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33

There's starlifting. Wikipedia, YouTube. Basically, the idea is that you get a large (humongous) magnet orbiting the star (or hovering over it artificially via solar wind sailing), with which you attract magnetically charged plasma of the star's surface (but a couple of other means are described at the respective links). You then collect the uplifted matter ...


26

Terrain considerations. Most ground-based propulsion has some kind of surface that they cannot function well in. Wheels spin out on loose sand, legs can topple on boulders, tracks lose traction in swamps and wetlands, and neither can move through deep water. Hover vehicles have none of these issues. Even if their altitude is limited to a few feet, they can ...


18

Whenever mechs and hover tanks are discussed people always only point out their drawbacks and ignore their advantages. However when we look at wheels versus tracks we can list various advantages and disadvantages, then use those to determine when you want to use one or the other depending on the vehicle's characteristics and usage. The same has to be done ...


16

Atomic transmutation (a.k.a. alchemy) is a gestalt technology. It changes everything. Mining is the process of digging through masses of undesirable material to find the comparatively rare desirable materials. When any material can be transformed into any other material at an atomic level, the whole idea of mining flies out the window. Dr. Emmett Brown ...


15

Giant mirrors in space. (Assuming you want a reasonably non-apocalyptic way of making "the Sun stand still", and a technological level within the current millennium) A large (sort of) statite is placed in the L1 Sun-Earth Lagrange point. Also, a Fresnel mirror is placed just beyond the Sun, focusing a stream of sunlight towards a third mirror in a ...


14

Reliability As you say, the tank relies on a fragile piece of complex tech. The thing is that tech can be made reliable enough that it can outweigh the downsides. Computers and electronics are physically fragile, potentially can be hacked and could be disabled without ever getting near the tank. Currently all modern tanks come with a plethora of electronics. ...


14

On Earth, the planet would need to suddenly stop spinning. At the equator, that's roughly 1000 mi/hr "just" to a dead stop. Woe betide the billions of people close enough to water to be drowned in the ensuing tsunamis. Not that most would notice, having already been pulped by buildings falling upon them or shredded by 1000-mile-an-hour winds. The ...


13

Antigrav hovertanks aren't necessarily fragile There's no particular reason that an antigrav system has to be overly vulnerable (more than, say, an internal combustion engine). Sure, it's pricey to repair and maybe you can't do it in the field, but as long as you don't get a bullet through it you'll be fine. With an antigrav system, you can have heavier ...


11

This is a great question, but let's start with the natural limitation In keeping with the laws of thermodynamics, the human body cannot generate more energy (for any purpose, including cooling or heat) than it can take in. In fact, since some of the energy it takes in must be used to keep the body alive, there's a substantial limitation to what the body can ...


9

Encasing yourself in a large blob of water which falls with you will totally protect you from the impact of falling into another body of water (lake, ocean, whatever). This will work because your water blob will enter and penetrate the water it hits, providing a very turbulent but soft cushion to fall on. A bit like going down a waterfall, where real danger ...


8

No, unless your incoming projectiles are bubbles or marshmallows. Bullets and missiles have a relatively high velocity. That means that the amount of time you have to deflect with an air-stream them is very small. Consider the frame of reference of a moving bullet. The entire time they are in flight, the air they pass through is effectively a VERY fast wind ...


8

Wind affects the motion of projectile, deviating it from its ideal parabolic trajectory. Drag, which is nothing else that air resistance, also affects the projectile trajectory, shortening it. So, yes, an air flow can disturb the trajectory of a projectile. However it will need long distances to have a noticeable effect, unless the flow velocity is very high....


8

Per this source (https://phys.org/news/2019-09-fast-universe-mystery.html) the universe is expanding at between 70 and 90 km/s/megaparsec. With the middle value being 82. A rocket, even a perfect one, is limited by the rocket equation: dv = ve (mo/mf) Substitute c for ve, and dv of 0.3c has an mf / mo of 74%. Just on the acceleration. Squared to include ...


8

An idea that gets tossed around a lot in this sort of scenario is false vacuum decay. Let's say we have a tiny ball on the end of an ideal spring, moving back and forth as a harmonic oscillator. The ball and spring have some amount of energy $E$, and knowing the value of $E$ tells us something about the dynamics of the system. There's a quantum analog to ...


8

If there is a powerful and abundant enough energy source, there is always the option of converting energy into matter, remembering that $E=mc^2$. That would allow for creating directly any nucleon and from them any atom. However mind that only to create 1 gram of matter one would need $10^{15}$ J. That's why I started with "If there is a powerful and ...


7

You're dead anyway I was going to calculate the parachute area required for base jumping with that mass, but then it came to me that mycelium is not a proper fabric for this. So your best bet would be to mushify all soft tissue for cushion, but then you will have no circulation and as such will be brain dead for want of oxygen. I think the death by impact ...


6

Resistance to land mines: If your antigrav device can function with armour between itself and the ground then it can withstand a small explosion that would blow the tyres or break the tread of a ground vehicle. If it distributes the weight of the vehicle over a larger area of ground than a tank's treads, or else if it makes the vehicle literally weightless, ...


6

No appreciable difference, as it can be seen by the many who get electrocuted while with one hand touch a live cable and with the other a conductive surface. The electric current flowing through one's heart/lungs would mess with its functioning pretty badly, regardless if the current is flowing up to down or right to left. Incidentally, this is why if one is ...


5

Yes, it is called radar jamming, and it is a very real technology that has existed since WWII. Jamming does not exactly make a fighter disappear from enemy radars. Instead, you fill the enemy radar with a giant false positive such that the entire sky appears full of possible targets. Radar only works if you can key in on the return signal, but by ...


5

While the typical military hovercraft have been landing craft, the Finns experimented with a missile boat on a hover craft chassis. While in many 'typical' situations, the hovercraft's 'fragility' (though modern materials for skirts might be bullet resistant) and difficulty of control may be an issue. The trick is finding environments where they work - the ...


5

Make it using lasers Just a couple of years ago, scientists discovered that an adequately powerful laser can be used to create matter out of a vacuum. If your advanced civilization has discovered some infinite or virtually infinite source of power, they may decide to simply fabricate new matter out of nothing. Although this technology technically exists ...


5

At about 250 megatons, the resulting energy would be about 10 times greater than the Mt. Saint Helens Volcanic Eruption. This would be enough energy to launch a mass of debris equal to a large mountain into the air, and at only 0.126G, a significant portion of it would be able to exceed escape velocity flying off into space. Calisto has a very minimal ...


4

Refer to Planetside 2, where this exact situation comes up with the levitating MagRider (the main battle tank of the Vanu) vs. the other two factions using more traditional tread technology. https://www.planetside2.com/ The core advantages of the hover tank in battle are: Ability to strafe tank shells, dumbfire missles, etc. Performance upgrades that 'boost'...


4

Every morning I take the bike for a ride, and every morning I wear a jacket made of synthetic material. Every time that I place the key in the slot to open the door and get out I see a spark. The spark happens because while I wear the jacket the friction between the jacket and my clothes produces electrostatic charges which then get to ground once the ...


4

Electricity by friction: not in usable quantities. But if your goal is to generate electricity from body movement, there are at least two approaches that work fine. One way is to use a mechanical inertia-to-motion-to-electricity charger, such as this Ampy Move They work fine, although the power produced is not as great as one could hope for, it is ample to ...


4

The problem isn't speed, it is mass While spinning black holes and any spinning massive objects do drag space around it using the frame dragging effect, this is only noticible on very massive objects. A few kilograms won't produce a noticable effect. The Earth is much more massive even taking into account the difference in speed and the effect of that on the ...


4

Big Rip is another good candidate. Dark energy is going to increase to the point that all matter in the universe is going to be ripped apart. Its downside is that if it's indeed going to happen, it will be billions or trillions of years in the future. But let's say we have strongly underestimated the dark energy. Let's say the dark energy is going to ...


3

You need some pretty chemically advanced substances (somehow I figure you're aiming for a "steampunk" vibe - this will not be it). However, what you want is something like linear perfluoropolyether. These are liquid, stable in a wide temperature range, non-conductor (which is good since you don't want stray currents in a fulminium core, I'd guess) ...


3

Your aliens stumbled onto a cache left by someone else. They simply know how to use what they have but have no understanding of either how it works or how to replace what they have if something breaks.


3

Setting aside that different models have just different approximation level of reality and there is no totally wrong one or totally right one, it's perfectly that case already with the theories we have developed so far. Take the Copernican model of the Universe vs the Ptolemaic model. A civilization using the first one would have no practical advantage ...


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