{"id":17,"date":"2026-01-25T00:23:17","date_gmt":"2026-01-25T00:23:17","guid":{"rendered":"https:\/\/learnx.ca\/um\/?page_id=17"},"modified":"2026-02-16T20:02:09","modified_gmt":"2026-02-16T20:02:09","slug":"number","status":"publish","type":"page","link":"https:\/\/imaginethis.ca\/u\/number\/","title":{"rendered":"Number"},"content":{"rendered":"\n<p>&#8220;I know numbers are beautiful. If they aren&#8217;t beautiful, nothing is.\u201d<br>\u2015 Paul Erd\u0151s<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Sets of numbers<\/h2>\n\n\n\n<p>Here is bird&#8217;s-eye-view of sets and subsets of numbers.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"690\" height=\"677\" src=\"https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/sets-of-numbers-v3.png\" alt=\"\" class=\"wp-image-321\" style=\"aspect-ratio:1.0192073911986386;width:466px;height:auto\" srcset=\"https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/sets-of-numbers-v3.png 690w, https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/sets-of-numbers-v3-300x294.png 300w, https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/sets-of-numbers-v3-624x612.png 624w\" sizes=\"auto, (max-width: 690px) 100vw, 690px\" \/><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>The story of numbers is much longer\u2014and stranger\u2014than it first appears.<\/strong><\/h2>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"alignright size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"180\" height=\"226\" src=\"https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/negative-cat-v2.png\" alt=\"\" class=\"wp-image-216\" style=\"aspect-ratio:0.7965152457996266;width:163px;height:auto\"\/><\/figure>\n<\/div>\n\n\n<p>The numbers we now take for granted did not arrive all at once. They appeared slowly, often with resistance, as if each new kind of number had to fight for its right to exist.<\/p>\n\n\n\n<p>Take negative numbers.<br>In the 7th century, the Indian mathematician <strong>Brahmagupta<\/strong> boldly wrote rules for adding and subtracting them\u2014an idea far ahead of its time. Yet for more than a thousand years afterward, many mathematicians refused to accept numbers \u201cless than nothing.\u201d To them, negatives were shadows, tricks, or bookkeeping fictions\u2014not real mathematics.<\/p>\n\n\n\n<p>Long before that, over <strong>2,500 years ago<\/strong>, the ancient Greeks stumbled onto lengths that could not be written as fractions\u2014like the diagonals of some square. These strange quantities later came to be called <strong>irrational numbers<\/strong>. The Greeks could measure them as geometric lengths, but the idea of irrational <em>numbers<\/em> remained unsettling for centuries. <\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"448\" height=\"184\" src=\"https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/irrational-v2.png\" alt=\"\" class=\"wp-image-323\" srcset=\"https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/irrational-v2.png 448w, https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/irrational-v2-300x123.png 300w\" sizes=\"auto, (max-width: 448px) 100vw, 448px\" \/><\/figure>\n\n\n\n<p>It wasn\u2019t until the 19th century that irrational numbers were finally given precise definitions.<\/p>\n\n\n\n<p>And what about zero? Well, let&#8217;s sing this song.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><iframe loading=\"lazy\" width=\"480\" height=\"239\" src=\"https:\/\/www.youtube.com\/embed\/zNmSIGhcA98?rel=0\" title=\"YouTube video player\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen=\"\"><\/iframe><\/td><td>ZERO. Written and performed by Lindi Wahl, Sara Wahl, Sue Wahl, and Michelle Wahl Craig.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>Today, we group these familiar characters together:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Real numbers<\/strong>: every point on the number line.<\/li>\n\n\n\n<li><strong>Rational numbers<\/strong>: real numbers that can be written as fractions.<\/li>\n\n\n\n<li><strong>Irrational numbers<\/strong>: real numbers that <em>cannot<\/em> be written as fractions.<\/li>\n<\/ul>\n\n\n\n<p>So far, so good.<br>But the story gets stranger.<\/p>\n\n\n\n<p>When mathematicians tried to take the square root of a negative number, they reached a dead end\u2014until the idea of <strong>imaginary numbers<\/strong> emerged. At first, people thought the name was a warning label: beware, these are not real.<\/p>\n\n\n\n<p>Then, in 1797, a Danish\u2013Norwegian surveyor named <strong>Caspar Wessel<\/strong> made an extraordinary proposal: imaginary numbers weren\u2019t mistakes\u2014they lived in a <em>different dimension<\/em>. If real numbers lay on a horizontal line, imaginary numbers stretched vertically, forming a second axis.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"alignright size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"222\" height=\"191\" src=\"https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/complex-plane.png\" alt=\"\" class=\"wp-image-205\" style=\"aspect-ratio:1.162412043855343;width:222px;height:auto\"\/><figcaption class=\"wp-element-caption\">[from Wikipedia]<\/figcaption><\/figure>\n<\/div>\n\n\n<p>With this insight, a new world opened.<\/p>\n\n\n\n<p>A number like <strong>4 + 4i<\/strong> was no longer nonsense\u2014it was a <strong>complex number<\/strong>, a point in a two\u2011dimensional plane, or even a vector with magnitude and direction. Complex numbers blended the real and imaginary into a unified whole.<\/p>\n\n\n\n<p>And so the <em>real<\/em> number line became a <em>complex<\/em> plane.<\/p>\n\n\n\n<p>Hmm. What about <strong>infinity<\/strong>?<br>That&#8217;s <a href=\"https:\/\/imaginethis.ca\/u\/index.php\/infinity\/\">another story<\/a>!<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><a href=\"https:\/\/imaginethis.ca\/u\/index.php\/infinity\/\"><img loading=\"lazy\" decoding=\"async\" width=\"213\" height=\"288\" src=\"https:\/\/imaginethis.ca\/u\/wp-content\/uploads\/2026\/02\/infinity-hand-ad.png\" alt=\"\" class=\"wp-image-226\"\/><\/a><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>&#8220;I know numbers are beautiful. If they aren&#8217;t beautiful, nothing is.\u201d\u2015 Paul Erd\u0151s Sets of numbers Here is bird&#8217;s-eye-view of sets and subsets of numbers. The story of numbers is much longer\u2014and stranger\u2014than it first appears. The numbers we now take for granted did not arrive all at once. They appeared slowly, often with resistance, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-17","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/imaginethis.ca\/u\/wp-json\/wp\/v2\/pages\/17","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/imaginethis.ca\/u\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/imaginethis.ca\/u\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/imaginethis.ca\/u\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/imaginethis.ca\/u\/wp-json\/wp\/v2\/comments?post=17"}],"version-history":[{"count":31,"href":"https:\/\/imaginethis.ca\/u\/wp-json\/wp\/v2\/pages\/17\/revisions"}],"predecessor-version":[{"id":515,"href":"https:\/\/imaginethis.ca\/u\/wp-json\/wp\/v2\/pages\/17\/revisions\/515"}],"wp:attachment":[{"href":"https:\/\/imaginethis.ca\/u\/wp-json\/wp\/v2\/media?parent=17"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}