{"id":28763,"date":"2022-01-21T11:45:35","date_gmt":"2022-01-21T11:45:35","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=103848"},"modified":"2022-01-21T11:58:13","modified_gmt":"2022-01-21T11:58:13","slug":"why-does-it-take-light-from-galaxies-so-long-to-reach-us-if-they-used-to-be-closer","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/why-does-it-take-light-from-galaxies-so-long-to-reach-us-if-they-used-to-be-closer\/","title":{"rendered":"Why does it take light from galaxies so long to reach us if they used to be closer?"},"content":{"rendered":"<p class=\"rssexcerpt\"><\/p><p class=\"rssauthor\">By Marcus Chown\n                \t\t<\/p><p class=\"rssbyline\">Published: Friday, 21 January 2022 at 12:00 am<\/p><hr class=\"no-tts wp-block-separator\"\/><?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n<!DOCTYPE html PUBLIC \"-\/\/W3C\/\/DTD HTML 4.0 Transitional\/\/EN\" \"http:\/\/www.w3.org\/TR\/REC-html40\/loose.dtd\">\n<html><body><p class=\"&quot;p5&quot;\">In the past, galaxies were closer together, and therefore closer to Earth. When this was the case, their light did take less time to reach us.<\/p>\n<p class=\"&quot;p6&quot;\">Take, for instance, a <a href=\"&quot;https:\/\/www.skyatnightmagazine.com\/space-science\/a-guide-to-galaxies\/&quot;\">galaxy<\/a> we are observing today whose light has taken 100 million years to get here. When it was closer, its light took, say, only 99 million years to get here.<\/p>\n<p class=\"&quot;p6&quot;\">This light, which took a million years less to get here than the light arriving from the galaxy today, arrived on Earth in the past. It is not the light we are observing today.<\/p>\n<p><em><strong>More from Marcus Chown:<\/strong><\/em><\/p>\n<ul><li><em><strong><a href=\"&quot;https:\/\/www.skyatnightmagazine.com\/space-science\/what-is-gravity-facts-about-force\/&quot;\">What is gravity?<\/a><\/strong><\/em><\/li>\n<li><a href=\"&quot;https:\/\/www.skyatnightmagazine.com\/space-science\/facts-about-space-universe\/&quot;\"><em><strong>Mind-blowing facts about the Universe<\/strong><\/em><\/a><\/li>\n<\/ul><p class=\"&quot;p6&quot;\">But this doesn\u2019t explain why light from the most distant matter in the Universe \u2013 stuff beyond the edge of the observable Universe \u2013 has not arrived here yet when, once upon a time, all the matter in the Universe was the barest whisker apart.<\/p>\n<p class=\"&quot;p6&quot;\">How could it get so far apart that light from the most distant objects hasn\u2019t reached us yet when, according to <a href=\"&quot;https:\/\/www.skyatnightmagazine.com\/space-science\/after-einstein-100-years-of-general-relativity\/&quot;\">Einstein\u2019s special theory of relativity<\/a>, no object can travel faster than light?<\/p>\n<div class=\"&quot;image-handler__container\" image-handler__container--full=\"\" style=\"&quot;padding-bottom:\" calc=\"\"> <picture><source media=\"&quot;(max-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?webp=true&amp;quality=90&amp;resize=300%2C205,\" https:=\"\" type=\"&quot;image\/webp&quot;\"><source media=\"&quot;(max-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?quality=90&amp;resize=300%2C205,\" https:=\"\" type=\"&quot;image\/jpeg&quot;\"><source media=\"&quot;(max-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?webp=true&amp;quality=90&amp;resize=355%2C243,\" https:=\"\" type=\"&quot;image\/webp&quot;\"><source media=\"&quot;(max-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?quality=90&amp;resize=355%2C243,\" https:=\"\" type=\"&quot;image\/jpeg&quot;\"><source media=\"&quot;(max-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?webp=true&amp;quality=90&amp;resize=405%2C277,\" https:=\"\" type=\"&quot;image\/webp&quot;\"><source media=\"&quot;(max-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?quality=90&amp;resize=405%2C277,\" https:=\"\" type=\"&quot;image\/jpeg&quot;\"><source media=\"&quot;(max-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?webp=true&amp;quality=90&amp;resize=554%2C379,\" https:=\"\" type=\"&quot;image\/webp&quot;\"><source media=\"&quot;(max-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?quality=90&amp;resize=554%2C379,\" https:=\"\" type=\"&quot;image\/jpeg&quot;\"><source media=\"&quot;(min-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?webp=true&amp;quality=90&amp;resize=620%2C424,\" https:=\"\" type=\"&quot;image\/webp&quot;\"><source media=\"&quot;(min-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?quality=90&amp;resize=620%2C424,\" https:=\"\" type=\"&quot;image\/jpeg&quot;\"><source media=\"&quot;(min-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?webp=true&amp;quality=90&amp;resize=408%2C279,\" https:=\"\" type=\"&quot;image\/webp&quot;\"><source media=\"&quot;(min-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?quality=90&amp;resize=408%2C279,\" https:=\"\" type=\"&quot;image\/jpeg&quot;\"><source media=\"&quot;(min-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?webp=true&amp;quality=90&amp;resize=556%2C381,\" https:=\"\" type=\"&quot;image\/webp&quot;\"><source media=\"&quot;(min-width:\" data-srcset=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?quality=90&amp;resize=556%2C381,\" https:=\"\" type=\"&quot;image\/jpeg&quot;\"><img class=\"&quot;wp-image-50829\" align=\"\" size-full=\"\" image-handler__image=\"\" image-handler__image--full=\"\" no-wrap=\"\" js-lazyload=\"\" data-src=\"&quot;https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2020\/07\/GettyImages-1015900082-b33ac06-e1594827120351.jpg?quality=90&amp;resize=620%2C424&quot;\" width=\"&quot;1500&quot;\" height=\"&quot;1027&quot;\" alt=\"&quot;Illustration\" of=\"\" the=\"\" expansion=\"\" universe.=\"\" understanding=\"\" more=\"\" about=\"\" this=\"\" phenomenon=\"\" could=\"\" reveal=\"\" clues=\"\" as=\"\" to=\"\" how=\"\" universe=\"\" will=\"\" end.=\"\" credit:=\"\" mark=\"\" garlick=\"\" science=\"\" photo=\"\" library=\"\" title=\"&quot;Illustration\"\/><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div><div class=\"&quot;caption-hold&quot;\"><figcaption class=\"&quot;wp-caption-text&quot;\"><span class=\"&quot;caption-copy&quot;\"><i class=\"&quot;icon-arrow\" icon-camera-circle=\"\"\/> Illustration showing the expansion of the Universe. Credit: Mark Garlick \/ Science Photo Library<\/span><\/figcaption><span class=\"&quot;im-image-caption&quot;\"\/><\/div>\n<p class=\"&quot;p6&quot;\">The answer is that immediately after the Big Bang, the Universe did indeed expand faster than light.<\/p>\n<p class=\"&quot;p6&quot;\">Consequently, light travelling to Earth was like a 100m sprinter trying to reach a finishing tape that is being pulled farther and farther away.<\/p>\n<p class=\"&quot;p6&quot;\">But how can space expand faster than the speed of light? Surely this violates special relativity?<\/p>\n<p class=\"&quot;p6&quot;\">However, the expansion involves acceleration, which is not covered by the theory of special relativity.<\/p>\n<p class=\"&quot;p6&quot;\">The theory that must be used instead is Einstein\u2019s general theory of relativity and, according to this, expanding space is like a stretchy fabric which can expand at any rate it likes.<\/p><\/body><\/html>\n<hr class=\"no-tts wp-block-separator\"\/>","protected":false},"excerpt":{"rendered":"<p>By Marcus Chown Published: Friday, 21 January 2022 at 12:00 am In the past, galaxies were closer together, and therefore closer to Earth. When this was the case, their light did take less time to reach us. Take, for instance, a galaxy we are observing today whose light has taken 100 million years to get [&hellip;]<\/p>\n","protected":false},"author":24,"featured_media":28764,"template":"","categories":[1],"acf":{"readingTimeMinutes":"2"},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/why-does-it-take-light-from-galaxies-so-long-to-reach-us-if-they-used-to-be-closer.jpg",1200,576,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/why-does-it-take-light-from-galaxies-so-long-to-reach-us-if-they-used-to-be-closer-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/why-does-it-take-light-from-galaxies-so-long-to-reach-us-if-they-used-to-be-closer-300x144.jpg",300,144,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/why-does-it-take-light-from-galaxies-so-long-to-reach-us-if-they-used-to-be-closer-768x369.jpg",768,369,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/why-does-it-take-light-from-galaxies-so-long-to-reach-us-if-they-used-to-be-closer-1024x492.jpg",800,384,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/why-does-it-take-light-from-galaxies-so-long-to-reach-us-if-they-used-to-be-closer.jpg",1200,576,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/why-does-it-take-light-from-galaxies-so-long-to-reach-us-if-they-used-to-be-closer.jpg",1200,576,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"By Marcus Chown Published: Friday, 21 January 2022 at 12:00 am In the past, galaxies were closer together, and therefore closer to Earth. When this was the case, their light did take less time to reach us. Take, for instance, a galaxy we are observing today whose light has taken 100 million years to get&hellip;","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed\/28763"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/rss_feed"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/28764"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=28763"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=28763"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}