Activity for HDE 226868
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Comment | Post #275787 |
@Mithrandir24601 I'd be willing to stretch it to textbooks, yeah. Presumably that's the same level of rigor, if not more in some cases. (And textbooks are written for the purpose of teaching . . . which I suppose is what this site is all about.) (more) |
— | over 4 years ago |
| Edit | Post #275820 | Initial revision | — | over 4 years ago |
| Question | — |
Renaming Researched Q&A 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 starting point based on the hard-science tag from Worldbuilding Stack Exchange "Referenced Q&A" "Ri... (more) |
— | over 4 years ago |
| Edit | Post #238492 | Question closed | — | over 4 years ago |
| Edit | Post #275817 |
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| Edit | Post #275817 |
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— | over 4 years ago |
| Edit | Post #275817 | Initial revision | — | over 4 years ago |
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How long will it be until the cosmic microwave background is undetectable? 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 recombination several hundred thousand years after the Big Bang. Right now, the CMB is quite cool, at a tempe... (more) |
— | over 4 years ago |
| Comment | Post #275787 |
@aCVn When you put it like that . . . fair point. What about something of a compromise: requiring the citation of papers for facts/results/numbers (e.g. the mass range for which a star would undergo carbon fusion late in life) but not requiring them for general equations? (more) |
— | over 4 years ago |
| Edit | Post #275787 |
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| Edit | Post #272187 |
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| Edit | Post #272187 |
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| Edit | Post #272647 |
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| Edit | Post #213392 |
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| Edit | Post #272264 |
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| Edit | Post #215703 |
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| Edit | Post #260423 |
Post edited: Fixed formatting and changed link to Codidact post - we might have to do link editing manually for a lot of posts. |
— | over 4 years ago |
| Edit | Post #261304 |
Post edited: Edited to fix formatting. |
— | over 4 years ago |
| Comment | Post #275800 |
(Note: I [answered the Worldbuilding version of this](https://worldbuilding.stackexchange.com/a/177616/627) shortly after the data import - thought I might as well copy it over manually.) (more) |
— | over 4 years ago |
| Edit | Post #275800 | Initial revision | — | over 4 years ago |
| Answer | — |
A: What would the sky view be like of a final stage massive merged galaxy? 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 numerical treatments shouldn't be that surprising. Nevertheless, they were able to determine certain properti... (more) |
— | over 4 years ago |
| Edit | Post #263434 |
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— | over 4 years ago |
| Edit | Post #272273 |
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| Edit | Post #272264 |
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— | over 4 years ago |
| Edit | Post #273254 |
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| Edit | Post #273254 |
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| Edit | Post #273869 |
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| Edit | Post #273681 |
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| Edit | Post #273887 |
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| Edit | Post #273887 |
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| Edit | Post #263075 |
Post edited: Fixed formatting. |
— | over 4 years ago |
| Edit | Post #207415 |
Post edited: Heavily edited answer to avoid it being essentially a giant copy-and-paste of my other answer - took the same content and just tailored it to the question. |
— | over 4 years ago |
| Edit | Post #244271 |
Post edited: Fixed formatting glitch |
— | over 4 years ago |
| Edit | Post #275795 | Initial revision | — | over 4 years ago |
| Answer | — |
A: Do we want to keep the [science-based] and [reality-check] tags? [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 based in science, it's probably not appropriate for the site, period. I'd definitely support removing t... (more) |
— | over 4 years ago |
| Comment | Post #275787 |
@Mithrandir24601 Excellent point - I definitely agree. (more) |
— | over 4 years ago |
| Edit | Post #275787 |
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— | over 4 years ago |
| Edit | Post #275787 | Initial revision | — | over 4 years ago |
| Answer | — |
A: Requirements of posts in Rigorous Science 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 good deal of thinking about their problem already. They don't have to know the field intimately, of cour... (more) |
— | over 4 years ago |
| Answer | — |
A: Can a galaxy be formed from a black hole? Directly? No. Indirectly? Yes. As Renan indicated in their answer, material that enters a black hole cannot leave; the only way around this is through evaporation. Even then, the Hawking radiation emitted is largely in the form of photons, gravitons and neutrinos. Even neutrinos require a black hole... (more) |
— | over 4 years ago |
| Answer | — |
A: Could special relativity be caused by aliens jamming the Solar System? The Copernican principle As L.Dutch pointed out, this would violate the Copernican principle, which essentially states that there's nothing special about observing the universe from any one place. Granted, this is not easy to test, as we humans only sit in one tiny portion of the cosmos. However, it... (more) |
— | over 4 years ago |
| Answer | — |
A: Do seasons occur on a tidally-locked planet? 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 means that over the course of a single orbit, this planet would receive different amounts of light from ... (more) |
— | over 4 years ago |
| Answer | — |
A: How far above the galactic plane could an Earth-like planet develop? This is actually a really interesting question. While there are many stars with orbits outside the galactic plane ("halo stars"), these tend to be old and metal-poor, as star formation in the halo has long since ended. This means that assumptions we make about exoplanets around stars in the disk migh... (more) |
— | over 4 years ago |
| Answer | — |
A: Would Alcubierre Drive Technology Allow for Artificial Event Horizons? The Alcubierre drive not only allows but actually necessitates the production of event horizons at superluminal speeds - but not necessarily the sort you're looking for. It's been shown (Finazzi et al. 2009) that once an Alcubierre drive exceeds the speed of light$^{\dagger}$, two event horizons for... (more) |
— | over 4 years ago |
| Question | — |
What would make a star good for star lifting? 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 units. This is obviously not an easy task, and so these beings are looking for any advantage they can get... (more) |
— | over 4 years ago |
| Answer | — |
A: Alcubierre Drive without FTL? The Alcubierre drive works by distorting space around a bubble: expanding space behind it and contracting space in front of it. It's a nice way to get faster-than-light travel without, well, technically traveling faster than light. But the basic mechanism behind it can, it works out, work at any spee... (more) |
— | over 4 years ago |
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A: Is radar better than visible light in deep space? The big problem with using radar in outer space is simply range. The received flux of a radar signal falls off as $1/r^4$ instead of the $1/r^2$dependence we're used to getting for signals emitted by a source far away. The $1/r^4$ arises from the fact that the signal has to travel from the transmitte... (more) |
— | over 4 years ago |
| Answer | — |
A: Is it possible for a moon to stay on the same side of its planet relative to the sun? This answer is meant as a supplement to notovny's. I agree with their conclusions (the scenario is impossible because of the instability of this Lagrange point, and the fact that the Hill sphere is too small), and I just want to derive the "curious relation" they came up with. We start with Kepler's... (more) |
— | over 4 years ago |
| Question | — |
What sets of stellar models are freely available for reference when worldbuilding? 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 particular planet, or determine what the sky would look like. To tackle any of these, I need to know a bit about... (more) |
— | over 4 years ago |
| Answer | — |
A: What percentage of stars would need to become Shkadov thrusters to move the whole galaxy? This wouldn't work. The big issue is that stars make up only a few percent of the Milky Way's total mass - estimates vary by a bit, but I've heard numbers in the 3-5% range. For instance, McMillan 2011 claims about 4.98%. Dark matter makes up a substantial amount, as do interstellar clouds - i.e. no... (more) |
— | over 4 years ago |