Posts by HDE 226868
Neutrinos have extremely low masses, and it's quite easy for them to reach high energies and speeds. As such, it almost always makes sense to treat a neutrino as being relativistic. I've been doing...
I've had a number of interesting conversations with people about how the cosmic microwave background (CMB) will evolve in the future. The CMB is the sea of photons left over from the epoch of recom...
The shell variant of a Dyson sphere consists of an artificially-made shell of material about 1 AU in radius encircling a star. The sphere captures most of the star's energy and stores it for future...
One way to achieve this would be to simply change the structure of Earth's magnetic field. At the moment, the field is that of a large magnetic dipole, with the field produced by the motion of flui...
Before launching the site, we had a discussion on Codidact Meta about naming the category we currently called "Researched Q&A". Other possibilities we explored included "Hard science", our sta...
[science-based] almost certainly should be removed - I think we can safely assume that a site called Speculative Science is going to require science-based answers across the board. If an post's not...
I was the mod who deleted the comment - thanks for bringing this up. The main reason I deleted it was that I figured that the comment was primarily for the benefit of the poster, rather than the co...
Yeah, that's my fault. I wrote up an answer and posted it, but I deleted it shortly afterwards (and later undeleted it . . . and then redeleted it). I did so because I've been extremely active on S...
The Earth would be broken into pieces if the total energy delivered by the impacts was comparable to the gravitational binding energy of the planet. Earth is a sphere, so its binding energy is $$U=...
The behavior of strange matter is not well understood - least of all under the conditions we're used to on Earth! Most theoretical treatments focus on places in which strange matter is likely to be...
A young B-type star (with a mass of about 10 M$_{\odot}$) is surrounded by a debris disk extending from about 2 AU to 1000 AU away. The disk has a mass of about 300 Earth masses - enough to form qu...
The known charge-conserving decay modes of free neutrons all involve the production of a proton, an electron and an electron antineutrino: $$n\to p^++e^-+\bar{\nu}_{e}$$ This beta decay is why, out...
Cox & Loeb 2008 performed one of the few simulations of the Milky Way/Andromeda collision of which I'm aware. It's not particularly easy to simulate a galactic merger, so the lack of detailed n...
The Milky Way and Andromeda will collide a few billion years in the future. Stellar collisions will be rare because - as Douglas Adams put it - "Space is big. Really, really big." In the galactic d...
Yes, if the orbit isn't circular. Seasons can definitely occur on a tidally locked planet. Just like normal planets, tidally-locked planets don't need to have perfectly circular orbits. This mean...
In most quantum field theories$^{\dagger}$, we have a quantity called the Lagrangian, from which we can derive information about the behavior of our system. It consists of a number of terms represe...
To accurately answer your question, you might need to use a stellar evolution code, either doing your own modeling or looking up existing data tables. I'd recommend the MESA code for the former app...
TL;DR You'll see the development of both aerial vehicles and the means to survive in harsh spaces. Technology will develope faster in this world - at least, technology related to this mountain. A...
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...
In a class discussion last week, someone pointed out that a typical core collapse supernova releases $\sim10^{46}\text{ J}$ of energy in the form of (anti-)neutrinos while only radiating $\sim10^{4...
Let's think about this in terms of peak emission. Wien's displacement law tells us that the peak emission wavelength of a black body, $\lambda_{\text{max}}$, is inversely proportional to its temper...
As I'm sure you know, four more exoplanets were recently discovered around TRAPPIST-1 (Gillon et al. (2017)), bringing the total to seven "” all, amazingly, presumably rocky and near the star's hab...
I'm going to make some assumptions in this answer: Two moons have masses $m_1$ and $m_2$ and orbit a planet of mass $m_p$, where $m_1, m_2\ll m_p$. The planet is far enough away from the star that...
The classic example here is Venus, with a sidereal day of 245 Earth days and a sidereal year of 224.7 Earth days - clearly less than its sidereal day. I wrote an answer related to this on Astronomy...
