Posts by HDE 226868
Is the light from the distant star significant? Does it illuminate the planet as much as, say, the earth's moon does at night when full, or is this basically just another bright star in the nigh...
Yes, it can. We can determine the distance to the source if we have an idea of what's causing that shift in velocity. Let's say that we have a source moving at a speed $v$ away from us. If it emit...
Question requirements I think it definitely falls on the asker to demonstrate first and foremost that the basic tenets of their idea are feasible. Their question should show that they've done a go...
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 particul...
In reality, if you want to build a star, you need to specify a mass and a chemical composition, and then use the equations of stellar structure. This requires some numerical integration, and it's f...
One of the cool things about the Moon is that the far side has a thicker crust that the near side.1 One theory explaining this is that the Moon was hit by an object, possibly a moonlet created by t...
My civilization is planning to being starlifting, mining a star by heating up portions of its surface and using a powerful magnetic field to channel the matter away from the star and into storage u...
Water is different from air, and sound waves propagate through water in a different way than they do in air (caused in part by interactions with the bottom of the body of water). For a society livi...
In response to a question about an asteroid filled with degenerate matter, Ender Look suggested that using matter from a black dwarf would be better than using matter from a white dwarf since black...
Yes, and the planets can orbit in the habitable zones. This page gives a long list of planets in these S-type orbits, and states For a few systems (2 so far), there are planets orbiting each m...
Avoid helicopters and airships. Try the WC-130 or WP-3D. First, airships are not fantastic choices for maneuvering in high winds. Helicopters are bad enough, but airships are large and slow, meani...
The redness of Mars' surface comes from the large quantities of iron in its crust. Other terrestrial planets in the Solar System also contain iron, but not at their surfaces. Mars in particular has...
Robots can do jobs humans can't. In fact, they can do a lot of jobs humans can't. They can Explore and clean up after a nuclear accident Go into a volcano to explore Travel the universe without w...
Temperature and luminosity Let's start with some calculations. For the sake of argument, I'll assume that we're talking about a planet that's identical to Earth orbiting a star that's identical to...
TL;DR There are several important factors considered when trying to determine if a group of stars are actually from the same stellar cluster, moving group, or association: Kinematics. Do the sta...
Let's look at two key equations: $$F_i=\frac{L_i}{4\pi r_i^2},\quad \lambda_{\text{max,i}}=\frac{b}{T_i},\tag{1, 2}$$ For a given star with luminosity $L_i$ and surface temperature $T_i$ a distance...
The Moon can appear to be different colors, as seen from Earth: A red, orange, or yellow moon can appear when the moon is near the horizon, and light has to travel through more of the atmosphere,...
A first approximation Let's calculate surface gravity. Assuming an object of density $\rho$ and radius $R$, the surface gravity is $$g=\frac{4\pi}{3}G\rho R\tag{1}$$ For a white dwarf, $\rho\sim10...
Greater endurance/stamina: A thicker atmosphere/higher oxygen levels Try a thicker atmosphere - or rather, a planet where the humans largely live at higher elevations. Altitude training is useful ...
This isn't going to happen, for a number of reasons (all of which boil down to "It's dangerous, and these bacteria will kill their hosts"). Organic materials may "spontaneously ignite" when they ...
The time it takes a moon to become tidally locked to a planet depends on a number of factors. In particular, $$t_{\text{lock}}\propto\frac{\omega a^6}{m_p^{2}}$$ where $\omega$ is the moon's initia...
Deriving the radius The heliopause is a place of equilibrium, where the ram pressure from the solar wind is equal to the pressure of the interstellar medium (ISM). There are a number of sources of...
Massive objects beyond the frost line are likely giant planets. Let's talk about the frost line, which you helpfully specified (3.94 AU). For anyone not familiar with the term, the frost line is t...
Reverse the War of the Currents. In the late 19th century, Thomas Edison supported the use of direct current, and his company, Edison General Electric, attempted to use it on a large scale. A majo...
The Earth-like planet I'm working on is the culmination of years of labor by the galaxy's best scientists. It consists of fully artificial ecosystems, and is, for all intents and purposes, like Ear...
