Activity for HDE 226868
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Edit | Post #278179 |
Post edited: |
— | about 4 years ago |
| Edit | Post #278179 | Initial revision | — | about 4 years ago |
| Answer | — |
A: Didn't get notified about reply to comment 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 commenter. Given that there's an edit history, even if you didn't remember the exact request you'd made... (more) |
— | about 4 years ago |
| Comment | Post #277146 |
@pnuts Let me know what's still confusing or unclear, and I'll be happy to clarify. (more) |
— | over 4 years ago |
| Edit | Post #277146 | Initial revision | — | over 4 years ago |
| Answer | — |
A: Rationale for rejecting suggested edits is very confusing 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, then, for three reasons: The user in question hadn't explicitly stated that they supported remov... (more) |
— | over 4 years ago |
| Comment | Post #276346 |
@pnuts I don't think there's anything wrong with trying to start a discussion, and aCVn did effectively start a list by suggesting science-based - and honestly, after a week of thinking about this, there aren't really many other tags (particularly meta tags) like science-based that are clearly redund... (more) |
— | over 4 years ago |
| Edit | Post #276609 | Post undeleted | — | over 4 years ago |
| Edit | Post #276624 | Initial revision | — | over 4 years ago |
| Answer | — |
A: I received a notification about a new answer to my question, but there are no answers 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 Scientific Speculation already - more so by far than any other user. That can be a double-edged sword;... (more) |
— | over 4 years ago |
| Edit | Post #276609 | Post deleted | — | over 4 years ago |
| Edit | Post #276609 | Post undeleted | — | over 4 years ago |
| Edit | Post #276609 | Post deleted | — | over 4 years ago |
| Edit | Post #276609 | Initial revision | — | over 4 years ago |
| Answer | — |
A: Would a huge amount of asteroids hitting Earth change its rotation speed or destroy the planet? 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 $$U=\frac{3GM{\oplus}^2}{5R{\oplus}}=2.24\times10^{32}\text{ Joules}$$ Randall says that to properly slow ... (more) |
— | over 4 years ago |
| Edit | Post #271690 |
Post edited: |
— | over 4 years ago |
| Edit | Post #271891 |
Post edited: |
— | over 4 years ago |
| Edit | Post #271891 |
Post edited: |
— | over 4 years ago |
| Edit | Post #276459 | Post edited | — | over 4 years ago |
| Edit | Post #276459 | Post edited | — | over 4 years ago |
| Comment | Post #276503 |
@OlinLathrop Structural requirements for a sphere are likely different than those for an array of panels, and that might impact materials choice. Plus, I figured I might as well keep it narrowed down to the structure I'm interested in. (more) |
— | over 4 years ago |
| Edit | Post #276503 | Initial revision | — | over 4 years ago |
| Question | — |
How efficient can a Dyson sphere be? 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 use. Unfortunately, the megastructure will lose energy. It has a non-zero temperature, and therefore it... (more) |
— | over 4 years ago |
| Comment | Post #276443 |
I think this kinda falls short of [what we're hoping for in Rigorous Science answers](https://scientific-speculation.codidact.com/help/rigorous-science) - we're still ironing out some kinks, but that's our working version of the requirements at the moment. (more) |
— | over 4 years ago |
| Edit | Post #276234 | Post edited | — | over 4 years ago |
| Comment | Post #261471 |
@OlinLathrop Yes, under the appropriate relativistic conditions, [the sound speed is $c_s=c/\sqrt{3}$](https://physics.stackexchange.com/a/54786/56299) (see also [Tews et al. 2018](https://iopscience.iop.org/article/10.3847/1538-4357/aac267)). On the point about size: Neutron star radii are on the or... (more) |
— | over 4 years ago |
| Comment | Post #261471 |
@OlinLathrop I've added the alternate phrasing, for the sake of clarity. Thanks for the feedback. (more) |
— | over 4 years ago |
| Edit | Post #261471 |
Post edited: |
— | over 4 years ago |
| Comment | Post #276232 |
Yeah, I'd settle for "kinda a beam and very low intensity" - that's certainly better than I expected. I hadn't considered the problem of low energies influencing decay - looks like the issue was even worse than I'd expected. (more) |
— | over 4 years ago |
| Comment | Post #261471 |
@OlinLathrop I thought that the phrase "tenth of a millisecond" flowed better than "100 µs", given that for most people, milliseconds are a more familiar quantity than microseconds. (more) |
— | over 4 years ago |
| Edit | Post #261471 |
Post edited: Fixed formatting error. |
— | over 4 years ago |
| Edit | Post #276211 |
Post edited: |
— | over 4 years ago |
| Edit | Post #276211 |
Post edited: |
— | over 4 years ago |
| Edit | Post #276211 |
Post edited: |
— | over 4 years ago |
| Edit | Post #276211 |
Post edited: |
— | over 4 years ago |
| Edit | Post #276211 |
Post edited: |
— | over 4 years ago |
| Edit | Post #276211 | Initial revision | — | over 4 years ago |
| Question | — |
Can pion production effectively shorten the lifetime of neutrons? 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, outside an atom, a neutron is unstable, with a lifetime of 15 minutes. This is actually quite a long time ... (more) |
— | over 4 years ago |
| Comment | Post #275788 |
@aCVn Are you okay with me co-opting some of the phrasing here for the help center page? I'd like to tentatively put something together based on the points we all agree on, and I think some of your wording is good. (more) |
— | over 4 years ago |
| Edit | Post #276170 |
Post edited: |
— | over 4 years ago |
| Edit | Post #276170 |
Post edited: |
— | over 4 years ago |
| Edit | Post #276170 |
Post edited: |
— | over 4 years ago |
| Edit | Post #276170 | Initial revision | — | over 4 years ago |
| Question | — |
Is it possible to create a beam of non-relativistic neutrinos? 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 some reading on non-relativistic neutrinos, with kinetic energies of $\lesssim$ 1 meV. These would inte... (more) |
— | over 4 years ago |
| Edit | Post #275773 |
Post edited: Category has now been renamed. |
— | over 4 years ago |
| Edit | Post #275834 |
Post edited: |
— | over 4 years ago |
| Edit | Post #275834 | Initial revision | — | over 4 years ago |
| Answer | — |
A: Can velocity drift be used to calculate a radio wave source's distance from Earth? 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 emits a photon of wavelength $\lambdae$, we will observe that photon to have a wavelength of $$\lambdao=\... (more) |
— | over 4 years ago |
| Edit | Post #271865 |
Post edited: Fixed formatting error. |
— | over 4 years ago |
| Comment | Post #275787 |
@aCVn My underlying concern is partially where we draw the line, why in particular we draw it there, and how we enforce it. I'm worried that we're going to run into disputes on every answer about whether a particular source is trustworthy, unless we can find a better way of objectively describing wha... (more) |
— | over 4 years ago |