Questions tagged [physics]

For questions regarding the physics relevant to fictitious worlds. General physics may be off-topic.

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4
votes
1answer
67 views

How to find the density of a planet and its core taking into account the gravitational compression in them?

Consider a planet $P$ of radius $r$ larger than Earth, whose mass is $r^3$. By the square–cube law, this planet will have the same density as the Earth... assuming that the gravitational compression ...
2
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2answers
80 views

pressurizing a space suit [on hold]

So was writing a short story about space and I had a random idea. Could you pressurize a suit with something other than gas/air? In theory you could literally put pressure on the person or fill the ...
20
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12answers
4k views

Justifying the use of directed energy weapons

In my scifi setting I want a broad range of slugthrowers (bullets, smart ammo, grenades,...), exotic weapons (flame/chemthrowers, high tech blades, nano-bots,...), and directed energy weapons (heat ...
23
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11answers
6k views

Plausible plasma weapons?

In a lot of science fiction, the advanced weaponry takes the form of guns firing directed bursts of plasma. These searing bolts of fire are classic ways to create weapons apparently rooted in science, ...
20
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6answers
4k views

What effects could a hole in a planet have?

On a planet with Earth-like attributes in every way, including physics and geography, what repercussions would there be for a relatively deep 'dent' in one quadrant of the spherical body? This is only ...
5
votes
1answer
236 views

Post-apocalyptic airship

I have: A post-apocalyptic scenario, set in the ruins of an American metropolis with flooded streets. The apocalypse was some decades ago, some primitive technologies have been re-invented. ...
0
votes
1answer
76 views

What trajectory would an interstellar asteroid move in if a super creature jumped off it? [on hold]

The recent interstellar asteroid Oumuamua is the inspiration for this question. if a humanoid creature that had all the abilities to survive in space had hitched a ride on this asteroid and chose to ...
0
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2answers
181 views

What would a Superconductive Fluid do if drank/inhaled by a human?

Hypothetically speaking, if there was a substance you could drink/inhale (in an alternate reality) with superconducting properties, how would it influence the brain and the body? The superconducting ...
26
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18answers
15k views

How might telekinesis and pyrokinesis work if they were possible?

New here! Now let me be clear: I'm well aware that telekinesis and pyrokinesis are both impossible, as I've been rudely informed on every science forum. Nonetheless, I don't just want to "make it up" ...
11
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8answers
6k views

How many people would you need to pull a whale over cobblestone streets?

A whale, lets say a humpback (~40 tons) has to be pulled about 250 m from the port to the town square. The road is classic cobblestone. People put hooks into the whale meat with ropes attached and ...
4
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7answers
724 views

Impact on the sciences with helium instead of nitrogen

Suppose we have a planet whose atmosphere has roughly the same gaseous proportions as Earth, but helium replaces nitrogen, and has a strong hydrogen presence in the upper atmosphere; has a ...
4
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3answers
114 views

How to find the radius of a planet given its internal composition?

Consider a planet very similar to Earth, with the same radius and the same mass. In a very simplified model of its interior, 70 % of its mass is magnesium silicate and the remaining 30 % is iron. This ...
3
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3answers
152 views

What energy sources could exist beyond fusion? [on hold]

I'm looking for possible sources of energy that could one day replace fusion. I'm not necessarily looking for cool sounding names, as I'm trying to avoid technobabble, but ones that could somewhat ...
3
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1answer
91 views

Looking for a layman's plasma simulator

Modelling plasma in a magnetic field is hard, it has to be or we would have fusion power already. Do you know of an application that could be used to simulate the rough / dumbed-down behaviour of a ...
10
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5answers
2k views

How big would my character's wings realistically be?

I'm not a professional at world building or character building, still starting out, but I do want to make an attempt at having my fantasy character be somewhat realistic. He's 11 years old, 4.8 ft (...
17
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0answers
290 views

Plausibility of helium dominated atmospheres on super-Earths

I've been using this helpful diagram a lot for worldbuilding. Now I came to think about the fact that helium is more massive than hydrogen, thus a scenario where hydrogen escapes, but helium is ...
-3
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1answer
106 views

How to calculate time to reach fractions of the speed of light when accelerating at 1g

Currently writing a scifi novel and am trying to do the math to establish time frame of the lore. The main points are that in 2068 CE Earth sent a generation ship to colonize Proxima Centauri. They ...
1
vote
4answers
211 views

Is using Casaba Howitzer like devices as precision-cutting implements plausible?

How well would something like a Casaba Howitzer work as a beam weapon? A Casaba Howitzer is a type of directional blast that focuses energy from an explosion into a specific shape or direction. For ...
17
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1answer
524 views

Electricity without electrons

The universe so far: If charged lepton fields are eliminated from the universe, charged pions become stable (having no decay path that preserves charge), replacing electrons to form bound "atomic" ...
6
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4answers
241 views

Scientific synonyms for “forward, backward, up, down, left, and right” [closed]

I am not talking about anterior, posterior, etc... I am looking for words specifically relating to movement. Long description... In the mythos I am working on, mages learn to control objects in three ...
1
vote
1answer
90 views

Planet spinning at 90 degrees [duplicate]

I'm creating a planet and I was wondering what would happen in its situation. The planet's rotation axis is rotated 90 degrees, but still spins. Its gravity is twice than that of the Earth, and ...
20
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11answers
5k views

Could there be a material that inverts the colours seen through it?

I had a vision of a creature that touched things, and wherever it touched, it left a mark opposite to the original colour. For example when it walked across the grass the grass had red footprints, ...
42
votes
1answer
4k views

What would the periodic table of a 4-Dimensional universe look like?

In this question, I asked about a universe with (amongst other things) 4 large spatial dimensions. In 3 dimensions, we have the familiar periodic table with its familiar arrangement of atoms in the S,...
4
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10answers
339 views

How would a fixed altitude magical Airship be propelled?

Background In my world, there are vehicles that can spatially "lock" themselves to a single altitude. The locking mechanism is a magical core, combined with runic metal bands extending around the ...
6
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6answers
313 views

Can a machine benefit from stored heat energy?

Setting Overview My world suffers from an abundance of a particular type of energy. This energy can be safely absorbed and utilized by living cells, enabling, for example, a dragon's flight and fiery ...
8
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4answers
563 views

Slowing the Heat Death of the Universe

I have an enormous civilization spanning a large amount of the universe. It is able to both travel and send information much faster than the speed of light without violating any laws of physics. ...
49
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7answers
10k views

Can I use a trebuchet to launch satellites into space from a lunar colony?

I've got a lunar colony that struggles to obtain resources, so they're looking for ways to launch satellites into orbit without using up a bunch of rocket fuel. One plucky engineer has suggested ...
2
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6answers
262 views

How can a twin on Earth grow old slower than his/her twin sibling?

I understand it might happen in a weak gravitational field. If I have twins on Earth, but one of them suddenly gets transported to intergalactic medium (without any great mass nearby), then the ...
71
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11answers
10k views

How can powerful telekinesis avoid violating Newton's 3rd Law?

Characters with powerful telekinesis are portrayed as being able to exert a superhuman force using only their minds. For example, they can throw a car. Based on what I remember from high school ...
14
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13answers
4k views

Aliens to play a mischievous space-time practical joke on Earth

Premise Suppose an earth-like world in the near-future. Then aliens come and decide to play a mischievous trick on this world on an epic scale. The goal is to disrupt Earth's time by 18 minutes. ...
8
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2answers
308 views

How would a rail gun affect the trajectory of a spacecraft?

What sort of force would a railgun need to produce to have a measurable affect on the trajectory of a large spacecraft? In the scifi book I am working on the primary craft of the story is a military ...
2
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0answers
102 views

Is Santa taking off risk creating a black hole, and will the good kids receive presents survive it? [closed]

Santa has to visit roughly 822 houses a second on Christmas day. At each house he has to stop, go down the chimney to deliver toys, then take off for the next home in a millisecond's time. As the ...
42
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23answers
10k views

What would be best way to re-melt Mars' mantle and core to revive its magnetosphere

Missing magnetosphere on Mars keeps popping up. Most likely caused by Mars core being cold, mantle not bubbly enough. Mars mantle is dormant, core does not move. What would be good way to get it ...
57
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13answers
16k views

An infinite train circling the planet that never stops

As a way to travel fast, my Earth-like planet is going to have a special train, circling it (the axis of the 'tracks' is aligned with the planet's axis of rotation). The thing about this train - it ...
8
votes
7answers
411 views

Could a mass-proportional physical speed limit on projectiles “nerf” guns but not ruin archery?

Like many other writers, I'm hoping to create some sort of justification for destroying the monopoly firearms have on the modern combat scene so that I can justify mixing things up with melee weapons, ...
2
votes
2answers
108 views

Is it possible for theoretical particles such as tachyons to interact and/or bond with normal matter

I understand that particles such as tachyons don't really exist and are unlikely, but say for the sake of this question they do. Would these particles bond or interact with atoms? By interactions I ...
102
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10answers
10k views

Would planets be cubic in my “cuboverse”?

Summary The main idea behind the "cuboverse" is that spacetime distances are measured by (something close to) the sup norm or infinity norm. Under this norm, spheres (the set of points at a fixed ...
5
votes
2answers
308 views

A universe without light?

In the story Wang's Carpets (and part of the novel Diaspora), Greg Egan sketchily describes a high-dimensional universe which contains no analog for light, such that the aliens who inhabit this ...
6
votes
1answer
201 views

Effectiveness of lasers of different wavelengths in space combat

I'm working on a game with combat between spaceships. It will not be hard sci-fi, but I'd like to base the mechanics on (simplifications of) real physics. When it comes to laser-weapons, I would like ...
0
votes
1answer
58 views

The ability to reduce the movement of particles [closed]

Let's say that there is someone with the ability to reduce the speed of particles' movement (or vibration), he can reduce the movement of molecules, atoms and electrons. I want to know what will this ...
3
votes
1answer
93 views

Particle Accelerator Explosion

I'm writing a science fiction novel where a linear accelerator buried underground has to explode. Above the linear accelerator is an enormous server room which ideally would be heavily damaged. Atop ...
5
votes
2answers
101 views

If the nucleons in an atom were heavier, could it still be stable? [closed]

If the protons and neutrons had, say, a hundred times more mass than they normally do, could the atom overall still be stable? Would it affect the atom's electron cloud somehow, or would it still be ...
44
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0answers
1k views

How soon can the first stars form?

Introduction In our universe, the cosmic microwave background was formed approximately 400,000 years after the Big Bang. It was hot, but within a few million years after the Big Bang, it would no ...
4
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1answer
146 views

Designing (a specific kind of) dark matter

There are exactly 2 force laws that can produce stable closed orbits: proportional (spring force) and inverse-square. The inverse square law occurs naturally for monopole central forces in 3 ...
29
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7answers
2k views

How do ballistic trajectories work in a rotating cylinder world?

For the sake of fixing some image in your mind, imagine you want to practice some sport in a rotating cylinder world: whether it be launching a javelin, strike a tee at the golf club or scoring a 3 ...
6
votes
0answers
178 views

Schwarzschild Metric in a universe with the same space time metric as that described in the orthogonal series, but with massive gravitons?

The universe described in the orthogonal series http://www.gregegan.net/ORTHOGONAL/00/PM.html is one, in which the minus sign in the space time interval is replaced with a plus sign. So this universe ...
5
votes
1answer
162 views

How might star formation work in a universe similar to the one described in the orthogonal series?

In our universe, in order for a cloud of gas to collapse into a star it needs to release heat energy in the form of radiation, so that it can cool down enough to collapse into a star. I read what ...
0
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7answers
292 views

How would a character build an explosive from natural elements?

A character is on an alien planet that is very much like any one of our large deserts. Sort of a Tatooine like on Star Wars. He needs to cause a diversion. There aren't any explosives on planet of ...
12
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3answers
3k views

Would skyscrapers tip over if people fell sideways?

Suppose that for some reason gravity magically changes, but only for people. While this goes on, instead of gravity pulling people down, it pushes them East. To be clear, it's just people. Not animals,...
3
votes
2answers
186 views

Ultimate fate of someone falling out of a skyscraper in warped gravity

At the climax of my story, most of the people on the planet have the way they interact with gravity magically altered. Until a week passes or they die (whichever comes first), instead of being pulled ...