Questions tagged [astrophysics]
For questions regarding the application of the laws of physics to orbital mechanics, stellar evolution, and other astronomical processes and celestial bodies.
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Detecting an escaping Earth
Suppose that, some day, for reasons, the Earth is mysteriously accelerated prograde until it reaches escape velocity. It then starts a trajectory that will take it off of the solar system. It might ...
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A 1 kilometre wide sphere of U-235 appears in an orbit around our planet. What happens?
Let's suppose that after seeing aliens get portrayed negatively in science fiction and wishing to end the discrimination, the ancient H'andh'wh'a'vians decide to destroy Earth and humanity.
As they ...
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Could a "super-Enceladus" moon exist?
Firstly, let us define the term "Super-Enceladus". In the context of this question, a "Super-Enceladus" is a moon that has permanent or near-permanent polar jets spewing out matter ...
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What are realistic numbers for the engineering/physics for a mag-lev train which would circumnavigate the entire planet earth?
Suppose that you were writing a science-fiction novel (or movie script).
In the story, a giant magnetic-levitation (mag-lev) train encircles the entire planet earth.
The ring-shaped train track is ...
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What If A Positively-Charged and a Negatively-Charged Planet Collided?
Let's say we have two planets. Both are around the same mass and radius as Earth, and are 1 year away from colliding with each other, each traveling at 20 km/s. At first. Planet 1 has a sufficient ...
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Making A Geosynchronous Orbit Impossible
Here's the idea: A geosynchronous orbit is an orbit that makes sure that the orbiting satellite is always above the same spot on the planet, so its orbital period is equal to a local day there. I've ...
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The Orbit Of Cryomoreth
Cryomoreth is the homeworld of the Cryomonians. Its year lasts for about 273.15 Earth years, and it is inhabitable for carbon-based life. Its orbit is very eccentric, which results in its seasons. ...
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Sigelon's Terrible Neighborhood
Sigelon is a mountainous world that's volcanically-active due to flybys with a larger neighboring planet that has a more eccentric orbit. These volcanoes release enough soot and smog to periodically ...
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Spinning up the Moon: does it survive the event?
The year is 2xxx. A large asteroid is spotted on a collision course with Earth. The more time it passes, the more it is clear that the impact cannot be avoided. But when most of humanity is starting ...
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Black hole at the center of the planet
Okay, picture a planet so massive, a black hole has formed in its center. The minimum mass of a black hole is 22 micrograms, or the Planck mass, and whatever the core is made of, it needs to be ...
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What if Theia Never Hit the Earth? [closed]
Let's say that for some reason, Theia never hit Earth during the formation of the solar system. However, the two heavenly bodies ended up in a stable orbit around each other. Due to this, the Earth's ...
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Perpetual Day Planet
I’d like to know if this is plausible: A habitable planet that’s always day. It kinda works like this: The planet orbits its largest sun, which is also orbited by three smaller suns that share the ...
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How could we recover from being ejected from the solar system?
I just finished watching the newest kurzgesagt video on if the earth got kicked out of the solar system here:
https://m.youtube.com/watch?v=gLZJlf5rHVs
And I wanted to use that scenario in a story but ...
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Destruction of a Trojan Asteroid by an RKV
The history
During the Great War between two nations, one sent an RKV (Relativistic Kill Vehicle) towards an enemy factory as a message to show their power but not kill needlessly. The base was in a ...
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Chameleon Particles: Space Weapons?
Dark Energy is a force said to be responsible for cosmic expansion, and one of the theorised carriers of this force is the Chameleon Particle. To describe its effects, due to its non-linear self-...
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What would a world look like if everything was a billion times more massive? [closed]
All atoms are still the same size/mass - it's just that the Earth, people, grass, bugs, etc - everything is more massive by a billion times.
So since the Earth would be a billion times more massive, ...
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What would be the biggest threat if gravity stopped? [closed]
Suppose that the law of gravitation suddenly “stops working” one day, and all gravitational forces cease to exist. What would this mean for people on Earth? Could we survive for very long? If not, ...
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Universe without Gravity
Imagine a theoretical parallel universe that does not have and never had a gravitational force. Loose hydrogen atoms would still have formed, and in some cases might have formed H2, but would not ...
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Equations for developing a hypothetical Solar System [duplicate]
I am currently going down the rabbit hole of writing a story but I would like it to be set in a universe which is believable. Therefore I am trying to create a hypothetical solar system in which the ...
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Viability of a mega star system
So my story hinges largely upon a precursor type race centered around a single star system that went extinct tens of thousands of years prior to the modern day. Obviously, the most common way to go ...
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When designing a map of the local universe how should currently unknown/obscured areas be treated?
I am building a map of the local universe for my story and for the time being I will base it on the real universe and our current understandings and observations although later will likely change the ...
user78658
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What elements are useful for humans, but rare in our galaxy?
I know for example there is an interesting gap in the amount of lithium, beryllium and boron compared to Helium and Carbon, but I don't know how useful they are. Here is a graph showing relative ...
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How large and bright has to be a spaceship so that you can see it with the naked eye moving at 0.99c near Pluto?
Today someone looks up at the night sky unintentionally directly towards Pluto. There is a bright light which is impossible to mistake for a star, satellite or shooting star, as it's shaped like a ...
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Is it possible to colonize the center of a planet with a cold core?
Let's say you have a planet(about the size of Earth) where the core of a planet has gone cold for whatever reason. So the planet is basically just a barren rock devoid of atmosphere or electromagnetic ...
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What it looks like inside a nebula from a spaceship?
People love nebulas and all in sci-fi, specially for space battles and all so the background looks more interesting than just black.
But I am wondering, if you are inside a nebula while in a warship, ...
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A planet that is entirely liquid
Is it possible that a body of significant size - at least several hundred kilometers in diameter - is entirely liquid, having no solid core? It can be either made of one homologous liquid or of ...
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What to do with planet nine if it is a Black Hole? [closed]
Recently it's been theorized that "planet nine" may be a black hole.
If this was the case what could we do with it? What unresolved problems in physics could be solved by having such a thing ...
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How could a breathable ultra-high pressure atmosphere form?
Some background: I'm developing a world that could, theoretically, be inhabitable by humans (with a high enough recruitment success to at least keep a stable population), randomly determining ...
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Long Term Evolution of Double Planet System in Close Orbit
So, I have a double-planet system in a solar system and I'd like to analyze the long-term evolution of these two planets. In particular, I'd like to know:
Is this setup unrealistic in some way? The ...
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Why would the most energy efficient shape be a cube instead of a sphere?
The most energy efficient shape in our universe is a sphere. However, in another universe it is a cube. Why and how would this happen?
I came across this idea while thinking about Minecraft and why ...
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Can a planet be in spin-orbit resonance with its parent and in resonance with other planets at the same time?
Mercury is tidally locked in a 3:2 spin-orbit resonance with the sun. Other resonances like 1:1, 2:1, 5:2 can occur as well. Many objects, like the moons of Jupiter, are locked in mean-motion ...
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Can my advanced civilization halt the expansion of the universe?
Do the laws of physics permit any chance for a Type III civilization on the Kardashev scale to halt or even reverse the expansion of the universe, or bring the galaxies back closer together, assuming ...
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What impact would a white dwarf-neutron star collision have on a civilization on a planet orbiting the white dwarf?
An advanced civilization lives on an Earth-like planet orbiting a white dwarf. Their star is on a collision course with a neutron star. I imagine this collision will cause a supernova, which will ...
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What is the crust of a habitable planet with Io-like heat-pipe tectonics made of?
The Jovian moon Io is geologically active like Earth, yet it experiences heat pipe tectonics instead of plate tectonics.
Heat-pipe tectonics is a cooling mode of terrestrial planets in which the ...
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Can you survive the birth of and then occupy a nearby new born universe?
An advanced species that does not have FTL travel methods lives in a universe with the same fundamental laws as our own. The species can either create,
or know when and where a new universe inflation ...
user69935
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Concerning asteroids and a trojan habitable planet
So I found a question on this site that talked about the possibility of having a habitable planet in a stable trojan position (a planet located at Lagrangian point L4 or L5 of a much bigger object). ...
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Tidally locked time keeping 2 [duplicate]
I have done some research and so much contradict one another or I simply fail to understand.
Can a moon be used as accurate time keeping and is it possible for it to revolve around the planet once an ...
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Do seasons occur on a tidally-locked planet?
I have done some research and so much contradict one another or I simply fail to understand.
Do seasons occur on a tidally locked planet that isn't tilted on its axis?
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How deep can the oceans be while still alowing some land?
Many alien worlds will most likely be water worlds. I was wondering what the deepest possible global ocean dept is where land is still possible. I think that volcanic islands will still have a chance ...
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What sets of stellar models are freely available for reference when worldbuilding?
Often, when I'm building a world, I want to start out by determining some of its key properties. Maybe I'm trying to calculate a habitable zone, or figure out how long a year would be on a particular ...
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Superfluid lifeform
Could a life form that uses superfluids as part of its biology exist?
I've read in places that the issue for life outside of Earth and especially the theorised silicon lifeforms is that the existence ...
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Could co-orbital planets also be double planets?
Double or binary planets are a really cool science fiction idea. A second Earth hanging ominously in the sky. Co-orbital or trojan planets are also interesting in that you have them on more or less ...
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Properties of a mysterious celestial body that creates a permanent eclipse on earth
Sometime in the near future, a strange heavenly body appears in the skies of Earth. Unbeknownst to everyone, it's actually the egg of a horrific, unimaginable cosmic entity, traveling through space ...
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Probable way to send a moon on a collision course with its primary?
Background
In my setting, there is some sort of cosmic war going on between two factions. This war climaxes in one of the warring sides having the moon of their home-planet being redirected into the ...
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How massive would a planet need to be to sustain negligible damage from impact with the Earth?
I'm curious what factors a terrestrial planet impacting the Earth would require for the impact to cause negligible damage to the larger planet, while destroying the Earth.
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Could I observe the black hole that created my area of space/universe?
My story has some very advanced robots that have spread throughout the galaxy. Their advanced technology has developed to massive radio and optical telescopes to view unexplored areas of space. When I ...
user69935
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How could you wipe out all life from the universe? [closed]
If you had as many resources as you needed, obviously making A LOT of assumptions about physics, how could you semi-realistically kill all living creatures in the universe?
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How fast would strange matter conversion go?
Background:
So this Kurzgesagt video talks about quark stars, and how two of them colliding could send strangelets flying towards Earth or the Sun. Now it's been said that since, theoretically (as ...
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Could a hypothetically big enough planet, with an earth-like atmosphere, be big enough so that you cannot see its curvature from above?
I want to know if a planet with an atmosphere identical to that of Earth could be big enough so that from no point in the lower atmosphere it would be possible to appreciate the curvature in relation ...
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My setting has a multiverse, how could the agency in charge of naming them and documenting them tell them apart?
They'd be documented and named similar to how NASA give names to planets or stars. Since there is literally an infinite number of universes, I think they'd have a name followed by a Roman numeral. ...
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