Notes to the presenter This is an interactive presentation best done for a small group (15-20 maximum) This is an interactive presentation best done for a small group (15-20 maximum) Practice setting up the interferometer first, so you know how to do it. With practice, you can set it up in 5-10 minutes Practice setting up the interferometer first, so you know how to do it. With practice, you can set it up in 5-10 minutes Total talk & demo can be done in minutes Total talk & demo can be done in minutes Participants should be encouraged to interact with the interferometer (which is why small groups work better) Participants should be encouraged to interact with the interferometer (which is why small groups work better) Dont forget to turn in an ambassador outreach form! Dont forget to turn in an ambassador outreach form! NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

PRESENTINGthe NCSLI Michelson Interferometer in a Pizza Box!

Objectives The roots of the metric system The roots of the metric system The definition of the meter The definition of the meter Albert Michelsons contribution to optics Albert Michelsons contribution to optics Principles of interferometry Principles of interferometry The geometry of the Michelson interferometer The geometry of the Michelson interferometer And you will interact with a working interferometer NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961 You will learn about

Origins of the metric system Prior to the French revolution, each region in France had its own standards Prior to the French revolution, each region in France had its own standards Different yard units for textiles (toise)Different yard units for textiles (toise) Different bushel units for grainDifferent bushel units for grain Different pint measures for beerDifferent pint measures for beer Idea of rationalizing units from 1670: Abbé Mouton proposes 1 minute of arc of the circumference of the earth as the primary standard of length; decimal divisions Idea of rationalizing units from 1670: Abbé Mouton proposes 1 minute of arc of the circumference of the earth as the primary standard of length; decimal divisions NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

More on the history of the meter Other proposals (including Thomas Jefferson) based on the period of a pendulum; also proposals to use base 12 divisions Other proposals (including Thomas Jefferson) based on the period of a pendulum; also proposals to use base 12 divisions During the revolution (1780s-1790s), the French Academy of Sciences is commissioned to reform units During the revolution (1780s-1790s), the French Academy of Sciences is commissioned to reform units Meter: 1 part in 10,000,000 of the meridian (longitude line) from the North Pole to the Equator, passing through ParisMeter: 1 part in 10,000,000 of the meridian (longitude line) from the North Pole to the Equator, passing through Paris NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

The early metric system 1 meter (1×10 -7 of the earth quadrant) 1 meter (1×10 -7 of the earth quadrant) Area and volume derived from the meter Area and volume derived from the meter Mass derived from volume: 1 gram = mass of water (at 0°C) in a volume of 1 cm 3 Mass derived from volume: 1 gram = mass of water (at 0°C) in a volume of 1 cm 3 Metric system not in widespread use until 1875 (May 20, 1875signing of the Convention of the Meter) Metric system not in widespread use until 1875 (May 20, 1875signing of the Convention of the Meter) meter is based on the Platinum-Iridium meter at BIPM in Paris; kilogram based on the international prototype in Paris; each signing nation has copies meter is based on the Platinum-Iridium meter at BIPM in Paris; kilogram based on the international prototype in Paris; each signing nation has copies NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

The meter in the US 1875: US signs the Convention of the Meter 1875: US signs the Convention of the Meter 1890: US receives K-4 and K-20 (kilogram standards) and meter 21 and : US receives K-4 and K-20 (kilogram standards) and meter 21 and : T. C. Mendenhall, Superintendent of Weights & Measures in the US orders the adoption of the international prototype meter and kilogram as US standards. 1893: T. C. Mendenhall, Superintendent of Weights & Measures in the US orders the adoption of the international prototype meter and kilogram as US standards. NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

Albert A. Michelson Grew up in Northern California & West Nevada Grew up in Northern California & West Nevada Appointed to US Naval Academy; returned as an instructor, then, to Case School of Applied Science, Clark University, and finally University of Chicago Appointed to US Naval Academy; returned as an instructor, then, to Case School of Applied Science, Clark University, and finally University of Chicago Did experiments to measure the speed of light, and also the Michelson-Morley experiment to determine the speed of travel of earth in the aether (1887) Did experiments to measure the speed of light, and also the Michelson-Morley experiment to determine the speed of travel of earth in the aether (1887) Visited BIPM to set up interferometers for measuring the meter bars! Visited BIPM to set up interferometers for measuring the meter bars! NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

The 1907 Nobel Prize in Physics The Royal Academy of Sciences has decided to award this year's Nobel Prize for Physics to Professor Albert A. Michelson of Chicago, for his optical precision instruments and the research which he has carried out with their help in the fields of precision metrology and spectroscopy. The Royal Academy of Sciences has decided to award this year's Nobel Prize for Physics to Professor Albert A. Michelson of Chicago, for his optical precision instruments and the research which he has carried out with their help in the fields of precision metrology and spectroscopy. NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

Interference and light Light exhibits constructive and destructive interference NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961 Incoming lightReflected light Dark Band Bright Band Dark Band

Michelsons interferometer NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

The LASER NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

Laser interferometer NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961 Mirror (moving) LASER SOURCE beamsplitter Mirror (fixed) DETECTOR Beamsplitter Laser light is: Monochromatic (all the same wavelength) Coherent (all the peaks and valleys are in phase with each other)

Michelson interferometer with laser NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

Demo time! In 1960, the meter was redefined to Krypton light wavelength In 1960, the meter was redefined to Krypton light wavelength In 1983, the meter was redefined to be the distance traveled by light (in a vacuum) in 1/ second In 1983, the meter was redefined to be the distance traveled by light (in a vacuum) in 1/ second c m/sc m/s NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961

For more information NBS SP447 (from NBS SP447 (from American Institute of Physics ( American Institute of Physics ( NCSL INTERNATIONAL SERVING THE WORLD OF MEASUREMENT SINCE 1961