159

My first thought is redundancy. You shouldn't send just one copy of the message, you should send thousands and through different methods. Some thoughts on possible methods: Rock carving in a protective sheath (e.g. amber or a similar substance). Shoot rockets to the Moon and Mars (vacuum doesn't decay things the way that atmospheres do). Build satellites ...


145

There's a very specific existing case study of nearly this exact question. In the 1970s, the US Department of Energy began investigating what is now known as the Waste Isolation Pilot Plant as a means of safely storing radioactive waste for the next 10,000 years. Considerable thought was put into the topic of signage: how to indicate to future ...


115

My qualifications I was a qualified Officer of the Deck in the US Navy. I have around 2000 hours watchstanding time and about 50 port and anchorage transits. Navigation skills A (competent) 1500s sea captain's navigational skills would be much higher than any modern day sailor's, just due to the lack of technology at the time. Modern navigation is, of ...


109

Natural Vaccination. Read about how Cowpox was used to vaccinate against Smallpox, this is our IRL first instance of vaccination against a disease. The word “vaccination,” coined by Jenner in 1796, is derived from the Latin root vaccinus, meaning of or from the cow. Once vaccinated, a patient develops antibodies that make them immune to cowpox, but they ...


108

It IS a front because if you openly state as the firm's mission and vision to summon a destroyer of worlds your business isn't going very far. Aside from that, there are some things that dark cults need that just aren't cheap, nor easy to arrange. For example, the summoning ritual may require the fresh blood of 600 healthy, young adult women. Try to ...


93

Dragons would run the FAA One day, you're flapping along, torching pigeons, and those runty little ground creatures that taste good with ketchup start making an awful racket. "Must be that Henry Ford again," you think to yourself. Humans these days and their internal combustion engines. Something sounds different this time. You look around and do a double ...


87

It's Texas. The big problem with an entire state rebelling is the rest of the US starving them of resources. Like, for instance, electricity. Most people aren't aware that a majority of the United States is electrically connected by three major power grids. Many of the states in each grid do not have the ability to produce enough power for their state ...


86

Main Answer I have a PhD in Mathematics and came across this question. To be honest, I dislike almost every single answer, except maybe L.Dutch's answer concerning Wile's proof of Fermat's last theorem. However, I do think there is a much, much better candidate, and one that would make every mathematician reading your story quite delighted: https://en....


85

Have YOU ever tried setting up classic rituals? Everything's going well with everyone in their matching robes and masks, and just as the Grand Priest is finishing the ritual to summon a Great Old One the hero swoops in and steals the book, or breaks the pentagrams and unleashes something that slaughters the worshipers too soon and the wrong kind of hell ...


82

I think we can all agree that whoever finds this message in 50,000 years isn't going to speak English. Or Mandarin. Or Hindi, French, Spanish, Swahili, or, in fact, any language spoken today. So we'll have to figure out a way to communicate with them in a language that we'll both understand. I'd look to communication with aliens for inspiration. There have ...


82

As a native I'm definitely biased here, but Ireland is actually a pretty good bet. Especially towards the West, Ireland has actually seen a decline in rural population. You can genuinely walk for miles and see no signs of civilisation. I'm talking even the grass has no footprints. Predators? Ha! St Patrick took care of our snakes, and our beloved English ...


78

Because some self-proclaimed health guru claims that it's good for you to have that disease. The miracle-virus causes your body to absorb free cosmic energies. Your constantly raising body temperature is proof that it works. The headache you feel is because your brain is reconfiguring itself to become more effective. When the process is over, you ...


77

They would make great infantry, and would pose a serious threat on the battlefield. Stronger Gorillas are stronger than a human being, and capable of carrying far more equipment/armor. Each of them could easily carry an LMG + ammo, while a regular human soldier would only have an assault rifle and far less ammunition. Having to reload less often, and ...


73

what policies would the world's various administrations put in place? Switch to digital currencies and eliminate paper money. Explain to the nice aliens that we were just settling on paper money. What we really wanted were Star Trek replicators and non-polluting power sources that don't require fuel. Thanks! ...and some of us would like spaceships ...


72

The tree was never supposed to be a tree, it was supposed to be a natural boost to the air quality and be a feature of the building. The architect had a great idea for a natural air circulation and freshening system. You plant this tree up the centre of the building, it acts as a visual feature through the middle of the tower up a central transparent air ...


70

TLDR: All you need is better Anti-Aircraft Guns There's a lot of good information here, but I think @Karl actually has the best and simplest answer to the question. Imagine a scenario where instead of pursuing multiple competing and disorganized efforts, the United States and Great Britain went All-In on Radar in the early '30s when it was first starting to ...


65

Can't realistically be done. As you pointed out, there is not enough water on the Earth. You could get away with a Grote Mandrenke, but no more (and you want "permanent"). Adding that much water through a "cosmic snowball" would require a more-than-Chicxulub-sized water asteroid: the kinetic impact alone would wreck the Earth. Actually the surface of the ...


64

This is basic asymmetric warfare. It can work. Ask the Viet Cong how they held off the most powerful superpower in the world... What you don't do is take on the modern army on their terms, or even the terms a knight would be used to. Avoid an open pitched battle, it would be suicide. Ditch the armour, take a dagger instead of a sword. Carry out a sneak ...


54

The smell. We don't notice it because it is everywhere but even low-level pollution would be noticed immediately -- the ability to smell low-level pollution would pass quickly though. The noise. There is elevated noise levels in many rural areas and all populated areas. The noise of a jet may well be the reason our time-traveler looks up in the sky and sees ...


52

For their day to day lives, people in different parts of the world would associate different times with different activities. While to someone in Greenwich 11:30 am might mean "lunch time", to people in the Eastern US it might mean "time to wake up", to others it might be "dinner time", or "middle of the night". No doubt if time zones were abolished ...


52

Real life solution - make guns scarce in your society In a country like US, where there are plenty of guns among the citizens, it's a no-brainer for criminals to use guns too. If they choose melee weapons, they would quickly find themselves bringing a knife to a gunfight. In a country like UK, where guns are harder to find, criminals largely resort to ...


52

Since you're interested in something currently unsolved, you don't really care about how protagonist will solve it, only that he does so, let's go for something extremely simple, simple enough that even a reader with only basics of mathematics can understand: Collatz conjecture (also known as 3n + 1 Conjecture) "Consider the following operation on an ...


51

Intelligence is not a singular trait There are many facets to intelligence. Let's start with some animal examples: Dogs. Everybody loves dogs and dogs love everybody. They have incredible social skills and are amazingly adapted to humans. They are the only domesticated animal that runs towards their "human" when frightened and not away. They can read ...


50

My home country (China) has very strict gun control laws. Basically, normal citizen will not be allowed to buy, sell guns, or make it themselves. If guns are involved in a crime case (say, robbery), the consequence will be much more severe. Surely you'll never stop people from making guns themselves, but they won't necessary use guns in conflicts - 6 months ...


47

Alaska There is, of course, a strong Alaskan independence movement led by the Alaskan Independence Party, an extremely large (relatively) third party. It has over 15,000 members. Interestingly enough, among their key principles are the desires to uphold a person's Constitutional rights and state/individual rights. It sounds like they would be eager to go ...


47

If the governments of the world are in any way intelligent (which is a stretch), they would quickly switch to using a combination of highly nutritious, pre packaged food bars, and fully charged high efficiency batteries as currency. Using the batteries and eating the food would remove some from circulation, helping them to retain their value. In the ...


47

Gated Nation One scenario that comes to mind is Monaco. One in three is a [multi-] millionaire. Most of the working-class do not live in Monaco, but commute from France. The "country" is full of rich people (is that a "rich country"?), but has a small if not non-existent middle class citizenry. "From Each According to His Ability, To Whatever." Another ...


47

No such thing exists. All mathematics is a type of language. Like language, it looks mysterious to people who don't speak it. But if you study it enough, you will understand it. There are no exceptions. (*) Calculus was once an arcane branch of knowledge known only to Newton, Leibniz, and their handful of peers. It made them gods in terms of their ability ...


47

Historically, knights were protected from firearms. Armour from the late 1400's on was "proofed" by firing a shot from a handheld firearm into it, allowing the purchaser to have a visible sign that the armour was capable of stopping a bullet. Handgonne from the 1400's Proofed suit of armour The issue was that while it was possible to create armour which ...


46

It happens that a friend of mine who was in the Peace Corps brought a friend from rural Malawi out to San Diego. Mozezi wasn't unaware of the modern world, in fact he at one time had owned a moped to drive into the small town 25 miles away, but even so the trip was constant sensory overload for him. Some things that REALLY bowled him over were: Pavement ...


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