106

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, Plougshares Fund, 2018 Federation of American Scientists, 2018 Assuming an average yield of 200 kilotons, which is what most US nukes have, we could assemble ...


104

Back in the day before portable electric lights, carbide lamps were used: A mechanism dripped water onto carbide, which then gave off acetylene gas, which burned in a controlled fashion. This was used for headlights on cars and bicycles and for miners' lamps, even for lighthouse lamps. Hence, this is an obvious answer to your question. Another option is to ...


90

Water Basins If every 300ft or so the tree grew water basins to catch rain, (or maybe as a place to deposit water that it had already pulled up from below?) the higher parts could draw from these basins instead of directly from the ground. This can also lend itself to the fertilization as well. If these basins were large enough they could become small ...


89

What I need is a substance which could have been mixed by an alchemist and is as gold-like as possible. How about gold itself? Bear with me, here: While there are a lot of things that look kinda like gold, nothing quite looks as good as the real thing (as pointed out in Cort Ammon's most excellent answer). So, why not use the real thing and have your ...


83

A pulsed fission engine like project Orion would have been able to move a 10 million ton ship into earth orbit. The downside is that they were achieving the propulsion with nuclear detonations. They would launch the atomic-bombs out of the back and detonate them a good distance away with a giant hemispherical "pusher-plate" which was basically a giant shock ...


81

No. No matter how much velocity you can give your satellite, its trajectory will either contain the point it was launched from or not be a closed curve. an object is in orbit if it returns to its previous position in phase space (assuming we are talking about a close orbit). if we assume the trebuchet to be the only source of speed, then it means the ...


71

I am going to claim expertise on this issue for a major reason: I live in the Arctic. I've also participated in search and rescues in the Arctic. The basic answer to this is that small groups of sufficiently-prepared people actively trying to evade detection and if no one is specifically looking for them can do it trivially by any number of means. It's hard ...


69

an atmosphere that is lethal if you get a breath or two but won't burn your skin off or poison you anyway when you walk out the door without your moon suit? take our atmosphere and remove all the oxygen, replacing it with an inert gas like nitrogen. Asphyxia will ensue after a couple of breathes. Asphyxia or asphyxiation is a condition of deficient ...


66

The dog is trained to recognize specific scents/people. It barks if it knows you, at which point the guard opens the door. New people can be introduced, at which point it knows your scent and you're authorized.


66

Forget it, there ain't no stealth in space. The linked site explains in excruciating detail why stealth in space either do not work or is, when it works, extremely unwieldy or practically useless. I will shorten the arguments in the link Vacuum means the only way to get rid of excess heat is radiating it or dump hot material. Remember, you need your crew ...


62

Radio Waves Are Hard To See, And We Didn't Think To Look At Them There are about 134,000 stars within 200 light years of Earth. That's a lot of stars. We can't look at even a significant fraction of all of them closely enough to detect the equivalent of human-made radio waves. A 200 ly radius is a sphere 33,493,333 ly3 in volume. The stellar density near ...


62

TMM;DR (Too Much Math, Didn't Read): For anyone who doesn't want to go through the derivations and calculations below, here are the important points from my answer: We're not working with the same space as normal, friendly, Euclidean space. This means that while we can still integrate and differentiate scalar functions defined on this space, we need to ...


62

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 continental crust and 2 km beneath oceanic crust. Recent estimates are that up to 70% of the microbial life on the planet is, in fact, in the deep biosphere. ...


58

They fail and suffer whatever evil fate awaits them. ...or this I say this mainly due to this pre-condition: The refugees are traders, not craftsmen or metal smiths. Iron is known to them but they don't have anything other than introductory knowledge of how to smelt iron or form tools. Having all the natural resources is great, but they have no ...


58

Depends on the car It also depends on luck, sometimes an EMP will do permanent damage, sometimes it won't. The chances are you'll blow a bunch of fuses at the very least. If you're running a diesel then it'll probably keep going. Not because the electronics are any more robust but because diesel doesn't actually need the glow plugs, it'll run on ...


56

This has already been tried and proven, and is referred to as the Kon-Tiki expedition: Heyerdahl believed that people from South America could have settled Polynesia in pre-Columbian times. ... His aim in mounting the Kon-Tiki expedition was to show, by using only the materials and technologies available to those people at the time, that there were no ...


55

It's physically possible. Put a spherical object in a geostationary orbit, make it rotate about its own axis at a rate suited to your own visibility/non-visibility requirements, and make a portion of it have very low albedo. Staying at a single point in the sky, the object will only be visible while the higher albedo portion is facing the planet and ...


54

Use the extra power to convert atmospheric CO2 to hydrocarbons and store it underground. This offers the long term storage requirements and ease of handling specified in the question. Various Energy Storage Options Batteries are known to lose charge over time, usually a few years. This isn't long enough. Capacitors are also known to slowly discharge over ...


53

My suggestion: 60% Xenon 20% Oxygen 15% Nitrogen 5% Carbon dioxide Why Xenon? Xenon is a noble gas. It has very few common chemical reactions, and is frequently used in situations where air is too reactive to be safe. It's safe to touch and even safe to breathe. It's also a very effective anesthetic. Present-day doctors in Europe use it because it is ...


51

It is possible...eventually To be clear @SilverCookie's answer is correct. In simple Kepler mechanics, when you give a single delta-v to an object there are two 'orbital' possibilities: the orbit returns to where it started, or it is not a closed orbit and your trebuchet payload is above escape velocity. However, in this specific case, it is very possible ...


50

As a general rule, it seems natural that you would want an opponent as absolutely far away as possible. The further away they are, the fewer tools they have to hurt you. However, there are a class of situations that demand rapid feedback to be effective. These show up when there are many unknowns that must become known before your attack can succeed. ...


50

Let's make a bunch of assumptions: The largest primary is about 3 times bigger than Jupiter. To really be a parent, the barycenter of a parent-satellite system must be within the parent. Everything has approximately the same density Orbital stability will magically work itself out (this will give us an upper bound) Let's call the twice the distance between ...


49

Yes, but not in the way you are thinking. One way this could happen is if some killer fungus starts growing unchecked throughout the planet, on land and sea. By killing all plant life it would destroy every other ecosystem, so it would wipe out all mammals. It would also practically wipe out all other members of the animal kingdom. This is part of the plot ...


48

On September 28 2003, Italy experienced a nation wide black out. After three hours, energy was restored in northern regions. Electricity was restored gradually in most places, and in most cities electricity was powered on again during the morning. Energy was restored first in the northern region because there is where hydroelectric plants are located, ...


47

Hydrogen. You can destroy the world with less hydrogen than with any other element, because it's available in smaller quantities than any other element. Of course, it's not easy to destroy the Earth with a single atom of hydrogen. It is, however, possible. We just need to get our hydrogen atom moving fast enough. Specifically, we need to get it to a speed ...


47

Assuming you can fix the water problem using some of the other answers given, like having pools along the height of the tree, extracting water directly from passing clouds, etc., you will still have to deal with the tree crushing itself under its own weight. The following is an engineering kind of answer to the question. Short answer The equation that ...


47

No. The mass of a proton is about $1.67\times10^{-27}$ kg. Therefore the total maximum energy released by its annihilation with an antiproton is $2mc^2= 2\times1.67\times10^{-27}\times9\times10^{16} = 3\times10^{-10}$ Joule. This is not much. Even if all this energy would be deposited inside the victims brain, it is a very small amount. But it would not. As ...


43

Hit the planet with an asteroid. Guide a 100 km wide asteroid at the planet at around 10 km/second and there will be a global extinction event. Anything larger than 3 km can cause extinctions, so the 100 km figure is simply to make sure the job gets done right.


43

As another answerer provided, Neutron stars already do this. So, I'm going to alter my answer somewhat to address whether there are other means by which a star-like object may exist, besides the one we already know about. In that regard, I'm afraid my ultimate answer to this is going to be 'No' or at least 'Not with our current laws and/or understanding of ...


42

I decided to try to extrapolate from some known data. I used various sources to find that: The Harpy Eagle at 6 to 9 kg can lift a Three-Toed Sloth of 3.5 to 4.5 kg A Peregrine Falcon of 0.3 to 1.0 kg can lift a feral Pigeon of 0.25 to 0.4 kg An adult Human is typically somewhere around 60 to 100 kg The largest (known) bird ever was Argetavis magnificens, ...


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