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243 votes
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Everything alive in the world dies this instant. Without bacteria to decompose anything, what happens to the remains? What does this look like?

They weather. https://www.livescience.com/18343-seal-mummies-antarctic-microbes.html Antarctica has dry valleys where, for some reasons, seals sometimes went. It is a bad place for seals, and they ...
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213 votes
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If everyone in the world disappeared except 35 random people, how long would it take for one of them to realize they're not alone?

Assuming that it's purely random, let's consider where these people would probably be. Taking the percentage of the population each country represents, we get: China: 18.2% = 6.37 people India: 17.5% ...
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  • 1,703
199 votes

If everyone in the world disappeared except 35 random people, how long would it take for one of them to realize they're not alone?

It's HF radio, or nothing The odds of anyone meeting again are almost exactly equal to the odds of at least two being either radio hams, or able to learn the skills from books. The population ...
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  • 3,137
143 votes

A 40km diameter alien saucer is floating 2km above the ocean for a long time. What are the effects on the sea ecosytem below?

The ocean is a dynamic and very large place, so it's unlikely to have many large-scale effects unless humans overreact. I'll focus on the local, immediate effects of this saucer from a physical, ...
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  • 12k
129 votes

Everything alive in the world dies this instant. Without bacteria to decompose anything, what happens to the remains? What does this look like?

The remains would mummify, petrify, erode, and eventually become just another mineral layer. Where water is available the organic remains will dissolve and be replaced with inorganic minerals to ...
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  • 16.8k
119 votes
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Is it possible to kill all life on Earth?

Not with the time constraint given. Let's start with the most destructive thing we've got: nukes. There are about 15,000 nukes worldwide, of varying yields. Sources: World Nuclear Weapon Stockpile, ...
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113 votes
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Building a road to escape Earth's gravity by making a pyramid on Antartica

The maximum height a mountain can have on Earth is a tad more than what Mount Everest is high. This is due to the fact that when you increase the height of the structure, you are also increasing the ...
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108 votes
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Reasons why healthy people would intentionally want to get infected?

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,...
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93 votes
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How long would it take until we realise that people stopped dying from natural causes?

One day. Few at most. In most modern countries death reports are passed to government agency on daily basis. Clerk responsible for them would be surprised that there are none in his area. He will ...
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  • 32.7k
93 votes

Would a squad of soldiers who can shapeshift into T. Rexes be useful in a modern battle?

I can imagine battlefield logistics would be much easier. One of the most dangerous and common tasks for infantry is shuttling supplies back and forth between the front lines and the forward camp. If ...
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  • 1,155
93 votes
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If all natural sources of oxygen production stop, how long do we have?

All the info we need to calculate this is in the wiki for the oxygen cycle. The atmosphere gains and loses about the same amount of oxygen each year: 3 $\times$ 1014 kg. It also currently holds 1.087 $...
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85 votes
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What would happen if the Earth struck a tiny but immovable object

As @Thucydides mentioned, researchers posited a similar magnitude of impact and thought they had found evidence for it, though they later retracted their findings they did calculate the potential ...
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  • 114k
83 votes

Building a road to escape Earth's gravity by making a pyramid on Antartica

You've already accepted an answer, but aside from the structural issues (and the sheer mindboggling amount of energy it would take to pump all that water up that high), there's another ...
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83 votes

Where on Earth is it easiest to survive in the wilderness?

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 ...
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  • 1,557
82 votes

How can a colony of teleporters make the most money while keeping their teleportation a secret?

First of all they should only teleport things, not people. People talk. Otherwise, they're in the shipping business. They should use their teleportation ability to mimic real world transportation so ...
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  • 4,648
81 votes

What are the effects of slicing the Earth in half with a particle beam?

All the people who said "We all die!" are correct with good answers, but for most people it won't be the earthquakes that kill them -- they'll already be dead. The leakage from the radiation beam ...
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  • 14.1k
80 votes

Reasons why healthy people would intentionally want to get infected?

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 ...
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  • 43.6k
80 votes
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How can a colony of teleporters make the most money while keeping their teleportation a secret?

Think Small Instead of moving items very large distances; why not move them small distances; it's not like you get paid per mile. You could almost entirely remove the equipment cost and drastically ...
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  • 1,176
77 votes

Can a human survive acceleration from 0 km/h to 310 km/h, and then back down to 0 km/h, all in 500 meters?

310 Km/h is 86 m/s. This means that on your 250 meters track (for acceleration), you'll have a mean speed of 43 m/s, meaning that you'll reach your 250m in 5.81 seconds. Now, 86 m/s reached in 5.81 s ...
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  • 5,281
76 votes
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How to tell if the entire Earth is just a copy?

Even the satellites and every sensors on Earth were returned to that exact moment and this only affects the entire region of space up to orbit of moon (...) Everything above the Moon will seem to ...
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69 votes
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Would evolution happen the same exact way if Earth restarted?

The first thing that it's important to understand is that evolution is a by-product of natural selection, not the driver of it. That is to say, every change introduced by DNA combinations and ...
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  • 53.8k
66 votes
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If an FTL spacecraft entered Earth orbit, how long would it take for humans to build a FTL spacecraft?

It depends on how far from the current production possibilities frontier this technology is. There are several possibilities, depending on the technology gap: It is like the Apollo Moon mission to ...
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66 votes

Is it possible to kill all life on Earth?

No. Most of the preceding responses have overlooked one relatively-recently identified home for life on the planet; within the crust itself. Researchers have found bacteria up to 4 kilometers down in ...
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66 votes
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Best place on Earth to fake being on a distant planet?

The problem your going to have in any open sky area however, is the familiarity of the moon and constellations - a dead giveaway that your still on earth. To that end, I'd suggest the best place for ...
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  • 675
66 votes

Dungeons for Real: 1. The Bottomless Pit

Indoor skydiving Indoor skydiving simulators are popular and not particularly difficult to build. A person who falls into a "bottomless pit" would feel like they're falling faster and ...
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  • 41.2k
64 votes

Could we reach the earth's core using today's nuclear arsenal?

No. On this scale, the Earth is not solid and rigid. It's more like extremely hot jello, with a thin and weak crust, a layer of hot floppy jello, the "mantle", a liquid outer core (actually molten ...
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  • 18.2k
61 votes

Would evolution happen the same exact way if Earth restarted?

No, but... If you restart evolution, you would end up with new species. But some of their features may be very similar to what we know in our world. The Nobel Prize winner Jacques Monod said that ...
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  • 1,188
60 votes

Best place on Earth to fake being on a distant planet?

This place cannot have any obvious life forms. Nothing too complex (Small microbial creatures are fine) No humans for at least a few hundred miles, and no signs of their presence. Must be ...
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  • 242k
59 votes
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How long would people live in the US if an immortality treatment was available?

The CDC estimates 187,000 people in the USA die from "injury" every year -- basically that includes homicide, suicide, vehicle accidents, and other forms of accidental death. This works out to a ...
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