Timeline for Minimum information required to measure your local physical environment
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
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| Jan 31, 2022 at 16:21 | comment | added | Cort Ammon | Let us continue this discussion in chat. | |
| Jan 31, 2022 at 16:18 | comment | added | Vogon Poet | "Trial and error" may be fatal; the goal is to use only extant scientific knowledge. You are safe, but how long? You need control. I feel we would require to determine: Am I on a planet or otherwise? Can I grow food? (take soil and air measurements like "The Martian"), can I control air breathability qualities? Can I control my own local temperature, pressure and humidity; build a radio tower, motor or engine, safely? Half-lives, celestial observation, or a timepiece make all of this simple, but without those, are we doomed to replicating all science? | |
| Jan 31, 2022 at 16:17 | comment | added | Vogon Poet | The "properties of your environment" condition may have been vague without understanding what Weir's amnesiac astronaut character was able to do after waking up in a strange room. He determined he was on a spaceship of a given mass and measured the rotational radius of his spin-gravity. Let's say you have all accumulated scientific knowledge from earth but you have arrived at an unknown location. You find that physical properties are somehow different, and you need to engineer and build practical things (buildings, engines, vehicles, weapons) - for survival. How tightly? (continued...) | |
| Jan 30, 2022 at 18:36 | comment | added | Cort Ammon | @vogonpoet if you're looking for the minimum, we would need more requirements. Which dimensions are you looking to measure when you're done (eg distance, time, mass) and what accuracies are you looking for. The "no watch" bit will be very very tricky. Historically, time was one of the trickiest dimensions to measure without a good standard to measure, but mass was the last thing that we finally pinned down. | |
| Jan 30, 2022 at 12:13 | comment | added | Vogon Poet | I was looking for the minimum information needed; i.e., a calibrated gauge or spring as you said. While many options exist to recreate early experiments, what information would be absolutely indispensable to someone making useful progress with the accumulated knowledge we have. It seems that the measure of time was needed for Weir's scenario. An article here seems to say a cesium clock would need a calibrated reference oscillator to start: science.howstuffworks.com/atomic-clock3.htm, and puts us back in a chicken-egg quandry. | |
| Jan 30, 2022 at 4:01 | comment | added | Cort Ammon | @VogonPoet I may have been misinterpreting your question. I was looking at what can you do if you lack any calibrated equipment. It sounds like you're considering letting someone bring calibrated equipment, just nothing that explicitly measures time. Which is a fun problem, don't get me wrong. Its just not quite the direction I was going with my answer. In fact, the changes to the SI system made in the last 3 years were done explicitly with the intent of pegging the SI units to physical constants rather than physical things, so that you could recreate it if need be. | |
| Jan 30, 2022 at 1:37 | comment | added | Vogon Poet | Actually precise linear measurements open many options; RC time constant (needs a capacitor with precise plate distance+conductor of known resistance [again, by length], and lead-acid Planté battery of known potential); or accurate mercury thermometer calibrated by your body temperature (needs precise capillary tube volume). Thermometer allows a known force (water pressure from heating), a known force can rotate a lead disk of known mass (𝑚=𝑝/𝑉) to a known RPM. So can a precise ruler derive from a precise prism diffracting a spectrum? (cut and diffraction angles are not relative)? | |
| Jan 29, 2022 at 23:34 | comment | added | Cort Ammon | And the solution, of course, is to have a time standard which doesn't depend on anything external in the new world. Perhaps something with springs whose oscillating frequency is well understood and uncorrelated with gravity. Or even better, a piece of quartz crystal and the mechanics to track its resonant frequency. As Douglas Adams put it: digital watches are a pretty neat idea. | |
| Jan 29, 2022 at 23:32 | comment | added | Cort Ammon | @VogonPoet Yes, its a pest trying to find these values without any knowns, like gravity. Of course, this is not too large of a surprise, given that it took us quite literally thousands of years to come up with non-relative measures. As for the clock, you do need an oscillator, but it does not have to be pre-calibrated. The caesium clock resonates at the specified frequency, creating a detectable change in energy. You look for that resonance, and that tells you when you're at the right frequency. (the devil, of course, is in the details there) | |
| Jan 29, 2022 at 21:03 | comment | added | Vogon Poet | Ugh. Nevermind... Knowing pressure with mercury or water requires known gravity. | |
| Jan 29, 2022 at 20:46 | comment | added | Vogon Poet | I may have solved my own problem... You know how to closely find 98.6F, you can create a pressure gauge w/ InHG or water; you know water viscosity at different temps & pressures. The time it takes water at a known temperature to move through a hole of known diameter with a known pressure differential can be measured without gravity. Derive the true second from this fluid xfer rate, then the other calculations follow. So the minimum information would be water properties and pressure conversion charts. Is this correct? | |
| Jan 29, 2022 at 20:34 | comment | added | Vogon Poet | Excellent answer, but Two parts: I neglected to mention that inches of mercury or water would be simple to measure, thus if you had conversion tables, pressure could be had to within the accuracy that you know your own height, or whatever other accurate measure you know (clothing measurement, etc). I don't know if there may be a round-about way to derive time via a known pressure gradient (Fluid mechanics and Viscosity?) Another thought: A cesium clock I believe would need a pre-calibrated reference oscillator to sweep the 9,192,631,770 Hertz microwave spectrum. Does that change this answer? | |
| Jan 29, 2022 at 7:36 | history | answered | Cort Ammon | CC BY-SA 4.0 |