A diagram of the mechanics of the Michaelson Morely experimental device.
[quote=“Polycarp, post:14, topic:507976”]
The Galilean-satellites method is on my list of The Big Three Coincidences of the Universe. (There may be others as intriguing, as improbable, and as important, but these are the ones that have struck me as such.
(It’s not an artefact of the measuring system; in metric, SOL is roughly 300,000 kps, and Earth’s orbit is juast about 300,000,000 km across.)*
also its because we have 10 fingers not twelve (decimal system)
You don’t need a whole lecture hall, and it’s better than just an estimate: You can measure the wavelength of a laser with a simple apparatus that fits on a tabletop, and to within a few percent. I don’t know of any direct way to measure the frequency, though, so you’re right, it’s not so great as a measurement method.
Well, you could get the frequency from the energy per photon and Planck’s constant, but then, the easiest ways to measure Planck’s constant also require knowledge of the Speed of Light. And you could measure both the frequency and wavelength of a radio wave without too much difficulty, but then you have the task of showing that radio waves are the same phenomenon as light.
I’m missing something here. Wouldn’t the method still work if the diameter of the orbit were, say, 673 light-seconds?
The experiment still works. He’s just saying that it’s quite a coincidence that the value is so close to 1000.
Of course, I think that 1000 number may have more to do with rounding in convenient places. 93 million is only an average distance from the sun, for one thing.
Of course it doesn’t depend on the unit of *distance *, since distance appears in both values. However, it’s completely dependent on the time unit. If you switch to hours, the speed of light is 1080 million km/h, while the Earth’s orbit is still 300 million km. No coincidence in that case.
I just want to thank everybody for showing me some new things and getting me a bit closer to understanding.
I still have some questions about the Michelson-Morley Experiment in particular, but I think I’ll save those until I’ve read a bit more about it so that I’ve either figured out the answers or can ask them in a way that would make sense. 
Again, thanks.
Hope this is the right one…
Here’s a video of Clifford Stall explaining how to measure (and possibly even measuring) the speed of light. It’s near the end of this video, but Clifford is pretty interesting to watch.
By the way, this is not some “on screen” persona. This is how Clifford actually is in real life. And yet, he somehow snagged himself a babe.
Cliff now sells Klein bottles which are one sided bottles. Or as my son tells me: The three dimensional shadow of the Klein bottle since Klein bottles really need four dimensions. (If Clifford can get a girl, maybe there’s still hope for my son.)
You can find Clifford Stoll’s Klein bottles at http://www.kleinbottle.com/. They make a great gift for the nerd in your life.
That’s Clifford Stoll 
I know that because he’s an amazing guy
apparently you can measure the speed of light using a bar of chocolate, some toothpicks, a microwave oven and a ruler.
Saffer, see posts 8,9, and 13. I’ll explain further in the other thread you started.
Yeah. The coincidence is that, owing to the duration of the second and the diameter of Earth’s orbit, light takes almost precisely 1000 seconds to cross the orbit. Of course, if we had eight fingers per hand like Acanthostega, saying it takes almost precisely 3E8 seconds…
If you scroll down that link, you will see on the faceplate, “Panasonic Microwave Oven…2450Mhz.”
You can’t trust that number. See the other thread I linked in my last post.
I vaguely remember that the NASA set a mirror on the moon during one of the first landings, then shot a laser at it and clocked it. Whether this was for mesuring the speed of light or the punctual distance terra-luna I don’t know, they must have known at least one factor.
Unless you are saying they looked up the wrong number for the speed of light or measured the wavelength wrong, I’d say you can trust it.
Since 1983, the speed of light in a vacuum has been defined as 299792458 m/s. Because it is defined, it cannot be measured.
Another one is the triple point temperature of water. It is defined as 273.16 K. Because it is defined, it cannot be measured.
Whoa…you think that the speed of light is dependent on what some standards association or legislature says it is? Don’t you think they derived that number from measurement?
What if someone measures it and obtains a different, but accurate number? Which shall we change – the length of a meter or the second?
It is now a defined number. Defined means defined. When they defined it, they chose a number that matched closely (thought not exactly) with previously measured speeds.
Measured it against what? It is now nonsensical to say that you want to “measure” the speed of light. The speed of light in a vacuum is now a fixed, defined value. Hence it cannot be “measured.”
As mentioned above, the temperature of the triple point of water is *also *a defined quantity. The temperature of the triple point of VSMOW water cannot be measured… it is exactly 0.01 °C.
The second is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom; the meter is then obtained as the distance light travels in precisely 1/299,792,458 of a second.