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# Tag Info

## Hot answers tagged physics

412

Tl/Dr: the smallest change isn't one to the laws of physics. It's a small change to the definition of magic. This is a favorite topic for me. I could talk for hours about it. Not kidding. Find me in chat if you want. There's more magic in the world than we often think! Let's start off slow, with the straight forward physics part of the question. ...

217

They can't swim. Normal humans are just barely buoyant enough to float in water. We need to generate some hydrodynamic lift to get far enough out of the water to breath. The average human body has a relative density of 0.98 compared to water. Your humans would have a relative density of 1.96. That means while a normal human swimmer just needs to create a ...

182

Apart from the horizon topic that was already covered by Separatix and Ctouw, they could quickly verify their observation by measuring the angle towards the sun at different points of the planet at the same time). Those angles will, much unlike at home, be almost identical, since they are measured from a plane a large distance from the observed object (the ...

161

Daybreak and nightfall would be spectacular A flat coin shape would have a day face and a night face with sudden transitions because unlike a sphere, it blocks all sunlight with its own shadow, there is no refraction around the sphere. If you start at noon, things would appear quite normal and stay so into twilight as the suns moves lower in the sky. But ...

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 ...

136

Shoot Him You just need someone to kill Nelson from behind or from a distance without being initially seen - you can't really stop time if you're already dead. A sniper bullet exceeds the speed of sound, so Nelson wouldn't be able to hear the initial shot and stop the bullet mid-flight. Or maybe that's too simple.

135

Allow me to generalize all of the other answers: No matter what his abilities, he can't prevent something if he doesn't know it's happening. So bullets, poison, lasers, stabbing etc. all work if they kill him before he sees them coming. If he sees the guy about to take the shot, he can prevent it. If he doesn't, he can't. Same if he sees the laser being ...

132

The problem is mostly one of semantics. You can't "do magic for real", because all of the things that you can do for real you consider to not be magic. You can have a conversation with a person on the other side of the world, and if you drop enough money on it you can have dinner with them tomorrow. But those things don't count as "magic", despite being ...

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 ...

118

A failure of the inertial dampeners. The overengineered ship hits the ground at 100 m/s and skids, scuffing up the hull and tossing things about in the interior... including the crew. All are dead from trauma by the time the ship, still functional, comes to a rest.

117

High altitude depressurization. It has happened in real life: Soyuz 11 Soyuz 11 was USSR space mission launched on June 6, 1971. After successful completion of work aboard space station Salyut, on June 30, 1971 the spaceship started the return trip. Everything was normal until audio contact with the crew was lost before reentry began. The descending capsule ...

116

A similar concept has been mentioned in other answers, but one way to make a train like this viable would be to have pods at stations that "dock" with the main train rather than many trains running at different speeds. There would be a period of acceleration followed by the pod locking on firmly. Here's an example where a pod docks to the top of a train at ...

109

A bug is just an undocumented feature. Anything we see from within the simulation is just going to be a part of the simulation. The only way to tell that what you see is a bug is by knowing what the expected behaviour of the program is, and god alone knows what that is (literally, in this case). Even seeing the Eiffel Tower do a dance would more likely be ...

106

A number of common situations could give them away. If you ever paid attention to people getting in and out of your car, you notice that it shifts by noticeably different amount depending upon the weight of the person. Maybe the fact that I notice this makes me a bit of a rarity. But there are other small things. How loud a floorboard or chair creaks. How ...

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 ...

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. ...

86

You do not. Period. I am not joking. This is the kind of thing science simply does not touch. Science is rooted in the world of empirical study. If you have a bubble where the laws of physics do not apply but appear to apply in every way shape or form, science simply will not detect this. A similar experiment is the brain-in-a-jar thought experiment: ...

85

Speed Not Required Give your sword a hydrophobic coating and it will never get any blood on it. The coating repels liquids, causing them to bead up like water on a lotus leaf and just run off. Bonus it stays nice and clean. Edit: A blade made of steel does not mean that It cannot have a coating that makes it repel blood. Furthermore, the surface ...

84

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 effects. The team, from the Southern Methodist University in Texas, analysed more than a million earthquake reports, looking for the tell-tale signal of ...

83

While hopping on one moving train seems reasonable for a healthy young adult, hopping two hundred seems a little excessive and dangerous... Also I would imagine that most people going on a long distance trip will be bringing luggage. I'm sure I could jog up and on to a slow moving train unhindered, but a little less sure about doing so with a suitcase in ...

82

An half submerged crater can give you a circular set of islands. You can choose among various craters: Volcanic craters, like Santorini Mountains subsided into the oceans or eroded by changing sea level, like all the coral atolls (the picture refers to French frigate shoals) Impact craters, resembling the Tycho crater all of the above can also provide ...

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 ...

81

This is exactly what used to happen to cars before Volvo introduced Crash Test Dummies When I was growing up, many of my parents' friends were constantly bemoaning the fact that cars 'just weren't built the way they used to be' and a big part of that was that they just didn't feel safe in cars that weren't built to be sturdy; Solid chromed bumpers, very ...

79

In such matters, it's always helpful to scale things down to the familiar. So, imagine for a moment that you are a 2-dimensional being. You can move freely left or right, back or forward, but you have no conception at all of up or down. Then suppose that your house exists on a sheet of paper. I, a three-dimensional being, can take that piece of paper and ...

79

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 will be large enough to fry pretty much everything. As it cuts through the atmosphere -- even before it hits the ground -- it will scatter a huge amount of energy, ...

78

The benefits and merits of using mecha are highly dependent on how big these mecha are. Under 9' Tall At the lowest end of the size scale, you have what is probably better coined powered armour. But mecha this big should be considered, if for no other reason than to illustrate where larger mecha sizes potentially don't have much use. A 90' tall isn't ...

77

Use Iron's allotropic forms Iron has a wide variety of allotropes. Two interesting ones are austenite, with atoms aligned face-centered cubic (FCC) and hexaferrum, where the atoms align in a hexagonal close packed (HCP) form. Here is the phase chart for iron: Both Austenite and Hexaferrum are denser than the Ferrite that they will phase transition into at ...

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 ...

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