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|May 7, 2007
|The speed of light has declined significantly over the history of the Universe. Estimates of the ratio run as high as 10<sup>60</sup>.<ref>http://www.conservapedia.com/C DecayC_Decay</ref><ref>http://www.ldolphin.org/recentlight.html</ref><ref>https://answersingenesis.org/theory-of-evolution/evidence/too-many-theories/</ref><ref>http://www.conservapedia.com/index.php?title=Essay:Quantifying_Openmindedness&oldid=147388</ref>
|A far-fetched assumption underlying the [[Theory of Relativity]] is that the speed of light has never changed (in a vacuum), despite the cooling of the universe.
|"So it turns out the speed of light might not be constant after all." <ref>https://www.newscientist.com/article/dn6092-speed-of-light-may-have-changed-recently</ref><ref>http://www.extremetech.com/extreme/184879-einsteinian-error-the-25-year-old-supernova-that-could-change-the-speed-of-light-forever</ref> Research shows that due to the impossibility of a perfect vacuum the idealized concept of 'the speed of light in a vacuum' cannot be achieved in practice.