Reputation
573
Top tag
Next privilege 1,000 Rep.
Create new tags
Badges
3 9
Newest
 Yearling
Impact
~50k people reached

  • 0 posts edited
  • 0 helpful flags
  • 33 votes cast
Oct
9
comment Why does public mains power use 50-60 Hz and 100-240 V?
@Schwern First what happens at 0 Hz? A short, therefore infinite magnetic flux. Now think of what happens as you lower the frequency, you'll have to approach this limit all else being equal. Therefore the magnetic flux becomes larger in the core and so to avoid saturating the core you have to make it larger.
Oct
8
answered Why does public mains power use 50-60 Hz and 100-240 V?
Oct
1
comment Calibration of a clock
Point taken; my "normal" is a person who has taken a couple of undergraduate physics and/or EE classes, which I have. Although, we did do a enough special relativity in high school to know c is a constant = 3e8m/s.
Sep
30
comment Calibration of a clock
I agree that some people have memorized Younge's modulus for some materials, and it is a valid answer. But I want to avoid solutions that depend on memorization of obscure numbers as much as possible...
Sep
30
comment Calibration of a clock
the speed of sound in air won't help because it's pressure and composition dependent. Pressure units are also derived from s, so building a pressure sensor won't help.
Sep
30
comment Calibration of a clock
That's basically were I'm stuck with this problem. I don't like using Younge's modulus to build a clock because no one knows off the top of their hand any value for any material. On the other hand building a radio is complicated. The question then becomes, can I build a radio from scratch? I think a talented enough person could...
Sep
29
revised Calibration of a clock
added 1414 characters in body
Sep
29
comment Calibration of a clock
@WetSavannaAnimalakaRodVance that's why I'm uncomfortable using biological clocks. Height will also change with large g, but there's only so much cartilage to compress and the difference shouldn't be more than a couple of cm.
Sep
29
comment Calibration of a clock
@MonkeysUncle optical solutions are fine, but the easier the better. I can build a mirror from a block of ice, I might be able to smelt copper and iron to extrude wire and have a core, but there's no way I'll make an atomic clock.
Sep
29
comment Calibration of a clock
Assuming a moon would cover a lot of potential scenarios. Myself, I was thinking if it would be feasible to build a radio transmitter and bouncing it off a moon
Sep
29
comment Calibration of a clock
I don't have a problem with biological standards except, most people haven't calibrated their counting (although I certainly will now), while we all know our heights.
Sep
29
comment Calibration of a clock
don't think it's easy! It is an interesting question :D, if I could measure the local g then it'd be done. I think it's only possible exploiting electromagnetism.
Sep
29
comment Calibration of a clock
Agreed, but how do you measure c? In the question I state that, if I can measure c the problem is solved. But how can I easily measure c as an individual having rudimentary means?
Sep
28
comment Calibration of a clock
It's actually quite hard. If I'm on earth, and I loose "time" I can derive the eq. for the period of a pendulum and calculate a pendulum whose period equals a second. But that depends on g being constant. I could use astrological observations, but I'd have to be able to observe, recognize and remember the properties of stars I could observe from Earth. It seems to me that the only thing that I can use to recreate the standard second is to exploit the universality of c and the fact that I know my own height to within less 1%. But that's "hard" to build without cmplx tools and materials
Sep
28
comment Calibration of a clock
They're all interesting questions. I'm not interested in tracking time per say, that's "easy" if I define a new standard second; a pendulum. My question is, how do I recreate the SI standard within 5% if I'm not on earth, I have no std weights or clock, using techniques that an individual could reasonably create from scratch using definitions remembered from school (i.e. c is 3E8m/s, my height is 178cm). This individual can re-create all the math he needs (for math comes from within), but he can't be expected to build an atomic clock, or remember the stiffness or half lives of materials.
Sep
28
comment Calibration of a clock
Also, I am a stranded individual not a civilization. Therefore I cannot realistically recreate an atomic clock or nuclear reactor. Nor am I interested in how to re-create the SI standard to within 1E-10 of the original. I'm interested in the techniques to get within 2-3%
Sep
28
comment Calibration of a clock
I think my question is a little bit different though since I have not lost my memory, but I'm in a different world. For example, I cannot assume g is the same, for example. I could try to measure G, but that's fraught with error. Thank you for pointing it out, however, it looks like a fascinating Q
Sep
28
revised Calibration of a clock
added 4 characters in body
Sep
28
asked Calibration of a clock
Sep
27
comment Action and Reaction between two people
You don't move because you're a big person hitting little people.