Timeline for I'm stranded on an alien planet. How do I measure an earth year without a clock?
Current License: CC BY-SA 3.0
8 events
| when toggle format | what | by | license | comment | |
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| Oct 24, 2018 at 14:19 | comment | added | Sherwood Botsford | If you run the calcs through, speed of sound in air depends only on temperature, and gas makeup. en.wikipedia.org/wiki/Speed_of_sound#Equations There is a pressure term in the equation, but it's balanced out by a density term. You could be messed up if your atmosphere has a high percentage of argon, but if it's breathable air and a reasonable temperature, the echo effect may give you a reasonable answer. | |
| Sep 28, 2015 at 18:26 | comment | added | Eph | The speed of sound is dependent on the ratio of specific heats and molecular mass in addition to temperature, so while you might be able to estimate temperature to within 5%, I very much doubt you could figure out what portions of argon, neon, nitrogen, oxygen, water, etc. you were breathing to determine average molecular weight to a factor of two. | |
| Sep 25, 2015 at 0:26 | comment | added | leftaroundabout | I agree with chepner that atmospheric composition will probably mess this up. Still the idea is pretty good, because apart from chemical composition, the biggest influence on sound speed is indeed temperature, and temperature is probably the quantity you can measure most precisely without any device. (You can clearly distinguish 17° C and 27° C, i.e. 290 K from 300 K – error less than 5%.) | |
| Sep 24, 2015 at 21:35 | comment | added | njzk2 | @chepner everything depends on a lot of factors. Pressure and temperature (and athmosphere composition) influence the speed of sound. However, you probably can tell the temperature to 10C. And pressure is not the biggest influence. | |
| Sep 24, 2015 at 20:55 | comment | added | chepner | "...depending on the pressure and temperature (which you can estimate)". That's a pretty big detail to gloss over. | |
| Sep 24, 2015 at 17:39 | comment | added | njzk2 | @PearsonArtPhoto, yes exactly. There are other answer that cover the local time measurement (water clock, pendulum, hourglass, heartbeat...) | |
| Sep 24, 2015 at 17:17 | comment | added | PearsonArtPhoto | This would only allow you to calibrate if you have some sort of local clock accurate to the second, but still is interesting. | |
| Sep 23, 2015 at 4:49 | history | answered | njzk2 | CC BY-SA 3.0 |