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150

They could brace themselves against the world behind them. Basically, they would subconsciously learn to simultaneously exert an equal and opposite force spread out over a much larger area behind them or anywhere else that isn't the car they're throwing. A sign of an amateur telekinetic could be being thrown back by their 'throws' because they haven't ...


129

This turned out unexpectedly fun... and for once the answer to a question involving 99.99% of the speed of light isn't "everybody dies" Where is this sphere being fired from? If it's from outside the solar system then hitting the earth as a sphere is.... a problem... The volume of 1000 kg of tungsten = 51.9 L Radius = 0.23 m That's 5439.5 moles of ...


87

They would be round, because that's the best format for storing gas. They would also probably be drifters with little flight control. So...


87

The torch burns quicker. A lot quicker, but you won't get a violent explosion. Fire requires three things - heat, fuel, and oxygen. You've increased the oxygen, but you haven't increase the fuel, so all will happen is that the torch will burn out far faster - if it lasts for 10 minutes, it might not even last for one. The oxygen won't ignite itself. ...


76

Laser beams have straight trajectories in anything other than totally unreasonable gravitational fields (where you won't be using bullets, that for sure). This makes them very easy to aim. Lasers beams propagate at the speed of light. This will be substantially faster than any projectile weapon, and a reasonable amount faster than any particle beam, too. You ...


74

Sure it is, and we can use modern technology to do it (NB: This relies on being able to see into the future further than the OP requirement, but if that's an acceptable change in scale, this would work.) So, have you ever heard of an RSA token? These are devices that work on the basis of giving you a passcode that changes every 30 seconds or so; similar to ...


70

I am not sure where the energy would come from for this It would come from the scanner itself. In order to make extremely-high-precision scans, the scanner itself has to direct considerable energy at the target of the scan. The more precision you want, the more energy you need to pump into it. Much of that energy is absorbed by the target, which is what ...


65

What you're looking for is largely the opposite of what we saw for the 1mm tall robots. Surface tension of water is a noticeable thing, there's a clear bulge that would seem smaller than memory suggests it should on any given surface. Of course we're not looking at such a pronounced effect in this case, but it would be significantly reduced. Gravity would ...


65

You won't be able to have this in a universe that uses our physics. The degree to which space itself expands or contracts is related to the cosmological constant and the density matter within that space. A universe full of water is going to have an insane matter density. Which can be balanced by a large cosmological constant. The problem arises in that ...


63

Easy Peasy. Fusion reactors. The primary challenge involved with fusion power is maintaining containment, which is a big challenge given the pressures and temperatures involved. Not only will the neutrons deposit energy in the blanket material, but their impact will convert atoms in the wall and blanket into radioactive forms. Materials will be ...


58

Yes There are several devices in existence that work based on similar principles as yours (with one or two adjustments). While they're used for plasma research, rather than weapons, they could presumably be adapted for your purposes. If you were to make a plasma cannon from scratch, you should probably model it at least in part after one of them. The major ...


57

Let's say your magical sphere has radius $r$ of 10km (so just poking up into the outer atmosphere) and is at a temperature $T$ of 1,250K (so glowing a nice warm yellow). The total radiative heat flux from the sphere is given by: $$ Q = \sigma T^{4}. 4\pi r^2 \approx 1.7 \times 10^{14} \mathrm{W} $$ Where $\sigma$ is the Steffan-Boltzman constant. A ...


56

In physics mirror symmetry is called parity, so the question is whether any of the fundamental interactions depend on the parity. It turns out that the electromagnetic and strong interactions do not depend on the parity, but the weak force does. In fact parity is maximally violated by the weak interaction - only left handed particles and right handed ...


55

Apollo Fire and Wick Effect I generally agree with Halfthawed, but I had some additional thoughts on the matter. There is one well known and documented incident with fire and people in a pure oxygen atmosphere: the 1968 Apollo 1 accident. The fanatic overexaggerated fear of a pure oxygen atmosphere is rooted in the horrible 1968 Apollo 1 accident where ...


54

This "weapon" has already been built. It's called the European X-Ray Free Electron Laser (XFEL), and it's used for super-accurate imaging of molecules. Point is, whenever the XFEL hits a target molecule, all the electrons are simply blasted away from the molecule, and the more inert rest of atomic nuclei dissolves in a Coulomb-explosion. The scattered X-...


53

Just because the heavens don't tick doesn't mean Earthly stuff won't tick as well. People are going to count their heart beats, breaths and bowel movements. Humanity may have used the sky as its sole time piece for millenia, but once we started to pay people by the hour we got creative. The sundial was the last time piece to depend on astronomy. The ...


53

While I have no actual evidence, I have a good bit of practical horse-riding experience. There are several possible scenarios. If you're doing a normal jump on a live horse (not from so great a height as to injure it), the horse's legs will flex, absorbing some of the shock. Then your legs in the stirrups absorb some more, and your crotch does not ...


51

Improved efficiency! Lifted from https://physics.stackexchange.com/questions/46788/how-efficient-is-the-human-body The MET (Metabolic Equivalent Task) readout on your gym equipment is your body doing 1Kcal/kg/h = 4184 J/kg/h and can be reasonably accurately measured by how much oxygen a test victim uses. Sitting still is roughly 1 met and ...


51

Gravity - Time of fall. Assuming they live in the same gravitational field as the non-giants then simply drop something and see how long it takes to hit the ground. A normal human is about $2m$ tall. It takes an object roughly $0.6$ seconds to fall $2m$ in our approximately $10\, ms^{-1}$ A $10m$ fall would take about $1.4$ seconds. The relevant formula ...


50

Let us consider the humble FET Here's a rudimentary description of a Field Effect Transistor (FET): Imagine water moving through a pipe. When the gate value is all the way open, water flows through the pipe freely. As you close the gate valve, the water through the pipe is restricted until the valve is finally closed and no water can flow. The magic? ...


50

A well trained horse can slide down a rather steep slope: My suggestion would be making it less of a cliff and more of a very steep slope - or, even yet, it is a cliff but there is a section of it that eroded into a steep slope or something of the sort, and have your rider slide down that thing on horseback. It would be more credible and make your main ...


49

The Fast and the Furiously Crazy Since you've eliminated the sensible solution (bypasses or double tracks), let's go with an insane one! All your trains have rail tracks running on top of them and extra wagons with ramps at the front and back. When a priority train approaches, they lower the ramps onto the rails and the priority train drives straight over ...


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 ...


46

You might be surprised to learn that even the full power version of this gun could be fired by an experienced shooter without physical augmentation. It's all about gun design. First, there's porting. This is a pair or symmetrical set of openings in the top of the barrel, near the muzzle (typically to either side of the front sight). Propellant gas, still ...


45

Bells. A large (hence deep-toned) bell can be heard for many miles. Couple with a reflective sound concentrator as in @L.Dutch answer, and bells should be audible for about as far as you could see a lighthouse. "Wait, you can't hear individual sounds over a great distance!" Well, you can't now -- but the world was quieter before there were cars and ...


44

According to WolphramAlpha, the relativistic kinetic energy of such a bullet would be $6.265 \cdot 10^{21} \ \mathrm J$, or 1.5 million megatons. The gravitational binding energy of Earth is $2 \cdot 10^{32} \ \mathrm J$, therefore we can stay assured that the planet won't be completely wiped out. Quoting from this useful page, the impact energy would be ...


42

"I'll be back before you can walk to the lake." If not an exact sense or measurement for time, maybe they'd have an approximate one based on distance. Just as we say "an hours' drive" or used to say "about a weeks' journey," though obviously people drive, cart, and walk at different speeds, a civilization may generally agree on a common-sense "average." ...


41

Two trains become one. On the track there is a train heading in one direction at 100 km/h and a second train heading towards it at 200 km/h. You do not specify the distance between them. If there is some distance there is time for this maneuver. Slow train slows down, stops, goes into reverse. Previously slow train accelerates, in reverse, until it is ...


41

The answer depends on a mighty host of factors, including how pointy your projectile needs to be. However, we can put together a pretty reasonable upper bound by looking at reentry vehicles. They are pretty much the fastest manmade things in the atmosphere. Apollo 10 came in at roughly 11km/s. The record fastest reentry vehicle was Stardust, which came in ...


40

If the light coming out of the amulet is well collimated (i.e. it can form a narrow beam that does not disperse - like a laser) and the light is emitted continuously rather than in pulses, then what it does will depending on the aperture (i.e. the cross sectional area) of the amulet. Assuming a diameter of 2-3 cm (wristwatch or locket sized), an intensity ...


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