Fun idea. You mean like the expansion of the universe is going 0.5 light speed at the edge of the void, so the spreading void is basically pulled back right? And then any photons that reached us from just before this void are traveling a tiny bit faster I guess? Being just outside the void?
Once you can get a good reference for one unit ypu can start to use it to determine the others. None of these are going to be perfectly accurate, but they should be good enough for day-to-day use.
I’d start with time. We’re going to make a sundial. To do this you need to make a drawing compass and some flat ground with plenty of sun. Find a v-shaped stick, or lash a couple together so you can scribe circles in the ground. Start by making one circle around a well marked centre point, then using the same compass, draw another circle centred on the edge of the first. Draw two more circles where the second crosses the first, and two more where those cross it. You should now have a central circle with the perimeter divided into six segments (this is the same technique for drawing a hexagon inside a circle). Put another stick upright in the centre and you have a sundial with 2 hour segments. You can bisect the lines between each of the points to get 1 hour segments, and if it’s big enough, busect again to get 30 minute segments. We’ll get shorter time measurements later.
The next unit to find is the meter. A one meter pendulum completes a swing from one side to the other every second. In order to minimise the effect of air resistance, find a heavy, but not too large rock and tie it to the end of a rope. Measure out approximately out meter of rope (measured from the centre of the rock) and tie it to a solid branch. Next is the tedious bit. Set it swinging as the sundial hits one of it’s marks and count the number of swings until the sundial hits the next mark. You should get 3600 per hour. If you get too many, lengthen the rope and try again, if you get too few, shorten it. Once you have the right number you have both your meter measure and your one second.
You can get a metric tonne, and thereafter a kilogram, by building a balance weigh beam, and a cube shaped container that is exactly one metre on a side. Attach the container to obe side of the beam, and a second container exactly the same distance away from the pivot on the other side. Add rocks to the second container until it balances with the empty first containor. Now fill the first with cold water. Add more weight to the second until it balances again. The additional weight should be exactly one metric tonne. By careful geometry you could reduce tge size of your first container to make this easier, but keeping it big and then dividing the result minimises measurement errors.
Temperature is harder to measure, but you can build a thermometer with any liquid that changes density with temperature. Even water works, although adding alcohol helps I believe. So, while you’re finding the meter, get some fruit and let it ferment. Use the resulting liquid in your thermometer. If you don’t have a glass tube, and can’t make one, use an opaque one, and float a light reed or similar on the liquid, with the end sticking out of the top. Calibrate it with boiling water for 100c, and, assuming a reasonable climate, wrap it against your body for a goid long while to get 37c. If you have accesd to ice, letting it just melt gives you 0c. Dividing the marks you get like this would involve some careful geometric construction, but should yield a usable thermometer. Converting that to Kelvin, as the SI unit, involves adding 273.16.
The ampere and candela are probably of less use in this situation, and are going to be tricky to measure. By assuming gravity is 9.81m/s^2 and using the kilogram you can derive the Newton. From that you have the Joule, and one Joule per second is one Watt. Assuming you build a generator, you can derive the Ampere from it’s older definition relating to the force, in Newtons, between two parallel wires. From there the volt can be derived.
Beyond that, I think you should just hope for rescue!
I hadn’t even thought about getting HH:MM from a sundial, that’s brilliant! Then getting seconds and the meter from a pendulum is just straight up elegant.
By careful geometry you could reduce tge size of your first container to make this easier, but keeping it big and then dividing the result minimises measurement errors.
I thought this was worth a callout for being a really important consideration in this thought experiment. Understanding that larger scale measurements generally reduce error, and perhaps also repetition with averaging of results, would be incredibly useful in fast tracking the redevelopment of precision.
If you have accesd to ice, letting it just melt gives you 0c.
This one I wondered about more because of the effect of atmospheric pressure(?) on melting point, such that I wondered if it would be worth using Fahrenheit’s Weird Brine ice slurry to get ~ -17.778 ° C instead. But that’s ofc also subject to air pressure influencing melting point so I’m unsure if it’d be worthwhile.
Relatively constant 9.81 m/s² gravity is also useful for deriving force as you mention, though it reminds me of learning, to my abject horror, in undergrad physics that gravity does vary quite a bit by geolocation :'D 9.81m/s² is a better starting point than nothing though
This one I wondered about more because of the effect of atmospheric pressure(?) on melting point, such that I wondered if it would be worth using Fahrenheit’s Weird Brine ice slurry to get ~ -17.778 ° C instead. But that’s ofc also subject to air pressure influencing melting point so I’m unsure if it’d be worthwhile.
Varying air pressure is certainly a concern, but repeating the experiment, as you said, would help to reduce the error, as would being as close to sea level as possible. Interestingly, if you have your meter measure you could use that to measure atmospheric pressure by seeing how far you could raise water in a column by suction. At standard atmospheric pressure you should be able to lift fresh water 10.3m.
Relatively constant 9.81 m/s² gravity is also useful for deriving force as you mention, though it reminds me of learning, to my abject horror, in undergrad physics that gravity does vary quite a bit by geolocation :'D 9.81m/s² is a better starting point than nothing though
Gravity is altogether too unreliable and should be abolished. Failing that, You could measure the local gravity by measuring how far a rock falls in a fixed time, say one second, and calculating back from that. If the rock is heavy enough we can ignore air resistance as the effect will be smaller than our measurement error.
Interestingly, if you have your meter measure you could use that to measure atmospheric pressure by seeing how far you could raise water in a column by suction. At standard atmospheric pressure you should be able to lift fresh water 10.3m.
Oh yeah! I should have remembered that actually, since I was just rewatching an episode of that mentions this height limit in the context of vacuum pump history (I think it’s detailed more in season 1 but I forget which episode). So 10.3 m is another key measurement that you want at least one human to have memorized :]
Gravity is altogether too unreliable and should be abolished.
This reads like a Douglas Adams quote and I love it.
Are you asking about how you reinvent the exact same meter? Well that won’t happen. Our units were arbitrary, useful, widely adopted, and then rigorously defined.
The book walks you through it all. You can don’t need to redo civilization exactly the same (the author even suggests some very important things to invent differently, especially in better orders)
That’s a fair point. Most likely if a group of people did some kind of Long Term Naked & Afraid experiment they’d just start with some length of particularly well-crafted cordage, call it a New Meter™ and go from there
I’d start with making a surface plate using Whitworth’s 3 plate method.
Next, make a perfectly square block, pick two opposing faces of that block, that’s your unit of length. Use your surface plate to make more and measure things against it.
If you’re really smart you would have made that block out of some sort of homogeneous material like steel and made it a perfect cube, not just perfectly square. That’s going to be your prototype weight.
Temperature is the easy one, make a thermometer. Mark where the liquid is at based on two different repeatability phenomenons. Subdivide as desired. Someone will come up with a “better” way later.
Time is another easy one, just build a pendulum and start counting.
That sould get you through most of the neo-industrial revolution.
The rest of the base units will come later for now focus on building a lathe.
Any answer to this will be an oversimplification, but my short answer is increased poverty makes for more people with unfulfilled needs. With holes to fill as it were. Food fills that hole. Not perfectly, but enough that people use food in place of what actually fulfills. But food is only a substitute, so it doesn’t sate. There are many things people can substitute for what’s actually fulfilling, but sugar is the cheapest “drug” on the market. The same dynamic is a huge part of what underlies the opioid epidemic.
Also once you are addicted to over consumption you cannot just give it up completely. Alcohol, gambling, opioids can all be stopped using a sensible program and never touched again. You ask any addict of those three if they would never lapse if they had to take them in moderate amounts every single day for the rest of their life and they would laugh at you.
Couple this with easy and cheap availability of the most addictive food types that are heavily advertised, it’s no wonder it is so hard.
This is so true and so sad. It is like eating disorders really truly clicked for me with this statement.
While I now live outside the US and have curbed my eating habits drastically and I am now no longer obese, just on the cusp of overweight/healthy weight, I struggle every day not to indulge in over-eating, as that has been a stress-response my entire life I’m pretty sure. Living abroad has made it easier to fight it because they don’t have aisles upon aisles of ready made crap. And the boxes/bags they come in are pretty small so you can’t eat say, an entire family size box of cheez-its or little Debbie’s because neither of those are even sold here. There is some junk food but variety is extremely limited, so that definitely helps.
There’s probably even a small handful of foods doing most of it, like white bread, sweetened cereal, soda. However maybe the trick is to require livable wages for all those fast food workers and hope there’s some truth to franchisee claims that it becomes an unsustainable business
There’s probably even a small handful of foods doing most of it
Sadly, no. This is a plague that goes across the board when it comes to processed foods. While some are worse offenders than others, some even healthy appearing foods (cereals, smoothies) are horrible dangers for your health.
My wife stopped eating out for nearly every meal recently and started cooking 90% of what we consume, best decision we’ve made for our health and our pocketbook. Food is processed less and we can control what’s in it, and in turn we’re both almost back to our college weight. Turning fresh produce and protein into a meal is where it’s at.
I suspect one of them is some people get shockingly little exercise. When I lived in the suburbs, my daily could often be “walk to car, walk from lot to office desk (taking the elevator instead of stairs), walk from there to car (via elevator), walk from car to home”. Total walking time less than five minutes.
When I moved to New York I got at least twenty minutes of walking to and from the subway every day just going into work. Plus now I walk to the grocery and other stuff.
That doesn’t really explain why obesity has increased. If anything, it is often easier to get by without a car today than 20 years ago. For example, my own city is full of bike paths that did not exist then.
They did add a bunch of bike paths in my town too, yet I’m 5 minutes by car from my nearest grocery store, but by bike have to cross a bridge with fenced sidewalks and no shoulder, ride on a 80km/h+ road, and a bunch of other BS just to get there. Bike infrastructure doesn’t mean good bike infrastructure I guess.
Sure, it’s still not good. But that can’t explain why people are more obese now than a couple of decades ago, since bike infrastructure was even worse then.
I wonder if part of it is more likelihood to have multiple cars, less likelihood to have someone prepare meals from scratch … or maybe that’s more than a couple decades.
COViD helped me discover a passion for cooking (baking too, but not just baking) so in the last few years my kids have had more meals prepared from scratch, more balanced and nutritious, and a lot more exposure to meals from other cultures.
One of the new tools I got is an air fryer. It’s a really convenient way to make the equivalent of grilled chicken or other foods …. But all too often I find myself feeding it processed junk like chicken strips and frozen fries
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