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How do scientist measure the speed of light?


The Architekt

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Wikipedia is a very good resource to find answers to such questions and similar information:

 

Measurement

There are different ways to determine the value of c. One way is to measure the actual speed at which light waves propagate, which can be done in various astronomical and earth-based setups. However, it is also possible to determine c from other physical laws where it appears, for example, by determining the values of the electromagnetic constants ε0 and μ0 and using their relation to c. Historically, the most accurate results have been obtained by separately determining the frequency and wavelength of a light beam, with their product equalling c.

 

In 1983 the metre was defined as "the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second", fixing the value of the speed of light at 299,792,458 m/s by definition, as described below. Consequently, accurate measurements of the speed of light yield an accurate realization of the metre rather than an accurate value of c.

http://en.wikipedia.org/wiki/Speed_of_light#Measurement

 

 

But if you want you can measure it yourself at home with a chocolate bar, microwave oven and a ruler.

Link to mooeypoo's experiment thread: http://www.scienceforums.net/topic/31094-experiment-measuring-the-speed-of-light/

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And why are light photzons referred to as bosooons??

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There are two groups of fundamental / elementary particles - Bosons (named after Indian Physicist Satyendra Bose) and Fermions (named after Italian-American Physicist Enrico Fermi). The particles in each group are distinguished by certain features (ie bosons have integer spin whereas fermions have half integer spin.) and each group obey certain rules(notably the Pauli Exclusion for Fermions). You can get bosons and fermions which are not fundamental - ie they are built up from the particles listed below, but we won't deal with them.

 

The standard model of particle physics divides the two groups as per the following diagram

300px-Standard_Model_of_Elementary_Particles.svg.png

 

The bosons are the red shaded squares on the right hand side - the photon, the gluon and the Z and W bosons. We also believe that in the fullness of time two more fundamental elementary bosons will be added - The Higgs Boson and the Graviton. You will note that these elementary fundamental bosons all link to interactions rather than matter - the photon is the gauge boson which mediates the electromagnetic interaction, the gluon for the strong nuclear etc. The fermions are the particles that we consider to make up matter - for instance the quarks join through the strong force (up and down quarks in different combinations form the proton and neutron) and with the electron make all regular atoms.

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thanks! I read about how light sabers in the movie Stars Wars in real life was impossible.

There are two groups of fundamental / elementary particles - Bosons (named after Indian Physicist Satyendra Bose) and Fermions (named after Italian-American Physicist Enrico Fermi). The particles in each group are distinguished by certain features (ie bosons have integer spin whereas fermions have half integer spin.) and each group obey certain rules(notably the Pauli Exclusion for Fermions). You can get bosons and fermions which are not fundamental - ie they are built up from the particles listed below, but we won't deal with them.

 

The standard model of particle physics divides the two groups as per the following diagram

300px-Standard_Model_of_Elementary_Particles.svg.png

 

The bosons are the red shaded squares on the right hand side - the photon, the gluon and the Z and W bosons. We also believe that in the fullness of time two more fundamental elementary bosons will be added - The Higgs Boson and the Graviton. You will note that these elementary fundamental bosons all link to interactions rather than matter - the photon is the gauge boson which mediates the electromagnetic interaction, the gluon for the strong nuclear etc. The fermions are the particles that we consider to make up matter - for instance the quarks join through the strong force (up and down quarks in different combinations form the proton and neutron) and with the electron make all regular atoms.

 

spinning mirror technique , WAS AWSOME THANKS! printed the page....

 

I did it with the spinning mirror technique, aka the Fizeau-Foucault Method, in college.

 

http://www.pas.roche...monstration.htm

http://en.wikipedia....cault_apparatus

 

 

 

Edited by The Architekt
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