字幕列表 影片播放 列印英文字幕 It's the week after Easter and that means that homes all across America are overflowing with stale peeps. Now you could eat those peeps OR you could use them to calculate the speed of light. "Finding the Speed of Light ... With Peeps!" The speed of light is one of those numbers that people have chased for centuries. Galileo wanted to figure out how fast light moves "Buona notte" So he proposed an experiment "Facciamolo!" He would uncover a lantern, and when the light reached his assistant The assistant would quickly uncover his own lantern. Using a water clock, Galileo would keep track of the time between uncovering his light, and seeing his assistant's light. Up close there was no noticeable delay except for the split second it took his assistant to react. Then, they started moving away from each other. Galileo figured the delay would get longer and longer because the light would need more time to travel the greater distance But even when they were a mile apart, there wasn't a noticeable pause. "Che rabbia!" He couldn't have guessed that light had made the trip in 1 hundred thousandth of a second. Centuries later, in 1849, a French scientist whose name I can't pronounce "Armand Hippolyte Louis Fizeau" Came up with an even better way to measure the speed of light Which was pretty impressive considering that people weren't even using lightbulbs yet. He took a toothed wheel and spun it faster and faster He shot a beam of light between the teeth [PEW] and reflected that beam of light off a mirror 5 miles away [BOING] By the time the light got back a tiny fraction of a second later, the teeth had moved over just enough to block the light. BONK PEW BOING BONK No light made back through But if he made the wheel spin a little faster, PEW BOING the teeth would move over one position and the light could get through So when "Fizeau" saw the light he knew the wheel was spinning so fast that a single tooth was moving over one place in the time it took light to travel 10 miles. With some quick math "Armand Hippolyte Louis Fizeau" determined that the speed of light was 700,000,000 miles per hour wHICH WE NOW KNOW WAS ONLY 5% OFF THE Actual VALUE Today I can find the speed of light in my Kitchen Which brings us back to the peeps "Finding the Speed of Light ... With Peeps!" And a microwave And just a little bit of physics Microwaves travel at the speed of light And like all waves, their speed is determined by how fast they go up and down - that's the frequency And their wavelength The frequency is written on the side of my microwave ... right here 2450 MHz so we've go the frequency To calculate the speed we just need to know the wavelength. and we can find the wavelength by microwaving peeps I'll set it on low so the peeps don't just explode And let it run for a minute or two. Inside microwaves are bouncing around. In some spots there isn't much energy at all, and the peeps in those area stay cold. In other spots there's lots of energy and the peeps get really hot Those hot spots are half a wavelength apart So in theory if I measure the distance between melted peeps I can find the wavelength Sure enough some of the peeps are really gooey, while others haven't melted at all Poking around, I found the rough location of a handful of hotspots And measured the distance between them... Those average out to 2.43 inches - so that's half a wavelength - so multiply by 2 so the wavelenght is 4.86 inches So now to find the speed of the microwaves - which IS the speed of light - I just have to do the math Frequency times wavelength - 2450 MHz times 4.86 inches Gives us about 12 billion inches per second - or ... 676,534,091 mph and that's pretty close to the actaul speed of light "We Just Found The Speed of Light ... With Peeps!"