{"id":179586,"date":"2025-01-01T19:27:59","date_gmt":"2025-01-01T19:27:59","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=179586"},"modified":"2025-01-01T19:28:01","modified_gmt":"2025-01-01T19:28:01","slug":"the-hubble-constant-is-about-70-km-s-per-mpc","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/01\/01\/the-hubble-constant-is-about-70-km-s-per-mpc\/","title":{"rendered":"The Hubble constant is about 70 km\/s per Mpc"},"content":{"rendered":"\n

The Hubble constant is about 70 km\/s per Mpc, which means that a galaxy would be moving away from us at 70 km\/s if it were 1 Mpc away. If a galaxy were 10 Mpc away, how fast would be appear to be moving away from us, in km\/s?<\/p>\n\n\n\n

The correct answer and explanation is:<\/mark><\/strong><\/p>\n\n\n\n

Answer:<\/h3>\n\n\n\n

If a galaxy is 10 Mpc away, it would appear to be moving away from us at 700 km\/s<\/strong>.<\/p>\n\n\n\n

Explanation:<\/h3>\n\n\n\n

The Hubble constant, denoted H0H_0, describes the rate of expansion of the universe and is often expressed in units of kilometers per second per megaparsec (km\/s\/Mpc). Its value is approximately 70 km\/s\/Mpc, meaning that for every additional megaparsec of distance from an observer, the apparent recession velocity of an object due to the expansion of the universe increases by 70 km\/s.<\/p>\n\n\n\n

The Hubble’s Law:<\/h4>\n\n\n\n

v=H0\u22c5dv = H_0 \\cdot d<\/p>\n\n\n\n

Where:<\/p>\n\n\n\n

    \n
  • vv is the recession velocity (in km\/s),<\/li>\n\n\n\n
  • H0H_0 is the Hubble constant (70\u2009km\/s\/Mpc70 \\, \\text{km\/s\/Mpc}),<\/li>\n\n\n\n
  • dd is the distance of the galaxy from the observer (in Mpc).<\/li>\n<\/ul>\n\n\n\n

    Using this formula:<\/p>\n\n\n\n

      \n
    • For a galaxy 1 Mpc away:
      v=70\u22c51=70\u2009km\/sv = 70 \\cdot 1 = 70 \\, \\text{km\/s}<\/li>\n\n\n\n
    • For a galaxy 10 Mpc away:
      v=70\u22c510=700\u2009km\/sv = 70 \\cdot 10 = 700 \\, \\text{km\/s}<\/li>\n<\/ul>\n\n\n\n

      This means that a galaxy 10 times farther away will have a recession velocity 10 times greater because the relationship between distance and velocity is linear in Hubble’s Law.<\/p>\n\n\n\n

      Significance of Hubble’s Law:<\/h4>\n\n\n\n

      This law is crucial evidence for the universe’s expansion. The linear relationship implies that all galaxies are moving away from us (and from each other) as space itself expands. Importantly, the observed velocity is not due to the actual motion of galaxies through space but the stretching of space itself, carrying galaxies with it.<\/p>\n\n\n\n

      Hubble’s constant also allows astronomers to estimate the age of the universe by taking the inverse of H0H_0, yielding an approximate timescale since the Big Bang. Thus, the simple calculation here reflects a profound insight into the structure and dynamics of the cosmos.<\/p>\n","protected":false},"excerpt":{"rendered":"

      The Hubble constant is about 70 km\/s per Mpc, which means that a galaxy would be moving away from us at 70 km\/s if it were 1 Mpc away. If a galaxy were 10 Mpc away, how fast would be appear to be moving away from us, in km\/s? The correct answer and explanation is: […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-179586","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/179586","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=179586"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/179586\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=179586"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=179586"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=179586"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}