Help | Physics Forums: Science Discussion, Homework Help, Articles

<!DOCTYPE html> <html id="XF" lang="en-US" dir="LTR" data-app="public" data-template="help_index" data-container-key="" data-content-key="" data-logged-in="false" data-cookie-prefix="xf_" data-csrf="1732515794,65f7f6a919b2fbfd51fb3f88725f1509" class="has-no-js template-help_index XenBase layout-default style-light sidebar-right xb-toggle-default xb-sidebar-show" > <head>  <script async src="https://www.googletagmanager.com/gtag/js?id=UA-2209856-4"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'UA-2209856-4'); </script> <meta charset="utf-8" /> <meta http-equiv="X-UA-Compatible" content="IE=Edge" /> <meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover"> <title>Help | Physics Forums: Science Discussion, Homework Help, Articles</title> <link rel="manifest" href="/webmanifest.php"> <meta name="theme-color" content="#466288" /> <meta name="apple-mobile-web-app-title" content="Physics Forums"> <link rel="apple-touch-icon" href="https://www.physicsforums.com/misc/PhysicsForums_logo_192.png"> <link rel="canonical" href="https://www.physicsforums.com/help/" /> <meta property="og:site_name" content="Physics Forums: Science Discussion, Homework Help, Articles" /> <meta property="og:type" content="website" /> <meta property="og:title" content="Help" /> <meta property="twitter:title" content="Help" /> <meta property="og:url" content="https://www.physicsforums.com/help/" /> <meta property="og:image" content="https://www.physicsforums.com/styles/physicsforums/images/physics-forums-logo-og.png" /> <meta property="twitter:image" content="https://www.physicsforums.com/styles/physicsforums/images/physics-forums-logo-og.png" /> <meta property="twitter:card" content="summary" /> <link rel="preload" href="/styles/fonts/fa/fa-light-300-min.woff2?_v=5.15.3.1679232723" as="font" type="font/woff2" crossorigin="anonymous" /> <link rel="stylesheet" href="/css.php?css=public%3Anormalize.css%2Cpublic%3Afa.css%2Cpublic%3Acore.less%2Cpublic%3Aapp.less&s=12&l=1&d=1728569821&k=9d0860d3ac6d1d035719345d5207661b971a33e3" /> <link rel="stylesheet" href="/css.php?css=public%3Athxpress_xf.less%2Cpublic%3Axb.less%2Cpublic%3Aextra.less&s=12&l=1&d=1728569821&k=5fe54ebe3f9839d8b4ffc65201f4addd159ab5ed" /> <script src="/js/xf/preamble.min.js?_v=637e8561"></script> <link rel="icon" type="image/png" href="https://www.physicsforums.com/favicon.ico" sizes="32x32" /> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-6580726045122001" crossorigin="anonymous"></script> <meta name="theme-color" content="#0275b4"> </head> <body data-template="help_index" class=" "> <div class="p-pageWrapper" id="top"> <div class="p-pageWrapper--helper"></div> <div class="xb-page-wrapper xb-canvas-menuActive"> <div class="xb-page-wrapper--helper"></div> <div class="xb-content-wrapper"> <div class="navigation-helper"></div> <div class="p-navSticky p-navSticky--primary" data-xf-init="sticky-header"> <div class="p-nav--wrapper"> <nav class="p-nav"> <div class="p-nav-inner"> <button type="button" class="button--plain p-nav-menuTrigger button" data-xf-click="off-canvas" data-menu=".js-headerOffCanvasMenu" tabindex="0" aria-label="Menu"><span class="button-text"> <i aria-hidden="true"></i> </span></button> <div class="p-nav-smallLogo"> <a href="/"> <img src="https://www.physicsforums.com/styles/physicsforums/xenforo/logo.png" srcset="" alt="Physics Forums: Science Discussion, Homework Help, Articles" width="274" height="51" /> <img src="https://www.physicsforums.com/styles/physicsforums/xenforo/logosmall.png" width="52" height="50" alt="Physics Forums: Science Discussion, Homework Help, Articles" class="logo-mobile" /> </a> </div> <div class="p-nav-scroller hScroller" data-xf-init="h-scroller" data-auto-scroll=".p-navEl.is-selected"> <div class="hScroller-scroll"> <ul class="p-nav-list js-offCanvasNavSource"> <li class="navthxlink_1"> <div class="p-navEl " data-has-children="true"> <a href="https://www.physicsforums.com/insights/" class="p-navEl-link p-navEl-link--splitMenu " data-nav-id="thxlink_1">Insights Blog</a> <a data-xf-key="1" data-xf-click="menu" data-menu-pos-ref="< .p-navEl" class="p-navEl-splitTrigger" role="button" tabindex="0" aria-label="Toggle expanded" aria-expanded="false" aria-haspopup="true"></a> <div class="menu menu--structural" data-menu="menu" aria-hidden="true"> <div class="menu-content"> <a href="https://www.physicsforums.com/insights/postindex/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="toc">-- Browse All Articles --</a> <a href="https://www.physicsforums.com/insights/science-math-articles/physics-articles/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="physarticles">Physics Articles</a> <a href="https://www.physicsforums.com/insights/science-math-tutorials/physics-tutorials/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="phystuts">Physics Tutorials</a> <a href="https://www.physicsforums.com/insights/science-math-guides/physics-guides/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="physguides">Physics Guides</a> <a href="https://www.physicsforums.com/insights/science-math-faqs/physics-faqs/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="physfaq">Physics FAQ</a> <a href="https://www.physicsforums.com/insights/science-math-articles/math-articles/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="mathart">Math Articles</a> <a href="https://www.physicsforums.com/insights/science-math-tutorials/math-tutorials/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="mathtuts">Math Tutorials</a> <a href="https://www.physicsforums.com/insights/science-math-guides/math-guides/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="mathguide">Math Guides</a> <a href="https://www.physicsforums.com/insights/science-math-faqs/math-faqs/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="mathfaq">Math FAQ</a> <a href="https://www.physicsforums.com/insights/science-math-articles/education-articles/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="eduart">Education Articles</a> <a href="https://www.physicsforums.com/insights/science-math-guides/education-guides/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="eduguide">Education Guides</a> <a href="https://www.physicsforums.com/insights/science-math-articles/biology-chemistry-articles/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="biochemart">Bio/Chem Articles</a> <a href="https://www.physicsforums.com/insights/science-math-guides/technology-guides/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="techguides">Technology Guides</a> <a href="https://www.physicsforums.com/insights/science-math-tutorials/computer-science-tutorials/" class="menu-linkRow u-indentDepth0 js-offCanvasCopy " data-nav-id="compscitut">Computer Science Tutorials</a> </div> </div> </div> </li> <li class="navforums"> <div class="p-navEl " > <a href="https://www.physicsforums.com/" class="p-navEl-link " data-xf-key="2" data-nav-id="forums">Forums</a> </div> </li> <li class="navhotthreads1"> <div class="p-navEl " > <a href="https://www.physicsforums.com/whats-new/hot-threads" class="p-navEl-link " data-xf-key="3" data-nav-id="hotthreads1">Trending</a> </div> </li> <li class="navfeaturedthreads1"> <div class="p-navEl " > <a href="https://www.physicsforums.com/threads/featured" class="p-navEl-link " data-xf-key="4" data-nav-id="featuredthreads1">Featured Threads</a> </div> </li> </ul> </div> </div> <div class="p-nav-opposite"> <div class="p-navgroup p-account p-navgroup--guest"> <a href="/login/" class="p-navgroup-link p-navgroup-link--textual p-navgroup-link--logIn" data-xf-click="overlay" data-follow-redirects="on"> <span class="p-navgroup-linkText">Log in</span> </a> <a href="/login/register" class="p-navgroup-link p-navgroup-link--textual p-navgroup-link--register" data-xf-click="overlay" data-follow-redirects="on"> <span class="p-navgroup-linkText">Register</span> </a> </div> <div class="p-navgroup p-discovery"> <a href="/whats-new/" class="p-navgroup-link p-navgroup-link--iconic p-navgroup-link--whatsnew" aria-label="What's new" title="What's new"> <i aria-hidden="true"></i> <span class="p-navgroup-linkText">What's new</span> </a> <a href="/search/" class="p-navgroup-link p-navgroup-link--iconic p-navgroup-link--search" data-xf-click="menu" data-xf-key="/" aria-label="Search" aria-expanded="false" aria-haspopup="true" title="Search"> <i aria-hidden="true"></i> <span class="p-navgroup-linkText">Search</span> </a> <div class="menu menu--structural menu--wide" data-menu="menu" aria-hidden="true"> <form action="/search/search" method="post" class="menu-content" data-xf-init="quick-search"> <h3 class="menu-header">Search</h3> <div class="menu-row"> <a href="https://www.google.com/search?q=physics+forums" rel='nofollow,noreferrer'><b>Google search</b></a>: add "Physics Forums" to query<br><br> <input type="text" class="input" name="keywords" placeholder="Search…" aria-label="Search" data-menu-autofocus="true" /> </div> <div class="menu-row"> <label class="iconic"><input type="checkbox" name="c[title_only]" value="1" /><i aria-hidden="true"></i><span class="iconic-label">Search titles only <span tabindex="0" role="button" data-xf-init="tooltip" data-trigger="hover focus click" title="Tags will also be searched in content where tags are supported"> <i class="fa--xf far fa-question-circle u-muted u-smaller" aria-hidden="true"></i> </span></span></label> </div> <div class="menu-row"> <div class="inputGroup"> <span class="inputGroup-text" id="ctrl_search_menu_by_member">By:</span> <input type="text" class="input" name="c[users]" data-xf-init="auto-complete" placeholder="Member" aria-labelledby="ctrl_search_menu_by_member" /> </div> </div> <div class="menu-footer"> <span class="menu-footer-controls"> <button type="submit" class="button--primary button button--icon button--icon--search"><span class="button-text">Search</span></button> <a href="/search/" class="button"><span class="button-text">Advanced search…</span></a> </span> </div> <input type="hidden" name="_xfToken" value="1732515794,65f7f6a919b2fbfd51fb3f88725f1509" /> </form> </div> </div> </div> </div> </nav> </div> </div> <div class="p-sectionLinks--wrapper"> <div class="p-sectionLinks"> <div class="p-sectionLinks-inner"> <div class="hScroller" data-xf-init="h-scroller"> <div class="hScroller-scroll"> <ul class="p-sectionLinks-list"> <li> <div class="p-navEl " > <a href="/whats-new/latest-activity" class="p-navEl-link " data-xf-key="alt+1" data-nav-id="defaultLatestActivity">Latest activity</a> </div> </li> <li> <div class="p-navEl " > <a href="/login/register" class="p-navEl-link " data-xf-key="alt+2" data-nav-id="defaultRegister">Register</a> </div> </li> </ul> </div> </div> <div class="p-sectionLinks-right"> </div> </div> </div> </div> <div class="offCanvasMenu offCanvasMenu--nav js-headerOffCanvasMenu" data-menu="menu" aria-hidden="true" data-ocm-builder="navigation"> <div class="offCanvasMenu-backdrop" data-menu-close="true"></div> <div class="offCanvasMenu-content"> <div class="offCanvasMenu-content--inner"> <div class="offCanvasMenu-header"> Menu <a class="offCanvasMenu-closer" data-menu-close="true" role="button" tabindex="0" aria-label="Close"></a> </div> <div class="p-offCanvasRegisterLink"> <div class="offCanvasMenu-linkHolder"> <a href="/login/" class="offCanvasMenu-link" data-xf-click="overlay" data-menu-close="true"> Log in </a> </div> <hr class="offCanvasMenu-separator" /> <div class="offCanvasMenu-linkHolder"> <a href="/login/register" class="offCanvasMenu-link" data-xf-click="overlay" data-menu-close="true"> Register </a> </div> <hr class="offCanvasMenu-separator" /> </div> <div class="offCanvasMenu-subHeader">Navigation</div> <div class="js-offCanvasNavTarget"></div>  <div class="offCanvasMenu-subHeader">More options</div> <div class="offCanvasMenu-linkHolder"> <a href="/misc/contact" class="offCanvasMenu-link" data-menu-close="true" data-nav-id="contactUs" data-xf-click="overlay">Contact us</a> </div> <div class="offCanvasMenu-linkHolder"> <a class="offCanvasMenu-link" data-menu-close="true" data-nav-id="closeMenu" role="button" tabindex="0" aria-label="Close">Close Menu</a> </div> </div> </div> </div> <div class="p-body"> <div class="p-body-inner">  <noscript class="js-jsWarning"><div class="blockMessage blockMessage--important blockMessage--iconic u-noJsOnly">JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.</div></noscript> <div class="blockMessage blockMessage--important blockMessage--iconic js-browserWarning" style="display: none">You are using an out of date browser. It may not display this or other websites correctly.<br />You should upgrade or use an <a href="https://www.google.com/chrome/" target="_blank" rel="noopener">alternative browser</a>.</div> <div class="p-body-main p-body-main--withSideNav"> <div class="p-body-sideNavCol"></div> <div class="p-body-contentCol"></div> <div class="p-body-sideNav"> <div class="p-body-sideNavTrigger"> <button type="button" class="button--link button" data-xf-click="off-canvas" data-menu="#js-SideNavOcm"><span class="button-text"> Help pages </span></button> </div> <div class="p-body-sideNavInner" data-ocm-class="offCanvasMenu offCanvasMenu--blocks" id="js-SideNavOcm" data-ocm-builder="sideNav"> <div data-ocm-class="offCanvasMenu-backdrop" data-menu-close="true"></div> <div data-ocm-class="offCanvasMenu-content"> <div class="p-body-sideNavContent"> <div class="block"> <div class="block-container"> <h2 class="block-header">Help</h2> <div class="block-body"> <a href="/help/howtopost/" class="blockLink ">How to post</a> <a href="/help/goldmembers/" class="blockLink ">Gold Membership Perks</a> <a href="/help/mentorforums/" class="blockLink ">Mentors and their assigned forums</a> <a href="/help/latexhelp/" class="blockLink ">Learn LaTeX for Math Equations</a> <a href="/help/terms-of-service/" class="blockLink ">Terms of Service</a> <a href="/help/member-privacy-policy/" class="blockLink ">Privacy Policy</a> <a href="/help/medals/" class="blockLink ">Medals and Awards</a> <a href="/help/homeworkhelp/" class="blockLink ">How to Ask for Homework Help</a> <a href="/help/speculation/" class="blockLink ">Policy on Speculative Discussions</a> <a href="/help/noanswer/" class="blockLink ">Why did nobody answer my post?</a> <a href="/help/threadprefixes/" class="blockLink ">Thread Level Prefixes</a> <a href="/help/smilies/" class="blockLink ">Smilies</a> <a href="/help/bb-codes/" class="blockLink ">BB codes</a> <a href="/help/trophies/" class="blockLink ">Trophies</a> <a href="/help/cookies/" class="blockLink ">Cookie usage</a> <a href="https://www.physicsforums.com/help/terms-of-service/" class="blockLink ">Terms and rules</a> <a href="https://www.physicsforums.com/help/member-privacy-policy/" class="blockLink ">Privacy policy</a> </div> </div> </div> <div class="block" data-widget-id="7" data-widget-key="forum_overview_forum_statistics" data-widget-definition="forum_statistics"> <div class="block-container"> <h3 class="block-minorHeader">Forum statistics</h3> <div class="block-body block-row"> <dl class="pairs pairs--justified count--threads"> <dt>Threads</dt> <dd>730,987</dd> </dl> <dl class="pairs pairs--justified count--messages"> <dt>Messages</dt> <dd>6,398,113</dd> </dl> <dl class="pairs pairs--justified count--users"> <dt>Members</dt> <dd>205,078</dd> </dl> <dl class="pairs pairs--justified"> <dt>Latest member</dt> <dd><a href="/members/dmeelevatorsandlifts.755217/" class="username " dir="auto" data-user-id="755217" data-xf-init="member-tooltip">dmeelevatorsandlifts</a></dd> </dl> </div> </div> </div> <div class="block"> <div class="block-container" data-widget-id="41" data-widget-key="aboutPF" data-widget-definition="html"> <h3 class="block-minorHeader">Our Mission</h3> <div class="block-body block-row"> Physics Forums aims to provide a community for students, scientists, educators or hobbyists to learn and discuss science as it is currently generally understood and practiced by the professional scientific community. <br /><br/> Our main focus is physics, but we also cater to other STEM fields including engineering, chemistry, biology, mathematics, etc. <br /><br/> STEM homework help for students is available, as well as academic and career guidance. </div> </div> </div> </div> </div> </div> </div> <div class="p-body-content"> <div class="p-body-pageContent"> <div class="p-breadcrumbs--parent "> <ul class="p-breadcrumbs " itemscope itemtype="https://schema.org/BreadcrumbList"> <li itemprop="itemListElement" itemscope itemtype="https://schema.org/ListItem"> <a href="https://www.physicsforums.com/" itemprop="item"> <span itemprop="name">Forums</span> </a> <meta itemprop="position" content="1" /> </li> </ul> </div> <div class="p-body-header"> <div class="p-title "> <h1 class="p-title-value">Help</h1> </div> </div> <div class="block"> <div class="block-container"> <div class="block-body"> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/howtopost/">How to post</a> </h3> How to create a new thread and reply to an existing thread </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/goldmembers/">Gold Membership Perks</a> </h3> Find out the perks gold members receive with their subscription </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/mentorforums/">Mentors and their assigned forums</a> </h3> This lists our Mentors and which forums they are assigned to </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/latexhelp/">Learn LaTeX for Math Equations</a> </h3> Learn how to write equations and read a short tutorial on LaTeX code </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/terms-of-service/">Terms of Service</a> </h3> Rules and Guidelines for the community </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/member-privacy-policy/">Privacy Policy</a> </h3> Privacy Policy and how we get, store and use data </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/medals/">Medals and Awards</a> </h3> Find out what medals are available and how to get them </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/homeworkhelp/">How to Ask for Homework Help</a> </h3> In order to get you help you must learn and use our structure found here </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/speculation/">Policy on Speculative Discussions</a> </h3> Learn the reasons and history behind our speculation policy </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/noanswer/">Why did nobody answer my post?</a> </h3> Trouble generating replies to your threads? Read some common causes here. </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/threadprefixes/">Thread Level Prefixes</a> </h3> This explains the B,I,A prefixes available when creating a new thread </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/smilies/">Smilies</a> </h3> This shows a full list of the smilies you can insert when posting a message. </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/bb-codes/">BB codes</a> </h3> The list of BB codes you can use to spice up the look of your messages. This page shows a list of all BB codes that are available. </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/trophies/">Trophies</a> </h3> You can earn trophies by carrying out different actions. This page shows a list of the trophies that are available. </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="/help/cookies/">Cookie usage</a> </h3> This page explains how this site uses cookies. </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="https://www.physicsforums.com/help/terms-of-service/">Terms and rules</a> </h3> You must agree to these terms and rules before using the site. </div> <div class="block-row block-row--separated"> <h3 class="block-textHeader"> <a href="https://www.physicsforums.com/help/member-privacy-policy/">Privacy policy</a> </h3> You must accept this policy before using the site. </div> </div> </div> </div> <div class="p-breadcrumbs--parent p-breadcrumbs--bottom"> <ul class="p-breadcrumbs p-breadcrumbs--bottom" itemscope itemtype="https://schema.org/BreadcrumbList"> <li itemprop="itemListElement" itemscope itemtype="https://schema.org/ListItem"> <a href="https://www.physicsforums.com/" itemprop="item"> <span itemprop="name">Forums</span> </a> <meta itemprop="position" content="1" /> </li> </ul> </div> </div> </div> </div> </div> </div> </div>  <footer class="p-footer" id="footer"> <div class="p-footer--container"> <div class="p-footer-default"> <div class="p-footer-inner"> <div class="p-footer-row"> <div class="p-footer-row-main"> <ul class="p-footer-linkList"> <li class="p-linkList-changeWidth"><a class="pageWidthToggle xb-toggle-default" role="button" tabindex="0" data-xf-click="toggle" data-target="html" data-active-class="xb-toggle-default" data-xf-init="toggle-storage" data-storage-type="cookie" data-storage-expiry="31556926" data-storage-key="_xb-width"> Change width </a></li> </ul> </div> <div class="p-footer-row-opposite"> <ul class="p-footer-linkList"> <li><a href="/misc/contact">Contact</a></li> <li><a href="https://www.physicsforums.com/insights/about-physics-forums/">About</a></li> <li><a href="https://www.physicsforums.com/help/terms-of-service/">Terms</a></li> <li><a href="https://www.physicsforums.com/help/member-privacy-policy/">Privacy</a></li> <li><a href="/help/">Help</a></li> <li><a href="/forums/-/index.rss" target="_blank" class="p-footer-rssLink" title="RSS"><span aria-hidden="true"><i class="fa--xf fal fa-rss" aria-hidden="true"></i><span class="u-srOnly">RSS</span></span></a></li> </ul> </div> </div> </div> </div> <div class="p-footer-copyright"> <div class="p-footer-inner"> <div class="p-footer-copyright--flex"> <div class="copyright-left"> 2024 © Physics Forums, All Rights Reserved </div> </div> </div> </div> </div> </footer> </div>  </div>  <div class="u-bottomFixer js-bottomFixTarget"> </div> <div class="u-navButtons js-navButtons" data-trigger-type="up"> <a href="javascript:" class="button--scroll button"><span class="button-text"><i class="fa--xf fal fa-arrow-left" aria-hidden="true"></i><span class="u-srOnly">Back</span></span></a> </div> <div class="u-scrollButtons js-scrollButtons" data-trigger-type="up"> <a href="#top" class="button--scroll button" data-xf-click="scroll-to"><span class="button-text"><i class="fa--xf fal fa-arrow-up" aria-hidden="true"></i><span class="u-srOnly">Top</span></span></a> </div> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script><script>window.jQuery || document.write('<script src="/js/vendor/jquery/jquery-3.5.1.min.js?_v=637e8561"><\/script>')</script> <script src="/js/vendor/vendor-compiled.js?_v=637e8561"></script> <script src="/js/xf/core-compiled.js?_v=637e8561"></script> <script> if (typeof jqProxy !== 'undefined') { jQuery = jqProxy; } </script> <script> jQuery.extend(true, XF.config, { // xlink: { platformId: 0 }, userId: 0, enablePush: true, pushAppServerKey: 'BHawDCc5f/kxves/mySH6irZC+n8kQpwVp6mw8IItmRcI/R6qHIwbanIkiZvdq/o+uUlVEU0XDw0ctRSlmUne1w=', url: { fullBase: 'https://www.physicsforums.com/', basePath: '/', css: '/css.php?css=__SENTINEL__&s=12&l=1&d=1728569821', keepAlive: '/login/keep-alive' }, cookie: { path: '/', domain: '', prefix: 'xf_', secure: true, consentMode: 'disabled', consented: ["optional","_third_party"] }, cacheKey: '3d79291bf12cdbc07f4377a513c5011d', csrf: '1732515794,65f7f6a919b2fbfd51fb3f88725f1509', js: {}, css: {"public:thxpress_xf.less":true,"public:xb.less":true,"public:extra.less":true}, time: { now: 1732515794, today: 1732514400, todayDow: 1, tomorrow: 1732600800, yesterday: 1732428000, week: 1731996000 }, borderSizeFeature: '3px', fontAwesomeWeight: 'l', enableRtnProtect: true, enableFormSubmitSticky: true, uploadMaxFilesize: 62914560, allowedVideoExtensions: ["m4v","mov","mp4","mp4v","mpeg","mpg","ogv","webm"], allowedAudioExtensions: ["mp3","opus","ogg","wav"], shortcodeToEmoji: true, visitorCounts: { conversations_unread: '0', alerts_unviewed: '0', total_unread: '0', title_count: true, icon_indicator: true }, jsState: {}, publicMetadataLogoUrl: 'https://www.physicsforums.com/styles/physicsforums/images/physics-forums-logo-og.png', publicPushBadgeUrl: 'https://www.physicsforums.com/styles/default/xenforo/bell.png' }); jQuery.extend(XF.phrases, { // CMTV_Code_copied: "Code copied to clipboard.", date_x_at_time_y: "{date} at {time}", day_x_at_time_y: "{day}, {time}", yesterday_at_x: "Yesterday, {time}", x_minutes_ago: "{minutes} minutes ago", one_minute_ago: "1 minute ago", a_moment_ago: "A moment ago", today_at_x: "Today, {time}", in_a_moment: "In a moment", in_a_minute: "In a minute", in_x_minutes: "In {minutes} minutes", later_today_at_x: "Later today at {time}", tomorrow_at_x: "Tomorrow at {time}", day0: "Sunday", day1: "Monday", day2: "Tuesday", day3: "Wednesday", day4: "Thursday", day5: "Friday", day6: "Saturday", dayShort0: "Sun", dayShort1: "Mon", dayShort2: "Tue", dayShort3: "Wed", dayShort4: "Thu", dayShort5: "Fri", dayShort6: "Sat", month0: "January", month1: "February", month2: "March", month3: "April", month4: "May", month5: "June", month6: "July", month7: "August", month8: "September", month9: "October", month10: "November", month11: "December", active_user_changed_reload_page: "The active user has changed. Reload the page for the latest version.", server_did_not_respond_in_time_try_again: "The server did not respond in time. Please try again.", oops_we_ran_into_some_problems: "Oops! We ran into some problems.", oops_we_ran_into_some_problems_more_details_console: "Oops! We ran into some problems. Please try again later. More error details may be in the browser console.", file_too_large_to_upload: "The file is too large to be uploaded.", uploaded_file_is_too_large_for_server_to_process: "The uploaded file is too large for the server to process.", files_being_uploaded_are_you_sure: "Files are still being uploaded. Are you sure you want to submit this form?", attach: "Attach files", rich_text_box: "Rich text box", close: "Close", link_copied_to_clipboard: "Link copied to clipboard.", text_copied_to_clipboard: "Text copied to clipboard.", loading: "Loading…", you_have_exceeded_maximum_number_of_selectable_items: "You have exceeded the maximum number of selectable items.", processing: "Processing", 'processing...': "Processing…", showing_x_of_y_items: "Showing {count} of {total} items", showing_all_items: "Showing all items", no_items_to_display: "No items to display", number_button_up: "Increase", number_button_down: "Decrease", push_enable_notification_title: "Push notifications enabled successfully at Physics Forums: Science Discussion, Homework Help, Articles", push_enable_notification_body: "Thank you for enabling push notifications!", pull_down_to_refresh: "Pull down to refresh", release_to_refresh: "Release to refresh", refreshing: "Refreshing…" , "svStandardLib_time.day": "{count} day", "svStandardLib_time.days": "{count} days", "svStandardLib_time.hour": "{count} hour", "svStandardLib_time.hours": "{count} hours", "svStandardLib_time.minute": "{count} minutes", "svStandardLib_time.minutes": "{count} minutes", "svStandardLib_time.month": "{count} month", "svStandardLib_time.months": "{count} months", "svStandardLib_time.second": "{count} second", "svStandardLib_time.seconds": "{count} seconds", "svStandardLib_time.week": "time.week", "svStandardLib_time.weeks": "{count} weeks", "svStandardLib_time.year": "{count} year", "svStandardLib_time.years": "{count} years" }); </script> <form style="display:none" hidden="hidden"> <input type="text" name="_xfClientLoadTime" value="" id="_xfClientLoadTime" title="_xfClientLoadTime" tabindex="-1" /> </form>  <script type="text/javascript" src="https://www.physicsforums.com/copyright.js" defer></script> <script> function parseNewPost(postid) { var newpost = document.getElementById("js-post-" + postid), npa = [newpost]; MathJax.typeset(npa); } function parsePreview() { var preview = document.getElementsByClassName("xfPreview"); MathJax.typeset(preview); } function parseNewConversationPost(postid) { var newpost = document.getElementsByClassName("convMessage-" + postid); MathJax.typeset(newpost); } function parseNewProfilePost(postid) { var newpost = document.getElementById("js-profilePost-" + postid), npa = [newpost]; MathJax.typeset(npa); } function parseTooltip() { MathJax.typeset(); } </script> </body> </html>

CINXE.COM

Help | Physics Forums: Science Discussion, Homework Help, Articles