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## Measuring the Speed of Light With Valentine's Day Chocolate126

Cytotoxic writes "What to do with all of those leftover Valentine's Day chocolates? — a common problem for the Slashdot crowd. The folks over at Wired magazine have an answer for you in a nice article showing how to measure the speed of light with a microwave and some chocolate. A simple yet surprisingly accurate method that can be used to introduce the scientific method to children and others in need of a scientific education."

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## Measuring the Speed of Light With Valentine's Day Chocolate

• #### Re:Why bother? (Score:2, Informative)

on Tuesday February 16, 2010 @04:16PM (#31159530) Journal

299792458 m/s, to be exact.

• #### Re:Why bother? (Score:4, Informative)

on Tuesday February 16, 2010 @04:20PM (#31159570) Journal

I think you mean approximately 300 000 km/s, not km/h. You're only out by a factor of 3600, no worries!

• #### Re:Why bother? (Score:4, Informative)

on Tuesday February 16, 2010 @04:53PM (#31160028) Homepage

Now this is very informative ;-)

Actually, not that much since you did not specify in which environment it has that "exact speed". Saying the speed of light is 194792442 m/s or any value is just as precise.

Now, saying that c is constant equal to 299792458 m/s is absolutely correct although, the speed of light is actually:

c/n where n is the refraction index.

In a microwave oven at sea level, the speed of light is *approximately* 299792458/1.0003 = 299702547 m/s

• #### Re:Slashdot doesn't recongnize this holiday! (Score:5, Informative)

<Bakkster,man&gmail,com> on Tuesday February 16, 2010 @05:20PM (#31160402)

Aslo, the article is wrong:

The demonstration works because microwave ovens produce standing waves -- waves that move "up" and "down" in place, instead of rolling forward like waves in the ocean.

Ocean waves don't "move forward".

While the individual particles do not, the wave itself does.

He is mistaken on the meaning of a standing wave. It is not the same as a transverse wave (which seems to be why he is comparing them to a longitudinal wave).

The oven is designed to be just the right size to cause the microwaves to reflect off the walls so that the peaks and valleys line up perfectly, creating "hot spots" (actually, lines of heat).

Disproved by direct observation. Go into any store and you'll see microwaves in various sizes. The perfect microwave doesn't have "hot spots".

Again, he's wrong about it being 'designed' for the purpose of having hot spots, but the design does result in hot spots. These occur regardless of oven size, they will simply be located in different locations. This is caused by reflections off internal surfaces acting like two signal sources.

While it may be conceivable to create a 'perfect' microwave with no standing wave nodes, it would be pointless. Besides, he wasn't using an 'ideal' microwave, just a regular off-the-shelf microwave, which does have standing waves.

• #### Re:Slashdot doesn't recongnize this holiday! (Score:3, Informative)

<fish@infidels.org> on Tuesday February 16, 2010 @06:36PM (#31161408) Homepage
She. Her name is Kathy Ceceri. She's a she, not a he.
• #### Re:Why bother? (Score:2, Informative)

on Tuesday February 16, 2010 @06:56PM (#31161632) Journal

Except that the speed of light in vacuum is exactly 299792458 m/s. Not approximately, exactly. By definition (of the meter).

• #### New here? (Score:2, Informative)

on Tuesday February 16, 2010 @06:57PM (#31161648) Homepage

"Valentine's Day chocolates? a common problem for the Slashdot crowd."

What is this Valentines Day? What does it have to with chocolate? ?

I think your new here, as that not on the list of IT holidays...

And there is NEVER left over chocolate, err.. REAL chocolate.. not that crap Hershey stuff (AND NO I don't buy Cadbury in the US! I know its licensed to be made by Hershey.. I have importers bring in the REAL CADBURYS!)

Just like beer if its made in the US, its junk. Same goes for chocolate.

Want cheap chocoloate, purchase all the Hershey you want.

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