Speed of light from tomato soup
A couple of weeks ago, I was heating soup in the microwave. I set it for 20 mins, and wandered off. When I got back the soup had exploded out of the bowl, evenly coated the walls of the microwave, and continued to cook.

So I set to cleaning it. What I noticed was that, now that the soup was static on the walls and not being moved on a turntable, it didn't cook evenly. Some parts were frazzled like flakey paint, and the areas in between were still damp. The areas where the cooking was concentrated were about 2 thumb lengths apart, or 6 cm.

I was looking at the half-wavelength of the microwaves, which would travel at the speed of light. A full oscillation would be 12 cm, or 0.12m. Looking at the safety information of the microwave, it operated at 2450 Mhz. To put it another way, it could pump out 2.45 billion of these 12cm lengths every second.

So a beam would travel 0.12 * 2450000000 meters in a second, which is a speed of 294000000 m/s. The official speed of light is 299792458 m/s. So I was 2% off calculating the speed of light from a bowl of exploding soup. Not bad.

Edit : As has been pointed out, this bit of cleverness has been nullified by leaving the soup on for 20 minutes to begin with.
(chutneyweasel, Fri 14 Oct 2011, 10:52, 14 replies)

Yeah, but you still set soup to cook for 20 minutes, Einstein!

( scarpe We Stole Bikes, Fri 14 Oct 2011, 11:03, closed)

Boring

(Eggstrovert isnt patronising you...honest..., Fri 14 Oct 2011, 11:08, closed)

^^ What Penis Erectus said ^^

( The Mock Turtle ™ --- Thinks you are a cunt, on, Fri 14 Oct 2011, 11:08, closed)

You'd have been 100% accurate
if they hadn't rounded to 2450MHz.
( Draconacticus Reject shampoo. Demand real poo!, Fri 14 Oct 2011, 11:22, closed)

*doffs hat*
(Schindler's Wrist Brimful of asha and a P45, Fri 14 Oct 2011, 11:45, closed)

I read about this experiment ages ago
but it suggested using a bar of chocolate and leaving it only for 30 s or so, until the chocolate had started to melt and then measuring the distance between the melted bits. Then you get to eat the chocolate instead of cleaning up tomato soup :p

Have a clicky from a science geek cos I think experiments like this that show how awesome physics is are great :D
(Petite chien is going to do science to it, Fri 14 Oct 2011, 11:55, closed)

The tidiest way to do it...
...is to use bread, buttered all the way to the edge. Take out the turntable and layer bread on the bottom of the microwave.
( TheAlmightyBeev, Fri 14 Oct 2011, 13:05, closed)

You have
really short thumbs.
(SausageWarrior destination Zululand, come on boys jump in the van, Fri 14 Oct 2011, 12:00, closed)

Surely you were calculating the speed of microwave radiation,
rather than the speed of light?
( monster munch person, man, woman... camera... TV?, Fri 14 Oct 2011, 12:33, closed)

*facepalm*
And there is no worse *facepalm* than a geek *facepalm*
( Scaryduck LIKES EGG, Fri 14 Oct 2011, 13:45, closed)

facepalm

You only “know” that the speed of microwave radiation is the same as speed of light because you’ve been told it’s so, third hand.

This guy is working from tomato soup based observations relating to microwaves and only microwaves.
( Ring Of Fire A petty, drooling belming butthurt retard., Fri 14 Oct 2011, 14:58, closed)

Eh?
The observable phenomenon was the action of the microwave radiation, thus the calculations described derive the speed of the microwaves (the fact that the speed is equal to the speed of light is coincidental).

If you're in a position to know that the speed of microwaves is equal to the speed of light, then odds are that you already know the speed of light, and thus don't need to calculate it (until RoF posted, I wasn't aware of the speeds being equal).
( monster munch person, man, woman... camera... TV?, Fri 14 Oct 2011, 18:40, closed)

He calculated the speed of electromagnetic radiation in air
Light is our word for EM radiation of wavelength 400-700nm, microwaves is our word for EM radiation with a wavelength on the order of a few centimetres. It's all photons in the end.
(Petite chien is going to do science to it, Fri 14 Oct 2011, 21:55, closed)

How do photons have wave lengths?

( Ring Of Fire A petty, drooling belming butthurt retard., Sat 15 Oct 2011, 17:03, closed)

The deBroglie equation

(Petite chien is going to do science to it, Sun 16 Oct 2011, 12:14, closed)

did this
last week to demonstrate just this calculation. I came up with the same value as you. My year 10 class weren't that impressed though. Boring shits.
(cypherspace is not a toaster, Wed 19 Oct 2011, 20:52, closed)