# Measuring the speed of light in your kitchen

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 40878.  Tue Dec 20, 2005 12:35 pm You can measure the speed of light in the average kitchen. Line a microwave proof dish with a single layer of tightly packed marshmallows. Zap this in the microwave on low power for about 1 minute (dont use the turntable). You will see a regular series of scorch marks on the surface, so measure repeatedly the distances between adjacent scorch marks & calculate the average distance - this is half the wavelength of the microwaves. Then look at the rating plate on the back of the oven - it will have something like 2450 Mz printed on it. (Thats the frequency). So now if you multiply the wavelength by the frequency you get the speed. ie 2,450,000,000 Hz * 0.122 Metres = 2.99 x 10 to the power of 8 This is within 5% & about the same figure Einstein was working with. What he would have given for a microwave oven huh? Does anyone have any other domestic science experiments ?

40929.  Tue Dec 20, 2005 3:27 pm

 jgh29447 wrote: Line a microwave proof dish with a single layer of tightly packed marshmallows. Zap this in the microwave on low power for about 1 minute

A tightly packed layer of marshmallows heated for 1 whole minute will give you a very messy microwave oven. If you haven't nuked marshmallows before try one for a few seconds. Fascinating to see to which size these things balloon in a few seconds. Result is a nice warm gooey marshmallow. Quite edible.

 40975.  Tue Dec 20, 2005 5:54 pm Gee, that's fascinating.

 40982.  Tue Dec 20, 2005 6:28 pm I remember trying that once when I was younger, my key mistake came when I left a spoon in with the marshmallows, it arced and set them microwave on fire....

40993.  Tue Dec 20, 2005 7:57 pm

 Quote: Does anyone have any other domestic science experiments

The ones my kids love are:

baking powder and vinegar

liver and hydrogen peroxide

dissolving a raw egg's shell in vinegar and seeing how hard you have to bounce it before it breaks (mum then having to clean up subsequent mess)

there are some more at :

scifun.chem.wisc.edu/homeexpts/homeexpts.html

41024.  Wed Dec 21, 2005 4:20 am

 Quote: Gee, that's fascinating.

I thought it was QI, personally!

:-)

Tas

 41086.  Wed Dec 21, 2005 9:18 am Well, as we have learned in Braniac yesterday it is quite dangerous to heat up your microwavable Christmas Pud, doused in Brandy if you leave some foil and a spoon on the dish by accident in a microwave. DO NOT TRY THIS AT HOME

41151.  Wed Dec 21, 2005 12:23 pm

 Corelina wrote: Well, as we have learned in Braniac yesterday it is quite dangerous to heat up your microwavable Christmas Pud, doused in Brandy if you leave some foil and a spoon on the dish by accident in a microwave. DO NOT TRY THIS AT HOME
?

So where can I try it?

 41157.  Wed Dec 21, 2005 12:33 pm They did it outside somewhere.

 41377.  Thu Dec 22, 2005 8:59 am And don't wear nylon clothing in a petrol station

 41415.  Thu Dec 22, 2005 10:44 am Or wave a flamethrower around, but I don't think that made the final cut.

 41702.  Sat Dec 24, 2005 9:42 pm Once you have taken your microwave oven outside & have constructed a bunker from which you can safely observe the results (H&FS requirements being met) try putting your xmas lights in the microwave oven.

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