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Old 2017-12-11, 17:34   #23
xilman
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Quote:
Originally Posted by The Carnivore View Post
With that said, I'm guessing 300 years for both the prime and the Moon landing. By that time, memory of 2017 will have faded considerably, and there'll be some debate about whether a return to 2017 conditions is even desirable after all.
The answer could well be: never. At least not for humanity. Some other species (my guess would be either a rodent or a mustelid) could develop intelligence and advanced technology within the next 10-100M years and they could well have some advantages which we presently do not.

Without easily accessible forms of concentrated energy (coal, gas and oil) it would be very difficult to support another industrial revolution of the kind we have seen in the past 300 years, even assuming perfect recall of that example by future humanity. I read a fascinating essay about this topic only a few months ago. I will see whether I can re-find it and post details here.
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Old 2017-12-11, 18:19   #24
chalsall
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Originally Posted by xilman View Post
The answer could well be: never. At least not for humanity.
This is actually a really interesting question. Most people assume that progress always continues forward. But we still don't fully understand how the Egyptians built the Pyramids, nor how the Romans built their roads.

We're now building 3D electronic circuits at the nm scale, which most of us walk around with and rely on.

One EM pulse could wipe out millions of these devices without immediately harming a single human.
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Old 2017-12-11, 20:03   #25
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Originally Posted by xilman View Post
Without easily accessible forms of concentrated energy (coal, gas and oil) it would be very difficult to support another industrial revolution of the kind we have seen in the past 300 years, even assuming perfect recall of that example by future humanity. I read a fascinating essay about this topic only a few months ago. I will see whether I can re-find it and post details here.
The earth would be returned to a 200,000 BC state with forests and deserts in places where our current cities are, so it would be reasonable to assume that Earth's fossil fuel supply is replenished and not partially depleted.

But even if that's not the case, it still could be easier the second time around. Unlike the first time, we know what fossil fuels can be used for, we know where they can be found, and we don't need as much production as before due to all of the mass die-offs.
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How do you propose keeping any useful information about moderately high technology (how to build a blast furnace, for example, available for even fifty years?
Immediate aftermath - first few months: Cave drawings and/or stone tablets. Write down as much as you can before it's forgotten.
First few months onward: Papyrus, followed by pencil/pen and paper. This can be distributed to various tribes, compared with the cave drawings in different regions, and edited to get as much correct information as possible. Knowledge might even be traded for food.

That's one possible timeframe and solution. I wonder if anyone has alternatives.
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Old 2017-12-11, 20:30   #26
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I think the solution is trivial for non mathematicians. Simply add an even number of known large primes to the largest known prime and submit the decimal expansion as a prime.
The wizard will have to take your word for it unless he can factor the ordinary prime using primo.
By the time all the millions of decimal digits are spoken generations will have past and the wizard will have to have died. Keep in mind that in absence of any technology, submitting such a number would take generations.
But on a slightly more serious note, the OP is pondering if a combined effort of a large group of people can be more effective in solving problems. Sadly affairs of the world and the world history would suggest otherwise.

Last fiddled with by a1call on 2017-12-11 at 20:32
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Old 2017-12-11, 20:34   #27
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Quote:
Originally Posted by The Carnivore View Post
T
First few months onward: Papyrus, followed by pencil/pen and paper.
Do you know how to make papyrus? Does papyrus grow in your part of the world? Do you know how to make ink and writing implements?

I do know how to make papyrus sheets from the plant (which does not grow around here) but I doubt I'm any good at it. Given the ingredients, I know how to make a serviceable ink, though I'm far from sure that I could catch enough animal fat which I didn't want to eat at much higher priority than using it to make ink; producing charcoal might not be entirely trivial though I do know, in principle, how to use frictional heating to start a fire. Making a quern grindstone is straightforward by comparison.

I'm somewhat unusual in that I've actually studied and used some ancient technology though not to any great extent. The vast majority of the world's population are almost completely clueless. How many people here can truthfully say that they have made and used their own flint tools, or practised writing cuneiform script on lumps of soft clay? The latter, BTW, is much more practical than writing on papyrus IMAO.

Last fiddled with by xilman on 2017-12-11 at 20:35
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Old 2017-12-11, 20:51   #28
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Suppose a magical wizard makes all man-made objects vanish and restores Earth to its pre-human, 200,000 BC state. What’s left is 7.4 billion naked humans, standing on grassy plains, in forests, in swamps, on tundra, and in deserts in the exact spots where their cities and villages were just a second ago.
...
Something that just occurred to me. If everything suddenly vanished then we wouldn't have everyone standing peaceably on plains, in forests, etc. We would have a sizable percentage of people standing on thin air where their 51st floor apartment used to be, or traveling at a high rate of speed where their car used to be, or both, for those unlucky enough to be on a plane at the time. These people are also likely to be the same people most useful to a post-apocalyptic prime-finding or society-rebuilding effort, simply because they can afford to be on high-speed, high-elevation man-made structures.
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Old 2017-12-11, 21:05   #29
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Once that prime number is found, the spell will be reversed and all man-made objects you had in 2017 will reappear.
I'd say that the majority of mankind would not be interested in having things restored. Sure, us rich Americans and Europeans would very much like that. But what's in in for the people of Africa, India, China etc. who have much less wealth and power? A fresh start would be beneficial to them, especially since they are much more used to a low-tech life (i.e. fewer of them would die after losing all technology).

However, once civilization has been rebuilt and technology approaches today's level, wars would break out. After all, controlling Europe and the USA means that you get all the precious stuff once the wizard makes it reappear.

So I'm not sure we would ever prove the next Mersenne Prime or fly to the moon. Maybe in 10,000 years, when nobody believes anymore in the 'myth' about the wizard's experiment.

P.S.
If the experiment actually took place, I'd be naked, facing a temperature of ~0Β°C (33Β°F) and half blind because my glasses have vanished. So.... my guess is 143,418,169 since that can't be worse than freezing to death.

Last fiddled with by nordi on 2017-12-11 at 21:06
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Old 2017-12-11, 21:47   #30
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Originally Posted by nordi View Post
I'd say that the majority of mankind would not be interested in having things restored. Sure, us rich Americans and Europeans would very much like that. But what's in in for the people of Africa, India, China etc. who have much less wealth and power? A fresh start would be beneficial to them, especially since they are much more used to a low-tech life (i.e. fewer of them would die after losing all technology).
A fresh start would be beneficial? Surely almost all of them would die, and I can't imagine that the remainder would consider themselves better off.
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Old 2017-12-12, 00:08   #31
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Do you know how to make papyrus? Does papyrus grow in your part of the world? Do you know how to make ink and writing implements?
No, but out of the few thousand or so survivors in most cities, I think that 5-10 people in each city would be able to come up with some approximation of pencil and paper. Papyrus was the first thing that came to mind since it was invented not too long after agriculture.
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I think the solution is trivial for non mathematicians. Simply add an even number of known large primes to the largest known prime and submit the decimal expansion as a prime.
The wizard will have to take your word for it unless he can factor the ordinary prime using primo.
If the wizard has the power to make all man-made objects vanish, I'm pretty sure he'll have the power to tell whether an arbitrary number is prime.

But putting that aside, how are you going to manually calculate the decimal expansion of 2^74207281-1 and add another large prime to it? It'll take years if not decades, and one wrong calculation would send you to the torture chamber.
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Round trip moon landing may well be easier.
I'm not too sure about that. More resources were involved in the moon landing than in the large prime. It would arguably have been possible to find M49 in the 1990s or even the late 80s if most of the world's computing power at that time was dedicated to the task.

You may be right after all, but the time difference between those two events would be something like 5-10 years instead of the real world difference of 47 years.
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Old 2017-12-12, 04:27   #32
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This thread got me thinking.

  • Has there ever been a distributed computing attempt at creating a sieved ledger?
    • Suppose Person 1 lists integers 2,3,4,..
    • Suppose person 2 sieves out behind him integers 2,4,...
    • .....
  • Now replace the above persons with a systematic pool of distributed computers
    • Also replace the ledger with an equivalent code which sieves out discovered primes


Thanks in advance.
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Old 2017-12-12, 05:27   #33
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Thanks for the responses, guys! There's lots of interesting conversation, indeed

Anyway, here's some clarification on various issues that were raised:
- All of Earth's resources will be in the same locations and quantities as they were in 200,000 BC. There'll be no depletion of fossil fuels or minerals such as copper, iron, and rare earths at the start of the wizard's spell.
- The wizard knows instantly whether a candidate is prime or composite, regardless of its size. Coerced guesses will not be allowed (for example, a dictator cannot round up a whole bunch of slaves and force them to submit guesses to the wizard). A proof is not required, but the wizard will not say whether a person's guess has already been submitted before by someone else from another part of the world. The torture is designed to be as long and painful as possible before death, and nothing but the victim's head will be given to his/her closest friend or family member.
- The initial food and water is provided to reduce the amount of initial panic and give people some time to think and coordinate a plan of action for the future.
- If/when humanity succeeds at finding the prime or completing the moon landing, they are free to reject the offer to bring back 2017's conditions (based on one person, one vote). If they reject the offer, their next chance of bringing back 2017 again will be when someone finds another 22,338,618+ digit prime or lands on the moon again.

My guess to find the prime is 400 years. 100 years to bring back large scale agriculture and civilizations like ancient Rome, another 50 years to bring back the steam age and get the Industrial Revolution going again, another 50 years to bring everything to 1900-like conditions, and another 70 or so years to bring back widespread high tech computers. That's a best-case scenario, so add another 130 years for delays due to war, pandemics, etc.
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