio/"><i>Physics World</i> portfolio</a>, a collection of online, digital and print information services for the global scientific community.</p> <div class="footer__podcasts"> <h4 class="footer__heading">Podcasts</h4> <a href="https://blubrry.com/physicsworldweeklypodcast/" class="footer__podcast" target="_blank" > <img width="150" height="150" src="https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1.jpg" class="attachment-profile_150 size-profile_150" alt="" decoding="async" loading="lazy" srcset="https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1.jpg 1500w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-317x317.jpg 317w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-211x211.jpg 211w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-768x768.jpg 768w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-1024x1024.jpg 1024w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-400x400.jpg 400w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-410x410.jpg 410w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-635x635.jpg 635w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-197x197.jpg 197w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-250x250.jpg 250w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-90x90.jpg 90w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-193x193.jpg 193w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-128x128.jpg 128w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-196x196.jpg 196w, https://physicsworld.com/wp-content/uploads/2018/05/PW-Podcast-WEEKLY-comp-1-412x412.jpg 412w" sizes="(max-width: 150px) 100vw, 150px" /> <div class="podcast-details"> <h4>Physics World Weekly</h4> </div> </a> <a href="https://blubrry.com/physics_world_science_podcast/" class="footer__podcast" target="_blank" > <img width="150" height="150" src="https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-150x150.jpg" class="attachment-profile_150 size-profile_150" alt="Physics World Stories podcast logo" decoding="async" loading="lazy" srcset="https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-150x150.jpg 150w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-211x211.jpg 211w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-1024x1024.jpg 1024w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-317x317.jpg 317w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-768x768.jpg 768w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-1536x1536.jpg 1536w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-400x400.jpg 400w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-410x410.jpg 410w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-635x635.jpg 635w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-197x197.jpg 197w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-250x250.jpg 250w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-90x90.jpg 90w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-193x193.jpg 193w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-128x128.jpg 128w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-196x196.jpg 196w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-412x412.jpg 412w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-24x24.jpg 24w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-48x48.jpg 48w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-96x96.jpg 96w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized-300x300.jpg 300w, https://physicsworld.com/wp-content/uploads/2021/01/PW-podcast-logo-STORIES-resized.jpg 2000w" sizes="(max-width: 150px) 100vw, 150px" /> <div class="podcast-details"> <h4>Physics World Stories</h4> </div> </a> </div> </div> <div class="col__border-top footer__grid-col--3"> <h4 class="footer__heading">Explore</h4> <div class="menu-footer-1-container"><ul id="menu-footer-1" class="menu"><li id="menu-item-65637" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-65637"><a href="https://physicsworld.com/p/about-us/">About us</a></li> <li id="menu-item-65638" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-65638"><a href="https://physicsworld.com/p/our-team/">Our team</a></li> <li id="menu-item-65639" class="menu-item menu-item-type-post_type menu-item-object-page current-menu-item page_item page-item-12553 current_page_item menu-item-65639"><a href="https://physicsworld.com/p/our-portfolio/" aria-current="page">Our portfolio</a></li> <li id="menu-item-65640" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-65640"><a href="https://physicsworld.com/p/advertising/">Advertising</a></li> <li id="menu-item-67467" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-67467"><a href="https://physicsworld.com/p/contact-us/">Contact us</a></li> <li id="menu-item-67496" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-67496"><a rel="noreferrer" href="mailto:pwld@ioppublishing.org">Feedback</a></li> </ul></div> </div> <div class="col__border-top footer__grid-col--4"> <h4 class="footer__heading">More information</h4> <div class="menu-footer-2-container"><ul id="menu-footer-2" class="menu"><li id="menu-item-65641" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-65641"><a rel="noreferrer" href="http://www.iop.org/">Institute of Physics</a></li> <li id="menu-item-67295" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-67295"><a rel="noreferrer" href="https://membership.iop.org/">Join the Institute</a></li> <li id="menu-item-66155" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-66155"><a rel="noreferrer" href="https://www.iop.org/slavery-and-human-trafficking-statement-financial-year-ending-31-december-2020">Modern Slavery Act</a></li> <li id="menu-item-66151" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-66151"><a rel="noreferrer" href="https://physicsworld.com/p/cookies-privacy-policy/">Privacy and cookies</a></li> <li id="menu-item-65642" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-65642"><a rel="noreferrer" href="http://ioppublishing.org/">IOP Publishing</a></li> <li id="menu-item-66154" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-66154"><a rel="noreferrer" href="http://ioppublishing.org/copyright/">Copyright</a></li> <li id="menu-item-66153" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-66153"><a rel="noreferrer" href="http://ioppublishing.org/legal-statements/terms-conditions/">Terms and conditions</a></li> <li id="menu-item-66152" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-66152"><a rel="noreferrer" href="http://ioppublishing.org/legal-statements/disclaimer/">Disclaimer</a></li> </ul></div> </div> </div> </div> </div> <button class="back-to-top">Back to top</button> </footer> <script id="js-onesignal-ga"> "use strict"; window.OneSignal = window.OneSignal || []; // In some browsers the console might be undefined const log = function (message) { console && console.log(message); }; const callback = function (payload) { log("OneSignal notification opened!"); OneSignal.getUserId(function (user_id) { ga("send", { hitType: "event", eventCategory: 'OSNotification', eventAction: 'u_id ' + user_id, eventLabel: 'n_id ' + payload.id }); }); // Allow future opens to also trigger the callback OneSignal.addListenerForNotificationOpened(callback); }; // Defer function until OneSignal has finished loading OneSignal.push(function () { log("OneSignal loaded!"); // Listen for notification opened OneSignal.addListenerForNotificationOpened(callback); }); </script> <script src="https://physicsworld.com/wp-content/plugins/leaky-paywall/js/micromodal.min.js?ver=4.21.5" id="zeen101_micromodal-js"></script> <script id="leaky_paywall_validate-js-extra"> var leaky_paywall_validate_ajax = {"ajaxurl":"\/wp-admin\/admin-ajax.php","register_nonce":"6496f7d95c","password_text":"Passwords do not match."}; </script> <script src="https://physicsworld.com/wp-content/plugins/leaky-paywall/js/leaky-paywall-validate.js?ver=4.21.5" id="leaky_paywall_validate-js"></script> <script id="leaky_paywall_script-js-extra"> var leaky_paywall_script_ajax = {"ajaxurl":"\/wp-admin\/admin-ajax.php","stripe_pk":""}; </script> <script src="https://physicsworld.com/wp-content/plugins/leaky-paywall/js/script.js?ver=4.21.5" id="leaky_paywall_script-js"></script> <script id="nine3-script-js-extra"> var nine3 = {"ajaxurl":"https:\/\/physicsworld.com\/wp-admin\/admin-ajax.php","nonce":"4273a4095f","marker":"https:\/\/physicsworld.com\/wp-content\/themes\/iopp\/images\/marker.png","debug":""}; </script> <script src="https://physicsworld.com/wp-content/themes/iopp/dist/js/main.d7213e1c73d0b06f3b57caecb7409889.js?ver=6.6.1" id="nine3-script-js"></script> <script src="https://physicsworld.com/wp-content/themes/iopp/static/js/sticky.min.js?ver=1645453936640" id="stickykit-js"></script> <script src="https://cdn.jsdelivr.net/gh/mathjax/MathJax@2.7.1/MathJax.js?config=MML_CHTML&ver=1645453936640" id="mathjax-js"></script> <script src="https://cdn.onesignal.com/sdks/OneSignalSDK.js?ver=1.0.0" id="remote_sdk-js" async data-wp-strategy="async"></script> </body> </html>