

Measure the Speed of Light Using Your Microwave - sdfx
http://orbitingfrog.com/blog/2008/05/13/measure-the-speed-of-light-using-your-microwave/

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FlorinAndrei
I remember measuring g (standard gravitational acceleration) in the pantry at
my parents' house when I was in high-school.

It involved a pretty hefty dumbbell, a long string and a watch. Basically, it
was the pendulum method - you need to time several oscillations, then measure
the length of the pendulum and the formula gives you g.

The pendulum was about 2 m long (6 ft) I guess, the dumbbell was maybe around
10 kg (20 lb) or so, and I managed to time perhaps 5 minutes worth of
oscillations - being pretty heavy, it continued to sway back and forth for a
long time without stopping.

I had to debate with myself the actual length of the pendulum, because I
couldn't know for sure where the center of gravity of the whole thing was. In
the end, I just postulated it was exactly on the axis of the dumbbell -
probably pretty close to reality.

I think I got something like 9.7 m/s2 IIRC, which is pretty close to the
average of 9.8 (which also depends on the latitude, altitude and a number of
other factors).

Physics is fun.

~~~
electromagnetic
> Physics is fun.

My wife still doesn't believe me when I say it, but yes physics is fun.

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SpacemanSpiff
This reminds me of trying to cook pancakes in a microwave back in the day. I
poured a shallow plate full of batter and popped it in. This particular
microwave had a rotating deck inside, but since the interior dimensions were
so small I ended up putting the plate nearly on the center of said deck. Turns
out the pancake "cooked" in concentric rings of alternating fluffy goodness
and raw batter. Could probably have determined the speed of light using those
too..

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cromulent
I did this with my kids a couple of months ago, using chocolate. It came out
about 290000 km/s. Lots of fun explaining it first and then using Google
afterwards to check our result. High fives all around.

Apparently you can see plasma, if you microwave a light bulb in the dark, with
the microwave light gaffa-taped over (put the bulb in a glass jar first for
safety). That's next.

~~~
electromagnetic
Compact fluorescents look cool, however I'd put one in a jar and silicone shut
the lid because the last place you want mercury is in an enclosed space where
you routinely put food your children are going to be consuming (it's not going
to hurt them, god knows a broken thermometer did nothing to me as a child but
it's an unnecessary risk when we're talking about life-time exposures and not
immediate exposure).

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RiderOfGiraffes
See also:

<http://news.ycombinator.com/item?id=1307291>

<http://news.ycombinator.com/item?id=1051011>

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bdfh42
This one (well this approach anyway) comes around like a revolving door

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JoeAltmaier
Hm. Seems like a tautalogy - given the frequency of light and the wavelength,
C = F X W. But you didn't measure the frequency at all - it was given.

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FlorinAndrei
At some point you have to rely on "givens". You can't go turtles all the way
down.

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JoeAltmaier
Sure you can. Ham operators bounce a wave off the moon. Time the round trip.
Speed of light. Or send a blip thru a spool of fibre optic cable, measure the
transit time. It CAN be directly measured.

~~~
sliverstorm
So how did you figure out how far away the moon was?

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lpgauth
You can also do this with a chocolate bar.

~~~
ghostDancer
And licorice
[http://translate.google.com/translate?client=tmpg&hl=en&...](http://translate.google.com/translate?client=tmpg&hl=en&u=http://www.madrimasd.org/blogs/astrofisica/2006/07/12/34948&langpair=es|en)
, it's always wondeful to feel the science so close , and when you show these
to some teens and you see their faces it's incredible.

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madmaze
this is certainly my new favorite way of making kids excited about science =)

i will have to try this with the next young and impressionable child i come
across lol

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asciimo
A more efficient method of deriving the value:
<http://www.google.com/search?q=speed+of+light>

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kirpekar
For those seeking efficiency, accuracy, rigor, error bounds, confidence
intervals, sigmas and such: get over it. This is fun; pure fun; a great way to
teach your kid how cool science is.

~~~
luxative
couldn't agree more; especially at a time where education is getting
increasingly 'pointless'to kids who sometimes think (often correctly) they can
get a more educative experience online.

