Posts by HDE 226868
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...
You might consider adding luminol to the creatures' bloodstreams. When mixed with an oxidizer (like oxygen) and a catalyst, it becomes luminescent. It turns out that the iron in hemoglobin is a ver...
I recently came across Could pulsars really act as "lighthouses" to help in interstellar travel?, asked a week ago. The author was trying to figure out if pulsars could be useful for interstellar F...
How much gold are we talking about? Well, let's use the approximation $$\Delta V\approx4\pi r^2\Delta r$$ If $r$ is about the radius of Earth and $\Delta r$ is $1\text{ meter}$, then $\Delta V\app...
The answer, as far as I can tell, is that there aren't any existing drugs that would do what you want. Drug-induced amnesia is, of course, a real thing. In your question, you alluded to drugs that...
What worries me about the bromothymol blue proposal is that it doesn't appear to be an organic chemical, i.e. no living organism produces it. This means that it's not possible (or at least unlikely...
The Coriolis acceleration is $$\mathbf{a}_c=-2\mathbf{\Omega}\times\mathbf{v}$$ where $\mathbf{\Omega}$ is the angular velocity vector of the cylinder and $\mathbf{v}$ is the velocity vector of the...
Let's make some assumptions: The moon is essentially spherical symmetric, with uniform density. There are no other gravitational effects from other celestial bodies. Denote the position of the ...
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) $$t=\frac{\omega a^6I_1Q}{3Gm_2^2k_2R_...
Fire the engines closer to the Sun for maximum efficiency. This is due to the Oberth effect. Assume the spacecraft undergoes a burn when it is farther away from the Sun. The expelled propellant wi...
Probably not. After some more consideration, I'm less confident that the proposal could work. There are two reasons: No guarantee of focusing at any one point, and an inability to control the para...
Interesting question. I'm reasonably certain that the answer boils down to a property of matter called the equation of state. An equation of state is a relation between several thermodynamic varia...
I'm reasonably sure that the $5\text{ G}$ there refers to $5$ Gauss. The Gauss is a unit of magnetic flux (named, of course, after Carl Friedrich Gauss). The $5\text{ G}$ figure makes sense, too; i...
Yes, it's been tried. Hashizume et al. attempted to use semiconductors (variants of which are also used in normal solar cells) which were subjected to gamma radiation from a radioactive isotope of...
As you've stated, the paper you cited gives the rate of atmospheric mass loss as approximately $\dot{M}=10^9\text{-}10^{11}\text{ g/s}=10^{6}\text{-}10^8\text{ kg/s}$ of hydrogen. We can convert th...
You want a cold disk. Mercury is an example of a volatile, which, for our purposes, means that it exists as a solid only at very low temperatures. One thesis (Funk (2015)) classifies it as "modera...
Short answer You have the two equations you need on the linked page under the heading "Stage two": $$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,...
