Inconceivably vast but relatively puny,
Galaxy NGC 2857 offers us a perfect view of a spiral galaxy.
Public domain image from the European Southern Observatory<\/figcaption><\/figure>\n\u00a0<\/p>\n
On pages 89-90, Carlo Rovelli, Reality Is Not What It Seems: The Journey to Quantum Gravity<\/em>, translated by Simon Carnell and Erica Segre (Penguin, 2017), tells an interesting and instructive story from twentieth-century physics. \u00a0One of the more dedicated detractors of my blog likes to dismiss my science-related entries here as \u201cjunk science.\u201d \u00a0At the risk of drawing that epithet from him yet again, I share a passage from Dr. Rovelli\u2019s book that I\u2019ve copied for my notes.<\/p>\n\u00a0<\/p>\n
In 1917, when Albert Einstein was trying to work the concept of a 3-sphere into his equations, he found himself encountering a problem:<\/p>\n
\u00a0<\/p>\n
He is convinced that the universe is fixed and immutable, but his equations tell him that this is not possible. \u00a0It isn\u2019t difficult to understand why. \u00a0Everything attracts, therefore the only way for a finite universe not to collapse on itself is for it to be expanding: just as the only way to prevent a football from falling to the ground is to kick it upwards. \u00a0It either goes up, or falls down \u2014 it can\u2019t stay still, suspended in the air.<\/span><\/p>\nBut Einstein does not believe what his own equations are telling him. \u00a0He even makes a silly physics mistake (he does not realize that the solution he considers is unstable) just to avoid accepting what his theory predicts: the universe is either contracting or expanding. \u00a0He modifies his equations, trying to avoid the implication that it is expanding. \u00a0It is for this reason that he adds the term Lgab<\/sub><\/em> in the equation written above [Rab<\/sub><\/em> \u2013 1\/2Rgab<\/sub><\/em> + Lgab<\/sub><\/em> = 8pGTab<\/sub><\/em>].*<\/strong> \u00a0But it is a further mistake: the added term is correct, but it does not change the fact that the equation predicts that the universe must be expanding. \u00a0For all his bravery, Einstein the genius lacks the courage to believe his own equations.<\/span><\/p>\nA few years later Einstein is forced to give up: it is his theory that is right, not his reservations about it. \u00a0Astronomers realize that all galaxies are indeed moving away from us. \u00a0The universe is expanding, exactly as the equations predicted. \u00a0Fourteen billion years ago, the universe was concentrated almost to a single, furiously hot point. \u00a0From there it expanded in a colossal \u2018cosmic\u2019 explosion \u2014 and here the term \u2018cosmic\u2019 is not used in any rhetorical sense: it is, literally, a cosmic explosion. \u00a0This is the \u2018Big Bang\u2019.<\/span><\/p>\nToday we know the expansion is real. \u00a0The definitive proof of the scenario foreseen by Einstein\u2019s equations arrives in 1964, when two American radio-astronomers, Arno Penzias and Robert Wilson, discover by accident a radiation diffused throughout the universe which turns out to be precisely what remains of the original immense heat of the early universe. \u00a0Once again, the theory turns out to have been correct, up to its most amazing predictions.<\/span><\/p>\n\u00a0<\/p>\n
*<\/strong><\/span> Please note that, owing to a peculiarity in the blogging software that I\u2019ve been unable to evade, I\u2019ve been obliged to substitute a Roman capital L<\/em> for the Greek majuscule lambda<\/em> that should properly be there.<\/p>\n\u00a0<\/p>\n
\u00a0<\/p>\n<\/body><\/html>\n","protected":false},"excerpt":{"rendered":"
\u00a0 \u00a0 On pages 89-90, Carlo Rovelli, Reality Is Not What It Seems: The Journey to Quantum Gravity, translated by Simon Carnell and Erica Segre (Penguin, 2017), tells an interesting and instructive story from twentieth-century physics. \u00a0One of the more dedicated detractors of my blog likes to dismiss my science-related entries here as \u201cjunk science.\u201d […]<\/p>\n","protected":false},"author":1019,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[7272,11770,11776,344,3790,11764,11761,1137,8307,132,11779,11767,11773,11447,10439,10130,8154],"class_list":["post-85238","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-albert","tag-arno","tag-astronomer","tag-astronomy","tag-big-bang","tag-constant","tag-cosmological","tag-cosmological-constant","tag-cosmos","tag-einstein","tag-equation","tag-expansion","tag-penzias","tag-radio","tag-robert","tag-universe","tag-wilson"],"yoast_head":"\n
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<\/a>