Who<\/STRONG>: Albert Michelson (1852-1931)<\/A> and Edward Morley (1838-1923)<\/A>, American physicists.<\/p>\n When<\/STRONG>: Their first results were reported in 1887.<\/p>\n What<\/STRONG>: The famous Michelson-Morley experiment<\/A>, which tried and failed to detect the motion of the Earth through the “luminiferous aether.” At the time, light waves were believed to be disturbances in some medium that permeated all of space, and was fixed in an absolute sense. In this picture, objects moving through space should also be moving relative to the aether, which should cause an apparent change in the speed of light along the direction of motion.<\/p>\n The exact pattern of fringes is extremely sensitive to the difference between the times taken for each of the two beams to make the round trip. If the time is different by half of the oscillation period of the light (about 10-15<\/SUP> seconds), you’ll get bright fringes where you had dark ones, and vice versa. If you take this device and set it up with one arm pointed along the direction of the Earth’s motion through the aether (about 30 km\/s as it orbits the Sun), you’ll see one pattern as the light on that path moves at a different speed than the light on the perpendicular path. If you then rotate the apparatus by 90 degrees, you switch the other arm into the direction of the Earth’s motion, and you should see a shift in the fringes. The change in the speed of light is a small one (about 1\/10,000th<\/SUP> of the speed of light), but the interferometer is so sensitive, you should see something.<\/p>\n Michelson and Morley set up their apparatus on a heavy granite slab (to eliminate vibrations), and floated the slab in a vat of mercury (to allow smooth rotation– OSHA didn’t exist in 1887), and made a long series of measurements as they rotated the interferometer, and saw absolutely nothing. The shift they reported was consistent with zero, that is, with no change in the speed of light due to the Earth’s motion through the aether.<\/p>\n Why It’s Important<\/STRONG>: There are conflicting stories about whether Einstein was aware of the Michelson-Morley result or not, and whether he cared about it if he was aware of it, but the Michelson-Morley experiment played an important role in paving the way for the acceptance of Relativity. The simplest explanation of their null result is that there is no aether, and without the aether, there’s no absolute rest frame. <\/p>\n Beyond that, it’s one of the earliest examples of the technique of interferometry, which is incredibly useful for measuring small changes in position, or small phase shifts. There are dozens of different schemes for interferometric measurements, which can be used to measure everything from obvious physical quantities like position and rotation to gradients in the gravitational field, and even gravity waves. The Laser Interferometer Gravity Wave Observatory (LIGO)<\/A> is in the process of building what is basically the world’s largest Michelson interferometer in an effort to detect tiny expansions and contractions of space itself as a gravitational wave passes.<\/p>\n Reasons to Vote for Them:<\/STRONG>: Their null result brought about a dramatic shift in the way we view the world, and invented a crucial precision measurement technique. Also, Morley was a Williams grad (Class of 1860).<\/p>\n Reasons to Vote Against Them<\/STRONG>: Nostalgia for an absolute frame of reference, belief in aether dynamics<\/A>.<\/p>\n (Michelson-Morley apparatus image stolen from this site<\/A>, by way of the textbook companion site<\/A> for my class this term.)<\/I><\/p>\n","protected":false},"excerpt":{"rendered":" The next experiment in the Top Eleven is probably the most famous failed experiment of all time. Who: Albert Michelson (1852-1931) and Edward Morley (1838-1923), American physicists. When: Their first results were reported in 1887. What: The famous Michelson-Morley experiment, which tried and failed to detect the motion of the Earth through the “luminiferous aether.”… Continue reading Top Eleven: Michelson and Morley<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"1","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[19,7,11],"tags":[],"class_list":["post-39","post","type-post","status-publish","format-standard","hentry","category-experiment","category-physics","category-science","entry"],"_links":{"self":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts\/39","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/comments?post=39"}],"version-history":[{"count":0,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts\/39\/revisions"}],"wp:attachment":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/media?parent=39"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/categories?post=39"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/tags?post=39"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"i-fe24eee45893230cac27bf097830695e-sm_1887_intf_color.gif\"](\"http:\/\/scienceblogs.com\/principles\/wp-content\/blogs.dir\/467\/files\/2012\/04\/i-fe24eee45893230cac27bf097830695e-sm_1887_intf_color.gif\")
<\/a>The speed of light is gigantic, so it was widely believed that measuring the change in speed would be impossible, but Michelson came up with a way to do it, using a device now known as a “Michelson Interferometer,” pictured at left. The idea is simple: you take a beam of light, and split it into two perpendicular paths of nominally equal length. Then you reflect the light back on itself, and re-combine the two beams. At the output of the apparatus, you will see a pattern of bright and dark lines (“fringes”) due to the interference of the two light waves.<\/p>\n
![this site<\/A>, by way of the](\"http:\/\/carnap.umd.edu\/phil250\/images\/1887_intf_color.gif\"){kind=link}