# Tag Info

## Hot answers tagged gravity

104

It makes perfect sense if your aliens are benthic marine creatures. Falling upwards into the sky doesn't make sense if your aliens are humanoids living on solid ground beneath an Earth-like atmosphere. However, if your aliens are, instead, benthic life forms living at the bottom of an ocean, a disease causing them to fall upwards would make a lot more sense....

88

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

84

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

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, ...

71

No, they will not be able to reach space. At least if we assume that our understanding of physics is correct. Since you do not state anything to the contrary, that's an assumption I am willing to make. Basically, what you have is a (very small) black hole. A black hole is a mass that is so dense that the escape velocity becomes greater than the speed of ...

68

Yes Under the equivalence principle anything on the "back" of the planet that wasn't strapped down would be left behind if you accelerated at >1g. we ... assume the complete physical equivalence of a gravitational field and a corresponding acceleration of the reference system. — Einstein, 1907 That includes people, atmosphere, water, large chunks ...

67

Your planet is a pulsar From Wikipedia, the acceleration caused by centrifugal force of a rotating object is $$\omega\times(\omega\times r).$$ Since the direction is known to be tangential to both the direction of rotation and the axis of rotation, and surface gravity acts in the opposite direction, we can just use the magnitude $\omega^2 r$. The ...

66

I'm going to say yes. Joe is actually in a rotating space habitat (I don't know how he got there, that would be the story). Upon exiting the narrow tunnel he can see the water "above" him on the opposite side of the round rotating habitat, if he were to walk forward the "wall" would become the floor and then the "ceiling" would also continue to feel down ...

63

The simple answer is "yes". The more complex answer is "it depends" and "how much heavier". Over time you could expect evolution to help, bones would thicken. Height would decrease, people might even move back towards shorter legs and great-ape-style 4-legged movement. That doesn't help the first poor victims though so lets think about this. Lets say an ...

58

Well, at best you're depositing in the planet (or the powdered remnants thereof) energy equal to its gravitational binding energy. According to Wikipedia, the one true source of truth, the gravitational binding energy of Earth is about 1032 J which is about as much energy as the Sun emits (in all directions) in a week. This is converted into kinetic energy ...

51

Sorry in advance. You won't like this answer. The "stuff" in white dwarf matter is more specifically known as degenerate matter. Basically, the more tightly you crush this matter, the more the valid quantum mechanical states for the electrons "fill up." For normal matter, there are so many more valid states than there are electrons, that we don't have ...

49

"Some kind of exotic particle? Or perhaps a form of gravity that we haven't encountered yet?" I'd go way more realistic: make it a virus, (maybe developed by some weird apocaliptic cult), and there you go. Wikipedia states that Aphasia is an inability to comprehend or formulate language because of damage to specific brain regions Which is perfectly ...

46

It would be 6,378km deep. The same depth as the radius of the Earth. The math To calculate the gravity of an infinitely flat plane we simply need to integrate the force felt from concentric rings from a radius of zero to infinity. This is a basic practice in college physics courses and is demonstrated here. It turns out, that the force on a mass above ...

46

As mentioned, anti-gravity and or gravity generators will let you pull magic out of thin air, but let's try it without magic. I can't imagine why anyone would bother doing it, but I decided to see what happens and ended up with a totally insane project that uses a lot of carbon nanotube (CNT) and crazy amounts of energy. But, you don't need unproven ...

45

There's plenty of ways to extract energy from Jupiter's gravity. The problem is how do you do so without lowering your house's orbit? Tidal Flexing? (probably not worth it) When two objects interact with gravity there is a tidal force. The sides closest to each other feel a stronger tug than the sides furthest away. This causes them to stretch just a ...

45

The surface gravity of Enceladus is 0.113m/s2. At such a low gravity, you cannot run, for the force you would use in a step will send you on a very long jump that may last more than a minute (if you don't hit anything along the way before you touch ground again). This may be quite dangerous. If you don't have the means to fly, like a jetpack, you may end up ...

43

The answer is cold welding. Modern engineers struggle to prevent cold welding in space from destroying moving parts. Maybe your engineers have come up with a coating for the inside of the guns that prevents moving parts from sticking together, but the forces involved when a semiautomatic fires, ejects the empty shell, and chambers the next would strip that ...

42

Our current understanding of physics does not have a mechanism for the sudden reversal of gravity. Any science based explanation of this effect requires a science sufficiently advanced to be indistinguishable from magic.

42

The River and the Lake are not water. The fluid is actually a non-Newtonian ferrofluid, which is to say it is a fluid that has magnetic properties. The ceiling of the cave is comprised out of some sort of naturally occurring magnetic lodestone.

42

Well, Mark Olson and Samuel provide some very respectable math that winds up with the world destroying shot being taken from about 1 AU or the distance from Earth to sun. Yes, yes; it seems very reasonable. But what fun is that? A little flash of light, a great disturbance in the force; bah. You want a ringside seat. I propose that your world ...

42

Turnover point doesn't need a period of zero-g or any kind of noticeable effect on the passengers. Simply don't stop thrusting. That is, when you get to the halfway point of the trajectory you start slowly turning the ship around while keeping your thrust at normal level. If you do your turn slowly enough, your passengers won't notice a thing, say over a ...

41

This is actually a fairly well-researched and entirely practical design concept for cheap, robust spacecraft with centrifugal gravity. Since the connecting "shaft" is entirely in tension, it could even be little more than a cable, and need not be stiff (in fact, in some designs you actually want it to be able to flex a bit--the reason for that should become ...

39

By the shell theorem any body inside an hollow spheric shell would not feel the gravitational attraction of the shell, for the very reason you mention. And that not only in the center of the sphere, but anywhere in the hollow space comprised by the shell. So, provided you can drill till the center of the planet and make an hollow space, any body placed ...

39

Yes, though Enceladus is probably much safer than Earth for these sorts of things. It all depends on how high the avalanche starts from and how much material is involved. A ton of rock or ice hitting you at 50 mph is going to hurt regardless of whether it's on Earth or Enceladus -- if anything, Enceladus would be worse because of the likelihood of damage ...

39

Oh. Oh my.. this is Not Good, but not for the reason you might immediately think. The reason is that the particle beam, while doing it’s slicing, will have turn the material it hits into plasma in order to get it to move out of the way. That isn’t immediately a problem. The problem is that the plasma is, from the point of view of the particle beam, pretty ...

39

Totally different idea. In late 2283, a research team at the University of New Tokyo finally cracked the Unified Field problem. This gained them one of the most prestigious Nobel Prizes ever awarded in history. The results of this were initially amazing: it allowed on demand gravity control, the benefits of which were immense. Needless to say, everyone ...

39

There are several problems with this. First of all, when someone fires a laser at you, you aren't going to know it until it hits you, so this would only work if Ship A were CONTINUOUSLY creating a gravity well in between itself and ship B. You couldn't use it reactively without letting it hit you first, although you could potentially limit the damage. ...

38

With a Lofstrom launch loop. Basically, you want to build a set of towers high enough that they can lift a train track all the way above the atmosphere. Then, in the absence of air resistance, you can accelerate your train all the way up to orbital velocity, and beyond. Now, building a tower in high gravity may not seem like it's really any better than ...

38

This setup wouldn't work, not even in a mathematical sense, at least as you described it. In four dimensions, you can't actually rotate with respect to an axis. Instead, a 4D rotation leaves either a plane or a single point invariant. In more detail, a rotation in a space of arbitrary dimension can be thought of as composed of simple rotations. It can be ...

38

Okay, from a height of 100 meters, the faller will reach a speed of 44m/s. Human terminal velocity, for a spread-eagle position like skydivers, is 53m/s, so drag is going to play a big role here, especially if he goes spread-eagle. Call it 32 m/s of landing speed. If our hero wants to stop in ten meters from this, assuming roughly constant acceleration, he ...

Only top voted, non community-wiki answers of a minimum length are eligible