/sci/ - Science & Math

[Anonymous No.10213267]

How did we measure the frequency of light from scratch? Especially when frequency is defined using seconds and seconds is defined using the oscillation of a cesium atom which is limited by 9Ghz?

[Anonymous No.10213270]

We didn't measure it. Some dead guys long ago measured it.

[Anonymous No.10213397]

>>10213270
In other words... we measured it

[Anonymous No.10213516]

>>10213397
Wrong.

[Anonymous No.10213521]

What I wanna know is how Newton discovered the gravitational constant

[Anonymous No.10213522]

>>10213521
equation balancing.

[Anonymous No.10213524]

>>10213521
He measured it.

[Anonymous No.10214078]

>>10213524
>>10213522
>>10213521
>>10213516
>>10213397
>>10213270
Clearly no one on this board is well versed in science. I asked the question because because google was being a cunt.

[Anonymous No.10214113]

>>10214078
Maybe you should take a nap.

[Anonymous No.10214124]

>>10213522
Sauce?

[Anonymous No.10214148]

>>10213521
Well, he postulated it as a proportionality factor to be experimentally determined later.

[math]F \propto m_1 \\
F \propto m_1 \\
F \propto r^{-2} \\
\rightarrow F= G \frac{m_1 m_2}{r^2}[/math]

Little g is pretty easy to measure though and it's enough to explain falling objects on earth.

[Anonymous No.10214153]

>>10214148
That was supposed to be [math]F \propto m_2[/math] in the second latex line

[Anonymous No.10214163]

>>10213267
https://en.wikipedia.org/wiki/Optical_spectrometer
Although you might want to derive electromangetism from scratch first

[Anonymous No.10214178]

>>10213267
Experimentally or mathematically?
It was definitely less accurate when we weren't using cesium because the second itself was less accurate, but you could still get pretty close probably. I don't know how they did it experimentally, but If you find the permittivity (constant related to electric field strength in a medium) and permeability (constant related to the magnetic field strength in a medium) of free space in electro/magneto statics you can derive the speed of light in air using maxwells equations. To find both of these constants you can set up experiments such as electrically charging two metal spheres (or just one because of how metal reacts to charge) and seeing how much they attract or repel each other at a certain distance. (of course this like all decent science needs to have tons of things rigorously characterized prior to the experiment along with a decent amount of mathematics to relate what is going on)
Solving the wave equation gives you a speed of propagation of one over the square root of both the permittivity and permeability.


Experimentally (this is only a guess) its probably done by reflecting something a bunch of times to increase the distance traveled so that slower technology can measure it. It's always fun to try and find out how you would measure stuff like this given very simple tools. Some of the best experiments are super elegant in there simplicity, all that the designer had was a very good intuitive understanding of how the phenomena worked.

[Anonymous No.10214182]

>>10213267
Frequency of light can be a lot of different things (radio waves, optical light, x rays). You probably mean the speed of light.

[Anonymous No.10214208]

>>10214182
>You probably mean the speed of light.
He clearly meant frequency. Clues:
>defined w/ seconds
>oscillation
>9GHz