# Tag Info

94

The crews have evolved on worlds with orientation, so their psychology and conventions reflect the reality that they are planetary creatures. Orson Scott Card captured the importance of orientation to human psychology very well with his "The enemy's gate is down" line in Ender's Game. Changing the perception of orientation changed the psychology of the ...

67

Problem: even if you could just stick a blanket over the sun, it is probably already too late. The solar system formed more than 4 billion years ago, and for all that time anyone who was watching and had suitably acute vision would have been able to see Sol, and almost certainly the protoplanetary disc around it and later the planets themselves. Certainly, ...

56

Plans for stealing the moon. Shrink it Well, this seems like the obvious solution. Just invent a shrink ray, zap the moon so it becomes the size of a basketball, then carry it home with you and mount it as a decoration in your home, a testament to your genius. Problems: Inventing a shrink ray. No science exists that could possibly turn the moon into ...

38

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

This scenario is quite problematic for two main reasons: evaporation and peak wavelength. The black hole's lifetime is too short We can make a rough estimate of the properties of the Hawking radiation coming from the black hole. First, let's start with the luminosity. Since $L\propto M^{-2}$, where $L$ is luminosity and $M$ is the mass of the black hole, ...

34

It's perfectly easy to steal the moon. Just register a claim on it in every country and start issuing legal notices. It's been done before: Spanish woman claims ownership of the sun

33

This is more or less my best guess. We're talking about a mass of about one hundred billion tons, composed of neutrons, previously held together by a terrifying gravitational field - and now unleashed. The cup starts falling down under the Earth's gravitational attraction, but at the same time it explodes outward (so, also downward) with a velocity ...

33

Generously spread the sail surface with self repair nanobots. Any impact with dust or sub-dust size object (which is more likely to happen) will pierce a hole through the sail (and leave a cloud of plasma behind it). Just "patch" it using the nanobots and keep traveling. For larger objects between the size of dust and meter sized asteroids, I would ...

31

In our world When you watch a movie, the ships are usually aligned. This is because of reasons that are most likely not based on our experience in space battle. I'm pretty sure I read about this and I will update if I find the reference. Here are some reasons: Visual aspect. A viewer is expecting that an organised fleet of spaceships will look, well, ...

30

The answer isn't entirely clear what the final state of the Neutron Star matter would be, but it would most definitely completely destroy the "Totally Normal Office Building", and most of the country... and probably most life on Earth. See this related question: https://physics.stackexchange.com/questions/10052/what-would-happen-to-a-teaspoon-of-neutron-...

29

A tiny piece of space debris is dangerous to the ship, as it may hit people, mechanisms, or fuel. But the damage to the hull itself would be negligible. It could simply be patched. The hull is the least of the concerns there. Solar sails typically don't contain people, mechanisms, or fuel that could be damaged. A solar sail with a tiny hole in it ...

26

Black body radiation The Sun is, approximately, a black body. That means that the light it emits follows a particular spectrum according to Planck's law, with the shape of the spectrum determined solely by the Sun's surface temperature. In particular, the wavelength of peak emission can be found through Wien's law, which is also a function of temperature. ...

26

As mentioned in comments, I don't have the full stability answer to hand (although see edit below). But I do have a practical answer. The practical answer is that no feasible human effort could change the orbit of the moon via Earth-mass-transfer. Here is how the net attraction between the earth and the moon would change as you moved Earth mass to the ...

23

A star shines because it has mass... You put enough mass together, it gets a dense core, heats up, and voila, solar fusion. Yes, that's an oversimplification, but, fundamentally, making a star not shine would require removing its mass. So let's figure out how to remove mass... But you said you want the mass to stay at the center so that orbital mechanics ...

20

From Hawking radiation? No. The Hawking radiation emitted is inversely proportional to the black hole's size. To make the black hole glow with enough light to be as bright as a star from Hawking radiation alone, it would need to be very small. The problem with very small black holes is they also have very short lifetimes due to the Hawking radiation ...

20

In theory if the two moons were in the exact same orbit on opposite sides of the planet then yes. Having the moons closer to the planet and smaller also makes that easier. For example geostationary satellites over opposite sides of earth will never have direct line of sight to each other. In practice though that would be a very unstable arrangement (even if ...

19

Nothing we know of could achieve that. There are two things that distort time: velocity and gravity 18 minutes per 24 hours is a dilation factor of 1.0125. ($\frac{24hours + 18minutes}{24 hours} = 1.0125$) Velocity Velocity is out of the question as you can't just accelerate the planet and have it keep a stable orbit around the sun. Also you would ...

19

Are you asking from the POV of TV shows and Movies? TV shows and movies always show fleets approaching one another in the same orientation and on the same plane. Why? For the convenience of the viewer and to better express the drama of the moment. The chaos of a true 3-D fight is very difficult to follow on a 2-D screen. An example might be the opening ...

18

You can't move the Moon, it just requires too much energy. But maybe we can deny everyone else the Moon... and ALL OF SPACE!!! Energy Required To Move the Moon out of the Earth's Orbit Let's say "stealing the Moon" means to move it out of Earth's orbit and refusing to put it back until you're paid a ransom. How hard is it to move the Moon out of Earth's ...

17

I'm looking for an alternative to building a complete Dyson sphere because my goal as an author is to write stories about the dark cold earth. There isn't sufficient matter in the solar system to build a Dyson sphere or swarm at one astronomical unit or farther (i.e. with the Earth inside the sphere) more than four meters thick. So you'd have to build it ...

16

Why only one sail? The word here is redundancy. Your sail will take damage, that much is pretty unavoidable, but the great thing about solar sails (unlike wind sails) is that the continuity of the sail isn’t important: only total surface area is. So break up the sail into a cluster of smaller sails. If one gets damaged then unclip it, replace it with a ...

16

"Can early astronomers determine the gravity of their planet's “moon” without ever going there?" Of course they can. Our Earth-bound astronomers did, and we know how they did it. The distance from the Earth to the Moon and the size of the Moon were known since the Antiquity. The Moon is close enough that the parallax method works well enough with the naked ...

16

Not enough money, not enough means. To 'steal' the moon you need to disturb its orbit. To disturb its orbit you need a heavy enough mass, at a trajectory and timing precisely to go past the moon to veer it off its orbit. The only kind of mass to pull it off in that time frame is another moon, perhaps one of Jupiters. But then you have the problem of ...

14

Looking at some real examples of quaternary and larger star systems, all of the stable configurations appear to be in pairs. Take Castor, for instance, which is composed of six (known) stars: Aa, Ab, Ba, Bb, Ca, and Cb. Each pair, such as Aa and Ab, orbits fairly close together, like a normal binary star. Then the A and B pairs themselves orbit each other, ...

14

how do we snuff out or obscure the light and heat of our Sun? You cannot completely hide the energy emitted by the Sun. You can just shift it to longer wavelengths as a consequence of using the usable content of the emitted energy, but, as madam Thermodynamic states, any transition results in some form of heat being emitted by a system at a lower ...

14

Such a shape cannot belong to a planet: a planet would be under hydrostatic equilibrium, thus it would be spherical or ellipsoidal. That body is therefore an asteroid. (Fun trivia: the word asteroid comes from the Latin word aster/astra, meaning star, exactly the shape it has). Its rotation will very likely be chaotic, and such would be also the night-day ...

13

It depends on the size of the planet. A key concern is whether the body is in hydrostatic equilibrium. An object in hydrostatic equilibrium is approximately spherical, although it may become oblate due to rapid rotation. The question, then, is whether the division of the planet places it below the critical size required for hydrostatic equilibrium. It turns ...

12

If humans were to travel from earth to another planet that was an exoplanet 5 times the mass of Jupiter, would they be able to survive? No. Jupiter's mass is 318x that of Earth, and you want 5x that, which gives about 1600x Earth's mass. That much mass in an rocky planet requires (using the formula for the volume of a sphere V=4/3πr^3, and presuming that ...

12

The mass of a star is directly related to how hot its surface is, which in turn, is responsible for the wavelengths of light it emits (This is called Black-Body Radiation). As a main sequence G2V star, the sun has a surface temperature of 5778 K. A smaller main sequence star will be cooler and therefore redder. A larger star will be hotter, and therefore ...

12

According to the answers to the Physics question linked by abestrange this would result in the Earth being hit by 250 million tonnes of neutrons travelling at .1c+. I feel confident this would turn everything above horizon radioactive including significant portion of the ground beneath. Neutron scattering would extend this beyond the horizon too. Bulk of ...

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