Measure the Speed of Light Using Your Microwave

http://orbitingfrog.com/blog/2008/05/13/measure-the-speed-of-light-using-your-microwave/

by sdfx • 16 years ago

72 21 16 years ago

orbitingfrog.com

asciimo• 16 years ago

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

jameskilton• 16 years ago

If efficiency was the only reason people did anything, life would be fantastically boring.

Besides, this is an awesome way to give a visual of what exactly a wave is. I'll have to remember this one for sure!

kirpekar• 16 years ago

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• 16 years ago

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.

InclinedPlane• 16 years ago

Finding the value from an authority is not the same as deriving the value.

Get ye back to remedial science education.

lpgauth• 16 years ago

You can also do this with a chocolate bar.

ghostDancer• 16 years ago

And licorice http://translate.google.com/translate?client=tmpg&hl=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.

bdfh42• 16 years ago

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

FlorinAndrei2• 16 years ago

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.

electromagnetic2• 16 years ago

> Physics is fun.

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

JoeAltmaier2• 16 years ago

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.

sliverstorm2• 16 years ago

Only in the sense that F = M * A is a tautology.

FlorinAndrei2• 16 years ago

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

JoeAltmaier2• 16 years ago

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.

nitfol• 16 years ago

Right, this experiment measures the wavelength of the microwaves. Apparently it is possible to independently calculate the frequency of microwaves. http://en.wikipedia.org/wiki/Speed_of_light#Cavity_resonance

cromulent• 16 years ago

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.

electromagnetic2• 16 years ago

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).

SpacemanSpiff• 16 years ago

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..

RiderOfGiraffes• 16 years ago

Measure the Speed of Light Using Your Microwave

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