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Measure The Speed Of Light With Your Microwave
maddmike writes "There is a very interesting article on About.com that shows how to measure the speed of light using your microwave to melt chocolate. "
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Just try to measure the speed of dar. . .
Oh, nevermind.
KFG
...don't try this at home. Theobroma cacao (chocolate) is a highly dangerous substance with known stimulant effects. It is also highly addictive and should be used with extreme caution. Overdose can cause morbid obesity, sluggishness, and death. Only qualified experts should handle this dangerous reagent at home.
I am experienced at handling this most hazardous material. Please wrap it carefully in a heatproof container, and mail it to me. It will be disposed of properly. (burp)
Honey, I shrunk the Cygwin
According to the website, using the formula, the speed of light is 24 cubits per moonphase.
Maybe we can unravel the mystery of the expansion of the early universe with a microwave and a set of unevenly expanding peeps. I envision a new era in science
Is it just my microwave, or is the speed of light 2m/s ?
There is a very interesting article on About.com that shows how to measure the speed of light using your microwave to melt chocholate.
Big deal...I can measure Hubble's Constant by charring bagels in my toaster. Pffft.
Yay! I did that experiment! According to my calculations light in air travels at 783 km/h. Wow, that's fast!
I was just writing a wikipedia page yesterday on Famous Experiments, and that's the one I added. I read that Galileo tried measuring the speed of light the same way they measured sound -- by having two people stand a large distance apart, and flash a latern (for light) or make a sound. Subtract out the handler delay (a known quantity dependant on the person), and divide by two to get the speed of the wave. This works rather well for sound, but never worked for light.
To make laws that man cannot, and will not obey, serves to bring all law into contempt.
--E.C. Stanton
Short informative read:S peedOfLight/measure_c.html
http://math.ucr.edu/home/baez/physics/Relativity/
...Your Local Fire Department by placing some metal in your microwave and putting a blanket over it. =P
Anyone can melt chocolate or heat water in their microwave.
Real geeks use microwaves for what they were intended for... nuking free trial CDs from AOL.
http://physics.about.com/library/weekly/aa01270
The link given in the story here is for the second page.
Bah.. I'm waiting for chocolate wafer-transistors.
think.. eatable cpu's! or better.. eatable storage for the paranoid
- I choked on the red pill and now I'm stuck in limbo
You cannot do it by measuring the dimensions of the magnetron cavities, because the calculation of the frequency based on dimensions assumes the thing you are trying to work out - the speed of light. Frequency counters that go up to 2.5GHz are a bit difficult to come by in most homes. One possibility might be to extract some energy from the cavity using a suitable antenna and mix it with the clock signal from a 2.4 or 2.53GHz motherboard, then try and pick up the resulting beat signal using a short wave or VHF radio. However, I'm not at all sure how to get the signal out of the P4.
Has anybody got a better and reasonably practical method of measuring the frequency?
Panurge has posted for the last time. Thanks for the positive moderations.
Summary of the method used in the article:
* Slightly melt chocolate chips in your microwave
* Measure distance between melted spots
* This gives you (half) the wavelength of your oven
* Multiply by the frequency of your oven, you get the speed of light
That's certainly interesting, but guess what? Many scientists have done better (and much more expensive) measures, so we already know the speed of light quite well.
What we might not know as well is the frequency of your oven. So I suggest you reverse the above formula, and you measure the frequency of your oven (not always printed on the back, as the article admits) this way.
Chocolate is dark, like the universe.
Chocolate is semi-soft, like the universe.
Chocolate is an emulsion, like the universe.
Chocolate is good...and evil, like the universe.
Chocolate may be going into or coming out of a black hole, like the universe (I had to).
So, inevitably, this bean is, indeed, a universe unto itself.
Speed of light approx 300 000 km/s = 3E8 m/s.
Actually, the easiest way to measure the speed of light is to measure the interval between the lights turning green and the first cab horn sounding during the morning rush hour in Manhattan, then measure the distance from the lights to the cab.
Neither original nor practical, but then I am tired and this is /.
Panurge has posted for the last time. Thanks for the positive moderations.
maddmike writes "There is a very interesting article on About.com that shows how to measure the speed of light using your microwave to melt chocholate. "
Bah, that's easy stuff. It's about time that About.com tackled the real holy grail of science - how to teach Slashdot editors to use a spelling checker.
"Accept that some days you are the pigeon, and some days you are the statue." - David Brent, Wernham Hogg
microwave experiments and links
The metre is defined in terms of the speed of light, so by definition c=299792458 m/s
Pretty pointless trying to measure it really.
Quidquid Latine dictum sit, altum videtur (anything said in Latin sounds important)
>could someone please provide me with the equation if mine has a turntable?
Step [1]: Using a highly detailed tool (1) you will first wrap around a plastic groove on the front of the microwave. You will then use this tool (1) putting a few newtons of pulling force translaterally against the groove. Too much pressure here may be dangerous, so use caution. If your microwave has no such groove, you'll press tool (1) against a reverse indentation on the front of the microwave using at least a few newtons of pressure. Overuse of pressure is not a danger when using the correct tool (1).
Step [2]: At this point you'll be able to access the inside of the microwave. If you cannot access the inside of the microwave at this point, you have not successfully completed step [1]. Please attempt it again as necessary to access the inside of the microwave. Once access has been gained, you will use tool (1) to grip the edges of the glass object inside. Do not grip the glass object extremely tightly or it may be damaged! Now, using tool (1) exert an upward pressure to the glass object, causing it to levitate to the middle of the microwave (this point will vary depending on model).
Step [3]: You must complete step [2] to continue to this step. If you are at this step, you are now gripping a glass object centered in your microwave. Pull this object towards you with tool (1). Continue to move this object and rest it on a flat, cool, surface. Ungrip the object. Using a choice of tool (2), exert a reverse pressure on the item disloged in step [1]. Continue to extert this pressure until a click is heard.
Step [4]: There is no step [4]. If you have completed step [3], your microwave is now ready for the experiment in the article.
Required Tools:
(1) fingers
(2) hand
Optional Tools:
(3) brain
(4) article
If you could be told what you can see or read, then it follows that you could be told what to say or think - BoC
It's 3x10^8 m/s
If I seem short sighted, it is because I stand on the shoulders of midgets
I'm no physicist but, seems to me, 6cm would be 0.06m, so more like 3 x 10^7 per solid Girardehli testing.
As my microwave didn't have a frequency reading on the back, I will use the 2.5GHz "typical" value I found after a brief web search.
Thus: the wavelength is
Then the speed is 0.12m x 2.5 x 10^9
What changed under Obama? Nothing Good
Some brave souls try to correct me by pointing out that "the microwave particles" are so small they can't be seen, so are clearly smaller than the holes.
I then introduce the notion of particle/wave and laugh as I watch them go completely blank...
Actually, the speed of light is 299792458 m/s by definition/p>
So, given the frequency of your microwave a priori, this is actually a rather elaborate way of determining the length of a met{re|er} :-)
I was about to attempt this fascinating experiment but my stomach had... other plans
Couldn't they have created this experiment with something less tasty, like broccoli?!
Business \Busi"ness\, n.;
A scam in which all people involved perceive as beneficial...
You can always use your network cables instead; brief description or full paper.
Anyone care to use the method with RFC1149 Avian Carrier Protocol, namely Using Ping to determine Speed of Flight!
Andrew Yeomans
you're wrong, or at least outdated: http://lamar.colostate.edu/~hillger/meter.htm
this is Slashdot we're talking about. I don't think a crowd of women is something regular denizens have to worry about very often.
There was this episode of Mystery Science Theater 3000 (Secret Agent Super Dragon?) where the main character flips a light switch, and about half a second later the light dimmed down. Crow said "Light travels slower in his world". Heh.
Hmmm.. sorry guys, it really is more of a visual joke.
"Derp de derp."
measuring the speed of microwaves, not light
Microwaves are light. They just have a longer wavelength. The speed is the same as for visible light. It is only dependent upon the medium.
if it needs 2 minutes to melt some chocolate, that's not very fast.
Otoh, I wholeheartedly agree with this statement.
"I assumed blithely that there were no elves out there in the darkness"
In a vacuum, they're the same - all electromagnetic radiation will travel at c - 299792458 m/s. In the inside of a microwave oven, typically filled with air, but in this case also a certain quantity of chocolate, both will be lower. However, the higher energy wave (microwave) won't be slowed as much as the lower energy wave (light). So in actual fact, he is measuring the speed of microwave radiation in air, which is neither the same as that of light in air, nor electromagnetic radiation in a vacuum (it'll be somewhere between the two).
HTH.
Second problem is that it is actually difficult to stop something rotating. You need an inverted soup bowel or something to give clearance over the turntable drive peg.
Ok, if I use enough clearance to prevent rotation I get about 1cm between hot spots.
See my journal, I write things there
If you google for "speed of light" you get "News: Measure the Speed Of Light With Your Microwave - SLashdot - 2 hours ago"
Complete with (incorrect) overusage of CAPS and everything.
This experiment has no place outside the elementary school classroom. In fact, I think it has no place even there, because this method will be so wildly inaccurate that kids will learn the wrong speed of light.
Is it a wonder education is going to hell? We keep coming up with stupid, irresponsible "hack" methods of science that teach people the WRONG thing because we're spending too much money service the national debt to afford decent educational tools. Of course, it doesn't help that the "Educational" price for scientific instruments is often 2 to 3 times more than the "corporate" price - companies sucking at the government teat, of course.
"Superintendent Chalmers, thank you for your request for purchase of a time-domain reflectometer for use in your science classroom. While we value the ability of your students to perform valid and accurate experiments in physics, we've read somewhere on the Internet that a microwave oven will do just as well. They're about $50 a walmart. Therefore, your request is denied. Besides, I need a new Lexus. Sincerely, School Board"
Go ahead, mod me down, you know I'm right.
You can also measure the speed of light using ants, the ants are small enough that they can fit into the low energy points of the microwave.
If you put some ants in the microwave, and switch it on, they all start moving from the heat into the cold spots, measure the distance between the cold spots and you have the wavelength.
Obviously, you shouldn't *actually* try this, unless the ants happen to climb in there looking for food, then they're fair game :) And take the turntable out, that's cruel.
The calculation (chocolate or ants) does still rely on prior knowledge of the frequency of the microwave(s) being used. Trying to measure the speed of light without a prior fixed frequency or wavelength is much more taxing. A shortwave radio can help though, or a flashlight and a large telescope (bouncing signals off the moon)
If you're going to experiment with your microwave, these should be fun. http://www.amasci.com/weird/microexp.html
-- http://qdbii.pyoko.org - Quote Database II I can't look at the words "Windows XP" and not think that Micro
A microwave oven is a resonant cavity, and the resonant frequencies for the modes (TE/TM) are given by
where A,B,C are the dimensions of the cavity and i,j,k are non-negative integers (not all zero) which specify the mode.
This experiment does not "measure" the speed of light. All this "experiment" does is tries to isolate out a specific mode (i = 2, j = k = 0) and verifies that the frequecy rating printed on the back of the oven corresponds to this mode (which is still a cool thing to do).
You see, the manufacturer already implicitly *used* the value of c above in designing the oven and calculating the value of the number printed on the back of it, so the "experiment" is not capable of making a (independent) measurement of c.
Lest you think I am nitpicking, this kind of problem plagues us physicists all the time!
"In a proper physics experiment all the quantities that affect the result have to be measured. In this one the frequency of the microwaves is taken for granted"
This seems wrong to me. Experiments seek to measure the unknown using the known.
Why is it less valid to measure the frequency by looking at the back (another person has measured the frequency and marked it on the device) than it is valid to measure the distance by comparing to a ruler where another person has has measured a set of lengths and marked them on your stick of wood.
More generally - do you expect scientists to measure the speed of light and the charge of an electron for every experiment they perform? If c and e cannot be taken as known - how about Pi?
If science is about accumulating knowledge - it seems odd to throw it all away for each experiment...
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Absolutely worthless to anyone who bought a microwave in the last 2 years because they switched to a slightly modulating, slightly moving frequency emmiter which makes sure that it heats all of the food as quickly as possible instead of little hot spots. So basically, it melts everything at once in a new microwave. At least in a "good" new microwave.
*There's Klingons on the starboard bow, scrape em off Jim!*
You didn't measure the speed of light, you measure a wavelength. Unless you can show that you had some way to confirm the frequency of the light source that is not dependent on knowing the speed of light, then when you looked up the frequency of the light source you were effectively looking up the speed of light and using it to determine the speed of light. No wonder your answer came out close!
I'm an American. I love this country and the freedoms that we used to have.
How can there be stable nodes in the electric field within the oven if the distance between the oven walls is not a whole multiples of a half-wavelegth? Aren't the dimensions of the cavity set so that multiple patterns of standing waves will co-exist, each with its own nodes?
1) The microwaves are lower energy waves than light. There's just "more" of them in that cavity than visible light from the appliance bulb.
2) Generally speaking, materials (esp. un-ionized gas) will have a lower refractive index as frequency decreases. Hence, microwaves will be slowed less so than visible light in the air cavity of the microwave.
3) The patterns formed in the chocolate are due to standing waves set up in the cavity. The chocolate is a thin layer at the bottom, so the nodes will not reflect standing waves set up INSIDE the chocolate, because the wavelength is too large. So the patterns reflect the wavelength of microwaves in air, which is negligably less than the speed of light in a vacuum.
Measurement error from the ruler is a much larger (orders of magnitude larger) factor here.
Fuck Beta. Fuck Dice
Wrong. The meter is defined by the distance from the Equator to the North Pole (divided 10 000 000).
No, it isn't. It really is defined from the distance travelled by light in one second. However, it was originally intended that there be 10,000 km from pole to equator: after performing the survey, the metre was defined by the length of a particular piece of metal. Unfortunately, their survey was not quite correct, and the actual distance (in terms of that piece of metal) from pole to equator was 10,002,090 m. The length definition changed in 1960 and then in 1983 to its present form. Likewise, although one cubic cm of water has a mass of one gram for most practical purposes, it is not formally defined as such.
There is no place like ~!
This only works if you can stop the mechanism by which the microwaves are scattered around to make for even heating. If you have a turntable in the bottom of your microwave, then removed it might do the trick, but most microwave ovens have a rotating metal "fan" that is enclosed in the upper surface over the cooking cavity, and that metal fan spins to scatter the waves around -- think of it like a flashlight and a mirrored pinwheel. Hence no turntable is required.
I'm not aware of any way of disabling that "fan", although I suppose you could drill a tiny hole in the shroud and poke in something to stop the spin, a la stopping a grinding PC fan. But I personally am not terribly interested in poking a drill into a microwave oven ...
One simple rule for its versus it's
At what temperature? And is that pure water? A mix of isotopes that normally occurs in nature, or the most common 18H2O?
Ambiguities like this is why the metric system was changed from such standards many years ago.
-Looking for a job as a materials chemist or multivariat
Some ovens have the fan-type stirrer you describe, but not all. Others solve the problem of hot and cold spots by putting a turntable at the bottom which rotates food in and out of the hot and cold spots.
The experiment is for an oven with a turntable. The article talks about taking the turntable out and putting the chocolate on something non-rotating.
The answer to your question about cavity size and standing waves is I Don't Know. In fact, I've wondered for a while why microwave oven designers don't use the same trick as recording studio architects, and make the walls non-parallel.
It's possible that they have to make the cooking cavity resonant in order for the magnetron to "see" the right kind of load on its output. But that shouldn't matter much as long as there's food absorbing the microwaves.
I read about a trick on the web a few years ago so I tried it at home and showed my family. I cut a grape in half length-wize, but left a little skin connecting the halve, lay the two round sides on a plate, placed it in the microwave, hit start, and **ZAP!!!** -- flames, sparks, toasted grape halves flying apart.
My brother thought it was "awesome," my mom feared for her microwave, and my dad (an EE) said "ah, the grapes are about the size of the wavelength of a microwave so the grape must be acting as a dipole antenna, neat" and walked away.