Posts by HDE 226868
Probably not. After some more consideration, I'm less confident that the proposal could work. There are two reasons: No guarantee of focusing at any one point, and an inability to control the para...
Apologies for taking a while to respond to this. When I used the phrase "hasn't been discussed", I was talking about the meta discussion at hand, rather than prior discussions. I rejected the edit,...
The answers so far have assumed that the galaxy in question is a spiral galaxy - and if we're talking about the Milky Way, then that's all well and good. But galaxies are pretty diverse, both in sh...
Anywhere from ancient times to the present. Question 1: Is there anything there? (answered pretty quickly) Sunspots, for instance, were first observed by the Chinese in 364 B.C., two millenia bef...
Use chicken manure. Other animals, besides livestock, also produce good manure, with different qualities. Now, not all manures are created equal; they differ in composition, volume, and production...
The idea of an ocean planet isn't too far-fetched. There are several moons in the Solar System - Enceladus and Europa, for instance - that have subsurface oceans. If the ice covering their surfaces...
There will be little difference. The lower atmospheres are the same. Let's assume that the atmospheric pressure, $P$, follows a simple exponential scale height model: $$P=P_0\exp\left(-\frac{z}{H}...
Most likely, yes. I wrote an answer here discussion how binary stars are born. The relevant part here is that there are several main theories for how binary stars form: Capture: In an interactio...
Building from scratch weather.gov gives three cases where lightning can suddenly become more intense or common in an area: "High instability" release: In this case, there is a large negative ver...
Asteroid Laser Ablation is a related technique, where a set of lasers heats up part of an asteroid, applying a torque that can change its orbit and (hopefully) send it moving away from Earth. Looki...
The number of moons Sean Raymond wrote a great answer to a similar question, and I'd like to base my answer on his. He used the following technique to estimate the total number of moons orbiting a...
The formula for the time a body $B_1$ orbiting another body $B_2$ of mass $m_2$ will become tidally locked to $B_2$ is (see Gladman et al. (1996), Equation 9) $$t=\frac{\omega a^6I_1Q}{3Gm_2^2k_2R_...
The spectral type of a star tells you, in general, its surface temperature. Unfortunately, there's one main issue here. Each spectral type can give way to a range of luminosities and properties (se...
I was rereading The Restaurant at the End of the Universe, the sequel to The Hitchhiker's Guide to the Galaxy, and I came across an interesting passage: Flare riding is one of the most exotic a...
Interesting question. I'm reasonably certain that the answer boils down to a property of matter called the equation of state. An equation of state is a relation between several thermodynamic varia...
I'm reasonably sure that the $5\text{ G}$ there refers to $5$ Gauss. The Gauss is a unit of magnetic flux (named, of course, after Carl Friedrich Gauss). The $5\text{ G}$ figure makes sense, too; i...
Yes, it's been tried. Hashizume et al. attempted to use semiconductors (variants of which are also used in normal solar cells) which were subjected to gamma radiation from a radioactive isotope of...
As you've stated, the paper you cited gives the rate of atmospheric mass loss as approximately $\dot{M}=10^9\text{-}10^{11}\text{ g/s}=10^{6}\text{-}10^8\text{ kg/s}$ of hydrogen. We can convert th...
You want a cold disk. Mercury is an example of a volatile, which, for our purposes, means that it exists as a solid only at very low temperatures. One thesis (Funk (2015)) classifies it as "modera...
Short answer You have the two equations you need on the linked page under the heading "Stage two": $$r_i=\sqrt{\frac{L_{\text{star}}}{1.1}},\quad r_o=\sqrt{\frac{L_{\text{star}}}{0.53}}$$ where $r...
Let's assume that the Moon is roughly a black body. Therefore, its luminosity can be approximated by the Stefan-Boltzmann law: $$L=4\pi\sigma R^2T^4$$ As you've said, $T=1100^\circ\text{ C}=1373\te...
On Earth, escape velocity is about 11 km/s, or 11,000 m/s. Assuming the opponent weighs around 70 kg (maybe more), that's a kinetic energy of at least $$\text{KE}=\frac{1}{2}mv^2=\frac{1}{2}\cdot70...
I wrote an answer on Physics Stack Exchange that discussed this a bit. I'll present a shorter and more focused version here. There are two main processes by which a planet can lose atmosphere: Jea...
A couple hundred years. In 2013, the Inter-Agency Space Debris Coordination Committee (IASDCC) published a report detailing comparisons of several independent models (one each from ASI, ESA, ISRO,...
Fire the engines closer to the Sun for maximum efficiency. This is due to the Oberth effect. Assume the spacecraft undergoes a burn when it is farther away from the Sun. The expelled propellant wi...
